Week 5 - energy and replication] Flashcards Preview

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1

redox

- 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

2

electron carriers

-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

3

aerobic respiration

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

4

aerobic respiration - oxidation of glucose

- 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

5

cellular respiration - stages

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)

6

glucosis

- 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

7

chemical energy ATP

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

8

PYRUVATE

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

9

kreb's cycle

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

10

KREB'S CYCLE - SEGMENTS

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

11

electron transport chain

- 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

12

chemiosmosis

- 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

13

recycling NADH

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

14

fermentation - lactic acid

- 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

15

interconversion - fats, carbs, protein

- 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