Week 15: lipids and amino acids, integration of metabolism Flashcards
Where is the site major of amino acid degradation?
LIVER
what happens to amino acids that are not used?
degraded
What breaks down amino acids in the stomach and intestine for adsorption?
proteolytic enzymes
to di and tri peptides
What absorbs amino acids?
intestinal cells and released into the blood for absorption by other tissues.
Is there a storage form of amino acids?
no
What is another way that the body generates free amino acids that it needs to deal with?
protein turnover
What is protein turnover?
forms a very important part of the intercellular quality control process
What is protein turnover important for?
rapid changed, damaged proteins have to be removed
Amino acids contains a amide side chain but where else can N be found?
some amino acids also contain nitrogen in the side chain
What is produced when amino acids are broken down?
NH3 (ammonia) & ammonium NH4+
Is NH4+ toxic?
YES
What can happen if there is a build up of Nitrogen compounds?
Leads to severe problems
needs a safe way of exerting excess Nitrogen
What are you left with after removal of alpha-amino group (N)?
carbon skeleton
What is the remaining carbon skeleton converted to after removal of alpha-amino group?
major metabolites intermediates
What can the major metabolic intermediates then be converted to?
converted to glucose or oxidised in the TCA cycle
What are the 2 categories of amino acids?
ketogenic AA
Glucogenic AA
What can ketogenic AA be degraded to?
- Degraded to acetyl-CoA or acetoacetyl-CoA
- Give rise to ketone bodies or fatty acids
What can glucogenic AA be degraded to?
- Degraded to pyruvate or TCA cycle intermediates
- Can be converted into phosphoenolpyruvate and then into glucose
What 3 disorders that effects amino acid degredation?
Alcaptonuria
Maple syrup Urine disease
Phenylketonuria
What type of amino acids are phenylalanine and tyrosine?
ketogenic and glucogenic AA
What enzymes are degraded and blocked in maple syrup urine disease?
degradation of valine, isoleucine
blockage of leucine
What enzymes are accumulates in Phenylketonuria?
phenylalanine in body fluids
What enzymes are degraded and blocked in Alcaptonuria?
phenylalanine degraded
tyrosine blocked
What is the prevention for maple syrup urine disease?
prevented by appropriate diet
What is the therapy for phenylketonuria?
Low phenylalanine diet
What happens when you have increased fat intake without appropriate energy expenditure?
increased number of adipocytes
more fat in adipocytes
obesity
How do you control energy balance in the body?
- Genetically linked factors (protein messengers regulating appetite
- Environmental factors (food abundance, fashionable foods)
What are medical complications of being obese?
diabetes type 2 coronary heart disease hypertension stroke arthritis gall bladder disease
What is fat required for?
- As an energy source
- For essential fatty acids (some polyunsaturated fatty acids can not be made by the body)
What can a deficiency in essential fatty acids lead to?
membrane disorders, increased skin permeability, mitochondrial damage
What are fat-soluble. vitamins stored in fat?
A, D, E , K
What can happen id you don’t have enough fat to store vitamins?
a secondary deficiencies can occur
efficiency in the vitamins
What is the building block of steroids?
cholesterol
Does cholesterol contain fatty acids?
Not usually
occur in natural fats
What is the chemical structure of cholesterol?
rigid structure, multiple rings, in cell membranes
changes membrane properties
What hormones is cholesterol an important pre-cursor for?
adrenocortical and sex hormones (progesterone, testosterone & oestrogen)
What is another form of fats that are needed to try and digest a meal?
Triglycerides
triacylglycerols
What is the main energy storage form in adipose tissue?
triglycerides
Why are triglycerides used as storage in the adipose tissue?
-Very compact
the acyl groups mean they are hydrophobic and don’t require water so become very compact
leads to a high energy yield per gram
What is the features of a fatty acid structure?
mainly straight chains
aliphatic (no rings)
usually an even number of c atoms (2-120 or more)
can be… saturated, unsaturated, polyunsaturated
Do fatty acids usually have odd branched chains?
