12. Respiration Flashcards
Define cell respiration
CELL RESPIRATION: controlled release of E from organic compounds to produce ATP
Types of cell respiration
- Aerobic: uses O2 to completely break down glucose in mitochondria to produce larger ATP yield
- Anaerobic: without O2 , partial breakdown of glucose in cytosol for smaller ATP yield
Main organic compounds used in respiration
- Carbohydrates (main) - the only in anaerobic
- Lipids
- Proteins
Aerobic respiration equation
Describe ATP
- 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)
Define glycolysis
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
Anaerobic products after glycolysis
- in animals: pyruvate => lactate (toxic)
- in plants/yeast: pyruvate => ethanol (toxic) and CO2
No further production of ATP beyond glycolysis if no O2
Purpose of anaerobic respiration
- 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
Generalised stages of aerobic respiration
Anaerobic respiration uses in industries
Anaeroobic respiration = fermentation
- food industry
- bioethanol: renewable e source
Define respirometer
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
Glycolysis vs aerobic respiration sites in cell
Can ATP be transported
No, not transferred from cell to cell - requires continuous supply
ATP in cell is immediately available for use
Uses of ATP in cells
Waste product of ATP conversion
HEAT
Aerobic vs anaerobic comparison
Aerobic respiration overview (steps, ATP release, NADH, cell locations)
Define phosphorylation, in ATP, opposite
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
ATP synthesis pathways
- From solar E - photosyntheis oncverts light E into chemical E - stored in ATP
- Oxidative processes - cell respiration breaks down organic compounds - chemical E stored in ATP
What is the pattern of E release in the breakdown of organic compounds
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
Redox reactions in respiration
when organic compounds broken - E transferred in redox reactions - transfer of e/H+/O
Hydrogen/electron carrier molecules
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
Intermediate steps of glycolysis
- Phosphorylation: hexose phosphorylated by 2ATP -> hexose biphosphate complex - makes the molecule less stable - more reactive, prevents diffusion out of cell
- Lysis: hexose biphosphate split into 2 triose phosphates (pyruvates)
- Oxidation: H are removed from each pyruvates to reduce 2NAD+ to 2NADH
- ATP formation: some E used to synthesise 2ATP from each pyruvate (4ATP total) in substrate level phsophorylation
Transition from glycolysis to Kreb’s cycle in aerobic respiration
LINK REACTIONS: pyruvate transported to mitochondria - links products of glycolysis with aerobic processes in mitochondria
- Carrier proteins in mitoch membrane transport pyruvate from cytosol into mitoch matrix
- Pyruvate loses 1C - decarboxylation - forms CO2
- 2C loses H in oxidation - NAD+ reduced to NADH - 2C forms acetyl group
- Acetyl combines with coenzyme A => acetyl CoA complex
Steps of Kreb’s cycle
Second stage of aerobic respiration - Kreb’s/citric acid/tricarboxylic acid (TCA) cycle in mitochondrion matrix
- CoA transfers 2C (acetyl) to 4C (oxaloacetate) compound => 6C (citrate) - CoA released - return to link reaction
- Decarboxylation - 6C (citrate) CO2 released + udergoes oxidation - NAD+ reduced to NADH - 5C (α-ketoglutarate)
- decarboxylation - 5C (α-ketoglutarate) CO2 released + phosphorylation - 1ATP produced, lose H - oxidation - NADH+ reduced to NADH => 4C (succinate)
- 4C (succinate) oxidised - FAD2+ reduced to FADH2 => 4C lost 2H (malate)
- 4C (malate) oxidation - NAD+ reduced to NADH => 4C lost H (oxoloacetate) => CYCLE AGAIN
Products per glucose molecule in Kreb’s cycle
Each NADH produces 3ATP at ETC
Each FADH2 produces 2ATP at ETC
Half equations of NAD+, FAD+ reduction
NAD+ + H+ + 2e- -> NADH
FAD2+ + 2H+ + 2e- -> FADH2
Anatomy of ETC
ETC in inner mitochondrial membrane - cristae - increases SA for ETC
Components:
- electron carriers/proton pumps => ETC
- ATP synthase
- inner mitoch membrane
- intermembrane space
- matrix
Mitochondria anatomy
- 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
ETC processes
Last stage of aerobic respiration => oxidative phosphorylation - oxidation of H carriers (NAHD, FADH2) gives off E for ATP production
- 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)
- 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
- Reduction of oxygen: for ETC to keep functioning - de-energised e must be removed - O<u>2 </u>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
Summary of oxidative phosphorylation
Explain splitting of H in NADH oxidation?
NADH → NAD+ + H+ + e-
H is split into proton and electron: H+ and e-
Images of mitochondria
Electron tomography used - cristae, membranes
Glycolysis reactions (E input phase)
Explain substrate level phosphorylation in glycolysis
Using an enzyme - locks substrate - glycolysis (common almost to all living cells)
Glycolysis reactions (E payoff phase)
Explain the structure of ATP synthase
Describe the full oxidative phosphorylation mechanism inside mitochondria
Which biological molecules are used in oxidative phosphorylation?
