Chapter 7: Energy and Cell Respiration Flashcards
What is the role of mitochondrial DNA?
Codes for rRNA, tRNA, and 13 proteins for respiration.
How are mitochondrial mutations inherited?
Through the mother.
What is the purpose of three-parent IVF?
(in vitro fertilization)
To prevent passing on mitochondrial disorders.
What do autotrophs use as a carbon source?
Carbon dioxide.
What do heterotrophs rely on for carbon?
Ready-made organic molecules.
Name two functions of organic molecules in cells.
Building blocks and energy storage.
What types of work do cells perform?
Synthesis, transport, mechanical movement, bioluminescence.
How do cells produce energy from glucose?
Through oxidation.
What molecule is the universal energy carrier in cells?
ATP.
Where does glycolysis take place?
Cytosol.
What is glycolysis?
Splitting of glucose into pyruvate.
What is the net ATP yield of glycolysis?
2 ATP.
What is the product of the link reaction?
Acetyl CoA.
Where does the Krebs cycle occur?
Mitochondrial matrix.
What molecule starts the Krebs cycle?
Acetyl CoA.
What is the main purpose of the Krebs cycle?
To produce NADH and FADH₂.
What are the products of one glucose molecule in the Krebs cycle?
6 NADH, 2 FADH₂, 2 ATP, and 4 CO₂.
What happens in oxidative phosphorylation?
ATP is produced using the ETC and ATP synthase.
What is the final electron acceptor in the ETC?
Oxygen.
What is the theoretical ATP yield of cellular respiration?
36 ATP.
What is the actual ATP yield of cellular respiration?
30 ATP.
Why is the actual ATP yield lower than theoretical?
Proton leaks and pyruvate transport.
What are the byproducts of anaerobic respiration in animals?
Lactate.
What are the byproducts of anaerobic respiration in plants?
Ethanol and CO₂.
Where does anaerobic respiration occur?
Cytosol.
What happens to lactate in mammals after anaerobic respiration?
It is converted back to pyruvate in the liver.
Why is ethanol production irreversible?
Carbon dioxide is released during the process, which readily diffuses away, making it difficult to reverse the reaction and regenerate pyruvate from ethanol (cause lost all the C)
What macromolecules besides glucose can be used in respiration?
Lipids and amino acids.
What happens to lipids in respiration?
Converted to acetyl CoA.
What is oxygen debt?
Extra oxygen required after exercise to restore balance.
How do cristae benefit mitochondria?
Increase surface area for reactions.
What is the role of the mitochondrial inner membrane?
Houses the ETC and ATP synthase.
What is the role of NADH in the ETC?
Transfers electrons.
What is ATP synthase?
Enzyme that produces ATP.
How is a proton gradient created in the ETC?
By pumping H⁺ ions into the intermembrane space.
Why do protons flow back through ATP synthase?
Due to the concentration gradient.
What happens to energy not converted to ATP?
Lost as heat.
Where is oxygen used in respiration?
As the final electron acceptor in oxidative phosphorylation.
What is the role of FADH₂?
Transfers electrons to the ETC.
How many ATP does one NADH produce?
3 ATP.
How many ATP does one FADH₂ produce?
1.5 ATP.
What regulates glycolysis?
ATP levels via feedback inhibition.
What enzyme catalyzes lactate formation?
Lactate dehydrogenase.
What enzyme catalyzes ethanol formation?
Alcohol dehydrogenase.
How does oxygen debt affect breathing after exercise?
Increases breathing to repay the deficit.
What is the role of coenzyme A in respiration?
Combines with acetyl groups to form acetyl CoA.
What is a respiratory substrate?
A molecule used for energy production in respiration.
Why is glucose the main respiratory substrate?
It is easily broken down for energy.
What happens during the oxidation phase of glycolysis?
ATP and NADH are formed.
How does anaerobic respiration differ from aerobic respiration?
It does not use oxygen and produces less ATP.
What type of molecule is NADH?
An electron carrier.
What are the two main steps of oxidative phosphorylation?
ETC activity and ATP synthesis.
