anatomy & physiology i (101 - 805 - ab) paul anderson...

ANATOMY & PHYSIOLOGY I (101 - 805 - AB) PAUL ANDERSON 2011

Key Concepts UNIT 3: CHEMICAL COMPOSITION OF THE BODY I. ELEMENTS OF THE HUMAN BODY 1. About 25 elements are essential for health (see Periodic Table). Depending on their

relative abundance in the body these are divided into MAJOR ELEMENTS and TRACE ELEMENTS, .

2. The following MAJOR ELEMENTS account for more than 99% of the human body's atoms and body mass. C, H, O, N, P, S, Ca, Na, K, Cl and Mg

3. H and O are the two most abundant atoms mainly because they occur in the most abundant molecule in organisms - WATER, H2O.

4. C, H, O, N, P and S occur in ORGANIC BIOMOLECULES (C, H and O occur in all

whereas N, P and S occur only in some).

5. Several major elements form INORGANIC IONS in body fluids (e.g. Ca+2, PO4-3, Na+,

K+, Cl- and Mg+2 ). Elements in the Human Body Element

% atoms

% mass

Main Functions

63 9.5 In all organic molecules/H2O; energy storage (C-H); affects pH (as

H+) 25.5 65.0 In all bio-organic molecules/H2O; substrate for cell respiration 9.5 18.5 In all organic molecules; determines molecular shape; oxidised in

cells to CO2 1.4 3.3 In proteins, amino acids, nucleotides, nucleic acids (as -NH2- amino

group) 0.3l 1.5 Forms hard matrix of bones /teeth: plasma clotting factor (as Ca+2);

Ca+2 stored in muscle cells triggers contraction 0.22 1.0 With Ca forms hard matrix of bones /teeth: Stores energy (as

terminal phosphate group -H2PO4) in ATP 0.35 Major intracellular cation; esential for normal nerve/muscle

function 0.25 Forms sulfhydryl group (-S-H) ; disulfide bond holds many

proteins together 0.20 Major extracellular anion (balances Na+); body fluid balance 0.l5 Major extracellular cation; esential for normal nerve/muscle

function and body fluid balance 0.06 major intracellular enzyme cofactor (as Mg+2) Trace Elements

0.2 see following table

Human Anatomy & Physiology 1 (805) Unit 3 Key Concepts

See Martini & Batholomew, Appendix 1 for complete Periodic Table


6. TRACE ELEMENTS are as follows: Trace Elements in Humans with Known Functions Element Role in Human Body essential component of respiratory proteins (hemoglobin,

myoglobin) and cytochromes): enzyme cofactor essential component of thyroid hormone (thyroxine) stabilises hard matrix of bones and teeth Chromium, Cr makes insulin more effective on glucose uptake by cells Manganese, Mn enzyme cofactor Cobalt, Co enzyme cofactor: component of vit. B12 (essential for red blood

cell formation) Copper, Cu enzyme cofactor Zinc, Zn enzyme cofactor Selenium, Se enzyme cofactor (in liver): antioxidant in cells Molybdenum, Mo enzyme cofactor Tin, Sn enzyme cofactor

7. TRACE ELEMENTS function as follows:

• Most act as INORGANIC COMPONENTS (COFACTORS) for ENZYMES: - a cofactor is an inorganic metal ion, essential for enzyme activity: the cofactor is

loosely bound to its enzyme: - enzymes are protein (organic) catalysts, essential for metabolic reactions.

• Some form key components of other large organic molecules (e.g. iodine in thyroid hormone and iron in hemoglobin).

• At least one (selenium) is an antioxidant.

- Antioxidants are reducing agents which donate electrons to unstable free radicals in cells (powerful oxidising agents). The antioxidant thus protects biomolecules from excessive oxidation which would otherwise destroy biomolecules.


