EQUINE MASSAGE THERAPY EQUINE PHYSIOLOGY
Chapters 1-15
EQUINE PHYSIOLOGY CHAPTER 1: CHEMISTRY
CHAPTER 1 CHEMISTRY
LEVELS OF ORGANIZATION
1. Chemical : Includes all chemical substances necessary for life. Together form the next higher level.
2. Cellular : Cells are the basic structural and functional units of the equine body & there are many different types of cells.
3. Tissues : A group of different cells that perform a specific function
4. Organs : An organ consists of 2 or more tissues that perform a particular function
5. Systems : An association of organs that have a common function
CHEMICAL ORGANIZATION
1) Atom: The smallest unit of matter that comprises a chemical element.
Structure of an Atom
An atom is composed of 3 types of subatomic particles: protons, neutrons and electrons.
Protons and neutrons exist within the nucleus of the atom, and electrons exist in shells orbiting the nucleus.
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Characteristics of an Atom
Every atom of a specific element will always have the same number of protons and always have the same number of electrons. The number of neutrons in atoms of an element can change. There are several ways to characterize atoms, based on the number of protons and neutrons they contain. Atomic number: Number of protons in an atom of an element - determines what element the atom belongs to.
Example:
Mass number: Total mass number of protons + neutrons.
Example:
Isotopes : Atoms of an element with different # of neutrons. Isotopes of an element have the same chemical properties. Radioisotopes are unstable isotopes that emit energy (radiation).
Example:
Atomic mass (atomic weight): The atomic mass of an element is the average mass of all its naturally occurring isotopes.
2) Element: are composed of atoms of the same type.
Elements are substances that cannot be divided into simpler substances by chemical means There are 92 naturally occurring elements Each of the elements has been named and given a symbol and has been arranged in the periodic table of the elements
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3) Ion: Any atom with an electrical charge (+ or -), not neutral
Since an atom has the same number of protons and electrons is said to be electrically neutral. When an atom or element gains or loses one or more electrons, making the number of protons and electrons unequal, it is called an ion .
Gaining electrons = Negative charge (-)
Loosing electrons = Positive charge (+)
Therefore:
Cation: a (+) charged atom Ex:
Anion: a (–) charged atom Ex:
Atoms interact with each other in order to gain stability. Two or more atoms can combine to form compounds and molecules.
4) Compound :
A compound is any two or more different elements that bind together or a chemical substance that can be broken down into two or more different elements by chemical means. A compound always contains atoms from two or more different elements.
Example:
5) Molecule : when any two or more atoms combine by sharing electrons.
Example:
**A ll compounds are molecules, but not all molecules are compounds **
WHY?
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CHEMICAL BONDS AND REACTIONS
1) Chemical Bonds
A bond is the electrical attraction that holds two atoms together, just like the bond between two oppositely charged magnets. The attraction is created by the number of electrons in the outer shell of an atom to the protons in the nucleus of the other atom. Valence shell : the outer most electron shell of an atom. The 1 st shell always only contains 2e- but the 2 nd + shells will contain up to 8e-. Octet Rule : Chemical stability occurs when an atom has 2/8e- in its valence shell – always want to fill the valence shell.
Example:
Types of Bonds
a) Ionic Bond: a chemical bond between an anion and a cation.
Attraction that holds oppositely charged ions together. “Opposites attract – Dating”
Example:
b) Covalent Bond :
Attraction between atoms that share electrons.
Strongest Bond and much more common in the body.
Single Covalent bond: Share 1 pair
Double Covalent bond: Share 2 pairs
Triple Covalent bond: Share 3 pairs
Example:
Nonpolar Covalent Bond: equal sharing of e-
Example:
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Polar Covalent Bond: unequal sharing of e-. The nucleus of one atom has a stronger attraction for the shared electrons than the nucleus of the other atom. Therefore, that atom will have a more negative charge, while the other atom will have a more positive charge.
Example:
Polarity of a molecule will determine whether or not it will dissolve in water.
c) Hydrogen Bond : the weak attraction of a hydrogen atom to a nearby oxygen nitrogen or fluorine atom. The polar covalent bonds between hydrogen and either F, O or N results in hydrogen being slightly positively charged When this positive hydrogen atom interacts with a free electron pair on the negatively charged F, O or N a hydrogen bond is formed Hydrogen bonds are approx. One-tenth as strong as covalent bonds, however, their true strength lies in number Hydrogen bonds may occur between atoms in neighbouring molecules or between atoms in different parts of the same molecule Hydrogen bonds are important in biological systems (they define the properties of water and define the structure of DNA)
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In order to understand reactions, we need to understand the forms of energy. All body functions require energy.
Forms of Energy
Energy: The capacity to do work.
a) Potential: inactive or stored energy b) Kinetic: the energy of motion – any object in motion has kinetic energy c) Chemical: is a form of potential energy. The breaking apart or formation of chemicals causes chemical energy (absorbed or released) in the form of radiant heat or electrical energy. Law of Conservation of Energy: Energy can be neither created nor destroyed, BUT CAN BE CONVERTED INTO ANOTHER FORM
2) Chemical Reactions
A chemical reaction occurs when bonds between atoms are formed or broken. The reaction proceeds as starting substances called reactants change and become products , or the end substances. Metabolism is the term used to describe the combination of all chemical reactions that occur in the body.
