12. Respiration

Question 1

Define cell respiration

Answer 1

CELL RESPIRATION: controlled release of E from organic compounds to produce ATP

Question 2

Types of cell respiration

Answer 2

1. Aerobic: uses O₂ to completely break down glucose in mitochondria to produce larger ATP yield
2. Anaerobic: without O₂ , partial breakdown of glucose in cytosol for smaller ATP yield

Question 3

Main organic compounds used in respiration

Answer 3

1. Carbohydrates (main) - the only in anaerobic
2. Lipids
3. Proteins

Question 4

Aerobic respiration equation

Answer 4

Question 5

Describe ATP

Answer 5

• adenosine triphosphate
• high E molecule which functions as an immediate source of power for cells
• when ATP is hydrolised - ADP + Pi - E released from the phosphate bond (exergonic)
• E stored in organic molecules repairs ATP from ADP and Pi (in oxidation)

Question 6

Define glycolysis

Answer 6

GLYCOLYSIS: anaerobic breakdown of glucose in cytosol (both in aerobic and anaerobic respiration)

6C => 3C + 3C (two pyruvates) + 2NADH + 4ATP

(4 produced but 2 used - net 2ATP produced)

First reaction in glycolysis - endergonic - coupled with exergonic hydrolysis of ATP

Question 7

Anaerobic products after glycolysis

Answer 7

• in animals: pyruvate => lactate (toxic)
• in plants/yeast: pyruvate => ethanol (toxic) and CO₂

No further production of ATP beyond glycolysis if no O₂

Question 8

Purpose of anaerobic respiration

Answer 8

• in plants/yeast: to restock NAD+ - needed for glycolysis to produce ATP
• in animals: high activity - high e demand - too little O₂ - to maximise ATP production - anaerobic respiration - stop exercise - lactate converted to pyruvate

Conversion of pyruvate to lactate/ethanol and CO₂ - reversible - pyruvate levels can be restored if O₂ present -> aerobic respiration

Question 9

Generalised stages of aerobic respiration

Answer 9

Question 10

Anaerobic respiration uses in industries

Answer 10

Anaeroobic respiration = fermentation

• food industry
• bioethanol: renewable e source

Question 11

Define respirometer

Answer 11

RESPIROMETER: device which determines an organism’s respiration rate by measuring O₂ and CO₂ exchange rate

• sealed container
• CO₂ absorbant (alkali/)
• O₂ consumption measured by change in pressure within the system - moves water in U-tube
• controlled variables: time, temperature, hydration, light (plants), age, activity levels

Question 12

Glycolysis vs aerobic respiration sites in cell

Answer 12

Question 13

Can ATP be transported

Answer 13

No, not transferred from cell to cell - requires continuous supply

ATP in cell is immediately available for use

Question 14

Uses of ATP in cells

Answer 14

Question 15

Waste product of ATP conversion

Answer 15

HEAT

Question 16

Aerobic vs anaerobic comparison

Answer 16

Question 17

Aerobic respiration overview (steps, ATP release, NADH, cell locations)

Answer 17

Question 18

Define phosphorylation, in ATP, opposite

Answer 18

PHOSPHORYLATION: attachment of phoshoryl group

Phosphorylation makes molecules less stable -> ATP reactive molecule that contains high E bonds

Opposite to phosphorylation - hydrolysis - phosphate group breaks off from ATP to form ADP, Pi + E

Question 19

ATP synthesis pathways

Answer 19

1. From solar E - photosyntheis oncverts light E into chemical E - stored in ATP
2. Oxidative processes - cell respiration breaks down organic compounds - chemical E stored in ATP

Question 20

What is the pattern of E release in the breakdown of organic compounds

Answer 20

Breakdown of sugars - linked processes - in steps

ADV.:

• lower activation E for each reaction
• released E not lost - transferred to activated carrier molecules via redox reactions

Question 21

Redox reactions in respiration

Answer 21

when organic compounds broken - E transferred in redox reactions - transfer of e/H+/O

Question 22

Hydrogen/electron carrier molecules

Answer 22

Carrier molecules - carry H+ - gain H+ - organic compounds undergo oxidation

• transport H+/e to mitochondrion cristae - ETC use energy transferred to synthesise ATP
• this requires oxygen - final e acceptor - only aerobic respiration can generate ATP from hydrogen carriers => hence aerobic respiration yields in higher ATP

Question 23

Intermediate steps of glycolysis

Answer 23

1. Phosphorylation: hexose phosphorylated by 2ATP -> hexose biphosphate complex - makes the molecule less stable - more reactive, prevents diffusion out of cell
2. Lysis: hexose biphosphate split into 2 triose phosphates (pyruvates)
3. Oxidation: H are removed from each pyruvates to reduce 2NAD+ to 2NADH
4. ATP formation: some E used to synthesise 2ATP from each pyruvate (4ATP total) in substrate level phsophorylation