II OXIDATION – REDUCTION (REDOX) REACTIONS

1. OXIDATION can refer either to the addition of oxygen or the loss of electrons or the

removal of hydrogen from a molecule. A molecule which removes electrons from another molecule, therefore oxidising it is called an oxidising agent (or oxidant).

2. REDUCTION can refer either to the addition of hydrogen or gain of electrons or the

removal of oxygen from a molecule. A molecule which adds electrons to another molecule, therefore reducing it is called a reducing agent (or reductant).

3. OXIDATION and REDUCTION always occur simultaneously i.e. a “redox” reaction

occurs in which one molecule is oxidised (by an oxidising agent) and another reduced (by a reducing agent).

In general:

As an example:

Na + Cl NaCl Na has lost an electron so is oxidised Cl has gained an electron so is reduced

L E O the lion says G E R

The following reversible reaction occurs in muscle cells.

For the above reaction complete the following. Pyruvic acid is an _____________ (oxidising/reducing) agent and is _____________ (oxidised/reduced) in the forward reaction to __________________. NADH2 is a _______________ (oxidising/reducing) agent and is ______________ (oxidised/reduced) in the forward reaction to _____________________.


III. WATER: KEY CONCEPTS 1. Water is the most abundant molecule in the body, comprising 45 - 60 % of the human

body’s mass. In some body fluids the water content is higher e.g. plasma = 92% H2O. 2. A water molecule consists of two hydrogen atoms joined by polar covalent bonds to an

oxygen atom. The water molecule is polar with the two hydrogen atoms bearing partial

positive charges (! +) on one side and the oxygen being slightly negatively charged (! -) on the other side.

3. Most of the important biological properties of water are related to its molecular structure

and its ability to form hydrogen bonds. 4. A HYDROGEN BOND is an attraction between the positive hydrogen atom of one polar

molecule and the negative atom of another polar molecule. Hydrogen bonds are important for the intermolecular bonding of water (each molecule can form 3 H bonds) and the intramolecular bonding of macromolecules (DNA and proteins).


5. In the body water has important physical, chemical and thermal properties.

6. THERMAL PROPERTIES H2O has unique thermal properties (e.g. high specific heat

and high latent heat of vaporisation), important for body temperature control. These properties are due to the ability of hydrogen bonds to absorb heat energy which otherwise would instead increase random molecular motions and cause a large-scale body temperature increase.

7. H2O is a liquid at body temperatures, which facilitates metabolic reactions (reactions

occur faster in a liquid because of the combination of molecular motion and molecular concentration, two requirements for molecular reactions).

8. CHEMICAL PROPERTIES Water acts as a SOLVENT for all charged compounds

(polar and ionic compounds) in body fluids. The charged regions of polar and ionic compounds become surrounded by oppositely charged ends of water molecules, causing these solutes to disperse (dissolve).

• Water - soluble substances are said to be HYDROPHILIC and include all ionic and polar compounds.

• Because it is a solvent water dilutes toxins and so is used to flush out soluble toxins from the body, via the kidneys.


9. HYDROPHOBIC substances are water - insoluble and include all non - charged compounds, i.e. with hydrophobic functional groups, mainly hydrocarbons. HYDROPHOBIC BONDS are the attraction between hydrophobic molecules in aqueous solutions. Such bonds are actually caused by the attraction of water molecules for each other, which pushes hydrophobic molecules together in clusters

10. Water participates in metabolic reactions, as a substrate for hydrolysis and as a product of dehydration synthesis and oxidation of glucose: water formed from metabolic reactions is called “metabolic water”.

11. PHYSICAL PROPERTIES Water lubricates internal surfaces and cushions organs,

e.g. the watery CSF cushions the brain, synovial fluid cushions joints. This property is due to the hydrogen bonds between water molecules which resist compression and minimise friction.

12. Because of these important properties, dehydration disturbs body functioning more

rapidly than malnutrition and so is a serious disequilibrium. Various homeostatic control systems restore water balance by controlling fluid intake (the thirst – drinking mechanism) or controlling urinary output (via the kidneys).

