L13 & 14: Cellular Respiration Flashcards
Define metabolism
All the chemical processes in the body
Define catabolism
Breaking down complex molecules
Are catabolic reaction exergonic or endergonic?
Exergonic
What key processes involve catabolism as an important part?
Glycolysis, Krebs cycle, electron transport chain
Define anabolism
The building of complex molecules
Are anabolic reactions exergonic or endergonic?
Endergonic
How do anabolic and catabolic reactions work together?
Energy produced in catabolism is used up in anabolism. ATP is the medium of transport for the energy transfer.
What controls the anabolic and catabolic reactions within a cell?
Enzymes
Is ATP used as an energy store?
No. It is used to transfer readily available energy quickly, each molecule lasting around 60 seconds.
What are the main energy stores used by the body?
Glycogen, triglycerides, and proteins
In starvation, the rate catabolism drops. Explain what happens to the rate of anabolic processes.
In starvation there is less energy available. Therefore, the rates of anabolic processes are also reduced.
In hepatocytes, does anabolism or catabolism predominate?
As the liver is responsible for breaking down toxins, catabolism would dominate.
In a pancreatic cell producing digestive enzymes, does anabolism or catabolism predominate?
Anabolism, as you are building complex molecules
What is ATP converted to as it is used for energy?
ADP
“Removal of electrons or hydrogen/addition of oxygen/decrease in potential energy” is what type of reaction?
Oxidation
“Addition of electrons or hydrogen/removal of oxygen/increase in potential energy” is what type of reaction?
Reduction
What is produced when you oxidise lactic acid?
Pyruvic acid
Name two key coenzymes in cellular respiration
NAD (nicotinamide adenine dinucleotide)
FAD (flavin adenine dinucleotide)
Why is glucose valuable to cells?
It is a good energy source as it is highly reduced (has a high ratio of hydrogens). This energy is liberated through oxidation reactions.
Are oxidation reactions exergonic or endergonic?
Exergonic
What is a coenzyme?
A non-protein molecule that binds to an apoenzyme to form a holoenzyme
Which is not true for ATP?
A. Each molecule contains a large amount of energy
B. It cannot leave the cell
C. It is created by catabolic reactions
D. It can be re-synthesised by enzyme-controlled reactions
A. Each molecule contains a large amount of energy
The bonds are considered to be high energy, but this is still just a small amount
Which of the following regarding FAD is true?
A. It is derived from niacin
B. It is reduced by the addition of two hydrogens
C. It is created by a catabolic reaction
D. It directly helps endergonic reactions proceed
B. It is reduced by the addition of two hydrogens
What does phosphorylation do to the potential energy of a molecule?
Increase its potential energy
What is substrate-level phosphorylation?
Transferring high-energy phosphate group from an intermediate directly to ADP
Where does substrate-level phosphorylation occur?
In the cytosol
What is oxidative phosphorylation?
Remove electrons and pass them through electron transport chain to oxygen
Where does oxidative phosphorylation occur?
Inner mitochondrial membrane
Which cells can convert most of the fructose and nearly all of the galactose into glucose?
Hepatocytes
Intestinal epithelial cells can convert ? into glucose.
Some of the fructose
What is the main use of glucose in the body?
ATP production
What are the possible uses of glucose in the body?
- ATP production (glucose is oxidised)
- Amino acid synthesis (protein synthesis)
- Glycogen synthesis (hepatocytes & muscle cells)
- Triglyceride synthesis; when glycogen storage is saturated, glycerol and FFA’s are made
What is insulin?
A peptide hormone
What does insulin do?
Binds to cell surface in liver, muscle, and adipose tissue to initiate the storage of glucose. Signal the start of phosphorylation of glucose within the cell, lowering the concentration inside the cell. This draws in more glucose via facilitated diffusion
Where is insulin synthesised?
Beta cells in the pancreas
Where will you find GluT1 & GluT3 transport proteins?
Membrane of most cells
What is the Km and Vmax of GLUT1 & 3? High or low?
Low Km; low Vmax
Which enzyme mediates the conversion of glucose to G-6-P?
Hexokinase
Why can’t glucose leave the cell?
It is phosphorylated upon entering; G-6-P can’t interact with GluT
What is the process of oxidising glucose to form ATP?
Cellular respiration
How many pyruvic acid, ATP, and coenzyme molecules are formed from glycolysis?
2 x pyruvic acid
2 x ATP (4 are made, but as 2 are consumed, the net production is 2)
2 x NADH
2 x H+
If glycolysis is the first step in glucose catabolism, what is the second step?