NO, usually even no. C atoms & no branches
What configuration are double bonds normally in?
cis/trans
What is the main products of fat digestion?
glycerol
fatty acids
monoglycerides (1 fatty acid + 1 glycerol)
Where is glycerol readily absorbed into?
intestinal epithelial cells
Where are fatty acids and monoglycerides absorbed into?
mucosal cells of intestine
Where do short and medium length fatty acids enter after being absorbed into mucosal cells?
enter portal blood
Where do long chain fatty acids and monoglycerides enter after being absorbed into mucosal cells?
Are re-synthesised to triacyglycerides in the mucosal cell
What are the monoglycerides and fatty acids coated with to form?
layer of protein, phospholipid, cholesterol to form
Chylomicrons (now can facilitate transport)
Where does the chylomicrons enter after synthesis
the lymph system then blood stream
What happens to chylomicrons when it reaches muscle and adipose tissue?
- Attacked and cleaved by lipoprotein lipases
- Release free fatty acids
What are the free fatty acids re-synthesised to in adipose tissue, for storage?
triacyglycerols
What does the stored triacyglycerols get oxidised to to provide?
ENERGY
outcome depends on energy needs
What is lipopolysis?
breakdown of lipids
Can fatty acids be straight oxidised to generate energy?
NO, have to be converted to CoA derivatives.
What is CoA role on fatty acid?
Forms as an activator, makes chains more active
Does the fatty acid+ CoA–> acyl CoA require energy?
YES 2 ATP
What does fatty acid bind to and what does it produce in order to be oxidised?
fatty acid+ CoA –> acyl-CoA
Where does the fatty acid pick up the CoA?
cytoplasm
must go to the mitochondria via carrier mechanism for it to be oxidised
need to get to the matrix
In the cytoplasm, fatty acids are transferred from acyl-CoA to what?
carnitine
When Acyl-CoA transfers its fatty acids to carnitine, what does carnitine become?
Acyl-carnitine and enters the matrix
When the acyl-carantine enters the mitochondrial matrix what can now occur?
beta oxidation
What is produced in the the beta-oxidation (cycle)?
1 acetyl-CoA
1FADH2
1NADH+ H+
1 fatty acyl-CoA, shortened by 2 carbon atoms
When does a free (second) CoA enter the beta oxidation (cycle)?
The last step added to 3-ketoacyl CoA
whhat are the 2 end products of the beta oxidation cycle?
acyl coA & acetyl CoA
What is the fate of acetyl-coA after beta oxidation?
TCA cycle
What produces more ATP, fatty acids or glucose?
FATTY ACIDS! 120ATP
Give and example of what a triglyceride is?
e.g 3 stearic acids bonded to a glycerol
What is glycerol?
the connector of the 3 fatty acids
How do you breakdown glycerol?
glycerol kinase activates the glycerol-3-phosphate
Where is the glycerol kinase present?
liver and kidney but not adipose tissue, skeletal and heart muscle
What is glycerol-3-phosphate dehydrogenated to?
dihydroxyacetone phosphate
DHAP
What can the DHAP be converted to (isomerism)?
G3P and enter glycolysis
What is the process of making fatty acids?
lipogenesis
when more energy is taken in than needed
Where does lipogenesis occur?
liver, kidney, mammary glands, adipose tissue & brain
What is the excess of carbohydrate converted to?
fatty acids and triglycerides in the liver
What are fatty acids then bound to in plasma? (excess of carbohydrate)
albumin
Where do triglycerides go after carbohydrate is converted to triglycerides?
triglycerides formed in the liver are transported to adipose tissue by VLDL for storage
What is VLDL?
very low density protein
transport triglycerides from liver to adipose tissue
Is lipogenesis reductive or an oxidative process?
reductive
electrons are required
What are the three states of your body in metabolism?
- Post prandial (after food)
- Post absorptive (after digestion is complete)
- Fast state (prolonged period of fasting)
