Lipid and amino acid metabolism Flashcards
What are lipids composed of
Carbon, hydrogen, oxygen
Common types of lipids
Triglyceride or neutral fat
Triglycerides can be removed from
Herbivores do not eat a lot of fat
Convert carbohydrates in excess to fat
Triglycerides can be removed from blood by liver and structurally altered
Lipolysis
Breakdown of fats
Triglycerides hydrolyzed to
1 glycerol
3 fatty acid chains
If there is a balance between carbohydrate and fat metabolism in triglyceredie metabolism
Most acetyl CoA produced by fatty acid metabolism goes through Krebs cycle
Route of triglyceride metabolism
Pyruvate → Acetyl CoA → Krebs Cycle
Pyruvate → glucose synthesis
Triglyceride metabolism steps
Glycerol catabolized to
dihydroxyacetone phosphate in cytoplasm
Enters glycolysis and is converted to pyruvate
Breakdown of fatty acids occurs in mitochondria
Beta oxidation
Acetyl CoA enters Krebs cycle
NADH and FADH2 enter the electron transport chain
Beta oxidation is
pathway in which a fatty acid chain is broken into acetyl CoA molecules
Triglyceride metabolism produces
FADH2 and NADH
Complete oxidation of what in triglyceride metabolism
Complete oxidation of one 18 carbon fatty acid chain is 148 ATP
Fat metabolization
Fat is more difficult to mobilize so is used as a reserve energy source
Lipids can be stored in fatty tissue to protect health when food supplies are low
When body cells need fatty acids for energy hormones such as epinephrine interact with adipose tissue
Epinephrine stimulates hydrolysis of triglycerides
Glycerol and fatty acids enter the bloodstream
Mobilized fatty acids form a lipoprotein with serum albumin in blood
Transported where they are needed
Glycerol is water soluble so dissolves in blood and is transported
Fatty acids stored in triglycerides are called on as energy sources from
By resting muscle and liver cells:
conserves the body’s glycogen stores and glucose for brain cells and red blood cells
What becomes the primary energy source during metabolsim
Fatty acids
What happens during Fasting metabolism
Level of glycolysis decreases
Reduced amount of oxaloacetate is synthesized
Oxaloacetate is used to make glucose
Lack of oxaloacetate reduces activity of Krebs cycle
More acetyl CoA is produced by fatty acid breakdown than can be processed through Krebs cycle
What happens to ketones during fasting
Excess acetyl CoA is converted into
ketone bodies in liver:
Acetoacetic acid, acetone, beta-
hydroxybutyric acid
Ketone bodies carried by blood to brain, heart and skeletal muscle
Ketone bodies can be oxidized for energy
Diabetes mellitus
Produces an imbalance in
carbohydrate and lipid metabolism
Not enough glucose enters cells to meet energy needs
Results in increased fatty acid metabolism
Excess acetyl CoA
Increase in ketone bodies in blood
Ketonemia
An elevated level of ketone bodies in blood
Ketosis
ketonemia, ketonuria, and
acetone breath existing
simultaneously
ketonuria
presence of ketone bodies in urine
Acetone breath
concentration of acetone in blood is so high it is expelled through lungs
Ketoacidosis
low blood pH due to elevated levels of ketone bodies
Triglyceride synthesis process
Excess energy-producing nutrients are converted to fatty acids and then to body fat
Conversion reactions occur in liver, adipose tissue and mammary glands
Fatty acid biosynthesis occurs in the cytoplasm
Fatty acid chains are built up 2 carbons at a time
Fatty acids then incorporated into triglycerides
Triglyceride synthesis is stored in and requires how much energy
Requires energy
Store in form of fat in adipose tissues
What can the liver do during triglyceride synthesis
Liver can modify body fats
Can lengthen or shorten fatty acid chains
Can saturate or unsaturate fatty acid chains
Most important function of amino acids
Building blocks for the synthesis of proteins
Amino acid pool is
total supply of amino acids in the body
digestion of food, degradation of tissue, and synthesis in the liver
Protein turnover
when body proteins are hydrolyzed and resynthesized
Amino acid metabolism
Amino acids in excess of immediate body requirements are not stored, but degraded
Nitrogen atoms are converted or excreted
Carbon skeletons are used for
Energy production
Synthesis of glucose
Conversion to triglycerides
The nitrogen of amino acids is either
Excreted
Used to synthesize other compounds
Bases for nucleotides, heme structures, neurotransmitters
Three stages to nitrogen catabolism
Transamination
Deamination
Urea formation
Transamination is and what happens during
Transamination – enzyme-catalyzed transfer of an amino group to a keto acid
Enzymes are called transaminases
Result is a new amino acid
Process occurs in mitochondria
Deamination is and what happens during
Deamination – process resulting in removal of an amino group
Ammonia (NH3),a keto acid, and NADH are produced
Keto acid can be used in:
Transamination reaction
Enter the Krebs cycle
Since ammonia is toxic most deamination reactions occur in the liver
Urea formation is and occurs in
Urea cycle occurs in the liver
Ammonia is converted to urea
Urea diffuses out of liver into blood
Kidneys filter urea out
Urea is excreted in urine
Uremia
Buildup of urea in blood
What can happen during liver and kidney failure
If kidney is diseased it may not excrete urea effectively
Uremia – buildup of urea in blood
High blood urea nitrogen (BUN) level
If liver is diseased it may not be converting ammonia to urea
Increased ammonia level
Low blood urea nitrogen level
If energy is not immediately needed during amino acid catabolism
Carbon skeletons can be converted to glucose or fat
What happens after transamination or deamination
After transamination or deamination
the remaining carbon skeleton is
degraded
Pyruvate, acetyl CoA, acetoacetyl CoA, or intermediates of Krebs cycle
Can be used to produce energy
Glucogenic amino acids
carbon skeleton is degraded to pyruvate or intermediate of Krebs cycle
Can be used to make glucose
Ketogenic amino acid
carbon skeleton is degraded to acetyl CoA or acetoacetyl CoA
Cannot be converted to glucose
Can be used to produce ketone bodies and fatty acids
Protein biosynthesis
Manufacture of new protein from nutrient building blocks important process
Cell function would halt without continued protein synthesis
Amino acids are joined by peptide bonds
Instructions for building proteins is contained in DNA
Amino acid biosynthesis
Body can synthesize non-essential amino acids
Key starting materials are intermediates of glycolysis and Krebs cycle
Body can readjust the relative proportions of amino acids to meet needs
Diet does not contain exact proportions required
Essential amino acids must be included in the diet
Stage 1 of starvation is
Body lowers basal metabolic rate
Needs less food for maintenance
To maintain blood glucose levels, body uses glycogen stores in liver
Depleted after several hours
Fat is catabolized to provide glycerol and fatty acids that can be used to produce glucose
Ketone body levels in blood rise
Glucose is synthesized from glucogenic amino acids
Hydrolysis of protein supplies the amino acids
Stage 2 of starvation includes
Change occurs that allows brain and other tissues to use ketones and glucose for energy
Stored fat is primary source of energy
Continues until fat reserves have been depleted
Normal body functions and survivability are not threatened until the fat stores are nearly depleted
Starvation stage 3 includes
Protein becomes main energy source
Glucose is synthesized from glucogenic amino acids
Liver and plasma proteins are used first
Next protein from GI tract, heart, skeletal muscles
Structures decrease in size
Decreased plasma proteins lead to changes in oncotic pressure
Fluid leaks into abdominal cavity causing distention – ascites
What happens to aniamls during starvation
Malnourished animals experience a negative nitrogen balance
Used muscle tissue to generate energy needed for vital metabolic functions
