Biological processes

Question 1

what is respiration

Answer 1

• conversion of cehmcial energy in molecular bonds into usable energy needed to drive processes of living cells
• respiration refers to use of oxygen, intake from environment and transport in blood

*external respiration = enterance of air into lungs and the gas exchange between alveoli and blood

*internal respiration = exchange of gas between blood and cells and intracellular processes of respiration

Question 2

what are the favoured feuld sources

Answer 2

carbohydrates and fats

• C-H bond is energy rich (Co2 has very little usable energy, its a stbale energy exhausted end product of respiration)

Question 3

what id dehydrogenation

Answer 3

• occurs during respiration, high energy hydrogen atoms are removed from organic molecules

(oxidation rxn)

• H is accepted by an H acceptr (oxygen in final step fo ETC), this is reduction comp of redox rxn

*this oringial oxidation reuqires energy input but has net energy production forming ATP

Question 4

what are the two main stages of glucose catabolism

Answer 4

• glycolysis and cellular respiration

Question 5

what is glycolysis

Answer 5

• first stage of glucose catabolism
• involves 9 steps, in step 4 6 carbon mol is split into a 3 carbon molecule which is isomerized into PGAL (glyceraldehyde 3 phosphate)
• one mol of glucose turns into 2 mol fo pyruvate, 2 mol of ATP and 2 mol of NADH

* production of ATP refered to as substrate level phosphorylation bc no participation of intermediate molecule like NAD+, tis directly coupled to glucose degredation

• all occurs in cytoplasm

net reaction: Glucose + 2 ADP + 2 Pi + 2 NAD⁺ –> 2 Pyruvate + 2 ATP + 2 NADP + 2H⁺ + 2 H₂O

Question 6

what happens to the pyruvate product of glycolysis

Answer 6

• pyruvate still has most of the energy from initial glucose mol
• if under anerobic conditions pyruvate is reduced by fermentation
• uner aerobic conditions its further oxidized during cellular respiration in mitochondria

Question 7

explain the process of fermentation

Answer 7

• NAD+ must be regenerated for glycolysis to continue in absence of O2
• pyruvate is reduced into ethanol or lactic acid, produces only two ATP per glucose moleculse

* not making any more ATP just using pyruvate to regenerate your NAD+ so glycolysis can cont

Alcohol Fermentation: occurs only in yeast and some bacteria, pyruvate produced in glycolysis is converted to ethanol to regenerate NAD+

Lactic acid fermentation: occurs in certain fungi, bacteria and human muscle during strenuous activity. When oxygen supply to muscles is not sufficient, still regen NAD+ to be used in step 5 of glycolysis

Question 8

what is cellular respiration: the net result and the different stages

Answer 8

• most efficient catabolic pathway to get energy from glucose
• yeilds 36-38 ATP
• aerobic process in which oxygen acts as the final acceptor of electrols passed along ETC
• 3 stages: pyruvate decarboxylation, the citric acid cycle and the electron transport chain

Question 9

explain pyruvate decarboxylation

Answer 9

• pyruvate formed during glycolysis is transported from the cytoplasm into mitochondria matrix where is it decarboxylated
• acetyl group is transfered to coenzyme A forming acetyl-CoA which then can enter the kerbs cycle
• 2NAD+ is reduced to 2NADH and also 2 CO2 is released

Question 10

explain the citric acid cycle

Answer 10

• aka krebs cycle
• begins w/ two carbon acetyl CoA mol which combine with oxalate ( a 4 carbon mol) to form a 6 carbon mol cirtrate
• through the cycle two CO2 are released and oxaloacetate is regenerated

net rxn: 2 acetyl CoA + 6 NAD⁺ + 2FAD + 2 GDP + 2 Pi + 4 H₂O —-> 4 CO2 + 6NADH + 2FADH₂ + 2 GTP + 4H⁺ + 2CoA

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Question 11

explain the electron transport chain

Answer 11

• carrier mechanism located on inside of inner mitochondrial membrane
• during oxidative phosphorylation ATP is produced when high energy potential electrons are transferred from NADH and FADH2 to oxygen be series of carreir mol on IMM
• as e- transfered from barrier to carrier free energy si released and used to form ATP

*most mol on ETC are cytochromes that resemble hemoglobin in the structure of their active site

*contain central iron capable of redox

• each carreir is reducaed as it accepts an electron and then is oxidized when it passes it to the next carrier
• last carrier is O2 which picks up a pair of hydrogen ions from surrounding medium to form