FLUID INTAKE ————> FLUID BALANCE ———> FLUID OUTPUT


IV. pH: KEY CONCEPTS Since enzymes are sensitive to pH, the pH of body fluids must be homeostatically controlled via BUFFERS and via the urinary and respiratory systems. 1. pH is a measure of the hydrogen ion concentration

of a given solution in moles per liter and equals the negative logarithm of the hydrogen ion

concentration i.e. pH = - log [H+].

2. Since the [H+] of any solution is always less than

1M, the negative log of [H+] will always be a positive number. This number is called the pH.

3. If the pH changes by 1 unit, it means

that [H+] has changed by a factor of

10 (ie.10x). AS THE [H+] GOES UP THE pH GOES DOWN.

4. A pH below 7 is ACIDIC. In this

range the hydrogen ion exceeds the hydroxide ion concentration

i.e. [H+] > [OH-]. 5. A pH above 7 is ALKALINE (or

BASIC). In this range the hydrogen ion concentration is less than the hydroxide ion concentration

i.e. [H+] < [OH-]. 6. A pH of 7 is said to be NEUTRAL

since it is neither acidic nor basic and

at this point [H+] = [OH-] = 10-7 M (as in pure water).

7. An ACID is an electrolyte (ionizing substance) which donates protons (H+) in aqueous

solutions, therefore raising [H+] and lowering pH. STRONG ACIDS dissociate completely whereas WEAK ACIDS dissociate partially. Most acids in the body are weak acids, e.g. organic acids.

8. A BASE is an electrolyte which

is a proton acceptor. In the body all bases are WEAK BASES, e.g. NH3, amino group: the anion of a weak acid is called the conjugate base of the acid.

9. Hydrogen ions are constantly produced within the body because of acids from cell

metabolism. Homeostatic control of pH involves three mechanisms: a. Control of breathing b. Control of urine production by the kidneys c. Buffers.

10. BUFFERS are chemical systems which resist pH changes. Buffers work by absorbing

H+ or OH- when these ions are in excess or by releasing these ions when they are scarce.


11. Buffer systems in the body consist of two components: i) a WEAK ACID (which partially dissociates) and

ii) the ANION of the weak acid which acts as a WEAK BASE. The anion of the acid is provided by the salt of the acid.

12. A stronger acid is more dissociated than a weaker acid at a given pH. Therefore a weak acid will always

buffer a stronger acid. This is because the excess H+ (from the more dissociated stronger acid) is

absorbed by the anion (A-) of the weak acid to form more of the undissociated weak acid (HA). The salt functions to maintain a high concentration of the basic anion so that more H+ can be absorbed and buffering capacity maintained.

13. Important buffer systems of the human body include reduced hemoglobin and the

carbonic acid - bicarbonate system. As an example lactic acid from exercising muscles

is buffered by HCO3-/carbonic acid in the blood plasma, which, in turn, is buffered by reduced hemoglobin in red blood cells.


ENZYME

SUBSTRATES PRODUCTS

V BIOCHEMICAL EQUILIBRIUM & SUBSTRATE CONCENTRATION 1. BIOCHEMICAL REACTIONS consist of substrates (or reactants), products and

enzymes. 2. ENZYMES are protein catalysts which react temporarily with a substrate molecule

enabling it to react faster, forming product molecules. Enzymes are highly specific to their substrate molecule and are unchanged by the reaction so can be reused.

3. For any reaction the reaction rate is proportional to the substrate concentration,

i.e. r " [S]. 4. BIOCHEMICAL EQUILIBRIUM is the condition in which the forward and reverse

reaction rates are equal for a reversible reaction i.e. r1 = r2.

5. The NET REACTION RATE for a reversible reaction equals the difference between the

forward and reverse reaction rates i.e. r1minus r2. In any reversible reaction there is a tendency for the reaction to attain a state of biochemical equilibrium, at which point the net reaction rate is zero.

