C1.2: Respiration Flashcards
(25 cards)
Why is ATP useful?
CHARACTERISTICS:
Small, soluble
Short term energy store
Move easily in cells (facilitated diffusion)
Important in linking energy requiring and energy yielding reactions
The universal energy currency
USEFUL BECAUSE:
Hydrolysis of ATP quick + easy -> fast source of energy using 1 enzyme (ATPase)
Useful quantity of energy -> reduces waste + gives control
Stable at cellular pH -> only breakdown if ATPase -> less waste
Recyclable -> same molecule reused in many reactions
Soluble -> easy movement to different areas of cell
What is the structure of ATP?
Ribose sugar + adenine base + 3 phosphate groups
1 phosphate group -> adenosine MONOphosphate (AMP)
2 phosphate group -> adenosine DIphosphate (ADP)
What are some life processes that rely on ATP (as a source of energy)?
When energy is released ATP -> ADP + Pi
-> ATP very reactive molecules -> not stored in living organisms
-> glucose + fatty acids (short term) and glycogen + starch + triglycerides (long term) used instead
Anabolic reactions -> synthesize larger molecules from smaller ones
-> proteins synthesis
-> DNA/RNA replication
Movement of molecules
-> active transport
-> vesicle transport
Enabling moment of the entire cell
Move cell components (eg: chromosomes) in the cell
Muscle contraction
Cell signaling
Generating heat to maintain body temp
Explain the hydrolysis of ATP
When ATP hydrolyzed -> ADP + Pi
As ADP forms -> energy released -> used for life processes
Remove one phosphate group: 30.5 kJ/mol of energy
Remove second phosphate group: 30.5 kJ/mol of energy
Remove third phosphate group: 14.2 kJ/mol of energy
Explain ATP synthesis
On average human use more that 50 kg of ATP/day
-> but only have max 200g of ATP in the body
Organisms cannot build large stores of ATP -> cell must reuse ATP
ATP formed when ADP + Pi
-> requires energy
-> water released as waste product (condensation reaction)
What is respiration?
A series of chemical reactions that happens in every cell, releasing energy in usable forms from chemical energy stored in food
-> cell respiration: the controlled release of energy from organic compounds to produce ATP
Multiple steps because if all energy released at once -> uncontrollable -> cell damage, tissue death
=> enzymes control release of energy through pathway
Final product: ATP
Why is glucose the main respiratory fuel?
Lipids + proteins can also be used but must first undergo numerous changes before entering respiratory pathway
-> protein mainly structural -> only used where glucose/lipid not available
Glucose can enter glycolysis directly -> easier to oxidize
What is aerobic respiration?
The process of breaking down a respiratory substrate in order to produce ATP using oxygen
Requires oxygen -> substrate completely oxidized/brokendown
=> large yield of ATP (approx. 36 ATP/glucose)
CO2 waste produce
Water byproduct -> helps organisms water needs (eg: camel)
Most of the reactions of aerobic respiration take place in the mitochondria (eukaryotes)
Glucose + oxygen
In cytoplasm:
ADP -> ATP
Glucose -> 2 x pyruvate
In mitochondria:
Pyruvate + Oxygen -> H2O + C2O
Mega ADP -> ATP
Whats is anaerobic respiration?
Occurs in the absence of oxygen
- when oxygen supply can’t keep up with demand
- condition where oxygen cannot reach the organisms
Breaks down a respiratory substrate but produces less ATP for the cell
Glucose only partially oxidized -> lower energy yield (2 ATP/ glucose)
Occur in the cytoplasm
Plants and yeast: produce ethanol and CO2
Animals: produce lactate -> builds up in muscle tissue -> oxygen needed to break it down (oxygen debt)
Glucose + oxygen
In cytoplasm:
ADP -> ATP
Glucose -> 2 x pyruvate -> CO2 + ethanol / lactic acid
What factors affect the rate of respiration?
