ASU NTR 241 Chapters 7 and 8

Metabolism?

sum of all chemical and physical processes by which the body breaks down and builds up molecules

Chemical reactions require or release energy

Calorimeter?

measures a food's caloric content

Anabolism?

process of making larger, chemically complex molecules from smaller ones; Requires energy

Is critical for what?-Anabolism

growth, repair, maintenance, and synthesis of chemical products essential for human functioning

Catabolism?

breakdown of larger, complex molecules to smaller, more basic ones; Releases energy

What is broken down for repair or replacement-Catabolism?

Old cells or tissues

What does catabolism begin with?

digestion—chemical reactions break down proteins, lipids, carbohydrates

ATP potential energy stored?

high-energy phosphate bonds

What is ATP?

organic compound used by cells as a source of energy

What happens when ATP bonds are broken?

energy is released-keep cells functioning

Metabolic Pathways?

clusters of chemical reactions that occur sequentially to achieve a particular goal; "Networking" of metabolic pathways

Where does metabolic pathways occur?

specific part of a cell; limited to specific organs or tissues

Primary site for ATP production?

Mitochondria

What is water released as during dehydration synthesis?

by-product

Dehydration synthesis?

is an anabolic process; A large molecule is broken apart with the addition of water

Hydrolysis?

catabolic process

What happens when simple units combine during dehydration synthesis?

form larger, more complex molecules

Phosphorylation?

addition of a phosphate group to a compound

What happens when high-energy phosphate bonds in ATP are broken?

Energy is released

Phosphate is transferred to other molecules

What happens when glucose is phosphorylated?

it can be oxidized for energy or stored as glycogen

Oxidation−Reduction Reactions?

Molecules exchange electrons (hydrogen)- Exchange reactions occur together

What happens when a molecule donates an electron?

it is oxidized

What are coenzymes?

non-protein substances that enhance or are necessary for enzyme activity

Metabolic Enzymes?

mediate chemical reactions

What are cofactors?

minerals required for enzyme activity

What function as cofactors?

Iron, magnesium, and zinc

What functions as coenzymes?

FAD, FADH2, and vitamins

What is converted into glucose in the liver?

Fructose and galactose

What happens when glucose is transported to the liver?

1. Phosphorylated and metabolized for energy or stored as glycogen
2. Released into circulation for other cells to use as fuel or stored as glycogen (muscle tissue)
3. Converted to fatty acids, if glucose exceeds energy needs, and stored as triglycerides in adipose tissue

Glycolysis?

Occurs in the cytosol
Anaerobic reaction

What are fatty acids used for?

energy

Lipolysis?

dietary and adipose triglycerides are broken down by lipase to yield glycerol and three free fatty acids

What is glycerol converted into?

pyruvate, then to acetyl CoA for entry into the TCA cycle

What happens during B-oxidation of fatty acids?

1. Attached to albumin, fatty acids are transported to working cells in need of energy (muscle or liver cells)
2. Fatty acids must be activated by Coenzyme A before being shuttled across the mitochondrial membrane by carnitine
3. Long-chain fatty acids are broken down into two-carbon segments to form acetyl CoA

Why is there no metabolic pathway to convert cetyl CoA into pyruvate?

Cells cannot convert acetyl CoA to glucose

When does ketosis occur?

ketones (acidic) inappropriately lower blood pH

Ketones?

by-products of fat catabolism

When does ketoacidosis occur?

blood pH falls, further resulting in severe dehydration

What is protein saved for?

metabolic functions that cannot be performed by other compounds

What does the body use as fuel sourceS?

fat and carbohydrates

What is protein used for?

fuel primarily when total energy or carbohydrate intake is low

Where are amino acids transported?

Liver

Proteolysis?

dietary proteins are digested into amino acids or small peptides

What is Proteolysis made into?

proteins

What happens after amino acids transported into the liver?

Released into the blood for uptake by other cells for building and repair functions

What is excess dietary protein used for?

energy or stored as triglycerides

What happens during starvation?

the body turns to its own tissues for energy

High levels of ammonia?

toxic

What is ammonia from amino acid deamination used as?

nitrogen source for synthesis of nonessential amino acids

What does liver convert ammonia into?

less toxic urea

Alcohol is oxidized primarily in the liver by what enzymes?

Alcohol dehydrogenase (ADH)
Aldehyde dehydrogenase (ALDH)
Microsomal ethanol oxidizing system (MEOS)

First-pass metabolism?

small amount of alcohol is oxidized in the stomach, before being absorbed into the bloodstream

What does gastric ADH activity do?

