PHYSIOLOGY - Metabolism

Question 1

What is cellular respiration?

Answer 1

Process by which energy is harvested

• complete oxidation of glucose
• food energy is the amount of energy in food that is available through digestion
• use this energy to do work

Question 2

What is the average amount of energy released by carbohydrates, lipids and proteins

Answer 2

Carbohydrates release 4.18Cal/g
Lipids release 9.46 Cal/g
Proteins release 4.32 Cal/g

Question 3

Define Metabolism

Answer 3

set of chemical reactions that occur in living organisms in order to maintain life divided into two categories

Question 4

Define catabolism

Answer 4

Set of metabolic pathways which break down molecules into small units and release energy

Question 5

Define anabolism

Answer 5

Set of metabolic pathways that construct molecules from smaller units

Question 6

Define digestion

Answer 6

Process by which the body breaks down food so it can be absorbed by the blood stream

Question 7

What is ATP?

Answer 7

Adenosine Tri Phosphate 
-energy currency of cellular metabolism in all organisms 
A nucleotide consisting of: 
-Adenine 
-Ribose sugar 
-Three phosphate groups 

Usually outermost high-energy bond is hydrolysed
ATP -> ADP + Pi (inorganic phosphate)
Pi is often attached to an intermediate molecule (signalling)

Question 8

Autotrophs and Heterotrophs

Answer 8

Organisms are classified based on how they obtain energy
Autotrophs - able to produce their own organic molecules through photosynthesis
Heterotrophs - live on organic compounds produced by other organisms
All organisms use cellular respiration to extract energy form organic molecules

Question 9

Cellular Respiration

Answer 9

• • -Describes the metabolic reactions and processes that take place in a cell or across a cell membrane to get biochemical energy from fuel molecules.
• Energy can be released by the oxidation of multiple fuel molecules and is stored as high-energy carriers (NAD+ and FADH)
• The reactions involved in respiration are catabolic reactions in metabolism

Question 10

Glucose catabolism

Answer 10

Glucose + Oxygen->Carbon Dioxide+ Water + ATP (& heat)

C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy

Question 11

Redox Reactions

Answer 11

Paired reaction in living systems in which electrons are lost from one atom and gained by another
OIL RIG

Question 12

Redox Reactions - Hydrogen and Oxygen Transfer

Answer 12

Redox - Hydrogen transfer

• Oxidation is the loss of hydrogen
• reduction is the gain of hydrogen

Redox - Oxygen transfer

• oxidation is gain of oxygen
• reduction is the loss of oxygen

Question 13

Glucose catabolism reaction

-what is oxidised and what is reduced

Answer 13

glucose is oxidised to carbon dioxide
while
oxygen is reduced to water

Question 14

Glucose catabolism and NAD+

Answer 14

When electrons are stripped from glucose, take with it a proton (H atom)
The H atom is transferred to a co-enzyme called Nicotinamide Adenine Dinucleotide or NAD+

NAD+ is called an electron acceptor
NAD+ accepts 2 electrons and one proton to become NADH
Therefore, NAD+ is reduced to NADH

Question 15

Substrate level phosphorylation

Answer 15

Transferring a phosphate directly to ADP from another molecule

Question 16

Oxidative phosphorylation

Answer 16

Use of ATP synthase and energy derived from a proton (H+) gradient to make ATP

Question 17

glycolysis

Answer 17

• occurs in the cytoplasm of the cell (not the mitochondria as glucose is too big)
• converts glucose (6 carbon molecule) into two 3-carbon molecules called pyruvate (can enter the mitochondria by diffusion)
• conversion occurs over 10 separate reactions/steps
• for each molecule of glucose that is converted into pyruvate –> cell nets 2 ATP molecules by substrate level phosphorylation

Question 18

Steps in Glycolysis - STEP 1

Answer 18

Preparatory phase or priming reactions

• as soon as a glucose molecule enters the cytosol, a phosphate group is attached to the molecule
• ATP is used
• phosphorylation: glucose 6-phosphate

Question 19

Steps in Glycolysis - STEP 2

Answer 19

Prepatatory phase, rearrangement of carbon molecules

• a second phosphate group is attached. Together, steps 1 and 2 cost the cell 2 ATP
• rate limiting step
• ATP i used - phosphorylation
• Fructose 6-phosphate becomes Fructose 1,6 -bisphate

Question 20

Steps in Glycolysis - STEP 3

Answer 20

Preparatory phase or cleavage

• the six carbon chain is split into two three-carbon molecules, each of which then follows the rest of this pathway
• results in the production of 2x glyceraldehyde-3-phosphate (G-3-P)

Question 21

Steps in Glycolysis - STEP 4

Answer 21

Payoff phase
-another phosphate group os attached to each molecule, and NADH is generated from NAD
-phosphorylation of G-3-P -> high energy bond
-oxidation of G-3-P
PRODUCE 1 NADH per G-3-P (reduction of 2 NAD+ to 2NADH)

Question 22

Steps in Glycolysis - STEP 5

Answer 22

Payoff phase

• one ATP molecule if formed for each molecule processed
• removal of high energy phosphate bond by ADP produces ATP

Question 23

Steps in Glycolysis - STEP 6

Answer 23

Payoff phase

• the atoms in each molecule are rearranged, releasing a molecule of water
• removal of water yields PEP molecule; PEP has high-energy phosphate bond

Question 24

Steps in Glycolysis - STEP 7

Answer 24

Payoff phase

• a second ATP molecule is formed for each molecule processed. This step produces 2 ATP molecules
• removal of high-energy phosphate bond by ADP produces ATP; Pyruvate Generated

Question 25

What happens to pyruvate?