Types of Reactions
Exergonic: Chemical reactions that RELEASE energy as they occur.
Endergonic: Chemical reactions that REQUIRE energy to occur.
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Synthesis/Anabolic Reaction:
Bonds being formed between elements. When two or more atoms, ions, or molecules combine to form new or larger molecules.
Example:
Decomposition/Catabolic Reaction:
The breakage of bonds between atoms. A chemical breakdown into smaller parts.
Example:
Exchange Reaction:
The breakage and the reformation of two original sets of products.
Example:
Reversible Reaction:
A reaction that can proceed in either direction. The product can revert to the original reactants.
Oxidation-Reduction Reactions (AKA Redox)
Oxidation : is the removal of electrons from a molecule and results in a decrease in the energy content of the molecule. Reduction : is the opposite of oxidation. It is the addition of electrons to a molecule and results in an increase in the energy content of the molecule. **Within a cell, oxidation and reduction reactions are always coupled. Whenever one substance if oxidized, another of reduced. This is an Oxidation-Reduction Reaction (Redox)
O xidation I s L oss
R eduction Is G ain
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Reaction Rates
Atoms, ions, and molecules are continuously moving (kinetic energy) and colliding with each other. Significant collisions can break existing or make new bonds.
The speed (rate) of a chemical reaction depends on several factors. These include:
i. Concentration of Reactants: Increased concentration of reactants = increases the rate of reaction. The more particles present in a confined region, the greater the chance that they will collide.
ii. Temperature: Increased temperature (increases particles speed) = increased rate of reaction
iii. Activation Energy : (Inversely Proportional) The initial input of energy needed for a chemical reaction to occur.
**Increase AE = Decrease rate of reaction**
iv. Catalysts: substances (protein) that can speed up chemical reactions. **They do not become a part of the product (they are not altered) **
FYI Catalysts in the human body are called Enzymes and function by lowering the activation energy needed for a reaction and properly orienting the colliding molecules.
Compounds can be classified into 2 categories: inorganic & organic.
Inorganic Compounds
An inorganic compound is one that is simple in structure and, most importantly, does not contain the element Carbon. Two important categories of inorganic compounds are water, acids, bases and salts. Many compounds contain ionic bonds. Water: Water makes up about 60% of body mass, making it crucial for survival. Many substances dissolve readily in water to form solutions, which is why it is often called the “universal solvent”. When molecules of inorganic acids, bases, or salts dissolve in water, they separate into ions through a process called Ionization or Dissociation.
Components of a Solution
Solute : A substance (liquid, solid, or gas) that dissolves in a solvent.
Solvent : Is a substance (liquid or gas) that a solute dissolves into. (Usually water = universal)
Solution : The combination of solvent + solute.
Solubility : The degree to which a molecule is able to dissolve in a solvent.
Other substances can be described according to their ability to dissolve in water as follows:
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Hydrophilic : Dissolves in water (“water-loving”) Ex:
Hydrophobic : Does not dissolve in water (“water-fearing”) Ex:
Amphipathic : Has both hydrophilic & hydrophobic properties Ex:
Chemical reactions involving water also have specific terms:
Hydrolysis reaction :
Broken down putting in H2O ( adding ) or split using H2O.
Dehydration synthesis :
The formation of a molecule through the removal of H2O ( removing )
Acids, Bases, and Salts
Acids, bases and salts are substances that separate into specific ions when they are dissolved in water. Acid : a substance that dissolves in water and dissociates into one or more Hydrogen ions (H+) and one or more anions. An Acid is also known as a proton donor (Since H+ is a single proton).
Example:
Base : a substance that dissolves in water and dissociates into one or more Hydroxide ions (OH) and one or more cations. A Base is also known as a proton acceptor.
Example:
Salts : is a substance that dissolves in water and dissociates into cations and anions neither of which is H+ or OH-
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Example:
Measuring Acids and Bases
Acids and bases can vary in strength, as determined by the amount of H+ or OH- they release into solution. The pH scale is used to measure levels of acidity and alkalinity. The more H+ released in solution the more acidic. The more OH- released in solution, the more basic or alkaline.
I-----------------------------------------------I------------------------------------------------I
0
7
14
(Gastric Juice = 1.2-3.0)
(blood = 7.35-7.45)
(Lye = 14)
I------Increased Acidic---------------Neutral-------------Increased Basic-------------I
It is important to maintain appropriate acid-base levels in the body. This is accomplished in part by buffers . Buffer : A Buffer is a substance that moderates changes in pH . Its function is to convert strong acids or bases which are unstable and ionize easily (contribute many H+ or OH- changing the pH drastically) into weak acids or bases which are more stable and do not ionize easily.
Organic Compounds
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Organic compounds are larger, more complex molecules that contain carbon . These molecules are responsible for carrying out most bodily functions. They are: Carbohydrates, Lipids, Proteins, Nucleic Acids, ATP
The Importance of Carbon
The key to the versatility of carbon is in its valence shell, which carries 4 electrons. This means that carbon has the ability to bind to numerous atoms and molecules to create many different substances.
