Respiration Part 1 - (Week 2) Flashcards
What is Respiration?
- chemical reactions in cells that sustains life
- metabolic reaction - creating energy from food
- metabolic reaction using created energy for biological process e.g. growth, division
- removal of waste products
What is metabolism?
- chemical reactions in cells required to sustain life
What is catabolism?
- breaking down of molecules
What is anabolism?
- building of molecules
Within Metabolism, what processes occur?
- carbohydrates to Glucose (vice versa)
- proteins to amino acids (vice versa)
- fats to glycerols/ fatty acids (vice versa)
ATP is only required for anabolic reactions. True or False?
False - also chemical synthesis
Give an example of what cellular work metabolism is known for.
Active transport of molecules.
What is active transport?
- movement of molecules where they don’t want to go
- required for some nerve transmission + some steps of respiration
- required for intracellular signalling (calcium pumps)
An average heart weighs 300g so how much ATP does it need in a day?
5kg - 5000g (16x it’s weight)
What is ATP?
- adenosine 5’ - triphosphate
- energy carrying molecule
- used for different processes e.g anabolism, active transport
- a chemical bond in “carrier molecules” that can diffuse rapidly throughout the cell
Which other molecules are important for carrying energy in respiration?
NADH
FADH2
What is ADP able to bind to?
- phosphate - bond between between the 2nd & 3rd bond gives high energy.
What is NAD+?
- nicotinamide adenine dinucleotide
- picks up energy in the form of 2 electrons and a proton (H+)
- can be regarded as electron donors/acceptors
What FAD+?
- flavin adenine dinucleotide
- picks up energy in the form of 2 electrons & 2 protons (H+)
- can be regarded as electron donors/ acceptors
Where does respiration take place?
- inside the body
- inside cells
- in the cytoplasm (glycolysis)
- in the mitochondria (matrix) - (link reaction, TCA cycle, oxidative phosphorylation)
What are key points of mitochondria? - timeline
- ‘mito’= thread, ‘chondrion’ = granule, grain like
- vary in number, size, and shape
- endosymbiotic theory
What are some aspects of the outer membrane?
- smooth
- composed of equal amounts of phospholipids & proteins
- contains porins
- porins render the members freely permeable to nutrient molecules ions e.g. ATP, & ADP
What are porins?
- integral membrane proteins that allow the passage of small molecules
What are some aspects of the inner membrane?
- multiple folded cristae - varying in number
- cristae/proteins - sites of various chemical reactions e.g. production of ATP
- only permeable to oxygen & ATP
Why is the cristae folded?
- increased SA
- gives a 5 -fold increase in SA - therefore more reactions at once
What is the inter membrane space?
- space between the outer & inner membrane
- largely same composition as the cytoplasm but a difference in protein content
What is the matrix?
- cytoplasm like region
- complex mixture of proteins & enzymes
- important in the synthesis of ATP molecules
- not encoded by the genomic DNA (gDNA) in the nucleus
What is glycolysis?
- splitting apart with glucose
- yields a small amount of DNA
- occurs in the cytoplasm
- does not require oxygen, (anaerobic & aerobic)
- generates pyruvate, then converted to lactate (causing pain in muscles)
- costs ATP (phosphates are added to glucose)
What are the 3 key steps of glycolysis?
- Phosphorylation of hexose (glucose) to hexose bisphosphate (fructose biphosphate)
- Splitting of hexose biophosphate (fructose biophosphate) into two triose phosphate molecules (glyceraldehyde phosphate)
- Oxidation to pyruvate, producing a small yield of ATP & reduced to NAD
What happens in phosphorylation?
Addition of phosphate groups
What happens within phosphorylation? - Step 1
- phosphate group = attached to glucose (hexose) from ATP
- trapped inside the group - cannot be transported back out
- isomerised to fructose (hexose)
- raises energy level - more reactive
- another phosphate group attaches to fructose
What is fructose biphosphate?
- carbon on the 6th phosphate
What happens in Step 2? - (splitting of hexose)
- fructose biphosphate (hexose) is split into 2 glyceraldehyde phosphate (triose) molecules
What happens in Step 3? - (oxidation to pyruvate)
- glyceraldehyde phosphate (triose) molecules oxidised
- H+ atoms removed - (anaerobically)
- NAD+ reduced as they accept the hydrogen atoms
- oxidation adds a second phosphate (not from ATP)
- Biphosphoglycerate (triose) no longer a sugar
What is substrate level phosphorylation?
- Enzymatic addition of phosphate to ADP
- 2 ATP produced when the phosphates are removed
What are the products of glycolysis? - for a single molecule of glucose
- 2 ATP
- 2 NADH (reduced NAD+)
- 2 pyruvate (~triose) - no longer a sugar
What happens to pyruvate after glycolysis?
