Lecture 19: Metabolism & Nutrition Flashcards
describe the fate of proteins
-Digested proteins are broken down into amino acids which are: Oxidized to produce ATP, or Used to synthesize new proteins
-Many proteins function as enzymes, in transportation, as antibodies, clotting blood, hormones, or part of muscle fibers
what is protein anabolism
creates new proteins by bonding together amino acids on ribosomes
what is protein catabolism
-For proteins to be used as energy: They must be converted into substances that can enter citric acid
cycle
-This conversion involves:
* Transamination
* Deamination
* Urea cycle
-Removal of amino group requires a coenzyme derivative of vitamin B6
-Cells oxidize amino acids to generate ATP via the Krebs cycle
describe transamination (protein catabolism)
-attaches amino group of amino acid to keto acid
-converts keto acid into amino acid: which then leaves mitochondrion and enters cytosol & is available for protein synthesis
-in transamination the amino group (-NH2) of one amino acid is transferred to a keto acid
describe deamination (protein catabolism)
-Removal of amino group and hydrogen atom: Generating a toxic ammonium ions in the liver
-Liver cells have enzymes that remove toxic ammonium ions by synthesizing urea: Through the urea cycle= Fairly harmless water-soluble compound excreted in urine
-Prepares amino acid for breakdown in citric acid cycle
-the amino group is removed and an ammonium ion is released
what happens in the urea cycle
it takes two metabolic waste products, ammonium ions and carbon dioxide and produced urea, a relatively harmless, soluble compound that is excreted in the urine
what are the key molecules at metabolic crossroads
Of the thousands of different chemicals in cells, glucose 6-phosphate, pyruvic acid, and acetyl coenzyme A are extremely important in metabolism
what pathways can it go from glucose 6-phosphate
- to glycogen (liver and muscle cells)
- to glucose (in blood)
- ribose 5-phospahte and NADPH -> DNA & RNA
- glycolysis (cytosol) and into pyruvic acid
what pathways can pyruvic acid go to
- anaerobic reactions with lactic acid (equillibrium)
- alanine (amino acid) (equillibrium) this is convergence of CHO and protein metabolism
- into the krebs cycle
- if low ATP & high O2-> through aerobic reactions in mitochondria into acetyl coenzyme A
what pathways can acetyl coenzyme A go to
- into the krebs cycle
- cholesterol
equilibrium with fatty acids with equillibrium with triglycerides & phospholipids
summarize glucose catabolism
complete oxidation of glucose (cellular respiration) is cheif source of ATP in cells; consists of glycolysis, krebs cycle, and electron transport chain. complete oxidationof 1 molecule of glucose yields maximum of 30 or 32 molecules of ATP
summarize glycolysis
conversion of glucose into pyruvic acid results in production of some ATP. reactions do not require oxygen
summarize krebs cycle
cycle includes series of oxidation-reduction reactions in which coenzymes (NAD+ & FAD) pick up hydrogen ions and hydride ions from oxidized organic acids; some ATP produced. CO2 and H2O are by-products. reactiosn are aerobic
summarize electron transport chain
third set of reactions in glucose catabolism: another series of oxidation-reduction reactions, in which electrons are passed from one carrier to the next; most ATP produced. reactions require oxygen (aerboic cellular respiration)
summarize glucose anabolism
some glucose is converted into glycogen (glycogenesis) for storage if not needed immediately for ATP production. glycogen can be reconverted to glucose (glycogenolysis). conversion of amino acids, glycerol, and lactic acid into glucose is called gluconeogenesis
summarize triglyceride catabolism
triglycerides are broken down into glycerol and fatty acids. glycerol may be converted into glucos (gluconeogenesis) or catabolized via glycolysis. fatty acids are catabolized via beta oxidation into acetyl coenzyme A that can enter krebs cycle for ATP production or be converted into ketone bodies (ketogenesis)
summarize triglyceride anabolism
synthesis of triglycerides from glucose and fatty acids is called lipogenesis. triglycerides are stored in adipose tissue
summarize protein catabolism
amino acids are oxidized via krebs cycle after deamination. ammonia resulting from deamination is converted into urea in the liver, passed into blood, and excreted in urine. amino acids may be converted into glucose (gluconeogenesis), fatty acids, or ketone bodies
summarize protein anabolism
protein synthesis is directed by DNA and utilizes cells’ RNA and ribosomes
what are metabolic adaptations
-Modification of body’s biochemical process to efficiently convert food into energy
-Metabolic regulation depends on: Chemicals in cells & Signals from the nervous and endocrine systems
-Some aspects of metabolism depend on time elapsed since the last meal
describe the absorptive state
-period following a mal when nutrient absorption is under way; lasts ~4 hours, three meals= 12 hour/day
-nutrients get to bloodstream, glucose is available for ATP formation
what are the hormonal regulation processes of metabolism in the absorptive state
-facilitated diffusion of glucose into cells, locations in most cells, stimulating hormone = insulin
-active transport of amino acids into cells, locations in most cells, stimulating hormone= insulin
-glycogenesis (glycogen synthesis), location in hepatocytes and muscle fibers, stimulating hormone= insulin
-protein synthesis, location in all body cells, stimulating hormones= insulin/ thyroid hormones/ and insulinlike growth factors
-lipogenesis (triglyceride synthesis), location in adipose cells and hepatocytes, stimulating hormone= insulin
what are the metabolic pathways in the absorptive state
describe the post absorptive state
-Complete absorption of nutrients from GI tract (SI)
-Energy needs are met by fuels already in the body – internal energy reserves: Remaining 12 h
-Normal blood glucose levels are maintained due to breakdown of nutrient stores– glycogen, fat, and gluconeogenesis