An organic molecule is generally composed of 2 parts:
Carbon skeleton : chain or ring of C atoms covalently bonded together (C-C-C-C) and can decompose easily making them a good source of energy. Functional group : a molecule or group of molecules attached to the carbon skeleton that gives it specific characteristics and functions.
1. Carbohydrates
Carbohydrates include sugars, starches, glycogen, and cellulose. They represent 2-3% of total body weight and are molecules that consist solely of Carbon, Hydrogen and Oxygen. They are hydrophilic and have names that end with the suffix –OSE.
Functions :
1. Energy Source
2. Building block for larger structures such as DNA
1) Monosaccharides : simple sugar, only one ring, the building blocks of carbohydrates. The prefix Mono means one or single.
Examples:
2) Disaccharides : simple sugar, two rings, two monosaccharide combine by dehydration synthesis to form one disaccharide molecule and a molecule of water. The prefix Di means two.
Examples:
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3) Polysaccharides : complex sugar, many carbon rings (10s to 100s)
Examples:
2. Lipids
Lipids comprise 18-25% of body weight and consist primarily of Carbon and Hydrogen , as well as some Oxygen . They are hydrophobic.
Functions : insulation, protection & energy storage.
1. Triglycerides: (fats and oils)
The body’s most highly concentrated form of chemical energy. Capacity to store triglycerides in adipose (fat) is unlimited. •
Excess dietary carbs, fats, oils are all
deposited in adipose tissue as triglycerides. •
Structure: single glycerol head with three
fatty acid (FA) molecules.
2. Phospholipids:
Major component of cell membranes; high
concentrations in nervous system (NS). Structure: glycerol, two FA chains attached to the first two carbons, with a phosphate group linked nitrogen to the third carbon
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3. Steroid:
cholesterol, sex hormones, cortisol, bile salts and vitamin D.
• Examples: • Structure: 4 carbon rings • Fat-soluble
4. Eicosanoids:
Subclasses: prostaglandins and leukotrienes Structure: 20 carbon fatty acid called an Arachidonic Acid Prostaglandins modify responses to hormones, contribute to inflammation, prevent stomach ulcers, dilate airways to lungs, regulate body temperature, influence the formation of blood cells. Leukotrienes participate in allergy and inflammatory responses.
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3. Proteins
Proteins make up 12-18% of the body and consist primarily of Carbon, Hydrogen, Oxygen and Nitrogen . They are large molecules that carry out complex functions and are amphipathic . They are made up of smaller molecules called amino acids.
Functions :
Form structural framework (ex: collagen & keratin)
Function as hormones, regulate physiological processes, control growth/development, mediate responses of the nervous system (ex: insulin) Allow muscle contraction (ex: myosin and actin) Immunological: aid in responses to foreign substances (ex: antibodies) Transport: carry vital substances throughout the body (ex: hemoglobin) Catalysts: act as enzymes and function in regulation of biochemical reactions (ex: amylase, lipase and lactase)
Protein Structure : Amino acid – Peptide – Polypeptide – Protein
Amino Acids (AA)
20 types (10 essential, 10 non-essential) building blocks of proteins made up of central carbon – C, amino group (NH2), a carboxyl group (COOH) and a side chain ‘R’ (is different for each AA.) bind together with a covalent bond called a Peptide Bond . It always forms between the carboxyl group of one AA and the amino group of another. Peptide bond water is removed therefore a dehydration synthesis reaction. 2 AA = dipeptide, 3 AA = tripeptide, 10-100 AA = Polypeptide 100+ AA = protein Ex: Hemoglobin has 4 polypeptide chains
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Protein Structural Development
Primary : sequence of AA making up the polypeptide chain (genetically determined)
Changes in primary structure can have serious effects (ex: sickle cell anemia)
Secondary : the repeated twisting or folding of neighboring AA in the polypeptide chain (clockwise spirals called alpha helix and pleated sheets)
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Tertiary : 3-dimensional shape, AA at opposite ends come close together.
Quaternary : a protein with more than one polypeptide chain and the arrangement relative to one another.
Purpose of Structure:
Proteins will vary in structure and shape and this is directly related to their function it was made for. The function of a protein will depend on its ability to recognize and bind to another molecule. (ex: enzyme binds to substrate, hormone binds to protein, antibody binds to foreign substance) In ‘hostile’ environments (temperature change, pH change, electrolyte concentration) the protein may unravel and loose it’s shape. This is called Denaturation (no longer functional).
Example: egg white (albumin) is clear – after heating, the proteins are denatured and turn white.
