Lipids and amino acids, intergration with metabolism

Question 1

where is a major site of amino acids degradation

Answer 1

the liver

Question 2

what do proteolytic enzymes in the stomach and intestine produce

Answer 2

single amino acids and di- and tri- peptides which are absorbed into intestinal cells and released into the blood for absorption by other tissues

Question 3

explain protein turnover

Answer 3

it is tightly regulated
it takes place at different rates
damaged proteins have to be removed

Question 4

what would be produced when amino acids are broken down

Answer 4

ammonia because of the nitrogen, can be toxic at high concentration

Question 5

what happens after the removal of alpha-amino groups

Answer 5

the remaining carbon skeletons are converted into major metabolic intermediates which can be converted to glucose or oxidised in the TCA cycle

Question 6

explain ketogenic amino acids

Answer 6

degraded to acetyl-CoA or acetoacetyl-CoA
can give rise to ketone bodies or fatty acids

Question 7

explain glucogenic amino acids

Answer 7

degraded to pyruvate or TCA cycle intermediates
can be converted into phosphoenolpyruvate and then into glucose

Question 8

what is Alcaptonuria

Answer 8

degradation of phenylalanine and tyrosine is blocked

Question 9

Maple syrup urine disease

Answer 9

degradation of valine, isoleucine, and leucine is blocked
urine smells like maple syrup
can cause mental and physical retardation
this can be prevented by diet

Question 10

phenylketonuria

Answer 10

phenylalanine accumulates in all body fluids
leads to severe mental retardation if untreated
therapy: low phenylalanine diet

Question 11

what does fat intake without appropriate energy expenditure lead to

Answer 11

increase in number of adipocytes, more of this leads to obesity

Question 12

what does control of energy balance depend on

Answer 12

genetically linked factors (such as protein messengers regulating appetit)

environmental factors (food abundance)

Question 13

BMI equation

Answer 13

weight/height(squared)

Question 14

what are some medical complications that come with being obese

Answer 14

diabetes
coronary heart disease
hypertension
stroke
arthritis
gall bladder disease

Question 15

what is fat also required for

Answer 15

energy

essential fatty acids, some polyunsaturated fatty acids can not be made by the body (linoleic acids, arachidonic acid)
deficiencies can lead to membrane disorders, increase skin permeability, mitochondrial damage

Question 16

what fat-soluble vitamins are needed

Answer 16

A,D,E,K, absorption of these vitamins is closely linked to that of fat stored in the body

Question 17

what is adrenocortical and sex hormones derived from

Answer 17

cholesterol

Question 18

what are triglycerides used for

Answer 18

main storage form in adipose tissue
compact
-they are hydrophobic
-they have high energy yield per gram

Question 19

structure of fatty acids

Answer 19

mainly straight chain
Aliphatic (no rings)
Usually contain an even number of C atoms (2-20 or more)
Branched chains and odd numbers of C are rare
fatty acids: can be saturated(no double bonds) or unsaturated (one double bond) or poly saturated (several double bonds)

Question 20

what are the main products of digestion?

Answer 20

glycerol (readily absorbed in intestinal epithelial cells)
fatty acids
monoglycerides

Question 21

where are fatty acids absorbed

Answer 21

into the mucosal cells of the intestine
-short and medium-chain fatty acids enter the portal blood
-longer chains are re-synthesized to triglycerides

Question 22

what are fatty acids coated with

Answer 22

a layer of protein, phospholipids and cholesterol (Chylomicrons)

Question 23

what happens to chylomicrons

Answer 23

they enter the lymph, then the bloodstream

at muscle and adipose tissue, chylomicrons are attacked and cleaved by lipoprotein lipases

once this has happened, fatty acids are: -resynthesized into triacylglycerols (in adipose tissue, for storage)
- oxidised to provide energy (in muscle)

Question 24

what lipolysis do

Answer 24

breakdown of lipids

Question 25

what happens when a triacylglycerol is cleaved

Answer 25

release of fatty acids and glycerol

Question 26

what happens before the oxidation of fatty acids to generate energy

Answer 26

they must be converted to CoA derivatives and this occurs in the cytoplasm

Question 27

explain the carnitine shuttle

Answer 27

in the cytoplasm, fatty acids are transferred from Acyl-CoA to carnitine
Acyl-carnitine transporterin inner membrane:
* facilitates antiport of acyl-carnitine into themitochondrion andcarnitine out
* Important for regulation offatty acid oxidation
* Net result: acyl-CoAlocated in mitochondrialmatrix

Question 28

Beta oxidation
what are the 4 steps in each cycle
and what are the products in each cycle

Answer 28

The cycle of reactions is in the mitochondrial matrix
the 4 steps are:
oxidation
hydration
Oxidation
Thiolysis
the products are:
An acetyl-CoA
1 FADH2
1 NADH+ H+
1 fatty acyl-CoA, shortened by 2 carbon atoms

Question 29

P/O ratio

Answer 29

FADH2: 1.5
NADH + H+: 2.5

Question 30

what is in a triglyceride

Answer 30

3 fatty acids and a glycerol

Question 31

explain the breakdown of glycerol

Answer 31

activated to glycerol-3-phosphate by glycerol kinase (presented in the liver and kidney but absent from adipose tissue, skeletal and heart muscle)

dehydrogenated to dihydroxyacetone phosphate

Question 32

another name for fatty acid synthesis

Answer 32

lipogenensis

Question 33

where does de novo synthesis of fatty acids occur

Answer 33

mainly in liver, kidney, mammary glands, adipose tissue and brain

Question 34

when does de novo synthesis of fatty acids occur

Answer 34

during excess energy intake

Question 35

what happens when excess carbohydrates are taken in

Answer 35

conversion to fatty acids and triglycerides in the liver
free fatty acids are transported in plasma-bound albumin
triglycerides formed in the liver are transported to adipose tissue by VLDL for storage

Question 36

what does it mean if lipogenesis is reductive

Answer 36

it requires electrons

Question 37

lipogenesis overview (mechanism for converting carbohydrates into fat)

Answer 37

dietary starch—> glucose —-> pyruvate —> acetyl-CoA —> fatty acids —> triglycerides

Question 38

postprandial

Answer 38

after food
-ongoing digestion
-most abundant energy sources
- blood glucose levels rise directly due to food source

Question 39

post-absorptive

Answer 39

after the digestion is completed
-at least 3-5 hours after meal, typically overnight
-blood glucose maintained by liver glycogen