The following equilibrium occurs in the blood. systemic tissues

lungs As blood passes through body tissues CO2 is added which disturbs the equilibrium by increasing [CO2 ]. Place vertical arrows to indicate whether each of the following will increase or decrease.

r1 will __ [H2CO3] will __ r3 will __ [H+] will __

The pH of venous blood leaving the tissue will therefore ___ As blood passes through the lungs CO2 is removed which disturbs the equilibrium by decreasing [CO2 ]. Place vertical arrows to indicate whether each of the following will increase or decrease.

r1 will __ [H2CO3] will __ r3 will __ [H+] will __

The pH of pulmonary venous blood leaving the lungs will therefore ___ Therefore HYPOVENTILATION causes ____________(ACIDOSIS/ALKALOSIS) and HYPERVENTILATION causes _____________ (ACIDOSIS/ALKALOSIS). Note that the buffering action of reduced hemoglobin normally prevents the pH of systemic venous blood from dropping too low (see previous page).


VI ELECTROLYTE COMPOSITION OF BODY FLUIDS & ELECTROLYTE BALANCE

1. Electrolytes exist mainly in the ionic state in body fluids.

2. There are 4 major CATIONS (Na+, K+, Ca++, Mg++) and 8 major ANIONS (Cl-, H2PO4-,

HPO4-2, PO4

-3, SO4-2, HCO3

-, protein- and the anions of organic acids) in body fluids. 3. The amount of anions and cations is exactly balanced in each body fluid (i.e. + = -).

4. Each body fluid has a different electrolyte composition. The ECF consists mainly of

Na+ balanced by Cl- and (to a lesser degree HCO3- ) whereas the ICF consists mainly

of K+ and Mg+2 balanced by the phosphate series , SO4-2 and protein anions. Proteins

are present in the ICF and PLASMA but are absent from the INTERSTITIAL FLUID. 5. Differences in electrolyte composition between body fluids are due to: a) The impermeability of the cell membrane and capillary membrane to proteins which

can therefore not "leak" into the IF. Plasma proteins are produced mainly by the liver and all cells synthesise their own ICF proteins.

b) The SODIUM/POTASSIUM PUMP in all cell

membranes which ejects Na+ from cells

while taking in K+ from the IF. c) HOMEOSTATIC CONTROL SYSTEMS involving selective excretion by the kidneys of excess amounts of electrolytes in the plasma

(e.g. K+ is excreted while Na+ and Cl-are conserved).

6. ELECTROLYTE IMBALANCES are serious forms of disequilibrium and, in turn, cause body fluid imbalance.

Compare Na+, K+, Mg+, Cl-, HCO3-, HPO4-2, SO4-2, protein- in ICF vs IF vs plasma.

ICF IF PLASMA Cations Anions Cations Anions Cations Anions

K+ HPO4-2 Na+ Cl- Na+ Cl-

Mg++ SO4-2 HCO3- HCO3- protein- protein-

BLOOD

K+ Na+ Cl-

URINE


MAJOR ANIONS & CATIONS OF BODY FLUIDS

CATIONS ANIONS Na+ Cl-

K+ HCO3 -

Ca++ PO4 –3 /HPO4

–2 /H2PO4 -

Mg ++ SO4 –2

protein - organic acids

(lactate - / pyruvate -)


VII FORMULAE & ISOMERS 1. Formulae are symbolic representations of molecules which indicate the component

elements (by atomic symbol) with the actual numbers of atoms (molecular formula) or their spatial arrangement (structural formula).

Example: Glucose

MOLECULAR FORMULA

C6H12O6

STRUCTURAL FORMULA

2. Isomers are organic compounds having the same molecular formulae but different

structural formulae. Isomers are metabolically important because enzymes are usually specific to one isomer and so each isomer requires a different enzyme and undergoes a different metabolism.

• As an example the blood sugar is glucose (dextrose), whereas its isomer galactose is

toxic when elevated in the blood of infants (a disease called galactosemia).

