Proteins and Amino Acids (F1 8/12) Flashcards
1
Q
LO’s
A
- Describe the difference between essential and non-essential amino acids
- Describe the difference between glucogenic and ketogenic amino acids and their relationship to intermediary metabolism
- Describe the production of nitrogenous waste
2
Q
Not a component of the electron transport chain:
- ATP synthase
- Co Enzyme Q
- Cytochrome bc1
- Cytochrome c oxidase
- NADH dehydrogenase
A
- ATP synthase: not part of the electron transport chain, even though it is AKA complex 5.
3
Q
The enzyme complex that controls oxidative decarboxylation:
- Pyruvate dehydrogenase
- Pyruvate kinase
- Hexokinase
- Phosphofructokinase
- Succinyl dehydrogenase
A
- Pyruvate dehydrogenase: this converts pyruvate into acetyl coA. The reaction is pyruvate + CoA + pyruvate dehydrogenase = CO2 + Acetyl CoA + NADH.
- Since this happens twices for one glucose, 2 NADH are made, which will go on to make 6 ATP.
4
Q
The location of the TCA / Krebs cycle:
- Cytoplasm
- Intermembrane space of the mitochondria
- Mitochondrial matrix
- Mitochondrial cristae
- Peroxisome
A
- Mitochondrial matrix
5
Q
Cyanide inhibits what component of the electron transport chain?
- Inhibition of the transfer of electrons from complex IV to O2
- Inhibition movement of protons through Complex V
- Uncouples Proton motive force
- Inhibits transfer of electrons from NADH
- Inhibits transfer of electrons from FADH2
A
Inhibition of the transfer of electrons from complex IV to O2. If O2 doesn’t act as a final acceptor, the chain is halted and there is no electrochemical gradient maintained. Remember complex 5 is ATP synthase, and is not part of the chain of electron transfer.
6
Q
What are the three steps in getting energy from food?
A
- Hydrolysing the food: proteins to amino acids; carbohydrates to monosaccharides and fats to glycerol/fatty acids.
- Converting the monomers to Acetyl CoA
- Oxidising Acetyl CoA to produce energy.
7
Q
What does an amino acid look like?
A
A carbon atom, with a hydrogen atom, a NH2 group, a R group and a COOH group.
8
Q
How is a peptide bond formed?
A
The OH of the COOH group of one amino acid, and the H of NH2 group of another acid form H2O.
9
Q
Amino Acid Metabolism Overview
A
- Eat protein
- Broken down into amino acids in stomach and small intestine.
- Amino acids in blood, absorbed into cells.
- Amino acids used by cell to make proteins; nitrogen containing compounds like DNA; or the amine group can be removed, and the resulting carbon skeleton can be oxidised to release energy.
- The amine waste is converted to urea, which is non-toxic, and is removed in urine.
10
Q
From which three sources does your body acquire amino acids?
A
- Diet
- Degrading own tissue proteins
- Makin its own amino acids, called de novo synthesis. The amino acids the body can make are called non-essential. (Essential amino acids must be obtained from diet).
11
Q
What can amino acids be used to make?
A
- hormones
- neurotransmitters
- cytochromes: a type of protein
- cellular proteins
- haemoglobin
- melanin
- nucleotides
12
Q
How are amino acids converted into a sources of energy in the fed state?
A
- They can incorporated into nitrogen containing compounds.
- They can be converted into proteins in skeletal muscle or liver.
- In the liver they can also be converted into pyruvate. Then they can become glucose and stored as glycogen. Or they can be converted into Acetyl CoA from pyruvate. Then they can become fatty acids, TAG, VLDL.
13
Q
What is the Amino Acid Pool
A
- There is no specific storage site for amino acids in the body
- Instead there is a amino acid pool in the blood circulation.
- The amino acid pool has nitrogen balance. In healthy people, the nitrogen intake = nitrogen excretion.
- Positive nitrogen balance is when your nitrogen intake is greater than nitrogen excretion. This is found in pregnant ladies, as nitrogen is needed for the fetus, and in children for growth.
- Negative nitrogen balance, when less nitrogen input than output. It is caused by low protein intake and starvation.
14
Q
Amino Acid Catabolism/ breakdown
A
- Excess amino acids are catobalised/ broken down to release energy.
- The main site of amini acid breakdown is the liver.
- To release energy from amino acids the amine group must first be removed. This leaves the carbon skeleton. To remove the amine group, two linked, enzyme steps happen:
- Transamination: firstly tranamination happens in the cytosol. The amino group is transferred to something called alpha-ketoglutarate, and turns it into glutamate. Whats left of the amino acid is called alpha-keto-acid. This reaction is catalysed by aminotransferases.
- Oxidative deamination: the amino group we added is removed, so glutamate goes back to alpha-ketoglutarate, and ammonia is formed. This is catalysed by glutamate dehydrogenase.
15
Q
Alpha-ketoacid metabolism
A
- The alpha-ketoacids are made in transamination, along with glutamate.
- Alpha-ketoacids can be glucogenic or ketogenic.
- The carbon skeletons of glucogenic amino acids are converted to pyruvate or TCA cycle intermediates (these can acts as substrates of gluconeogenesis).
- The carbon skeletons of ketogenic amino acids are converted to acetoacetate or a precursor of acetoacetate, acetyl CoA or acetoacetyl CoA
- Glucogenic and ketogenic pathways converge forming seven intermediate products:
- PYRUVATE
- ACETYL CoA
- ACETOACETATE
- a-KETOGLUTARATE
- SUCCINYL CoA
- FUMARATE
- OXALOACETATE
