Respiration Flashcards
(27 cards)
Which two processes do cells do continuously to regenerate ATP during respiration through?
Substrate level phosphorylation: direct transfer of a phosphate group from a donor molecule to ADP.
Chemiosmosis: using movement of protons across a membrane to drive ATP synthesis
What are the 4 stages of aerobic cellular respiration?
- Glycolysis
- Link reaction
- Kreb cycle
- Oxidative phosphorylation.
Outline glycolysis:
Location:
cytoplasm
Process:
breakdown of 6C glucose into 2x 3C pyruvate molecules by specific enzymes, is an anaerobic process,
Products:
per glucose, 2 pyruvate, 2 ATP, 2 reduced NAD
Outline the link reaction.
Location: matrix of mitochondria
Process: conversion of pyruvate to acetyl CoA
Products: 1 acetyl, 1 reduced NAP, 1 CO2
Reactants: pyruvate, NAD Coenzyme A
Outline the Krebs cycle:
Location: matrix of mitochondria
Process: a series of reactions starting with acetyl CoA
Products: for each molecule of CoA, 1 ATP, 3 reduced NAP, 1 reduced FAD, 2 CO2
Describe the main steps of glycolysis
Phosphorylation of glucose:
2 ATP molecules donate phosphate groups to glucose, forming Hexose biphosphate
Lysis:
Hexose biphosphate molecules split into two molecules of Triose phosphate
Phosphorylation of TP:
A second phosphate group is added to each TP molecule, converting them to 2 molecules of Triose bisphosphate
Dehydrogenation: 1 hydrogen removed from each Triose bisphosphaet molecule (they are oxidised) and used to form 2 reduced NAD, 2 pyruvate and 4 ATP all together through substrate phosphorylation
(Net if 2 ATP)!!!!1
Reactants: 1 glucose and 2 ATP
Product: 2 pyruvate, 2 reduced NAD, 2 ATP net
What does the stucture of a mitochondrion include?
Outer membrane
Inner membrane
Inter membrane space
Cristae
Matrix
Mitochondrial DNA
Mitochondrial ribosomes
Function of inter membrane space?
Space between inner and outer membrane which protons are pumped into during oxidative phosphorylation. Is small so the proton conc gradient between the inter membrane space and mitochondrial matrix build up quickly
Function of cristae?
Significantly increase inner membrane SA so it can contain more proteins like those in electron transport chain and enzyms like ATP synthase
Describe the key steps of the link reaction:
Active transport of pyruvate:
Pyruvate from glycolysis is actively transported into mitochondrial matrix by specific carrier proteins
Decarboxylation:
In mitochondrial matrix each pyruvate molecule is decarboxylated, losing one CO2
Removal of CO2
CO2 diffuses out of the mitochondria as waste
Oxidation of pyruvate
2 hydrogen atoms are removed from pyruvate to form acetate
Reduction of NAD
2 hydrogen atoms are used to reduce the coenzyme NAD, forming reduced NAD
Formation of acetyl CoA
Acetat binds to CoA to form acetyl coA
Describe the Krebs cycle.
It’s processes acetyl CoA to prepare substrates for the final stage of aerobic respiration
- Acetyl CoA merges with a 4C molecule oxaloacetate to create 6C citrate
- Citrate is decarboxylated, releasing 2 molecules of carbon dioxide
- Citrate is dehydrogenase’s releasing hydrogen that reduce 3 molecules of NAD and 1 FAD
- For each acetyl CoA that enters the cycle, 1 ATP is synthesised directly;y via substrate level phosphorylation
- Oxaloactetate is regenerated fo rnext turn of cycle
What is the role of coenzymes in respiration?
They oxidise molecules, accepting electrons and protons and becoming reduced themselves. Then later donating electrons to electron transport chain to facilitate transfer of electrons which is crucial for ATP synthase
What is the importance of teh Krebs cycle?
It oxidises and break down large nutrients into smaller ones e.g co2 then can be removed as a waste product
Generates reduced NAD and reduced FAD which carry protons and electrons into oxidative phosphorylation
Generates 4C oxoloacetate molecule that combines with acetyl CoA molecule
Provides a variety of intermediate compound such as fatty acids, amino acids, chlorophyll
What are the reactants and products of oxidative phosphorylation?
Reactants: reduced NAD, reduced FAD, oxygen, ADP and inorganic phosphate
Products: NAD, FAD, water, ATP
What is chemiosmosis in aerobic respiration?
Diffusion of protons across partially permeable inter mitochondrial membrane down their electrochemical gradient through ATP synthase channels
The movement of protons releases energy used to synthesis ATP and coverts teh energy form teh electrochemical gradient into chemical energy stored in ATP molecules
Key steps of oxidative phosphorylation?(8)
- Reduced NAD and reduced FAD release hydrogen which transfers protons and electrons to matrix
- High energy electrons are passed to an electron carrier from reduced NAD and reduced FAD
- Electrons are passed along a series of electron carrier molecules, releasing energy as they are transferred.
- Energy is used to actively transport protons across inner membrane from matrix into inter membrane space
- Accumulation of protons in inter membrane space makes electrochemical gradient of protons across inert membrane
- Protons diffuse back into matrix down gradient through ATP synthase
- This releases energy and catalases synthesis of ATP from ADP and inorganic phosphate
- Oxygen is final electron acceptor and combines with electrons and protons to form water
Differen es betweenanaerobic and aerobic respiration? (3)
- Some of aerobic respiration is in mitochniderai while all of anaerobic is in cytoplasm
- Only aerobic respiration has link reaction, Krebs cycle and oxidative phosphorylation
- Aerobic yields about 34 ATP per glucose, anaerobic only 2
What is an obligate anaerobe?
Organisms that cannot survive in presence of oxygen
What is a facultative anaerobe?
Organisms that switch between aerobic and anaerobic respiration, depending on oxygen availability
Obligate aerobes:
Organism that depends of oxygen to synthesis ATP and coverts
Describe alcohol fermentation:
- occurs in in yeast and some plants
- pyruvate loses a molecule of CO2 and is converted into ethanal
- ethanal accepts a hydrogen from reduced NAD
- Produces ethanol and regenerates NAD
- ethanol cannot be further metabolised so is removed as a waste product
Describe lactic acid fermentation:
- occurs in some animals and bacteria
- Pyruvate accepts hydrogen from reduced NAD, catalysed by lactate dehydrogenase
- this forms lactic acid and regenerates NAD
- lactic acid can be oxidised back to pyruvate to generate more ATP or stored as glycogen
What happens in a muscle cell if too much anaerobic respiration occurs?
The reduced quantity of ATP produced is insuffient to maintain vital processes for long time, lactic acid accumulated causing cramp and muscle fatigue and reduces pH effecting enzymes
How can proetins be used as respiratory substrates?
They are hydrolysed into amino acids
Amino group is removed (deamination) from amino acids
3C compounds are converted to pyruvate while 4 and 5C compounds are converted into intermediates in Krebs cycles