Enzymes
A protein, typically ending with the suffix “-ase”, that functions primarily as a biological catalyst in chemical reactions Normal body temp. and pressure(s) are too low to allow for rxns to occur fast enough to maintain life. However, raising the temperature can cause faster chemical rxns, but could also cause denaturation of proteins. The solution = enzymes. Enzymes speed up rxns by lowering the activation energy and properly orienting the molecules for better collision. The enzyme will not be permanently changed or used up in the reaction. Each enzyme has a binding site which binds to the substrates. Once binding has taken place, the substrates are brought close together and to the enzyme’s active site , which promotes the actual chemical reaction between the substrates. Some enzymes require cofactors or coenzymes . Management:
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Specificity – each enzyme only affects one specific substrate. …one key fits one lock. Efficiency – under optimal conditions, enzyme catalyze rxns up to 10 billion times faster than without a catalyst. Control : determined by the cells environment
4. Nucleic Acids
Nucleic acids are very large molecules consisting of Carbon, Hydrogen, Oxygen, Nitrogen and Phosphorus . They store & transmit genetic material. Nucleotides – the building blocks of nucleic acids. They also carry energy and form coenzymes Nucleotides consist of 3 parts: 1. Nitrogenous Base – a carbon-nitrogen ring either called a pyrimidine (C, T, U) or purine (A & G)
2. A Pentose Sugar – 5 carbon sugar
3. A Phosphate Group – PO4
Different nucleotides are made up of different bases, sugars and phosphates. There are 2 varieties:
DNA : Deoxyribonucleic Acid, the inherited genetic material inside a cell.
1. Bases: adenine, guanine, cytosine & thyamine 2. Sugar: Deoxyribose 3. Phosphate group
RNA : Ribonucleic Acid relays instructions from the genes to guide the cell’s assembly of AA into proteins.
1. Bases: adenine, guanine, cytosine & uracil 2. Sugar: Ribose 3. Phosphate group
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DNA
RNA
Deoxyribose (Sugar)
Ribose (Sugar)
Bases: ATCG
Bases: AUCG
In nucleus only
throughout the cell
Double stranded
single stranded
Self-replicating (copy itself)
not self-replicating
1 type
3 types: mRNA, tRNA, rRNA
5. Adenosine Diphosphate & Triphosphate (ADP & ATP)
ATP and ADP are some of the smallest nucleotides. They are the energy currency of the body.
They contain the nitrogenous base Adenine (A), the sugar Ribose and 2 or 3 phosphate groups (PO4). When the terminal PO4 on ATP is hydrolyzed by the addition of a H2O molecule the reaction liberates ENERGY leaving ADP. This energy that is released is used by our cells to carry out functions.
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CHAPTER 1 REVIEW QUESTIONS
1. Define the following terms:
a) polar covalent bond _____________________________________________________
b) non-polar covalent bond _________________________________________________
c) hydrogen bond _________________________________________________________
d) hydrophilic ____________________________________________________________
e) hydrophobic ___________________________________________________________
f) amphipathic ___________________________________________________________
f) acid __________________________________________________________________
g) base _________________________________________________________________
h) organic _______________________________________________________________
i) atom _________________________________________________________________
j) atomic number _________________________________________________________
h) ionic bond _____________________________________________________________
2. What is the difference between protons, neutrons and electrons?
________________________________________________________________________
3. Please describe the difference between a cation and an anion and give an example of
each.
________________________________________________________________________
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4. What is a compound? What is a molecule?
________________________________________________________________________
5. Why are not all molecules compounds?
________________________________________________________________________
6. Describe octet rule.
________________________________________________________________________
7. What is the difference between kinetic and potential energy? Give an example of each.
________________________________________________________________________
8. Name the 2 main types of reactions.
________________________________________________________________________
9. Na+ + Cl- NaCl is an example of anabolic or catabolic reaction?
________________________________________________________________________
10. Explain OILRIG
________________________________________________________________________
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11. What are the 4 factors that affect reaction rates?
________________________________________________________________________
12. What are catalysts also known as in the body?
________________________________________________________________________
13. Why is water known as the universal solvent?
________________________________________________________________________
14. Hydrolysis is the use of
to
a compound.
15. What is a dehydration reaction? _____________________________________________
16. When an acid is dissolved in water it dissociates into what? And a base? And a salt?
________________________________________________________________________
17. What does the pH scale measure? ____________________________________________
18. What is another name for basic? _____________________________________________
19. Why are buffers important? _________________________________________________
20. What are the classifications of carbs? _________________________________________
21. What is the main function of carbs? __________________________________________
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22. What are the classifications of lipids? _________________________________________
23. Lipids are hydrophilic True or False? __________________________________________
24. Describe the structure of a triglyceride.
________________________________________________________________________
25. Protein consists mainly of what elements? _____________________________________
26. What is a peptide bond? ___________________________________________________
27. Describe primary, secondary, tertiary & quarternary structure of proteins.
________________________________________________________________________
28. What does denaturation mean? _____________________________________________
29. Nucleic acids are made up of
__________________________________
30. What are the key differences between DNA & RNA?
________________________________________________________________________
31. What is so important about ATP?
________________________________________________________________________
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EQUINE PHYSIOLOGY CHAPTER 2: CELLS
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CHAPTER 2: CELLS
Cellular Components
The typical cell is organized into 2 distinct components: the plasma membrane & cytoplasm
1. Plasma Membrane
The plasma membrane is a moving structure composed of fluid, free-floating lipids and different proteins that are either free-floating or anchored to parts of the membrane. It defines the cell from it’s external environment.
