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Metabolism & Energetics (Nutrition)

Terms in this set (28)

Steps of ATP Production
1. Glyclosis
2. TCA Cycle
3. Oxidative Phosphorylation
Metabolism
refers to all chemical reactions occurring within the body
Catabolism vs. Anabolism
CATABOLISM: break down complex molecules; exergonic (produces more energy than it consumes)

ANABOLISM: combines simple molecules into complex ones; endergonic (consumes more energy than they produce)
Adenosine Triphosphate (ATP)
energy currency; ADP + energy + P ---> ATP
Oxidation-Reduction or Redox Reactions
OXIDATION
-removal of electrons
-decrease potential energy
-dehydrogenation: removal of hydrogens
-FAD NAD transfer hydrogens
-Glucose oxidized

REDUCTION
-addition of electrons
-increase of potential energy
Mechanisms of ATP Generation
1. SUBSTRATE-LEVEL PHOSPHORYLATION:
transferring high-energy phosphate group from intermediate directly to ADP

2. OXIDATIVE PHOSPHORYLATION:
remove e-, pass them through e- transport chain to O2

3. PHOTOPHOSPHORYLATION:
chlorophyll containing plant cells
GluT Transporters
bring glucose into cell via facilitated diffusion

insulin increases their rate of entry into cells

glucose trapped in these cells after phosphorylated
Glucose Catabolism/Cellular Respiration
1. GLYCOLYSIS: anaerobic respiration, no O2 required

2. Formation of acetyl coenzyme A

3. KREBS CYCLE rxns

4. E- TRANSPORT CHAIN rxns
Glycolysis
Splits 6-carbon glucose into 2 3-carbon molecules of pyruvic acid (pyruvate)
Consumes 2 ATP but produces 4

10 enzymatically driven rxns

Fate of Pyruvic Acid depends on O2 availability:
-ANAEROBIC: O2 scarce; reduce to lactic acid, cori cycle can reverse back to pryuvic
-AEROBIC: pletiful O2; convert to acetyl coenzyme A
Cellular Respiration: formation of coenzyme A
Each pyruvic acid-->2-carbon acetyl group (1 CO2 as waste)-->attaches to coenzyme A-->acetyl coenzyme A

during this ea. pyruvic acid also loses 2 hydrogen atoms NAD+ reduced to NADH + H+
Cellular Respiration: The Krebs Cycle/Citric Acid Cycle
series of redox rxns in mitochondria matrix

2 decarboxylation rxns release CO2

Reduced coenzymes (NADH and FADH2) are the most important outcome

One molecule of ATP generated by substrate-level phosphorylation
Cellular Respiration: The E- Transport Chain
Series of electron carriers in inner mitochondrial membrane reduced and oxidized

As electrons pass through chain, exergonic reactions release energy used to form ATP

CHEMIOSMOSIS:
-Carriers act as proton pumps to expel H+ from mitochondrial matrix
-Creates H+ electrochemical gradient - concentration gradient and electrical gradient
-Gradient has potential energy - proton motive force
-As H+ flows back into matrix through membrane, generates ATP using ATP synthase


O2 final e- acceptor; forming H2O

in addition to krebs, 36-38 ATP formed
Glycogenesis
glucose storage; only carb stored in humans; Insulin stimulates hepatocytes and skeletal muscle cells to synthesize glycogen
Glycogenolysis
glucose release; Glycogen stored in hepatocytes broken down into glucose and released into blood
Via pancreatic hormone Glucagon (alpha cells)
Gluconeogenesis
stimulated by cortisol/glucagon; formation of glucose from proteins/fats
APOPROTEINS
proteins in outer shell of lipid, named by density ratio of lipids:proteins

1. CHYLOMICRONS
form in small intestine mucosal epithelial cells;
transport dietary lipids to adipose tissue

2. VERY-LOW-DENSITY LIPOPROTEINS
VLDLs; form in hepatocytes; transport endogenous lipids to adipocytes

3. LOW-DENSITY LIPOPROTEINS
LDLs, bad cholesterol; carry 75% of total cholesterol in blood; deliver to body cells for repair/synthesis, can deposit cholesterol in fatty plaques

4. HIGH-DENSITY LIPOPROTEINS
HDLs; good cholesterol; remove excess cholesterol from body cells/blood--deliver to liver for elimination
Sources of Cholesterol in Body
food, hepatocytes
What happens as total blood cholesterol increases?
Risk of coronary artery disease begins to rise

treated w. exercise/diet/drugs
How can lipids provide ATP?
by being oxidized, if ATP not needed lipid stored in adipose tissue
Major Function of Adipose Tissue
remove triglycerides from chylomicrons and VLDLs, store them until needed

98% of all body energy reserves
Lipolysis
Lipid Catabolism;
Triglycerides split into glycerol and fatty acids

Must be done in muscle/liver/adipose tissue to oxidize fatty acids

enhanced by epi/noriepinepherine
Lipogenesis
Lipid Anabolism;
liver cells/adipose cells synthesize lipids from glucose/amino acids

occurs when more calories consumed than needed for ATP production
Protein Catabolism
proteins from worn out cells broken down into amino acids; must be removed before entering krebs--deamination; ammonia--urea--urine
Protein Anabolism
ribosomes; humans must get 10 essential amino acids via diet through complete (beef, poultry, fish, eggs)/incomplete proteins(leafy greens, legumes, grains)
other 10 synthesized via transamination
Pivotal Molecules to Metabolism
GLUCOSE 6-PHOSPHATE:
-made shortly after glucose enters body
-synthesis of glycogen/nucleic acids, release of glucose, glycolysis

PYRUVIC ACID:
-aerobic--ATP
-anaerobic--lactic acid, alanine, glyconeogenesis

ACETYL COENZYME A:
-ATP low, O2 plentiful, most pyruvate will go to ATP production via this molecule
-entry into krebs
-synthesis of some lipids
BMI
(Mass x 703)/(height inches)^2
Minerals
inorganic elements occurring naturally in crust of earth

calcium, phosphorus, iron, iodine needed

excess ingestion of these eliminated

help regulate enzymatic reactions
Vitamins
organic nutrients required in small amounts to maintain growth/normal metablism

don't provide energy, most not synthesized by body

FAT SOLUBLE: ADEK
WATER SOLUBLE: BC
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