Link reaction. Forms acetyl coenzyme A. This is a transition step to prepare pyruvic acid for entry into the Krebs cycle. Also produces NADH & H+ & CO2
Summarise the Krebs cycle
Oxidises acetyl coenzyme A and produces ATP, CO2, NADH, H+, & FADH2
Summarise electron transport chain
Oxidise NADH, H+, and FADH2 and transfers their electrons through electron carriers
What does a kinase generally do?
Works on phosphate groups - either adds or removes. Any time you see phosphate groups being added or removed, think kinase.
Glycolysis converts glucose into what?
2 molecules of pyruvic acid
How many reactions take place in glycolysis?
10
Which glycolysis reactions use ATP? Which enzymes play a role in these steps?
Reaction 1 (Hexokinase) and Reaction 3 (Phosphofructokinase).
Which glycolysis reactions produce ATP? Which enzymes play a role in these steps?
Reaction 7 (Phosphoglycerate kinase) and Reaction 10 (Pyruvate kinase)
Which enzyme is the key regulator of glycolysis?
Phosphofructokinase
If PFK activity is high, what are the ADP levels like?
Elevated - phosphofructokinase uses ATP and produces ADP
If PFK is low, what happens to glucose?
It is shunted away from glycolysis to the glycogen storage pathway
Which step in glycolysis produces NADH and H+?
Reaction 6, glyceraldehyde 3-phosphate > 1,3-bisphosphoglycerate.
Enzyme used is GPD (glyceraldehyde phosphate dehydrogenase)
How many ATP’s can liver and cardiac cells generate from the NADH and H+ produced in step 6 of glycolysis?
6
NADH molecules are regenerated back into NAD+ molecules. When and how does this take place?
Following glycolysis, if conditions are anaerobic, 2 pyruvates are reduced by 2 NADH molecules. This produces 2 lactic acids and 2 NAD+. These are used over again in step 6 of glycolysis, and the lactic acid is turned back into pyruvate by the liver cells
Following glycolysis, what happens to the pyruvate if conditions are aerobic?
It is converted into acetyl coenzyme A and enters the Krebs cycle
Why can glycolysis occur in red blood cells but Krebs can’t?
Glycolysis takes place in the cytosol, which RBC’s have; Kerbs takes place in the mitochondria, which RBC’s don’t have.
What is the link reaction that occurs between glycolysis and Krebs?
Pyruvates enter the mitochondrion and are given a Coenzyme A group each (also lose CO2 each). 2 NADH molecules formed, 2 acetyl coenzyme A molecules formed.
What happens to the CO2 generated in glycolysis and the link reaction?
It is taken to the lungs through the blood and exhaled
Between glycolysis and the link reaction, what is produced (net gain)?
2 ATP
4 NADH
2 acetyl coenzyme A molecules
What are the electron carriers in Krebs?
NADH and FADH2
True or false: Glycolysis occurs in the cytoplams
True
True or false: Red blood cells don’t use glycolysis
False. They do glycolysis; but not Krebs
Pyruvate dehydrogenase deficiency is characterised by a build up of lactate
True
True or false: Glycolysis has a net ATP production of 4
False. It makes 4 but uses 2, therefore the net production is 2
True or false: Pyruvate is the end product of glycolysis
True
True or false: Most cells use GluT 2
False. Most use GluT 1 and 3
True or false: GluT 4 is regulated by insulin
True
True or false: GluT 1 has a high Km
False
True or false: The link reaction is cytoplasmic
False, it occurs on the inner mitochondrial membrane
True or false: Tarui disease is characterised by a lack of PFK
True
True or false: Pyruvate dehydrogenase deficiency is a sex-linked condition
True
True or false: Hexokinase and phosphofructokinase generate ATP
False. They use it up
True or false: Hexokinase is the key regulatory enzyme of glycolysis
False, PFK is the key regulator
True or false: The link reaction requires pyruvate dehydrogenase
True
Which process occurs in the cytoplasm?
A) Glycolysis
B) Link reaction
C) Krebs cycle
D) Electron transport chain
A) Glycolysis
Which process occurs on the mitochondrial membrane?
A) Glycolysis
B) Link reaction
C) Krebs cycle
D) Electron transport chain
B) Link reaction
Which process occurs in the mitochondrial matrix?
A) Glycolysis
B) Link reaction
C) Krebs cycle
D) Electron transport chain
C) Krebs cycle
During the Krebs cycle, what kind of reaction transfers energy to NAD+ and FAD+?
Redox
During the Krebs cycle, how many steps directly produce ATP?
1
How many ATP are produced, directly or indirectly, from one cycle of Krebs?
12
How many ATP are produced by each NADH formed during Krebs?
3
How many NADH are produced during Krebs?
3
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