Reduces alcohol absorption
Genetic differences in amount of activity

How long does liver oxidizes alcohol?

1 per hour

What happens during alcohol absorption?

Most is absorbed into the blood and transported to be oxidized by the liver

How does the constant rate of alcohol vary?

individual's genetic profile, state of health, body size, use of medication, and nutritional status

Where does excess alcohol go?

back into the blood

When can stored energy be used?

during times of sleep, fasting, or exercise

The body has no mechanism for?

storing amino acids or nitrogen

What is extra energy stored as?

Carbohydrate in limited amounts as liver and muscle glycogen
Fat (triglycerides) in unlimited amounts

Gluconeogenesis is from what?

glucogenic amino acids

Gluconeogenesis?

making new glucose from nonglucose substrates

What is the small amount of Gluconeogenesis called?

glycerol (triglyceride)

What does Gluconeogenesis do?

Maintains blood glucose during sleep, fasting, trauma, and exercise

Protein catabolism?

glucose production can draw on vital tissue proteins (skeletal and heart muscles and organ proteins)

Lipogenesis (de novo synthesis)?

making fat from nonfat substances such as carbohydrates, amino acids, and alcohol

What forms when fatty acids combine with glycerol?

triglycerides?

What happens when consuming excess calories?

acetyl CoA units form fatty acid chains

where does lipogenesis occur?

liver cells

Where does amine group come from?

transamination

What happens during amino acid synthesis?

The body makes the carbon skeleton of nonessential amino acids (NEAA)

When does the synthesis of NEAA occur?

only when the body has enough energy and nitrogen

What happens when essential amino acids cannot be synthesized?

must be consumed

What does insulin do?

Increases in the blood after a meal
Activates storage enzymes
Signals cellular uptake of glucose, fatty acids, and amino acids

Insulin is the?

primary anabolic hormone

What do the catabolic hormones do?

Trigger the breakdown of stored triglycerides, glycogen, and body protein for energy

What are the catabolic hormones?

Glucagon, epinephrine, and cortisol

What is anabolic state?

bloodstream is enriched with glucose, fatty acids, and amino acids

What happens to glycogen after saturated in the anabolic state?

remaining glucose is stored as triglycerides

What happens during anabolic state?

Glucose is stored as glycogen

How are fatty acids stored in the anabolic state?

adipose tissues

What happens to amino acids and carbo skeletons?

animo acids are deaminated and carbon skeletons are converted to fatty acids for storage as triglycerides

How do the cells react during fasting?

switch to using fatty acids as fuel to conserve glucose for brain and other cells that rely on glucose as fuel

What happens during fasting?

Liver glycogen is broken down, releasing glucose into the blood

What do ketones form during fasting?

acetyl CoA units are blocked from entering TCA cycle

what happens during glucose synthesis when fasting?

from glucogenic amino acids and glycerol

What happens to the blood glucose during starvation?

maintained to support brain and red blood cells

Metabolic reaction to starvation?

The body shifts to survival mode

What happens during starvation in the body?

Decline in activity, body temperature, and resting metabolic rate

What do the fatty acids become during starvation?

become primary fuel

what do the brain cells do during starvation?

start to use ketone bodies

What does the muscle protein supply during starvation?

glucose

B-vitamins

important for energy metabolism

coenzyme

a molecule that combines with an enzyme to activate it

energy metabolism (vitamins)

thiamin, riboflavin, B6, niacin, pantothenic acid, biotin

cell regeneration/red blood cell synthesis (vitamins)

folate, B12

thiamin: B1 (vitamin)

--metabolism of carbs and chain amino acids
--synthesis of neurotransmitters
--production of RNA and DNA
--food sources: pork, legumes
--deficiency: beriberi (muscle wasting, nerve damage)

riboflavin: B2 (vitamin)

--oxidation reduction reactions
--part of coenzyme: glutathione peroxidase (antioxidant)
--lights sensitive
--food sources: milk, meat
--deficiency: ariboflavinosis (sore throat)

niacin: B3 (vitamin)

--NAD (coenzyme)
--oxidation reduction reactions of carbs, fats, proteins
--can be made from tryptophan
--food sources: poultry, fish
--toxicity: supplements
--deficiency: pellagra/flushing and redness of skin

pyridoxine: B6 (vitamin)

--coenzyme in amino acid metabolism and gluconeogenesis
--food sources: meat, fish, starchy veggies
--toxicity: supplements (nerve damage, skin lesions)
--deficiency: affects skin, blood, nerve tissues