HOW METABOLICALLY ACITVE THE CELL IS:
Eg: muscle cell higher rate of respiration -> higher energy needs
SIZE OF ORGANISM:
Smaller organisms -> higher SA:V reaction -> high rate of respiration (compensate for heat loss)
OXYGEN SUPPLY:
Oxygen low -> cell respire anaerobically
SUPPLY OF RESPIRATORY SUBSTRATES:
Glucose low -> lower rate of respiration
TEMPERATURE:
Rate of respiration increase with optimum temp for enzymes
PH:
CO2 released lower pH -> denature enzymes
How can you determine the rate of respiration?
RESPIROMETER:
Used to measure and investigate rate of oxygen consumption during respiration in organisms
General design:
Seal container with living organism and air
Alkaline solution -> absorb CO2
Capillary tube connect container to graduated scale (manometer)
How it works:
Organisms respire -> absorb oxygen from air (CO2 released absorbed by alkali) -> reduces air pressure in container -> manometer fluid moves towards organisms (because of pressure drop)
=> must stay same temp -> water bath
Oxygen sensor or CO2 monitor can measure concentration in real-time
Data logger record data for future analysis
What is the equation for calculating a change is gas volume (using a respirometer)?
Volume of O2 consumed (mm3/min) -> worked out using radius of lumen of capillary tube (r) and distance moved bu manometer fluid in a minute:
πr2h
Volume of O2 consumed -> determine average rate of respiration
What are the strengths and weaknesses of different ways of measuring respiration?
Inverted measuring cylinder:
Strengths:
Easy to set up
Reliable
Weaknesses:
Higher level of uncertainty
Pressure sensor:
Strengths:
Accurate
Weakness:
Rely on tech
Harder to setup
Carbon dioxide sensor:
Strengths:
Accurate
Weaknesses:
Rely on tech
Harder to set up
Prone to tipping over -> mess up sensor
Respirometer:
Strengths:
Low level of uncertainty
Weaknesses:
Strong alkali used
Hard to use
What is oxidation and reduction?
Occur at the same time -> redox reactions
Oxidation:
Loss of hydrogen
Loss of electron
Gain of oxygen
Release energy (exergonic)
-> molecules with tendency to gain electrons -> oxidizing agents
Reduction:
Gain of hydrogen
Gain of electrons
Loss of oxygen
Absorb energy (endergonic)
-> molecules with tendency to lose electrons -> reducing agent
What are electron carriers?
Molecules that accept or donate their electrons
-> when it accepts electron = reduced
-> when it transfers electron = oxidized
=> redox reaction
NAD+ (nicotinamide adenine dinucleotide) -> primary electron carrier
NAD++ 2e-+ 2H+-> NADH + H+ (reduced)
NADH ->NAD++ 2e+ 2H+ (oxidized)
FAD (flavin adenine dinucleotide) -> other electron carrier
FAD+ 2e-+ 2H+→ FADH2 (reduced)
FADH2→ FAD+ 2e+ 2H+ (oxidized)
What are the different stages/reaction in anaerobic respiration?
Glycolysis -> link reaction -> krebs cycle -> electron transport chain -> chemiosmosis
Oxidative phosphorylation = ETC + chemiosmosis
CELL RESPIRATION: explain the steps of glycolysis
Occurs in the cytoplasm
-> trap glucose in cell by phosphorylating
-> split glucose into 2 pyruvate molecules
-> net gain 2 ATP (4 made - 2 used)
-> 2 NADH
PHOSPHORYLATION:
Glucose (6C) -> phosphorylation using 2 ATP -> Fructose-1,6-bisphosphate
=> 6C less stable
LYSIS:
Fructose-1,6-bisphosphate -> 2 x triose phosphate (3C)
OXIDATION:
Hydrogen removed from TP (dehydrogenase enzyme) -> 2 x glycerate-3-phosphate
4H + 2NAD -> 2NADH + 2H+
ATP FORMATION:
2 x phosphates from each GP (4Pi) + 4ADP -> 4 ATP
2 x GP -> 2 x pyruvate
ANAEROBIC CELL RESPIRATION: explain how lactate is produced
Cells oxidize NADH produced during glycolysis -> used for further hydrogen transport -> glycolysis continue -> small amount of ATP made