Structure of the Plasma Membrane
The plasma membrane is a flexible lipid bilayer covering the entire cell surface with embedded protein channels and cell junctions that offer both stability and routes for communication.
Lipid component (40%): a double layer of lipids provides the structural framework of the plasma membrane. (a) Phospholipids
Hydrophilic heads (“water loving”) Hydrophobic tails (“water fearing”)
(b) Cholesterol (c) Glycolipids -sugars attach to fat
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Protein component (60%): act as ion channels; transporters, receptors, cell identity markers, enzymes and linkers.
(a) Integral proteins - extend into or through the lipid bilayer and are firmly embedded in it. Most are transmembrane proteins spanning the entire lipid bilayer and protrude into both the cytosol and the extracellular fluid –touches both sides all the way through. Most are Amphipathic (hydrophilic parts touch fluids and Hydrophobic extend among the FA tails). (b) Peripheral proteins - not firmly embedded in the membrane. They are generally located outside and inside of the membrane (phospholipid). They do not go all the way through. (c) Glycoproteins – sugar attached to protein
Functions of Membrane Proteins
1. Ion Channels (Integral) Pores or holes through which specific ions can flow to get into or out of the cell. Most are “selective” allowing only a specific ion to pass (most commonly K+ and Cl-). 2. Transporters (Carrier) (Integral) Selectively move substances or ion (polar – hydrophilic) from one side of the membrane to the other (ex: amino acids enter cells through transporters) 3. Receptors (Integral) Serve as cellular recognition sites. Each type of receptor recognizes and binds a specific type of molecule (a “Ligand” of that receptor) 4. Enzymes (Integral & Peripheral) Catalyzes a reaction(s) inside or outside the cell. (ex: lactase on the lining of the small intestine splits the lactose in your milk) 5. Cell Identity Markers (Mostly Peripheral) Distinguishes your cells from others (unless you are a twin). (ex: MHC – Major Histocompatibility Proteins or ABO blood type markers) 6. Linkers (Integral & Peripheral) Anchor proteins in the plasma membranes of neighbouring cells to one another.
Properties of the Plasma Membrane
1. Membrane Fluidity Adjacent phospholipids and proteins that make up the plasma membrane exhibit fluid- like movement with respect to each other and allows for self-repair. (Ex: Needle puncture)
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2. Membrane Permeability The plasma membrane is selectively permeable, because it allows certain substances to pass through it, while preventing the passage of others. • Lipids –
• Na+ -
• K+ -
• H2O –
• O2 & CO2 –
3. Membrane Gradients (Potential)
The plasma membrane maintains an electrochemical gradient produced by the influence of concentration and electrical gradients of ions and molecules in the ICF and ECF. This is important to help move substances across the membrane (Ex: a substance may move from an area of high concentration to an area of low concentration to reach a balance)
2. Cytoplasm
The Cytoplasm of a cell consists of the cytosol and organelles .
Cytosol (intracellular fluid or ICF) is the fluid that surrounds the organelles within the cell. Cytosol is 75-90% water, and includes ions, carbohydrates, lipids and proteins (glucose, AA’s, FA’s, ATP and waste products). **Most chemical reactions occur in the CYTOSOL ** Organelles are structures with specialized shape and function that contribute to cellular growth, maintenance and reproduction. Each organelle has a specific set of enzymes to aid specific reactions and serves as a functional area for specific biochemical processes. Organelles often cooperate for the benefit of the cells balance.
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1. Cytoskeleton The cytoskeleton is a network of protein filaments found throughout the cytosol that provides a structural framework for the cell. It also maintains the shape and function of other organelles, and aids movement of material through the cytosol.
4 types of filaments make up the cytoskeleton
i)
Microfilaments :
Composed of protein Actin
Thinnest fibres
Found at edge of the cell
Generate movement and provide mechanical support defining the basis strength and shape of the cell. Aid in movement such as muscle contraction, cell division, and cell locomotion (migration of embryonic cells during development)
ii)
Intermediate Filaments : Medium sized
Found throughout the cell at stress points Function: to withstand mechanical stress
iii)
Thick Filaments :
Composed of Myosin
Larger than Intermediate but smaller than Microtubules Myosin is only found in muscle cells
iv)
Microtubules : Largest Found in the middle of the cell and radiate out from Centrosome Maintain cell shape Facilitative movement of cell organelles
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2. Centrosome
The centrosome is a bundle of microtubules and other proteins responsible for the formation of microtubules and growth of the mitotic spindle during cell division.
There are two parts to the centrosome: i) Centrioles : Pair of microtubule bundles lined perpendicular to each other
ii) Pericentriolar material : microtubule rings that make up/ form the mitotic spindle
3. Cilia and Flagella
Cilia and flagella are microtubule (hair-like) extensions that project from the plasma membrane to allowmovement of substances over the surface of the cell, as well as movement of the cell through ECF. (Ex: Respiratory tract – sweeps foreign particles away from the lungs – CF creates excess mucus interfering with the cilia function)
i)
Cilia : Short hair like tubules of the plasma membrane
ii) Flagella : small tail like projection in order to propel the sperm cell
4. Ribosomes
Ribosomes are the organelles responsible for protein synthesis. They are bundles of protein, and RNA that can exist either free in cytosol or bound to other organelles. (Synthesise Proteins)
i. Free Ribosomes: Freely floating, produces proteins in cytoplasm
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ii.