Answer 25

Fate ofpyruvate depends on whether oxygen is present in the system - aerobic respiration (oxygen present) - anaerobic respiration (without oxygen) Consider the pathway when oxygen is present -pyruvate is oxidised in a decarboxylation reaction -pyruvate (3C) -> Acetyl CoA (2C) + CO2 -NAD+ is reduced to NADH -reaction involves a coenzyme - coenzyme A (small organic non-protein molecules that carry chemical groups between enzymes)

Question 26

Mitochondria and pyruvate

Answer 26

``` Outer membrane -contains large diameter pores -permeable to ions and small organic molecules (pyruvic acid) Inner membrane -contains carrier protein -moves pyretic acid into mitochondrial matrix Intermembrane space -separates outer and inner membranes ```

Question 27

The citric acid cycle

Answer 27

CAC = tricarboxylic acid cycle (TCA) = krebs cycle - occurs in the matrix of the mitochondria - series (8) of enzyme-catalysed reactions - oxidation of oranic molecules derived from pyruvate - Acetyl CoA enters the cycle - carbon from Acetyl CoA exits the cycle as CO2 - generate NADH and FADH2

Question 28

Aim of citric acid cycle

Answer 28

Overall aim of this cycle is to remove electrons, in the form of NADH and FADH2, from the organic molecules that enter the cycle Very little ATP is made during CAC

Question 29

Electron transport chain: steps

Answer 29

1. a coenzyme strips two hydrogen atoms from a substrate molecule 2. NADH and FADH2 deliver hydrogen atoms to coenzymes embedded in the inner membrane of a mitochondrion 3. coenzyme Q releases hydrogen ions and passes electrons to cytochrome b 4. electrons are passes along the electron transport system, losing energy in a series of small steps 5. oxygen accepts the low energy electrons, and with hydrogen ions, forms water

Question 30

Electron transport chain: FMN or Flavin Mononucleotide

Answer 30

prosthetic group of Complex l or NAD dehydrogenase

Question 31

Electron transport chain: FAD or flavin adenine dinucleotide

Answer 31

Complex ll or Succinate Dehydrogenase

Question 32

Electron transport chain: Q or ubiquione

Answer 32

not a protein, small mobile hydrophobic molecule

Question 33

Electron transport chain: cytochrome C

Answer 33

a small mobile protein

Question 34

Electron transport chain: other two proteins/molecules

Answer 34

b or Complex lll, cytochrome bc1 complex a & a3 or complex lV cytochrome c oxidase

Question 35

Chemiosmosis

Answer 35

ATP synthase (aka F0-F1 ATPase) - F0 is the proton channel - when H+ moves through the channel -> conformation change (ions aren't lipid soluble) - conformation change transmitted to F1 (change allows it to move across the membrane) Catalyses the phosphorylation of ADP -> ATP in the mitochondrial matrix 1 ATP made for every 3 H+ that moves into the matrix

Question 36

Alternate Electron Acceptors

Answer 36

Allows for the oxidation of NADH and FADH2 in the absence of oxygen - produce less energy than during aerobic respiration - oxygen is NOT the terminal electron acceptor - processes require another electron acceptor to replace oxygen - CO2 (eg. archae) - sulfates (eg. prokaryotes) - fermentation of organic molecules (e.g. eukaryotes)

Question 37

Fermentation of organic molecules

Answer 37

Anaerobic respiration (occurs in cytosol) - anaerobic respiration is often used interchangeably with fermentation - lactic acid fermentation - alcohol fermentation

Question 38

Alcohol fermentation

Answer 38

- Allows the cell to oxidise NADH back to NAD+ in the absence of oxygen **why it is a reverse reaction - NAD+ can be reused during glycolysis to generate ATP

Question 39

Lactic acid fermentation

Answer 39

- allows the cell to oxidise NADH back to NAD+ in the absence of oxygen - NAD+ can be reused during glycolysis to generate ATP

Question 40

How does the body know when ATP is needed?

Answer 40

-cells regulate the entry of substrates into the series of reactions depending on the needs of the cell (dynamic) Excess substrates can be stored: Glucose --> glycogen or fat

Question 41

Regulation of cellular respiration: Step 3 glycolysis - Phosphofructokinase

Answer 41

- allosteric enzyme: multiple binding sites - what would happen if ADP binds to it? - what would happen if citrate or ATP bound to it?