Glucose Galactose


VIII FUNCTIONAL GROUPS A functional group is an atom or radical (group of inter-connected atoms) within an

organic molecule which gives distinctive properties to the molecule. Some of the major functional groups are as follows:

Group

Formula Properties Examples

Hydrocarbon

- C-H

hydrophobic

all lipids methyl, ethyl, propyl groups

Alcohol (Hydroxyl)

- O-H

hydrophilic all sugars

Carboxyl (Organic Acid)

- COOH

hydrophilic weakly acidic

all amino acids all fatty acids

Ester Linkage

- COO -

joins carboxyl and alcohol groups

all triglycerides (fats/oils)

Phosphate

-H2PO4

hydrophilic weakly acidic can store energy added to sugars to ionise and trap sugars in cells

all nucleotides ADP/ATP DNA/RNA

Amino

- NH2

hydrophilic weakly basic

all amino acids proteins

Sulfhydryl

- S- H

can be oxidised to form disulfide bonds in proteins

some amino acids


IX MAJOR MOLECULES OF LIVING ORGANISMS

MOLECULE COMPONENT ELEMENTS PROTEINS C, H, O, N. (+S) CARBOHYDRATES C, H, O, combined in the ratio Cn (H2O)n (in simple sugars) glucose = C6(H2O)6 or C6H12O6 LIPIDS C, H, O (+P, N) NUCLEIC ACIDS C, H, O, N, P WATER H, O

Organic Biomolecules exist as large molecules called Polymers, made up of repeating subunits or "building blocks" called Monomers, joined by specific bonds. Monomer Polymer Bonds Formula of Bond Amino Acids Polypeptides

Proteins

Peptide Bond (joins amino to carboxyl group of amino acids)

Monosaccharides e.g. glucose

Polysaccharides Glycosidic Linkage (joins hydroxyl groups of two sugars)

Fatty Acids, Glycerol Triglycerides

Ester Linkage (joins hydroxyl group of glycerol to carboxyl group of fatty acid)

Nucleotides (e.g. ATP)

Polynucleotides (DNA, RNA)

Phospho Diester Linkage (joins acidic phosphate group to hydroxyl of a sugar)

X DEHYDRATION SYNTHESIS & HYDROLYSIS REACTIONS 1. Monomers are formed from the breakdown (decomposition) of Polymers using water

as a substrate to break the specific bonds connecting the monomer units. This reaction is called Hydrolysis.

2. Monomers form Polymers by elimination of water as a product to form the specific bonds connecting the monomer units. This reaction is called Dehydration Synthesis)


X1. CARBOHYDRATES A. Definition 1. Carbohydrates are hydrates of carbon i.e. carbon + H2O (H - C - O- H) 2. Carbohydrates have the general molecular formula Cx(H2O)y

a. where x = y for monosaccharides; x > y for disaccharides and polysaccharides, b. because of H2O lost in dehydration synthesis.

3. Carbohydrates are H2O soluble because of the many hydrophilic hydroxyl groups. 4. Both hydrocarbon and hydroxyl groups store energy, which is released during dehydrogenation (oxidation) reactions of cell respiration. B. Functions of Carbohydrates

1. Carbohydrates provide "IMMEDIATE" ENERGY” for cells. Blood sugar (dextrose or glucose) is the "fuel molecule" used by all cells (especially brain cells) for ATP synthesis. Energy is released for biological work when glucose is oxidised in the process of aerobic cellular respiration (ATP temporarily stores the energy).

2. Carbohydrates provide STORED ENERGY as glycogen (mainly in liver, muscles). Hepatic glycogen acts as a reservoir for the blood sugar.


3. FAT FORMATION; excess dietary carbohydrates are converted to fat by adipose tissues, a process stimulated by insulin.

4. Carbohydrates provide a source of DIETARY FIBER, (mainly in the form of non -

digestible cellulose). Dietary fiber promotes mechanical digestion and elimination.