Bound Ribosomes: Bound to the ER membrane.
5. Endoplasmic Reticulum (ER)
ER is a collection of flattened sacs in cytoplasm that facilitate protein and lipid synthesis. 2 types of ER:
i) Smooth/Agranular - does not synthesize proteins due to a lack of Ribosomes. It synthesizes FA’s, steroids, inactivates and detoxifies drugs, stores and releases Ca++ (Calcium) ions that trigger muscle contraction.
ii) Rough/Granular : -contains Ribosomes and is responsible for protein synthesis. Proteins enter the ER and are sorted and processed
6. Golgi Complex
The Golgi complex is a series of flattened sacs lying close to the nucleus of the cell. They are responsible for the modification, sorting and packaging of proteins from the rough ER, for transport to different destinations.
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3 types of vesicles are released from the Golgi Complex i) Membrane vesicles : transport proteins to the plasma membrane ii) Transport vesicles : transport proteins to cell organelles iii) Secretory vesicles : transport proteins out of the cell (breast feeding)
7. Lysosomes
Lysosomes are vesicles formed by Golgi Complex that contain digestive enzymes for recycling, cleanup and digestion of bacteria and cell debris.
2 functions of lysosomes:
i) Autophagy : worn out organelles are digested, and the digested parts are returned to the cytosol for future use (recycling – ex: liver cell recycles 50% of its contents each week. ii) Autolysis : lysosomes degrades and destroys whole cell (self destroy).
**Some Lysosomes work outside of the cell – sperm head**
8. Peroxisomes
Peroxisomes are similar in structure to lysosomes and are responsible for the removal of hydrogen atoms from organic molecules, a process called oxidation . A by-product of oxidation is hydrogen peroxide. Example: they oxidize toxic substances like alcohol.
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9. Proteasomes
Have enzymes that break down proteins. Proteasomes are responsible for the destruction of proteins in the cytosol that are damaged or no longer required. The amino acids that result from protein breakdown are recycled by the cell. Some diseases are theorized to result from faulty Proteasomes such as Parkinson Disease and Alzheimer’s. Clumps of unfolded, denatured proteins have been found in these patients. This is on-going research.
10. Mitochondria
A mitochondrion is called the “powerhouse” of the cell, as it is responsible for the production of energy in the form of ATP. It is the site of aerobic cellular respiration. A cell may have a few to 1000’s. The higher the need for energy consumption, the higher the amount (#) of Mitochondria. Mitochondria is self replicating meaning it has its own mitochondrial DNA (Circular).
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11. Nucleus
Most cells have a nucleus. Some have more than one. The nucleus is called the “brain” of the cell, as it contains genetic code that drives all reactions and process in the body. It is also the starting point of protein syntheses. Within the nucleus are the cells hereditary units called Genes. Genes are arranged along Chromosomes (equines have 64, 32 from each parent) Each chromosome is a long molecule of DNA coiled with proteins and some RNA called a Chromatin (beads-on-a-string structure) Each bead is a Nucleosome consisting of double-stranded DNA wrapped twice around a core of 8 proteins called Histones. String between the bead is called the Linker DNA holding adjacent nucleosomes together. Coiling of nucleosomes in larger diameter loops is Chromatin Fiber. Total genetic information is called the Genome
Nucleus Structure : i) Nuclear envelope : phospholipid bilayer surrounding the nucleus ii) Nuclear pores : in the nuclear envelope surrounded by proteins. That allow substances to pass through iii) Nucleolus : cluster of DNA, RNA, and proteins within the nucleus iv) Chromatin : complex bundle of strands of DNA and RNA wrapped around a protein (in the nucleus) v) Chromatid : strand of DNA that has been concentrated in order to prepare for cell division.
TRANSPORT
For the cells to perform their functions, they must be able to receive materials from the blood stream and the interstitial fluid, as well as to get rid of waste products and deliver materials to these other fluid compartments. Depending on the material being transported, different methods are used. They are categorized broadly as those that do not require energy (passive transport) and those that need energy (active transport) and those needing to be transported within another structure (vesicle transport).
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A. Passive Transport Passive transport involves the movement of a molecule down a concentration gradient or electrochemical gradient. When a substance moves in this direction, it uses its own kinetic energy which is intrinsic to the particles that are moving. There is no input energy from the cell.