- actively transported into the mitochondria (aerobic)
- remains in the cytoplasm ( under anaerobic conditions)
What happens in pyruvate transport?
- transport into the mitochondria
- with a proton, down the proton conc. gradient
- gradient = maintained by proton pumping costing energy (active transport)
What happens in link reaction?
- pyruvate cannot directly enter the TCA Cycle
- converted to acetate
- linked to coenzyme A (CoA)
- required for enzyme reactions
- acetyl CoA can enter the TCA cycle
What happens in decarboxylation?
- removal of a carboxyl group (lost as CO2)
- catalysed by pyruvate decarboxylase
Fact about enzymes:
Enzymes usually do what they say e.g. pyruvate decarboxylase, removes a carbon from a pyruvate molecule
What happens in dehydration? (Link reaction)
- removal of protons, accepted by NAD+
- catalysed by pyruvate dehydrogenase
What happens in CoA Addition? (Link reaction)
- Coenzyme A joined to acetate forming acetyl coenzyme A
- allows acetate to enter the TCA cycle
In a link reaction, for each glucose entering glycolysis 2 pyruvate molecules are made. True or False?
True - 2 link reactions occur
- the molecules bind to NAD+ and CoA (3 carbons)
- producing acetyl CoA and NADH, making H+ ions and carbon dioxide (2 carbons)
Who was the Krebs Cycle first sequenced by?
Hans Krebs
What happens in Step 1 of the TCA cycle?
- acetyl CoA (2c) from the link reaction combines with oxaloacetate (4c) to make citrate (6c)
What happens in Step 2 of the TCA cycle?
- citrate (6c) is decarboxylated & dehydrogenated
- forms alpha-ketoglutarate (5c), CO2 and NADH
What happens in Step 3 of the TCA cycle?
- alpha-ketoglutarate (5c) = decarboxylated & dehydrogenated
- forms oxaloacetate (4c), CO2, NADH, FADH2, ATP
- ATP from substrate level phosphorylation process from the enzyme
- oxaloacetate (4c) can start the cycle again
What are the products of link reaction and TCA cycle?
For a single molecule of pyruvate (triose):
- 1 ATP (substrate level phosphorylation)
- 4 NADH (reduced NAD+)
- 1 FADH2 (reduced FAD+)
- 3 CO2
- values double for a glucose (hexose) molecule
In a link reaction and TCA cycle, the equivalent of a glucose molecule is lost as carbon dioxide. True or False?
True - 6C in , 6C out + energy
What happens in oxidative phosphorylation?
- in 2 parts
electron transport chain (ETC): - electrons = passed from one member of the transport chain to another in a series of redox reactions
- produces a proton gradient
Chemiosmosis: - proton gradient used to produce ATP - uses energy stored here
What happens in Step 1 of Electron Transport Chain?
- NADH and FADH2, reduced in previous steps & carry electrons
- transfer their electrons to the beginning of the transport chain
- become oxidised again e.g. back to FAD+
- to be reused in other steps of respiration, cycle of redox reactions
What happens in Step 2 of Electron Transport Chain?
- electrons = passed down the chain of proteins (cytochromes & redox enzymes)
- electrons move to a lower energy level releasing their energy
- some of the energy pumps protons (H+ ions) from the matrix into the inter membrane space
- pumping establishes an electrochemical gradient, same principle as a concentration gradient
What happens in Step 3 of Electron Transport Chain?
- at the end of the electron transport chain, electrons = transferred to molecular oxygen (O2)
- oxygen splits in half + reacts with 2H+ to make H2O
What happens in chemiosmosis?
- gradient-driven synthesis of ATP - using the proton gradient
- ETC established a proton electrochemical gradient
- protons (H+ ions) flow back to this gradient into the matrix
- pass through the enzyme ATP synthase
- drives the enzyme to synthesise ATP ( part of ATP production by photosynthesis)
- also used in bacteria rather than aerobic respiration - maintains an electrochemical gradient between the cytoplasm & their environment
How many molecules of ATP can be produced by oxidative phosphorylation by each NADH?
2.6 molecules
What is the overall production of ATP?
- 30 ATP Yield per glucose molecule by oxidative phosphorylation
- 4 ATP per glucose molecule by substrate level phosphorylation
- 34 Total ATP - per glucose molecule
Is oxidative phosphorylation possible in anaerobic conditions?
No, as there is significantly less energy produced.
What is ATP yield reduced by?
- energy required for active transport into mitochondria e.g ADP
- energy required for active transport out of mitochondria
- dissipation of the proton gradient (leaky membrane) - protons leaking out of the mitochondria = wasted instead of driving ATP production