How many ATP molecules are generated in glycolysis per glucose molecule?
4 ATP, with a net gain of 2 ATP.
What determines mitochondrial count in cells?
The cell’s energy demand.
What cells have the highest mitochondrial density?
Liver cells.
What is bioluminescence?
Light production in some organisms using ATP.
What is the first step of glucose metabolism in cells?
Glycolysis.
What happens to NADH in the absence of oxygen?
It transfers hydrogens to pyruvate or ethanal.
What happens during pyruvate dehydrogenation?
Removal of hydrogen atoms.
What happens during pyruvate decarboxylation?
Removal of CO₂.
Why do red blood cells rely on glycolysis?
They lack mitochondria.
What is the primary fuel for respiration?
Glucose.
What process regenerates NAD⁺ in fermentation?
Reduction of pyruvate or ethanal.
How many ATP molecules are produced per glucose in fermentation?
2 ATP.
What is the role of the outer mitochondrial membrane?
Regulates molecule entry and exit.
Why does lactic acid build up in muscles?
Due to anaerobic respiration during oxygen deficit.
What maintains the H⁺ gradient in the mitochondria?
Proton pumping by the ETC.
Why is oxidative phosphorylation oxygen-dependent?
Oxygen is the final electron acceptor.
What is the main energy yield of the Krebs cycle?
NADH and FADH₂.
How do lipids enter the respiration pathway?
As acetyl CoA.
Why are cristae longer in active cells?
To maximize ATP production.
What molecules store energy in respiration?
NADH, FADH₂, and ATP.
What is the significance of coenzymes in respiration?
They assist in electron transfer and energy release.
The need for energy in living organisms
Why is Carbon a vital element?
for living organisms
All macromolecules are made of Carbon
-> Requires Carbon to synthesize
The need for energy in living organisms
What are organisms that use inorganic carbon source called?
CO2, synthesizing their own organic molecules
Autotrophs
like plants
The need for energy in living organisms
What are organisms that use organic Carbon supply called?
ready-made organic supply of C
Heterotrophs
like animals
The need for energy in living organisms
2 uses of organic molecules in living organisms?
related to catabolism and anabolism
- Anabolism: building blocks to form macromolecules
- Catabolism: store chemical potential energy in bonds
break the bonds for energy
Work that cells do
What is work?
- Energy consumption
- Energy in transition between states/objects
Work that cells do
Some types of doing work in living organisms?
just name a few
- synthesis of macromolecules
- active transport (pumps)
- muscle contraction
- bioluminescence
- cellular movements
The need for energy in living organisms
Relationship between autotrophs and heterotrophs?
Heterotrophs depend on autotrophs
‘cause they can’t make their own organic supply
Work that cells do
What process of what substance gives energy for cells to do work?
Oxidation of glucose
Work that cells do
Equation for oxidation of glucose?
C6H12O6 + O2 -> 6 CO2 + 6 H2O + 2870 kJ
exergonic (energy of product < energy of reactant => released energy)
Work that cells do
Why won’t cells simply burn glucose but need respiration?
Too much energy released at once:
* wasted
* harm cells
Work that cells do
Why must cells convert energy into ATP?
adenosine triphosphate
Store energy for later use
energy currency of cells
ATP
How is energy extracted from ATP?
Removes phosphate group 1 by 1
dephosphorylate
ATP
Dephosphorylation of the 1st and 2nd phosphate group gives 30.5 kJ/mol, but the 3rd only gives 14.2 kJ/mol. Why?
Link between γ-β and β-α phosphate group is phosphoanhydride, while α-ribose is phosphodiester
Energy of phosphoanhydride > phosphodiester
ATP - Synthesis of ATP
How?
- Using energy released by chemical reaction to phosphorylate ADP (substrate-linked reaction)
- Movement of H+ down a concentration gradient (chemiosmosis)
glycolysis, Krebs cycle and oxidative phosphorylation
ATP - Synthesis of ATP
Which method is more used by a cell to create ATP?
substrate-linked-reaction or chemiosmosis
Chemiosmosis
ATP - Synthesis of ATP
What is oxidative phosphorylation?
