GI biochemistry

Question 1

gluconeogenesis

Answer 1

formation of glucose from precursors (AA, lactate, glycerol)

lactate- SM, anaerobic
AA-muscle, proteinolysis
Glycerol- TAG, lipolysis

Question 2

where is glycogen found

Answer 2

liver, muscle

Question 3

function of liver glycogen

Answer 3

broken down during meals to maintain BGL

Question 4

function of muscle glycogen

Answer 4

cannot be broken down to main BGL

Broken down by glycolysis and TCA to provide energy in physical activity

Question 5

Sources of blood glucose

Answer 5

Dietary, Gluconeogenesis, glycogenesis

Question 6

Structure of glycogen

Answer 6

polymer of glucose, a1-4 glycosidic bonds in chains

a1-6 glycosidic branching

Question 7

Can one glucose start a new Glycogen?

Answer 7

No
Glucose must add to an existing glycogen chain
need glycogen primer containing 4 glucose attached to glycogenin

Question 8

What must attached to glucose for it to add to glycogen chain

Answer 8

UDP

Question 9

Four enzymes involved in glycogen synthesis

Answer 9

Hexokinase (phosphorylates glucose)
Phosphoglucomutase (changes position of phosphate)
UDP glucose pyrophosphorylase (binds UDP)
glycogen synthase (UDP-glucose onto glycogen)

Question 10

Function of glycogen synthase and its limitations

Answer 10

adds UDP glucose to glycogen

can only add one at a time, can’t introduce branching, can’t start a new molecule

Question 11

What enzyme can start a1-6 glycosidic chains

Answer 11

transglycosylase (every 10 residues)

Question 12

Enzyme that catalyses glycogenolysis

Answer 12

glycogen phosphorylase

Question 13

Equation for glycogenolysis and what happens to products

Answer 13

glucose + Pi –> G-1-P + [glucose]n-1

G1P-> G6P

Question 14

Glycogenolysis in liver vs skeletal muscle

Answer 14

in liver, the G6P can be dephosphorylated to glucose - bloodstream

SM- G6P cannot be dephosphorylated

Question 15

what enzyme causes G1P to turn into G6P in glycogenolysis

Answer 15

phosphoglucomutase

Question 16

Precursors, energy source and location of gluconeogenesis

Answer 16

Lactate, AA, Glycerol
FA oxidation
mostly liver cells, some kidney

Question 17

reversible reaction enzymes of glycolysis

Answer 17

hexokinase
phosphofructokinase
pyruvate kinase

Question 18

four liver enzymes required for gluconeogenesis

Answer 18

Glucose -6-phosphostase
Fructose-1,6-phosphotase
PEP carboxykinase
Pyruvate carboxylase

Question 19

what is the Cori Cycle

Answer 19

when lactate is the precursor of gluconeogenesis

lactate carried to the liver, liver converts lactate to glucose and releases glucose

Question 20

what does glucagon signal

Answer 20

• Glucagon signals fasted state

Question 21

what does insulin signal

Answer 21

Insulin signals the fed state

Question 22

components of triglycerides

Answer 22

1 glycerol, 3FAs

Question 23

T/F most triglycerides have long chains and have rings

Answer 23

T- most have long FA chains

F- most are aliphatic (no rings)

Question 24

normal configuration of double bonds in FA

Answer 24

cis-kink

Question 25

which FA are solid and which are liquid @RT

Answer 25

up to 8= liquid | >8 solid

Question 26

effect of double bonds on Melting point of TAG

Answer 26

double bonds reduce MP

Question 27

Main products of FA digestion

Answer 27

glycerol, FA, monoglycerides

Question 28

what happens to short and medium chain FA

Answer 28

Enter portal circulation via stomach

Question 29

what happens to long chain FA and monoglycerides

Answer 29

combine to from Triglycerides

Question 30

where do chylomicrons go to once formed

Answer 30

lymph-blood stream- muscle and tissue

Question 31

what happens to chylomicrons at muscle and tissue

Answer 31

cleaved by lipoprotein lipase

Question 32

what must happen to FA before they can provide energy

Answer 32

Must be oxidated to acyl CoA in the cytoplasm Requires 2 ATP Further oxidation occurs in mitochondrial matrix (requires carrier)

Question 33

2 additional enzymes required for beta oxidation

Answer 33

enoyl - CoA Isomerase | 2,4 Dienoyl CoA reductase

Question 34

what happens in carnitine shuttle

Answer 34

acyl-CoA moves into mitochondrial matrix via conversion to CoA

Question 35

Where does Beta oxidation occur

Answer 35

Mitochondrial matrix

Question 36

products of beta oxidation

Answer 36

1FADH2 1 acetyl CoA 1NADH, H+ 1 fatty acyl-CoA

Question 37

P/O ratio

Answer 37

No of phosphate added onto ADP to create ATP divided by no of oxygen atoms consumed by oxidative phosphorylation to make water

Question 38

where are ketone bodies formed and what from

Answer 38

liver mitochondria | from acetyl CoA from Beta-oxidation

Question 39

what are ketone bodies important for

Answer 39

renal cortex and heart muscle

Question 40

Ketosis in Diabetes and starvation | how can ketosis be detected

Answer 40

acetyl CoA is converted to ketones which are acidic and lead to severe acidosis impairing CNS smell of acetone on breath

Question 41

Major site of AA degradation

Answer 41

Liver

Question 42

potential problem with breakdown of AA

Answer 42

produces NH3 and NH4 (toxic at high levels)

Question 43

where is urea formed

Answer 43

liver | excreted by kidneys

Question 44

Steps in the synthesis of urea

Answer 44

AA is converted to glutamic acid by transamination Glutamic acid to NH4 by deamination NH4 and aspartic acid make urea

Question 45

where does transamination occur | where does deamination occur

Answer 45

all tissues | liver

Question 46

Degradation of carbon skeleton

Answer 46

carbon skeletons converted to glucose or go to TCA cycle

Question 47

Ketogenic AA

Answer 47

Degraded to acetyl CoA or acetoacetyl CoA | Can make ketones or FA

Question 48

glycogenic AA

Answer 48

Degraded to pyruvate or TCA cycle intermediates | can be converted to glucose

Question 49

if the yield of Beta oxidation is C18 how many cycles was this

Answer 49

8 | 18/2=9, 9-1=8

Question 50

what is the FA precursor

Answer 50

malonyl CoA

Question 51

What is FA synthesis and where does it occur

Answer 51

lipogenesis | Brain, kidneys, mammary glands, liver, kidneys

Question 52

what happens when excess carbs are taken in

Answer 52

converted to FA and TAG in liver | transported in plasma bound to albumin to adipose tissue via VLDL for storage

Question 53

T/F Lipogenesis is an oxidative process

Answer 53

False | reductive-electrons required