**NADH produced 3 ATP and FADH2 produces 2 ATP in ETC

Question 12

what is substrate level phosphorylation

Answer 12

• degradation of one glucose molecule yield a net of two ATP from gylcolysis and one ATP for each turn of the citric acid cycle

*total 4 atp produced by substrate level phosphorylation

(not using NAD or FAD)

Question 13

what is the production fo ATP from oxidative phosphorylation

Answer 13

• produces more than 90% of ATP used by cells in our body
• at the end of the ETC, respiratory enzyme pump H ions from matrix of mitochondria to intermembrane space creating a alrge conc gradient
• H ions pass through chnnels in respiratroy enzymes along concentration gradient, energy created used to convert ADP into ATP

* two pyruvate decarboxylations = 2 NADH

*each turn of kerbs produces 3 NADH and 1 FADH2, since happens twice per glucose mol 6 NADH and 2 FADH2

• each FADH2 generates 2 atp and each NADH generates 3 ATP

Question 14

what are the alternative energy sources

Answer 14

• carbohydrates, fats then proteins

Question 15

how are carbohydrates used for energy

Answer 15

• disaccharides are hydrolyzed into monosaccharides which can then be converted into glucose or glycolytic intermediates
• glycogen stored in liver can be converted when needed into a glycolytic intermediate

Question 16

how are fats used as energy

Answer 16

• stored in adipose tissue in the form of triglycerides
• when needed hydrolyzed by lipases to fatty acids and glycerol and carried by blood to other tissues for oxidation
• glycerol can be concerted to PGAL (glycolytic intermediate)
• fatty acids must first be activated in the cytoplasm, process reuqires two ATP then transported to mitochondrion and undergoes beta oxidation into 2 carbon fragments
• fragments then converted to acetyl CoA which enters the citric acid cycle

* for each round B oxidation of a saturated fatty acid one NADH and 1 FADH₂ produced

Question 17

how are proteins used as energy

Answer 17

• amino acids undergo transamination reaction: lose an amino group to form a alpha-keto acid
• carbon atoms of most amino acids are converted into acetyl CoA, pyruvate or an intermediate of the citric acid cycle

Question 18

what is oxidative deamination

Answer 18

• removes an ammonia molecule direcctly from the aminoa cid
• amminoa is toxic in certebrates

Question 19

what are enzymes

Answer 19

• organic catalysis: affect rate of reaction w/o itsel fbeing changed
• decrease activation energy
• proteins, somtimes conjugated and have a nonprotein coenzyme (both must be present for enzyme to function)
• highly seletive
• do NOT alter equilibrium constant
• are NOT consumed in reaction
• are pH and temp senstive

Question 20

what is the lock and key theory

Answer 20

• spatial structure of an enzymes active site is exactly complementary to spatial strucutre of its substrate

Question 21

what is enduced fit theory

Answer 21

• active site has flexibilty of shapre
• when approprate substrate comes in contact w/ active site the conformation of active site changes to fit the substrate

Question 22

enzyme specificity

Answer 22

• enzyme action is dependent on temp, pH and conc of enzyme and substrate
• as temp inc rte of enzyme inc intil optimal temp is reached: beyond that the shape of active site is altered and deactivates enzyme
• opperate at an optimal pH, typically 7.2, unless something like pepsin which works in stomach at pH2
• inc of conc of substrate inc rate until all active sites of enzyme is occupied, then reach a Vmax where inc substrate conc will not help

Question 23

explain competitive inhibition

Answer 23

• active site is specfici for particular substrate or class of substrates, similar mol can bind
• is conc are similar will be competition of occupation fo active site
• can outcompete if inc the concentration of substrate

Question 24

explain noncompetitive inhibition

Answer 24

• inhibitor forms a strong covalent bond w/ enzyme making ti unable to bind with tis substrate
• noncompetitor cant be displaced (irriversible inhibition)
• excess substrate will not help, rxn will never reach Vmax
• can have allosteric inhibition in which inhibitor binds to another site than active but it changes the shape of the active site

Question 25

what is hydrolysis

Answer 25

- reaction functions to digest large molecules into smaller components ex: **lactases** hydrolyze lactose into monosaccharides glucose and galactose

Question 26

what do proteases and lipases

Answer 26

- proteases degrade proteins into amino acids - lipases breaj down lipids into fatty acids and glycerol

Question 27

what are cofactors

Answer 27

non protein molecule, required by a lot of enzymes to become active - can be metal cations like ZN²⁺ and Fe²⁺ ot small organic groups called coenzymes - most coenzymes cannot be synthesized in the body and must be obtained from diet as vitamin detivates - cofactors bind to enzyme by strong covalent bonds called prosthetic groups