Week 5 - energy and replication]

Question 1

redox

Answer 1

• energy is generated by OXIDATION of organelle compounds
• the transfer of electrons during chemical reactions releases energy stored in organic molecules
• DURING RESPIRATION the released energy is ultimately used to synthesise ATP

Question 2

electron carriers

Answer 2

• Types: SOLUBLE, membrane-bound, move within membrane → ALL CARRIERS CAN BE EASILY OXIDISED AND REDUCED
• some just carry electrons, some electrons & protons
• the electron carriers help to ‘carry’ electrons betw. cellular processes in a safe * controlled manner
• NAD+ acquires 2 electrons & a proton to be NADH

Question 3

aerobic respiration

Answer 3

• oxygen used to oxidise glucose
• glucose is oxidised to form carbon dioxide
• oxygen is reduced to form water

Question 4

aerobic respiration - oxidation of glucose

Answer 4

• C-H & O-H bonds will be broken
• electrons will be transferred to carriers NAD & FAD → glycosis & krebs cycle
• the electrons will be passed through a transport chain
  → the energy from the electrons used to pump protons
  → energy from diffusion of protons to make ATP

Question 5

cellular respiration - stages

Answer 5

1. GLYCOSIS - breaks down glucose into 2 molecules of pyruvate
2. CITRIC ACID CYCLE/ KREBS CYCLE- completes breakdown of glucose
3. OXIDATIVE PHOSPHORYLATION- (accounds for most of ATP synthesis) further subdivided into electron transport & then chemiosmosis (atp synthesis)

Question 6

glucosis

Answer 6

• breakdown of glucose to pyruvic acid →occurs in cyto plasm & anaerobic
• two ATP molecules are used to energise glucose
• as glucose is metabolised, enough energy is released: :
  make 4 ATP molecules
  → 4 ATP make - 2 ATP used= net production of 2 ATP reduce 2 NAD+ to mak e NADH

Question 7

chemical energy ATP

Answer 7

cells able to make ATP via:

1. SUBSTRATE-LEVEL PHOSPHORYLATION
   - transferring a phosphate directly to ADP from another molecule
   - this occurs in one step of glucolysis
2. OXIDATIVE PHOSPHORYLATION
   - use of ATP synthase and energy derived from a proton (H+) gradient to make ATP

Question 8

PYRUVATE

Answer 8

WITH OXYGEN PRESENT:

• pyruvate is oxidised to acetyl-CoA which enters the Krebs cycle ( TCA cycle)
• aerobic respiration

WITHOUT OXYGEN PRESENT:

• pyruvate is reduced to oxidise NADH back to NAD+
• fermentation

Question 9

kreb’s cycle

Answer 9

AKA citric acid cycle/ tricarboxylic acid → BREAKDOWN of pyruvic acid, released as CO2
enough enrgy is released as one pyrivic acid molecule is metabolised to :
- make 1 ATP
- reduce 4 NAD+ to form 4 NAHD
- reduce 1 FAD to form 1 FADH2
- regenerates oxaloacetate

occurs in the MITOCHONDRIAL MATRIX

Question 10

KREB’S CYCLE - SEGMENTS

Answer 10

oxidises the acetyl group from pyruvate
biochemical pathway of 9 steps in 3 segments
1. acetyl - CoA+oxaloacetate → citrate
2. citrate rearrangement and decarboxylation
3. regeneration of oxaloacetate

Question 11

electron transport chain

Answer 11

• ECT is a series of membrane-bound electron carriers
• embedded in the inter mitochondrial membrane
• electrons from NADH & FADH2 are transferred to complexes of the ETC
  →protein pump that helps to create a protoon gradient across the inner mitochondrial membrane
  →trnasfers electron to next carrier

Question 12

chemiosmosis

Answer 12

• ACCUMULATION of protons in the intramembrane space drives protons via diffusion
• membrane relatively impermeable to ions
• most protons can ony re-enter matrix through ATP synthase →uses energy of gradient to make ATP to form ADP + P

Question 13

recycling NADH

Answer 13

for glycolysis to continue, NADH must be recycled to NAD+ by either

1. AEROBIC RESPIRATIONL oxygen is available as the final electron acceptor - produces significant amount of ATP
2. FERMENTATION- occurs when oxygen is not available

Question 14

fermentation - lactic acid

Answer 14

• starts w/ glycolysis
• during lactic acid fermentation: pyruvic acid is reduced to form lactic acid while NADH is oxidised to NAD+
• Muscle cells have the enzumes to perform fermentation, but brain cells dont
  → muscle cells can survive brief period of oxygen deprivation but braincells cant
  →lactic acid ‘burns are offten described as a feeling one gets in muscle upon rigorous exercise

Question 15

interconversion - fats, carbs, protein

Answer 15

• all can be used for energy → glycolysis & krebs cicle allow these types of molecules to be interchanged
• if more calories are consumed than used → excess food is stored
  → once organism has all protein needed & carb stores are full : remainder is convered to and stored as fat