Process where ATP produced using energy from transfer of electrons in the electron transport chain
in cristae
Respiration
Definition?
technically oxidation
Organic molecules broken down in a seris of stages
* Releases chemical potential energy
* Synthesize ATP
Respiration
Stages of glucose breakdown?
Glycolysis -> Link reaction -> Krebs cycle -> Oxidative phosphorylation
Link reaction = Pyruvate oxidation
Respiration
Where does respiration occur in prokaryotes?
Cytosol and Plasma membrane
PM only for oxidative phosphorylation
Respiration
Where does respiration occur in eukaryotes?
Cytosol -> Mitochondrial matrix (2) -> Inner mitochondrial membrane
Respiration
What is the input of respiration?
Glucose, O2
Respiration
How is glucose moved through membranes?
Using GLUT enzyme
GLUcose Transporter
Respiration
What is the output of respiration?
CO2, ATP, H2O
Respiration
Why is CO2 an indicator of the end of oxidation?
CO2 is the most oxidised form of Carbon (C+4)
end products of glu. oxi. are always CO2 and H2O
Respiration - Glycolysis
Where does glycolysis occur?
Cytoplasm
Respiration - Glycolysis
Why does glycolysis occur in cytoplasm?
- Glycolytic enzymes are present
- Doesn’t need to further diffuse glucose
Respiration - Glycolysis
Final product of glycolysis from 1 glucose?
2 pyruvate, 2 ATP, 2 NADH
Respiration - Glycolysis
How is the concentration of pyruvate regulated?
End-product inhibition, excess C% of pyruvate will block enzymes
Respiration - Glycolysis
Which enzymes are involved in glycolysis?
3 major control points (in 10)
- Hexokinase
- Phosphofructokinase (afffects most if blocked)
- Pyruvate kinase
Respiration - Glycolysis
3 main stages of glycolysis
Phosphorylation -> Lysis -> Oxidation
fructose biphosphate -> 2 triose phosphate -> 2 pyruvate
https://cdn.kastatic.org/ka-perseus-images/3ac5f05c70a76473139a0abb96318146af528f48.png
Respiration - Glycolysis
How many ATP are used and produced?
Use 2 make 4
Respiration - Glycolysis
What are 2 ways to use pyruvate? And when?
- O2 present: aerobic respiration (moves to link reaction)
- O2 absent: anaerobic respiration (moves to fermentation)
Respiration - Glycolysis
What is NAD?
Nicotiamide Adenine Dinucleotide
a coenzyme, binds to enzyme to catalyze it
Respiration - Glycolysis
What is the process of taking in H- called?
electron
Reduction
NAD+ + H- -> NADH
Respiration - Glycolysis
Why must glucose be phosphorylated to fructose biphosphate before going through ‘lysis’?
Makes more active and charged -> can’t interact with GLUT to leave cytoplasm
Respiration - Glycolysis
What does oxidation of triose phosphate create?
Pyruvate, forming ATP and NADH
How many CO2 are created if all pyruvate are completely oxidised?
6
Because glucose is C6
Where does the link reaction occur?
Matrix (cytosol if prokaryotic cells)
What happens to acetyl CoA?
Moves to Krebs cycle.
Where does the Krebs (TCA/citric acid) cycle occur?
Matrix (or cytosol of prokaryotic cells)
Where does oxidative phosphorylation occur?
Inner mitochondrial membrane
Summarize
What is oxidative phosphorylation?
- ETC, coupling energy from the electrons from NADH and FADH2 as they move from one high energy level to a lower one, pumps H+ into the intermembrane space.
=> Creates gradient, stacking H+ outside of membrane - Chemiosmosis, H+ diffuses readily back into matrix through the enzyme ATP synthase (channel).
- ATP synthase couples the energy of H+ to phosphorylate ADP into ATP.
What happens to NADH and FADH2?
Passed to ETC (complex of 4 proteins and other molecules)
-> H is removed, split into H+ and electron
Do electrons carry energy?