5. PROTEIN SPARING; dietary carbohydrates prevent excessive catabolism of proteins. Carbohydrate deficiency therefore depletes the body's supply of essential proteins (by causing increased tissue protein breakdown). This occurs in 2 states:

• Diabetes Mellitus, in which cells cannot obtain glucose (in the absence of insulin -

pancreatic diabetes-TYPE 1) or else cannot respond to insulin (TYPE 2). • Starvation, in which there is a lack of dietary carbohydrates.

C. Types of Carbohydrates

1. Monosaccharides: "Single sugars", Cn(H2O)n

a. Hexoses C6(H2O)6 or C6H12O6

• glucose ("dextrose"); blood sugar, cell’s “fuel molecule” and monomer unit for disaccharides and polysaccharides • galactose; used for the synthesis of lactose by the breast: converted to glucose by liver. • fructose : converted to glucose by liver.


b. Pentoses. C5(H2O)5 or C5H10O5; c. Trioses C3(H2O)3 or C3H6O3

• deoxyribose in DNA •glycerose: formed from hexoses in cells • ribose in ATP, RNA

MONOSACCHARIDES


DISACCCHARIDES Disaccharides ; ("double sugars") C12H22O11, consisting of 2 hexoses joined by one

glycosidic bond. • maltose (2 glucoses); • lactose (glucose + galactose) = "milk sugar"; • sucrose (glucose + fructose)


POLYSACCCHARIDES Polysaccharides consist of "many sugars" joined by glycosidic bonds: (C6H10O5) nH2O • starch (dietary carbohydrate); • glycogen (energy storage in muscles, liver) • cellulose (dietary fiber)


XII. LIPIDS

A. Definition: Lipids have many hydrocarbons groups and so are hydrophobic (e.g. fats) or amphipathic (partly hydrophobic, partly hydrophilic), e.g. phospholipids, fatty acids, cholesterol, bile salts. B. Some Major Types of Lipids 1. Triglycerides (fats) are composed of 3 fatty acids joined by ester linkages to glycerol.

Figure 2-13, from Martini & Bartholomew: Fig. 2-15 from Martini

Because of their large number of hydrocarbon groups, fat molecules can store a lot of energy. This energy is released when they are oxidised by dehydrogenations.

2. Phospholipids are composed of 2 fatty acids joined by ester linkages to glycerol with a

phosphate group and N - containing choline attached to the third –OH of glycerol. The hydrocarbon chains of the fatty acids form hydrophobic tails and the phosphate and choline groups form a hydrophilic head so the molecule as a whole is amphipathic.

Figure 2-15 from Martini


Because of their amphipathic properties, the hydrophilic heads of phospholipids are attracted to the aqueous ECF and ICF. Therefore they form a molecular double layer (bilayer) in cell membranes with a two layers of hydrophobic tails sandwiched inside the membrane.

ICF 3. Steroids are all basically composed of 4 saturated hydrocarbon rings ("steroid nucleus"):

Double bonds and various other groups or sidechains may be added to this nucleus. If –OH is present the molecule is an alcohol steroid called a sterol (e.g. cholesterol). Steroids include sex hormones, bile salts and cholesterol. All steroids are derived from cholesterol, many of these functioning as hormones (e.g. estrogens and testosterone).

Figure 2-14, Martini & Bartholomew

Fig. 2-16, Martini C. Functions of Lipids 1. Energy storage (as fats); fats store 2 x as much energy per g as carbohydrates/proteins. 2. Major components of cell membrane (as phospholipids, cholesterol and glycolipids). 3. Steroid Hormones (e.g. estrogen, testosterone). 4. Emulsification of dietary fats by bile salts, promotes digestion and absorption of fats. FAT + BILE SALT EMULSION 5. Special fatty acids act as prostaglandins (" local acting" hormones).