2 types of Passive Transport:
1) Diffusion : The passive movement of molecules down their concentration gradient or electrochemical gradient. This occurs until equilibrium is reached on either side of the membrane. No cellular input energy is required. The greater the concentration gradient, the greater the rate of diffusion. a) Simple Diffusion: The passive process in which substances move freely through the lipid bilayer of cell plasma membranes without the help of membrane proteins. Simple diffusion is important for the movement of CO2 and O2 between blood and body cells. Examples include: b) Facilitated Diffusion: Substances too polar, hydrophilic/lipophobic or highly charged move through the lipid bilayer by facilitated diffusion. In this case, an integral protein assists the substance across the membrane (either an ion channel or carrier). Most ion channels are specific to the ions. Some channels are “Gated” which means they change shape in one way to open the channel and another to close the channel. Examples include:
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Factors Affecting Diffusion
i) Concentration: the difference in the amount of a substance on either side of the membrane (the steepness of the gradient). The greater the difference, the higher the rate of diffusion. ii) Temperature : the higher the temperature, the faster the rate of diffusion. iii) Mass : the larger the mass of the diffusing particle, the slower the rate of diffusion. iv) Surface Area : larger the surface area available for diffusion, faster the rate of diffusion. v) Distance : the thickness of the membrane that a substance must dissolve across. The greater the distance, the slower the rate of diffusion.
Factors Affecting facilitated diffusion:
i) Transport Maximum : the maximum number of transport proteins available ii) Saturability: the ability of the plasma membrane to have all transport proteins in use.
2) Osmosis : Water moving across a selectively permeable membrane (higher water concentration to lower water concentration). Water moves across the lipid bilayer by simple diffusion or by aquaporins which are integral membrane proteins functioning as water pores. Osmosis only occurs when a membrane is permeable to water.
Tonicity: the ability of a solution to change cell volume by altering its water content via Osmosis. (Related to SOLUTE concentration!!)
Isotonic solution: Same number of solutes on either side
Hypotonic solution: lesser concentration of solutes & more water in the solution
Hypertonic solution: greater concertation of solutes & less water in the solution
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B. Active Transport: Active transport is a process that requires energy and involves the movement of solutes across the membrane against their concentration gradient (they need to move “uphill”) Examples include:
2 Types of Active Transport:
i) Primary Active Transport : Energy derived from the hydrolysis of ATP changes the shape of a carrier protein, which “pumps” a substance across a plasma membrane against it’s concentration gradient (low concentration to high concentration) Example:
ii) Secondary Active Transport : Energy stored in a Na+ concentration gradient is used to drive other substances across the membrane against their concentration gradient (low concentration to high concentration). The energy was produced during Primary Active Transport (the hydrolysis of ATP).
2 Transport in Vesicles
Some substances are enclosed in vesicles to be transported from one structure to another within a cell, or between cells. Vesicles also import and release substances from the extracellular fluid. Transport in vesicles requires energy and are therefore classified as Active Transport.
3 types of vesicle transport:
i) Endocytosis: substances are transported into the cell.
a) Receptor-mediated endocytosis: A highly selective type of endocytosis by which cells take up (in) specific Ligands (molecules that bind to specific receptors) Examples: Cholesterol (LDL), transferring, some vitamins, certain hormones, and antibodies.
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b) Phagocytes : A form of endocytosis in which the cell engulfs large solid particles, such as worn out cells, whole bacteria, or viruses. Two main types include: Macrophages and Neutrophils (WBC). This is a vital defense mechanism protecting the body from disease. c) Pinocytosis (Bulk-Phase Endocytosis) : A form of endocytosis in which tiny droplets of extracellular fluid are taken in. Results in smaller molecules such as AAs and FAs to be used elsewhere in the cell.
ii) Exocytosis: Substances are transported out of the cell. Examples include secretory cells that liberate digestive enzymes, hormones, mucus, or other secretions. Nerve Cells are another example that release Neurotransmitters.
iii) Transcytosis: Substances are transported into a cell on one side, and out of a cell on the other side. Said another way: Endocytosis on one side of the cell, and exocytosis on the other side of the cell.
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Protein Synthesis
The production of proteins begins in the nucleus of a cell. Specific proteins are made based on a particular genetic sequence on a strand of DNA. This DNA sequence is then converted, or transcribed , to RNA. Each segment of RNA is then translated into specific amino acids, which are then linked by peptide bonds to form a protein.
Protein Synthesis is the formation of proteins by transcription and translation .
DNA – RNA – AMINO ACIDS – PROTEIN
Terminology
DNA: Gene: Sequence of nucleotides that code for a specific sequence of amino acids in a protein. Codon: Coded blocks of information corresponding to an AA sequence. DNA and RNA store genetic information as sets of 3 nucleotides. A Base Triplet is a series of three nucleotides of DNA that codes for a specific amino acid. Promoter Codon: Specific triplet code that identifies where transcription STARTS . Terminator Codon: Specific triplet code that identifies the END of transcription. RNA: mRNA (messenger RNA): are long strands of RNA that are transcribed from DNA and that travel to the ribosomes to direct precisely which amino acids are assembled. tRNA (transfer RNA): transports amino acids to the ribosome and position each amino acid to the correct place. rRNA (Ribosomal RNA): found in the ribosome and provides the site where polypeptides are assembled.
a) Transcription
Transcription is the first step of Protein synthesis and is the transfer of information from DNA to RNA, which occurs when an mRNA copy of the gene is produced.