Yes. It is extracted at the ETC, as chemical potential energy in chemical bonds weren’t fully released in the earlier steps.
What is the final electron acceptor?
Oxygen
O2 + 2 e- + 4 H+ -> 2 H2O
What if oxygen is absent?
Oxidative phosphorylation won’t occur.
How much ATP does FADH2 and NADH generate?
1.5 and 2.5, respectively.
4 H+ = 1 ATP
What is the ATP yield of respiration from 1 glucose?
Theoretical net yield: ~36 ATP
Actual net yield: ~30 ATP
What is the percent yield of respiration? Why?
~34%, because:
* Leakage of H+ across membrane
* Energy cost for transporting ATP, ADP & NADH across membrane
* Shuttle of electrons: FADH2 instead of NADH
* Lose as heat => thermogenesis
Why is there a difference in ATP yield between FADH2 and NADH?
NADH starts donating from protein complex 1, while FADH2 from PC 2
PC1: NADH dehydrogenase
PC2: succinate dehydrogenase
FADH2 was created in Krebs using PC 2 => can’t interact with PC 1
Why is the enzyme catalase necessary in cell respiration?
present in peroxisome and cytosol
Under oxidative stress or ETC not functioning normally
-> e- escapes normal pathway, reduces O2 incompletely
-> forms ROS (O-1)
-> ROS turns into H2O2 (hydrogen peroxide) by superoxide dismutase (because O-1 is harmful)
-> H2O2 is also very reactive, can harm cells
=> broken down into H2O and O2 by catalase
How do RBC create energy? Why?
Through anaerobic respiration, because no mitochondria for more space to carry oxygen.
no nucleus too
Where does anaerobic respiration occur?
Cytosol
What are 2 types of fermentation?
Lactic and alcoholic
Which organisms use alcoholic fermentation?
Plants, yeasts
Which organisms use lactic fermentation?
animals
Summarize
What is alcoholic fermentation?
Pyruvate is decarboxylated into ethanal,
then reduced by alcohol dehydrogenase into ethanol
ethanal = CH3CHO
Summarize
What is lactic fermentation?
Pyruvate is converted into lactate by lactate dehydrogenase
lactic acid
Why is the formation of ethanol/lactate necessary?
Let NADH release H to become NAD and ready to receive H again from glycolysis
=> maintain glycolysis
Glycolysis is the only way of producing energy when oxygen is absent
What is the key difference between alcoholic and lactic fermentation?
aside from product and organism
Alcoholic is irreversible
Lactic is reversible
What happens to lactate after a while?
Moved to liver through blood, converted into glycogen.
Effect of ethanol/lactate on cells?
Toxic, cells will die if ethanol/lactate accumulates indefinitely
=> emergency only
When does fermentation occur?
- can’t produce energy (no oxygen)
- energy consumption > energy production
e.g. muscle cells during workout
Main goal of fermentation?
emergency pathway to maintain energy, temporary replacing glycolysis at the cost of toxins
Why do cells still undergo fermentation if it harms them?
Aerobic respiration is still ongoing, but not fast enough
=> anaerobic respiration to mass produce ATP & comply with instant demand
What is oxygen debt?
Oxygen deficit because of overconsumption
(e.g. oxygen deficit during exercises because hearts and lungs can’t work fast enough)
How is oxygen debt paid back?
Extensive fast-paced breathing even after exercising
-> converts lactate to glycogen
-> hemoglobin reoxygenate
-> higher metabolism rate
absorb oxygen at higher rate
Role of outer mitochondrial membrane?
Seperates contents of mitochondria
compartmentalize
Role of mitochondrial matrix?
Internal cytosol-like area, contains enzymes for link reaction and Krebs cycle
Role of crista(e)
- Tubular regions surrounded by membrane
=> increase surface area - Narrow
=> low volume but same surface area so steeper gradien
=> higher diffusion rates
cristae number increases as the cell’s activity increases
Role of inner mitochondrial membrane?
Contains carriers for ETC & ATP syntahse for chemiosmosis
Role of intermembrane space?
A reservoir for H+ ions, creating the gradient for chemiosmosis
