Biochemistry of Metabolism Summary

Question 1

can fatty acids be used for gluconeogenesis?

Answer 1

yes

Question 2

true or false, some lipids contain phosphate groups, carbohydrates or proteins

Answer 2

true

Question 3

Lipid absorption is required for the absorption of some vitamins, true or false?

Answer 3

true

Question 4

what are the main storage form of lipids in the human body?

Answer 4

triglycerides

Question 5

what is the first step of catabolism?

Answer 5

lipolysis

Question 6

do fatty acids have to first be activated to acetyl-CoA in fat metabolism?

Answer 6

no

they have to be activated to acyl CoA

Question 7

where does activation occur in fat metabolism?

Answer 7

cytoplasm

Question 8

what is beta-oxidation?

Answer 8

the pathway for the breakdown of fatty acids

Question 9

where does beta oxidation occur?

Answer 9

in the mitochondrial matrix

Question 10

how many oxidation occur in beta-oxidation, Eg for a C14 fatty acid?

Answer 10

6
14/2 -1 = 6
For even numbered fatty acid (C2n), Number of oxidations = n-1

Question 11

How many steps are in each cycle of beta-oxidation?

Answer 11

4

Question 12

What are the products of each beta-oxidation cycle?

Answer 12

1 acetyl CoA
1 FADH2
1NADH + H+
1 fatty acyl CoA, shortened by 2 carbon atoms (goes on to restart cycle)

Question 13

what would be the products of the breakdown of a C14 fatty acid?

Answer 13

6 acetyl CoA
6 NADH + H+
6 FADH2

Question 14

Where are ketone antibodies formed and how?

Answer 14

formed in liver under fasting conditions from acetyl CoA and Beta-oxidation and diffuse into the blood

Question 15

what is the function of ketone antibodies? How do they do this?

Answer 15

sustain normal function during starvation via energy production and neurotransmitter synthesis
Converted back to acetyl CoA which enters TCA cyle

Question 16

name the 3 ketone bodies

Answer 16

Acetoacetate
D-3-hydroxybutyrate
Acetone (causes fruity breath)

Question 17

can ketone bodies act at sites distal to site of synthesis?

Answer 17

yes

Question 18

Ketone bodies are toxic to peripheral tissues which prefer glucose, true or false?

Answer 18

false

Question 19

ketone bodies can lead to ketoacidosis, true or false?

Answer 19

true

Question 20

what are the steps in fatty acid synthesis (eg insulin or glucagon)?

Answer 20

glucose used to generate Acetyl CoA
Acetyl CoA carboxylase converts acetyl CoA to malonyl CoA (regulated by nutrient/energy status)
Malonyl CoA = major fatty acid synthesis precursor

Question 21

what 2 substances stimulate acetyl CoA carboxylase in the conversion of acetyl CoA to Malonyl CoA?

Answer 21

Inulin (signals fed state)

Citrate (stimulates allosterically when Acetyl CoA and ATP are abundant)

Question 22

what 4 substances inhibit acetyl CoA carboxylase in the conversion of acetyl CoA to Malonyl CoA?

Answer 22

Palmitoyl CoA (when excess fatty acids)
AMP
Glucagon (in starved state)
Epinephrine

Question 23

is fatty acid synthesis reductive?

Answer 23

yes

Question 24

citrate transports acetyl groups from mitochondria to the cytoplasm, true or false?

Answer 24

true

Question 25

fatty acid synthesis is induced during conditions of glucagon-mediated glucose release, true or false?

Answer 25

false | induced in fed state

Question 26

what is the donor molecule of carbon atoms to a growing fatty acid?

Answer 26

Malonyl CoA

Question 27

what does the phrase "citrate stimulates allosterically" mean?

Answer 27

citrate binds to separate site on acetyl CoA carboxylase activating the catalytic activity when there is lots of citrate

Question 28

how is urea synthesised?

Answer 28

complex series of reactions in (mainly) the liver driven by ornatheen(urea/ornithine cycle)

Question 29

what is the purpose of the urea cycle?

Answer 29

method of dealing with excess nitrogen

Question 30

where are the nitrogen and carbon required for the urea cycle taken from?

Answer 30

1 nitrogen from free ammonium (toxic) 1 nitrogen from aspartic acid (aspartate) Carbon from CO2

Question 31

how are amino acids converted into urea and where does this happen?

Answer 31

removal of amino group > amino acid skeletons enter TCA cycle Occurs in the mitochondrial matrix

Question 32

what is the rate limiting step in glycogen breakdown?

Answer 32

phosphorylation of glycogen to glucose 1 phosphate via glycogen phosphorylase

Question 33

what are the 2 possible outcomes of glycogen breakdown?

Answer 33

glycolysis | conversion of glucose 6 phosphate to glucose > glucose transported into blood via GLUT2 transporter

Question 34

Does gluconeogenesis require ATP?

Answer 34

yes | requires hydrolysis of ATP

Question 35

what is the difference between glycolysis and gluconeogenesis?

Answer 35

gluconeogenesis requires 4 unique enzymes

Question 36

what substance allows TCA cycle in gluconeogenesis to proceed by accepting acetyl groups ?

Answer 36

oxaloacetate | synthesised in the mitochondria

Question 37

what is glycogenin?

Answer 37

protein that sits at the centre of a glycogen polymer and can bind up to 4 glucose molecules to start the formation of glycogen

Question 38

amino acids serve as precursors for gluconeogenesis, true or false?

Answer 38

true

Question 39

when are amino acids oxidised?

Answer 39

during the TCA cycle

Question 40

can glycogen synthase introduce new branches?

Answer 40

no

Question 41

what is liver glucose and muscle glycogen used for?

Answer 41

``` liver = blood glucose muscle = energy generation in muscle ```

Question 42

glucose has to be bound to UDP before it can be transferred onto glycogen, true or false?

Answer 42

true

Question 43

what does glucagon do?

Answer 43

inhibits glycogen synthesis and stimulates glycogen breakdown

Question 44

what does insulin do?

Answer 44

inhibits glycogen breakdown and stimulates glycogen synthesis

Question 45

glucagon inhibits gluconeogenesis, insulin stimulates it, true or false?

Answer 45

false | other way around