Lipids and amino acids, intergration with metabolism Flashcards
where is a major site of amino acids degradation
the liver
what do proteolytic enzymes in the stomach and intestine produce
single amino acids and di- and tri- peptides which are absorbed into intestinal cells and released into the blood for absorption by other tissues
explain protein turnover
it is tightly regulated
it takes place at different rates
damaged proteins have to be removed
what would be produced when amino acids are broken down
ammonia because of the nitrogen, can be toxic at high concentration
what happens after the removal of alpha-amino groups
the remaining carbon skeletons are converted into major metabolic intermediates which can be converted to glucose or oxidised in the TCA cycle
explain ketogenic amino acids
degraded to acetyl-CoA or acetoacetyl-CoA
can give rise to ketone bodies or fatty acids
explain glucogenic amino acids
degraded to pyruvate or TCA cycle intermediates
can be converted into phosphoenolpyruvate and then into glucose
what is Alcaptonuria
degradation of phenylalanine and tyrosine is blocked
Maple syrup urine disease
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
phenylketonuria
phenylalanine accumulates in all body fluids
leads to severe mental retardation if untreated
therapy: low phenylalanine diet
what does fat intake without appropriate energy expenditure lead to
increase in number of adipocytes, more of this leads to obesity
what does control of energy balance depend on
genetically linked factors (such as protein messengers regulating appetit)
environmental factors (food abundance)
BMI equation
weight/height(squared)
what are some medical complications that come with being obese
diabetes
coronary heart disease
hypertension
stroke
arthritis
gall bladder disease
what is fat also required for
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
what fat-soluble vitamins are needed
A,D,E,K, absorption of these vitamins is closely linked to that of fat stored in the body
what is adrenocortical and sex hormones derived from
cholesterol
what are triglycerides used for
main storage form in adipose tissue
compact
-they are hydrophobic
-they have high energy yield per gram
structure of fatty acids
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)
what are the main products of digestion?
glycerol (readily absorbed in intestinal epithelial cells)
fatty acids
monoglycerides
where are fatty acids absorbed
into the mucosal cells of the intestine
-short and medium-chain fatty acids enter the portal blood
-longer chains are re-synthesized to triglycerides
what are fatty acids coated with
a layer of protein, phospholipids and cholesterol (Chylomicrons)
what happens to chylomicrons
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)
what lipolysis do
breakdown of lipids
what happens when a triacylglycerol is cleaved
release of fatty acids and glycerol
what happens before the oxidation of fatty acids to generate energy
they must be converted to CoA derivatives and this occurs in the cytoplasm
explain the carnitine shuttle
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
Beta oxidation
what are the 4 steps in each cycle
and what are the products in each cycle
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
P/O ratio
FADH2: 1.5
NADH + H+: 2.5
what is in a triglyceride
3 fatty acids and a glycerol
explain the breakdown of glycerol
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
another name for fatty acid synthesis
lipogenensis
where does de novo synthesis of fatty acids occur
mainly in liver, kidney, mammary glands, adipose tissue and brain
when does de novo synthesis of fatty acids occur
during excess energy intake
what happens when excess carbohydrates are taken in
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
what does it mean if lipogenesis is reductive
it requires electrons
lipogenesis overview (mechanism for converting carbohydrates into fat)
dietary starch—> glucose —-> pyruvate —> acetyl-CoA —> fatty acids —> triglycerides
postprandial
after food
-ongoing digestion
-most abundant energy sources
- blood glucose levels rise directly due to food source
post-absorptive
after the digestion is completed
-at least 3-5 hours after meal, typically overnight
-blood glucose maintained by liver glycogen