PYRUVATE TO LACTATE:
NADH transfers hydrogen to pyruvate -> pyruvate reduced by lactate dehydrogenase -> lactate
-> NAD+ can be reoxidized without oxygen
-> pyruvate continue to form
METABOLIZATION OF LACTATE:
Lactate can either:
1. Be oxidized back to pyruvate -> channelled into Krebs cycle -> ATP production
2. Converted into glycogen for storage in liver
Oxidation of lactate -> pyruvate needs extra oxygen
-> extra oxygen = oxygen debt
ANAEROBIC CELL RESPIRATION: yeast anaerobically respirates
ALCOHOL:
Yeast used in alcoholic fermentation
-> ethanol main ingredient in alcoholic drinks like beer and wine
-> CO2 produced add carbonation
BAKING:
Yeast when mixed with flour (starch) -> aerobically respirate -> yeast cells grow rapidly -> dough become anaerobic -> CO2 bubbles form -> dough rises
Baking kills yeast and evaporates alcohol
Glucose -> 2 x pyruvate and 2 x ATP -> pyruvate decarboxylated (CO2 produced) -> ethanal -> ethanal reduced (H+ from NADH) by enzyme alcohol dehydrogenase -> ethanol
AEROBIC RESPIRATION: explain the steps of the link reaction
Pyruvate still has substantial amounts of chemical energy -> used for more ATP
If oxygen available -> pyruvate into mitochondrial matrix
THE LINK REACTION:
Oxidative decarboxylation:
CO2 removed from pyruvate -> 2C molecule
2C molecule oxidized (NAD -> NADH) -> acetyl compound
Acetyl compound + coenzyme A -> acetyl coenzyme A (CoA)
pyruvate + NAD + CoA → acetyl CoA +CO2 + NADH
! x 2 because 2 pyruvate molecules !
AEROBIC RESPIRATION: explain the steps of the Krebs cycle
Takes place in the matrix of mitochondria
Acetyl CoA (2C) enter -> oxaloacetate (4C) accepts 2C acetyl fragment from acetyl CoA -> citrate (6C)
- coenzyme A released and reused
Citrate (6C)
Decarboxylation: CO2 + 5C compound
5C compound
Oxidized (release H+): NAD -> NADH
Decarboxylation: CO2 + 4C compound
4C compound
Oxidized: 2 x NAD -> NADH and 1 FAD -> FADH2
Substrate-level phosphorylation: Pi from intermediate + ADP -> ATP
=> oxaloacetate (4C)
! Happens x 2 because 2 pyruvate molecules !
For one glucose molecule:
4 CO2
2 ATP
6 NADH + H+
2 FADH2
AEROBIC RESPIRATION: explain the electron transport chain
Electron transport chain -> series of redox reactions occur via membrane proteins (electron carriers) embedded into inner mitochondrial membrane
-> electron carriers close -> electron pass between
-> Cristae of mitochondria impermeable to protons -> electron carriers need to pump
-> efficient but relies on abundance of O2
STEPS:
NADH and FADH2 oxidized:
Electrons go to electron carrier -> passed to next carrier -> release energy to pump protons -> repeat
Protons released -> carrier proteins pump protons across cristae -> intermembrane space -> proton gradient created
=> when protons down gradient -> release energy -> ATP synthesis
At final electron carrier -> oxygen final electron acceptor (+ H+) -> water
AEROBIC RESPIRATION: explain chemiosmosis and ATP synthesis
Movement of electrons through ETC -> proton/electrochemical gradient
Protons built up in intermembrane space -> only pass through phospholipid belayer by facilitated diffusion through membrane-embedded protein (ATP synthase)
ATP synthase = water wheel
-> turned by flow of protons
ATP synthase turns -> catalyzes phosphorylation of ADP -> ATP
Why is oxygen so important in aerobic respiration?
Oxygen -> final link in ETC -> final/terminal electron acceptor
=> reduced by electrons + protons from matrix -> water
IF NO OXYGEN:
NADH and FADH2 not oxidized -> no regenerate NAD+ and FAD -> no hydrogen transport
ETC stop -> ATP no longer produced by chemiosmosis
Not enough ATP -> cells can’t carry out reactions needed to function
