Metabolism 2

Question 1

what is glycolysis

Answer 1

ATP production from glucose

Question 2

what are hexokinases

Answer 2

enzymes that phosphorylate hexose sugars

Question 3

what is the the significance of having hexokinases with different affinities

Answer 3

different affinities are found in specific tissues
high affinity hexokinases= muscle rbc and brain
Low affinity hexokinases = liver

Question 4

why does glucose need to be phosphorylated

Answer 4

glucose is phosphorylated, it traps glucose within the cell (can no longer diffuse in and out of the cell)

Question 5

what is anaerobic respiration

Answer 5

respiration in the absence of oxygen (using electron acceptors)

Question 6

what happens in glycolysis

Answer 6

glucose -> glucose 6P (use 1xatp) -> fructose 6P -> fructose 1,6bP (use 1xATP) -> pyruvate (produce 1x NADH, 2x ATP)

Question 7

how is pyruvate broken down

Answer 7

lactate dehydrogenase enzyme
NADH-> NAD+
formation of lactic acid

Question 8

what are two potential pathways fructose

Answer 8

1. production of pyruvate

2. production of glycerol 3p (lipogenesis)

Question 9

what are the three pathways pyruvate can take

Answer 9

1. lactate
2. oxidation/biosynthesis in mitochondria
3. protein production

Question 10

where does oxidative phosphorylation occur

Answer 10

in the mitochondria

Question 11

how is the mitochondria adapted to the function it performs

Answer 11

double membraned
outer membrane contains transport proteins that enable the shuttling of pyruvate from the cytosol

inner membrane has electron transport chain and ATP synthase

inner membrane is arranged into folds (cristae) that increase the SA:Vol

Question 12

what is the general role of NADH and FADH in energy metabolism

Answer 12

carry electrons (reducing power) from catabolic reactions to the site where ATP is synthesised in mitohondria

Question 13

why do people lose weight when they have cancer

Answer 13

cancer cell types use glucose anaerobically even when oxygen is present (Warburg effect). Because this is an inefficient process, they need to use glucose at a very high rate.

Question 14

how is acetyl coA formed from carbohydrates

Answer 14

carbohydrates broken down to glucose.
undergoes glycolysis to pyruvate.
pyruvate dehydrogenase catalyses formation of acetyl coA

Question 15

how is acetyl coA formed from glycerol

Answer 15

undergoes glycolysis to pyruvate. (1xATP and 1xNADH)

pyruvate dehydrogenase catalyses formation of acetyl coA (NADH byproduct)

Question 16

how is acetyl coA formed from fatty acids

Answer 16

b-oxidation of fatty acids (FADH2 and NADH byproducts) forming either

1. pyruvate
2. acetyl coA
3. directly Citric acid cycle

Question 17

how is energy produced from proteins

Answer 17

AA broken down (NH3 byproduct) to either

1. pyruvate
2. acetyl coA
3. directly Citric acid cycle

Question 18

how do acetyl coA and NADH form inside mitochondria

Answer 18

pyruvate cross membrane and into matrix

1. carboxyl group removed from pyruvate. (CO2 byproduct). Left w/ two-carbon molecule (called acetyl)
2. acetyl bonds ith CoA

Question 19

what is the role of coA in energy metabolism

Answer 19

CoA is sometimes called a carrier molecule, and its job here is to carry the acetyl group to the citric acid cycle

Question 20

how is acetyl coA formed from fatty acids

Answer 20

1. Activation and membrane transport of free fatty acids by binding tocoenzyme A.
2. Oxidation of the beta carbon to a carbonyl group.
3. Cleavage of two-carbon segments resulting inacetyl-CoA.
   (each cycle of b-oxidation = 1xAcetylCoA and 1x FADH2 and 1x NADH)

Question 21

why do we need amino acids

Answer 21

synthesis of:
proteins (structural, catalytic, signalling)
peptides (intra- and inter-cellular communication)

Question 22

why do we metabolise Amino acids

Answer 22

important sources of carbohydrates during fasting, trauma, sepsis

Question 23

what must happen to amino acids before they can be used for glucose/lipid synthesis

Answer 23

Amino acid needs to be deaminated (though transamination) which is excreted as urea

Question 24

why is nitrogen excreted as urea more than ammonia

Answer 24

It’s less toxic than ammonia and therefore requires less dilution and fluid excretion

Question 25

how are amino acids mtabolised

Answer 25

AA + ketoacid -(transaminase)-> ketoacid + AA
(where terminal carbon with the NH2 is attached to the variable group on the ketoacid)
(where terminal COOH on the ketoacid is attached to the variable group on the AA)

ketoacids are then used to produce energy and the amino acid is then used to produce ure .

Question 26

explain the TCA cycle

Answer 26

1. Oxalaocetate (4c) + acetyl coA (2c) -> citrate (6c) with coA as a byproduct. coA can then be recycled reform acetyl coA.
2. isomerised to isocitrate
3. Isocitrate
   dehydrogenase removed CO2 to form Ketoglutarate (1xNADH byproduct)
4. Ketoglutarate dehydrogenase removed CO2 to form Succinate (4C)
   (1xNADH, 1xGTP byproduct)
5. Succinate (4C) oxidised to oxaloacetate (4C)