Transcription Process:
Transcription is initiated when the enzyme RNA Polymerase binds to a particular sequence of nucleotides called a Promotor Codon located at the beginning of the gene. Starting there, the enzyme begins to partially unwind the DNA and move into the gene section. As it encounters each DNA nucleotide, it adds the corresponding complementary RNA nucleotide to a growing mRNA strand. GCTA in DNA would signal the addition of CGAU to the mRNA. The mRNA codes for a specific AA sequence.
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When the RNA polymerase arrives at the terminator codon (stop signal) disengages from the DNA and releases the newly assembled RNA chain called Pre-mRNA . The chain is a complimentary transcript of the genetic code from which it was copied. The processed pre-mRNA strand leaves the nucleus and travels to the ribosomes .
b) Translation
Translation is the second step in Protein synthesis. Translation is the transfer of information from mRNA to protein, which occurs when the information contained in the mRNA transcript is used to direct the sequence of amino acids during synthesis of polypeptides by the ribosomes.
Translation Process:
The rRNA molecule within the ribosome binds to the (start) codon on the mRNA. The mRNA lies on the ribosome in such a way that only one of its codons is exposed at the polypeptide making site at any time. A tRNAmolecule possessing the “complimentary” triplet sequence ( anticodon ) binds to the exposed codon on the mRNA. Because this tRNA molecule carries a particular amino acid, that amino acid and no other is added to the polypeptide in that position. The ribosome moves along the mRNA molecule three nucleotides at a time or one triplet at a time. Successive codons on the mRNA are exposed and a series of tRNA molecules bind one after another to the exposed codons. The ribosome continues until it encounters the “stop” codon and then disengages from the mRNA and releases the completed polypeptide.
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Cell Division
Cells must divide in order for an organism to grow and function properly. The process of cell division involves duplication of all the contents of the cell, including DNA, followed by the packaging of the contents into two separate cells. Most body cells undergo somatic cell division . Reproductive cell division involves the division of sperm and egg cells during the reproductive process. Somatic Cell Division: creates new somatic cells (any cell in the body other than a germ cell) to build tissues and replace dead or damaged cells. In somatic cell division, a cell undergoes nuclear division called MITOSIS.
Reproductive Cell Division: A germ cell is a gamete (sperm or oocyte) or any precursor cell destined to become a gamete. The process is called Meiosis. Discussed later.
Somatic Cell Division
A. Interphase: the cell replicates its DNA and also produces additional organelles and cytosolic components in anticipation of cell division. In Interphase the cell IS NOT dividing yet. Interphase consists of 3 phases:
G1 – Cell organelles, cytoplasm and centrosome replication begins. Cells can remain in this phase forever ( G0 – Dormant phase; cell remains in this phase until ready to divide)
S – DNA replication occurs, and the cell is COMMITTED (point of NO RETURN) to the division process. AS a result, the two daughter cells formed at the end of this process have the same genetic material.
G2 – Cell growth continues, enzymes and other proteins are synthesized. Replication of centrosomes is complete. Preparing for mitosis.
DNA Replication is the process by which the cell makes a copy if its entire genetic code. Each strand of DNA is unwound by enzyme DNA polymerase, and complementary DNA strands are synthesized from each parent strand. This process is described as semi-conservative because one-half of the original DNA strand is conserved in each new strand (an original is paired).
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B. Mitotic Phase: the phase in which the nucleus, followed by the cytoplasm, of the cell divide into two distinct daughter cells.
1. Mitosis – also called nuclear division Two complete sets of chromosomes are distributed into each of two nuclei
i) Prophase: Chromatids condense and pair up to become chromosomes Mitotic spindle forms and centrosomes move to opposite poles. Nucleolus disappears and the nuclear envelope breaks down. ii) Metaphase: Microtubules attach themselves and align centromeres a long the midline of the cell iii) Anaphase Centromeres split separating the two members of each chromatid pair, which are pulled toward opposite poles of the cell by the microtubules of the mitotic spindle. Once separated, the chromatids are termed Chromosomes. iv) Telophase The final stage of mitosis beginning after chromosomal movement stops. Two identical sets of chromosomes at opposite poles uncondensed (uncoil) and revert to the threadlike chromatin form. A nuclear envelope forms around each chromatin mass, and nucleoli reappear in the identical nuclei. The mitotic spindle is broken down.
2. Cytokinesis – also called cytoplasmic division The division of cytosol and organelles into two identical daughter cells Begins in late anaphase or early telophase
i) Cleavage furrow forms along the midline of plasma membrane ii) Contractile ring of actin filaments pinches the cell into two identical daughter cells along the cleavage furrow
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CHAPTER 2 REVIEW QUESTIONS
1. What is the structure of the plasma membrane? ________________________________
2. Phospholipids make up
% of the plasma membrane.
3. Please differentiate between integral & peripheral proteins.
________________________________________________________________________
4. What are the 6 functions of the membrane proteins?
________________________________________________________________________
5. What does selectively permeable membrane mean? _____________________________
6. What does the cytoplasm consist of? _________________________________________
7. What % of cytosol is made up of water? _______________________________________
8. Describe the 4 types of filaments that make up the cytoskeleton.
________________________________________________________________________
9. What are ribosomes responsible for? _________________________________________
10. Please differentiate between smooth & rough ER.
________________________________________________________________________
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