ECF ICF


XIII AMINO ACIDS, PEPTIDES & PROTEINS

A. Amino Acids 1. Amino Acids are the monomer units of peptides (polypeptides & proteins). 2. The variable R group distinguishes each amino acid and may contain hydrophobic groups or various hydrophilic groups (e.g. acidic, basic) or a sulfhydryl group (see Martini, appendix III; Marieb Fig. 2.15). 3. When the carboxyl group of one amino acid reacts with the amino group of another

amino acid a dehydration synthesis reaction occurs to form a peptide molecule. This reaction occurs in all cells using the genetic code in DNA to build a specific peptide. (see Martini & Bartholomew, fig. 2-16/2-15: Martini, fig. 2-19; Marieb Fig. 2.16).

4. Amino acids and peptides act as BUFFERS in body fluids. For this function the amino

and carboxyl groups of amino acids and proteins can accept H+ (at a low pH where the

[H+] is high) and give up H+ (at a high pH where the [H+] is low).


5. Peptides include polypeptides and proteins. • polypeptides are peptides with 3 - 49 peptide units, e.g. the hormone glucagon(29): • proteins are large polypeptides with 50+ peptide units, (e.g. insulin, 51, hemoglobin,574)

B. Proteins 1. Proteins have four levels of structure.

fig. 2-20 from Martini (fig 2-17, Martini & Bartholomew)

2. Primary Structure is the number, type & sequence of amino acids in a protein, held

together by covalent peptide bonds and is determined by the primary structure of the gene in DNA controlling that protein (i.e. genes control proteins).

3. The primary structure of proteins determines individual genetic variation since each

person makes slightly different proteins.


4. The primary structure causes the chain to coil and bend and so determines all other

levels of protein structure and so determines the protein’s function. 5. Secondary structure is the regular coiling or bending of a polypeptide chain caused by

hydrogen bonding between oppositely charged polar groups. This creates either an

alpha helix or a beta pleated sheet 6. Structural (Fibrous) Proteins (e.g. collagen, keratin, elastin) are composed mainly of

secondary structure which allows them to be elongated along one axis. Fibrous proteins form insoluble tough fibers in epithelial and connective tissues.

7. Tertiary structure is the complex irregular folding of alpha helical proteins caused by

bonding between distant R groups along the same peptide chain. 8. Tertiary bonds are mainly weak (e.g. H bonds, hydrophobic bonds) but include

covalent disufide bonds (between S - containing amino acids). 9. In the tertiary structure hydrophobic hydrocarbon R groups are forced to the inside of

the molecule (away from water) with hydrophilic groups on the surface (attracted to water), forming globular proteins.

10. Tertiary structure gives each globular protein its unique shape and therefore its specific

biological function, e.g. enzymatic action (each enzyme has a specific shape, complementary to its substrate)

11. Globular proteins have a complex specific shape and include enzymes, antibodies,

hormones, plasma proteins, hemoglobin, membrane proteins and myoglobin.


12. Denaturation is the destruction of a globular protein's 3 - D shape (especially 3o structure) by rupture of weaker non - covalent bonds and loss of biological activity (see Marieb Fig. 2.19). Denaturing agents include heat, U/V radiation, alcohol, extremes of pressure, pH etc. and is exploited clinically in sterilisation of wounds, instruments e.g. autoclave, alcohol.

17. Quaternary Structure occurs in large proteins and is the grouping of separate

polypeptide chains, each with its own 1o and 2o structures (and 3o structure for globular proteins) held together mainly by non - covalent bonds. Examples are hemoglobin, collagen and keratin.

18. Functions of proteins. Proteins can have a variety of primary structures (determined by

which genes are present) and so proteins have many functions: these include: • buffers of plasma and ICF • enzymes • antibodies • oxygen transport and storage • storage and transport of iron • osmotic pressure of blood plasma • transport of lipids in blood plasma • redox reactions in cells ( proteins form the electron transport chain in mitochondrion) • structural roles in tissues • hormones • membrane proteins (e.g. carriers)

anatomy & physiology i (101 - 805 - ab) paul anderson...

Documents