Question 24

Transition from glycolysis to Kreb’s cycle in aerobic respiration

Answer 24

LINK REACTIONS: pyruvate transported to mitochondria - links products of glycolysis with aerobic processes in mitochondria

1. Carrier proteins in mitoch membrane transport pyruvate from cytosol into mitoch matrix
2. Pyruvate loses 1C - decarboxylation - forms CO₂
3. 2C loses H in oxidation - NAD+ reduced to NADH - 2C forms acetyl group
4. Acetyl combines with coenzyme A => acetyl CoA complex

Question 25

Steps of Kreb's cycle

Answer 25

Second stage of aerobic respiration - Kreb's/citric acid/tricarboxylic acid (TCA) cycle in _mitochondrion matrix_ 1. CoA transfers 2C (acetyl) to 4C (oxaloacetate) compound =\> 6C (citrate) - CoA released - return to link reaction 2. Decarboxylation - 6C (citrate) CO₂ released + udergoes oxidation - NAD+ reduced to NADH - 5C (α-ketoglutarate) 3. decarboxylation - 5C (α-ketoglutarate) CO₂ released + phosphorylation - 1ATP produced, lose H - oxidation - NADH+ reduced to NADH =\> 4C (succinate) 4. 4C (succinate) oxidised - FAD²⁺ reduced to FADH₂ =\> 4C lost 2H (malate) 5. 4C (malate) oxidation - NAD+ reduced to NADH =\> 4C lost H (oxoloacetate) =\> CYCLE AGAIN

Question 26

Products per glucose molecule in Kreb's cycle

Answer 26

Each NADH produces 3ATP at ETC Each FADH₂ produces 2ATP at ETC

Question 27

Half equations of NAD+, FAD+ reduction

Answer 27

NAD⁺ + H⁺ + 2e^- -\> NADH FAD²⁺ + 2H⁺ + 2e^- -\> FADH₂

Question 28

Anatomy of ETC

Answer 28

ETC in _inner mitochondrial membrane_ - _cristae_ - increases SA for ETC Components: - electron carriers/proton pumps =\> ETC - ATP synthase - inner mitoch membrane - intermembrane space - matrix

Question 29

Mitochondria anatomy

Answer 29

- _cristae_: projections of inner membrane - increase SA available fo oxidative phosphorylation - _ribosome DNA_: expression of mitochondrial genes - _matrix_: enzymes for Kreb's and link reaction - _inner mitoch memebrane_: ETC chains and ATP synthase to produce ATP - _outer mitoch membrane_: separate contents of mitoch from the cell, creates intermembrane space - _intermembrane space_: small so H conc builds up quickly - H pumped into it from matrix by transmembrane proteins

Question 30

ETC processes

Answer 30

Last stage of aerobic respiration =\> **_oxidative phosphorylation_** - oxidation of H carriers (NAHD, FADH₂) gives off E for ATP production 1. _Generating proton motive force:_ NADH and FADH oxidised - high E e and H released - e transferred to ETC - e pass through transmembrane proteins in ETC - lose E which is used to pump H+ from matrix against conc gradient - _electrochemical gradient_ created (proton motive froce) 2. _ATP synthesis via chemiosmosis:_ proton motive force causes H+ to move back along conc gradient back into matrix - diffusion or H+ - _chemiosmosis_ - _facilitated_ by transmembrane protein - ATP synthase - as H+ move into matrix - trigger _molecular rotation_ of ATP synthase - ATP synthesis 3. _Reduction of oxygen:_ for ETC to keep functioning - de-energised e must be removed - _O_₂ _final acceptor of e_ - prevents ETC from blocking - 0.5 O₂ also binds free protons to form water - keeps H gradient = if not O2 - e cannot be transffered from ETC - blocks

Question 31

Summary of oxidative phosphorylation

Answer 31

Question 32

Explain splitting of H in NADH oxidation?

Answer 32

NADH → NAD⁺ + H⁺ + e^- H is split into proton and electron: H⁺ and e^-

Question 33

Images of mitochondria

Answer 33

Electron tomography used - cristae, membranes

Question 34

Glycolysis reactions (E input phase)

Answer 34

Question 35

Explain substrate level phosphorylation in glycolysis

Answer 35

Using an enzyme - locks substrate - glycolysis (common almost to all living cells)

Question 36

Glycolysis reactions (E payoff phase)

Answer 36

Question 37

Explain the structure of ATP synthase

Answer 37

Question 38

Describe the full oxidative phosphorylation mechanism inside mitochondria

Answer 38

Question 39

Which biological molecules are used in oxidative phosphorylation?

Answer 39