Biochemistry

Question 1

Glycogenesis

Answer 1

Synthesis of glycogen from glucose

Question 2

Glycogenolysis

Answer 2

Breakdown of glycogen to form glucose

Question 3

Gluconeogenesis

Answer 3

New synthesis of glucose from metabolic precursors

Question 4

Glycogen

Answer 4

Main storage of glucose in liver and muscle cells

Question 5

Liver glycogen

Answer 5

Broken down between meals and released to maintain blood glucose levels for red blood cells and brain

Question 6

Muscle glycogen

Answer 6

Not available for maintenance of blood glucose levels

Provides energy via glycolysis and Krebb’s Cycle during bursts of physical activity

Question 7

Primary source of glucose overnight when hepatic glycogen is depleted

Answer 7

Gluconeogenesis

Question 8

Glycogen structure

Answer 8

Polymer of glucose molecules
Joined by alpha 1-4 carbon glycosidic bonds
Branches joined with 1-6 carbon glycosidic link

Question 9

Glycogenin

Answer 9

Protein covalently attached to a glycogen primer

Primer contains at least 4 glucose residues

Question 10

UDP glucose

Answer 10

Activated form of glucose

Question 11

Glycogen synthase

Answer 11

Synthesises glycogen from UDP glucose
Adds one glucose molecule to glycogen at a time
Can only extend chains of glycogen , not introduce branches

Question 12

Rate limiting enzymes of glycogenesis

Answer 12

Glycogen synthase

Question 13

Transglycosylase

Answer 13

Branching enzymes, introducing 1-6 glycosidic branches into glycogen

Question 14

Glycogenolysis is catalysed by

Answer 14

Glycogen phosphorylase

Question 15

Glycogenolysis in liver

Answer 15

Glucose 6p can be de-phosphorylated and resulting glucose enters blood stream

Question 16

Glycogenolysis in skeletal muscle

Answer 16

Glucose 6p cannot be de-phosphorylated but instead used to provide energy via glycolysis and TCA cycle

Question 17

Cori Cycle

Answer 17

Lactate as a precursor for gluconeogenesis
Blood transports lactate to liver
Liver converts lactate back to glucose
Glucose released into blood stream

Question 18

Carnitine shuttle

Answer 18

In cytoplasm, fatty acids transferred from Acyl-CoA to carnitine
Means Acyl-CoA ends up located in mitochondrial matrix

Question 19

B oxidation

Answer 19

Cycle of reactions
Four steps
Products = acetyl CoA, FADH2, NADH +H+ fatty acyl CoA

Question 20

High AMP or ADP

Answer 20

Low energy

Question 21

High ATP

Answer 21

High energy

Question 22

Fructose 2,6-biphosphate

Answer 22

High in fed state

Low in starved stat

Question 23

Fatty acids with up to 8 C atoms are

Answer 23

liquid at room temp

Question 24

Plant fats are liquids at room temp because

Answer 24

They contain large amounts of unsaturated fatty acids

Question 25

Animal fats are solid at room temp because

Answer 25

They contain mostly palmitic and stearic acid

Question 26

Main products of fat digestion

Answer 26

Glycerol Fatty Acids Monoglycerides

Question 27

Chylomicrons

Answer 27

Enter lymph, then blood stream | At muscle and adipose tissue they are attacked and cleaved

Question 28

Ketone bodies

Answer 28

Formed in liver mitochondria Diffuse into blood stream and to peripheral tissues Important molecules of energy metabolism for heart muscle and renal cortex Converted back to acetyl-CoA which enters TCA cycle

Question 29

Ketosis in starvation

Answer 29

``` Oxaloacetate consumed for gluconeogenesis Fatty acids oxidised to provide energy Acetyl-CoA converted to ketone bodies High levels in blood Too much for extrahepatic tissue Ketone bodies are moderate acids Accumulation leads to severe acidosis Impairs tissue function, CNS Smell of acetone can be detected in breath ```

Question 30

Main site of amino acid degradation

Answer 30

Liver

Question 31

Nitrogen

Answer 31

``` Some amino acids contain nitrogen Amino acid breakdown produces NH3 and NH4+ (ammonia and ammonium ions) NH4+ is toxic at high concentrations Build up = problem Need a safe way of excreting ```

Question 32

Nitrogen containing excretory molecules

Answer 32

Urea (80%, formed in liver) Uric acid Creatinine NH4+

Question 33

Synthesis of Urea, 3 steps

Answer 33

Transamination De-amination Urea Cycle

Question 34

Transamination

Answer 34

Aminotransferases move amino group from alpha amino acid to alpha keto acid Gives glutamate Amino group of glutamate is transferred to pyruvate = alanine OR to glutamate = glutamine

Question 35

Alanine and glutamine

Answer 35

major carriers of nitrogen in blood to liver

Question 36

De-amination

Answer 36

In liver | Amino group of glutamate is converted to free ammonium ion

Question 37

Degredation of carbon skeletons

Answer 37

After removal of alpha amino group the remaining carbon skeletons are converted to metabolic intermediates

Question 38

Ketogenic amino acids

Answer 38

Degraded to acetyl-CoA | Can give rise to ketone bodies of fatty acids

Question 39

Glucogenic amino acids

Answer 39

Degraded to pyruvate | Can be converted into phosphoenolpyruvate and then glucose

Question 40

Alcaptonuria

Answer 40

Degradation of phenylalanine and tyrosine is blocked

Question 41

Maple syrup urine disease

Answer 41

Degredation of valine, isoleucine and leucine is blocked Urine smells like maple syrup Mental and physical retardation Prevented by appropriate diet

Question 42

Phenylketonuria

Answer 42

Phenylalanine accumulates in all body fluids Leads to severe mental retardation if untreated Therapy = low phenylalanine diet

Question 43

Defect in urea cycle enzyme

Answer 43

Accumulation of urea cycle intermediates Glutamine levels increase Elevated levels of ammonia in blood, toxic Treat = low protein diet, drugs removing nitrogen