Nutrition Chapter 8: Metabolism

Catabolism:

Refers to metabolic pathway that break down larger molecules into smaller ones

Insulin: Anabolic Metabolism

When blood glucose levels rise, the secretes insulin. insulin attaches to special receptors on the cell membranes. this attachment results in signal to glucose proteins that are also in the cell membrane. in response to the signal, the glucose transport molecules pass the monosaccharide across the cell membrane into the cytoplasm.

with oxygen pyruvate is converted into what?

acetyl coenzyme A

ketogenic

enter the catabolic energy pathways as acetyl CoA

what happens when liver glycogen stores are depleted?

glucagon stimulates the liver to convert amino acids to pyruvate and then into glucose (gluconeogenesis)

primary energy sources for humans

glucose and fatty acids

what is the result of insulin binding to insulin receptors on certain cells?

these cells allow glucose and to enter them an the cells can store energy

what does insulin direct liver and muscle cells to do?

to slow down their glycogenolysis rates and increase their rates of glycogenesis.

Influx of fatty acids stimulates what?

triglyceride synthesis in the liver

ketone bodies

(excess Acetyl CoA production in liver ) acetoacetate, beta-hydroxybutyrate, and acetone.

glucagon

(made by the alpha cells of the pancreas) it is secreted in response to low blood sugar levels. Glucagon signals liver to increase glycogenolysis and gluconeogenesis . this raises blood glucose levels.

Ketoacidosis:

(potentially life threatening, fruity odor to breath, coma-if untreated)

how many molecules of ATP are produced with the complete catabolism of glucose?

30-32

a moderate drinker with a healthy liver can metabolize about how much alcohol?

12-15g/hr

ATP:

Adenosine triphosphate; high energy phosphate compound

Catabolic Metabolism:

Glucagon, Cortisol and epinephrine are hormones that instruct cells to use rather than anabolic pathways.

cortisol

a catabolic hormone made in the adrenal cortex of the adrenal glands. protein catabolism and stimulates the liver to increase use of amino acids for gluconeogenesis.

epinephrine

a catabolic hormone made in the adrenal glands, it stimulates catabolism by increasing glycogenolysis in the liver and muscle, as well as by increasing triglyceride break down (lipolysis ) in adipose tissue.

alcohol pathway

a catabolic pathway that metabolizes alcohol in the liver.

cirrhesis

a condition characterized by the accumulation of scar tissue in the liver, likely leading to its irreversible damage.

ketogenic diet

a high fat diet

Microsomal ethanol oxidizing system (MEOS)

a secondary pathway for processing alcohol in the liver. it wastes energy in the form of heat.

ethanol

a simple two-carbon molecule that is more commonly called alcohol. it can be used as a fuel source.

in obesity, the increase in adipose tissue results in what?

abnormal metabolic changes in fat and muscle cells. these changes make the cells resistant or unresponsive to the effects of insulin.

what happens over a long period of fasting?

additional changes are made: -muscle cells rely more on fatty acids for energy -adipose tissue increases lipolysis, so fatty acids increase in the bloodstream -liver cells rely more on kelogenesis to convert acetyl CoA to ketone bodies. During a prolonged fast even the brain can catabolize ketone bodies for energy.

VLDLs very low density lipoprotein.

after a fatty meal. most of the lipids are incorporated into these which are then released into the blood stream where adipocytes and other cells can access them.

nonalcoholic fatty liver

an abnormal accumulation of fat in the liver that is not caused by alcohol consumption.

gastric alcohol dehydrogenase

an enzyme that detoxifies some alcohol while it is in the stomach.

aldehyde dehydrogenase

an enzyme that reactors with acetaldehyde to from acetate, a less toxic substance. converted to acetyl CoA.

a standard drink

approximately 12 oz of beer or wine cooler, 5 oz of wine or 1.5 oz of liquor

how does the body detoxify alcohol?

by converting it into less damaging compounds.

glucogenic

can be broken down into either pyruvate or intermediates of the citric acid cycle

only what 4 things can be utilized for energy?

carbohydrates lipids proteins alcohol (cells cannot release energy form vitamins, minerals or water)

amino acids

cells use these to synthesize essential proteins (enzymes), structural molecules and certain hormones

Beta-oxidation:

chemical pathway that is involved in the catabolism of an activated fatty acid

citric acid cycle:

complex series of chemical reactions that are involved in energy metabolism

hormone sensitive lipase (HSL):

enzyme in fat cells that removes the three fatty acids from a triglyceride

what is the primary function of adipocytes?

fatty acid storage

metabolic syndrome

glucose still produced and released into blood-stream blood glucose levels rise pancreas secretes more insulin excess body fat is a major risk factor.

Coenzyme:

group of organic cofactors that often have B vitamins in their chemical structure

where does ATP synthesis occur?

in the cytoplasm

what are the effects of insulin?

increases fatty acid uptake and triglyceride synthesis of adipocytes, stimulates protein synthesis in cells, and promotes energy storage.

oxabacetate

involved in the first reaction and the ending point of the citric acid cycle.

Energy Metabolism:

involves the chemical pathways that enable the human body to obtain use energy from macronutrients and alcohol

coenzyme pyridoxal phosphate (PLP)

is needed for the conversion of glycogen to glucose molecules

microsomal ethanel-oxidizing system (MEOS)

is used when excessive amounts of alcohol are consumed

without oxygen pyruvate is converted to what?

lactic acid

electron transport chain:

linked series of enzymes that synthesize water and ATP during aerobic energy metabolism

primary site for metabolism of alcohol that has been absorbed by the digestive tract:

liver

have insulin receptors on their membranes that insulin will bind to to convey specific information not the cells.

muscle, fat and liver cells

glycogenolysis:

pathway that breaks down glycogen into glucose molecules

stomach and small intestine absorption of alcohol?

rapidly absorbed. absorption is if consumed with meals.

what are the effects of limiting fat to less than 50g/day?

rapidly depletes glycogen stores and results in (the formation of excess keno bodies) side effects of ketosis is loss of appetite)

Anabolism:

refers to the metabolic pathway that build larger molecules from smaller ones

beta cells

secrete insulin when blood glucose levels rise

what physiological factors account for the variability in alcohol metabolism?

sex, body size and composition, age, prior drinking history, genetic background

attachment of insulin to cell membranes results in what?

signals sent to the glucose transport proteins that are also in cell membranes . in response to signal, glucose transport molecules pass the monosaccharide across the cell membrane into the cytoplasm.

Chemical pathways:

specific chemical reaction that occur in sequences

chemical reactions that occur in living cells requires:

specific enzymes

glycogen

stored glucose molecules

Metabolism

sum of all chemical reactions that occur in the body

lipogenesis

synthesis of fatty acids

Energy

the capacity to perform work (can cannot be created or destroyed)

glycogenesis

the chemical pathway that enables muscle and liver cells to store glucose as glycogen

glycolysis

the first phase of glucose catabolism. it is a pathway. Where glucose is converted into two three carbon molecules of pyruvate

ketogenesis

the formation of ketone bodies in liver cells from excess of Acetyl CoA produced

acetaldehyde

the highly toxic substance formed during the first step of the alcohol dehydrogenase pathway.

insulin resistance in muscle cells and adipocytes occurs because

the insulin receptors no longer function properly. thus, obesity is highly associated with insulin resistance, a condition that can lead to type II diabetes. they do not take up glucose and fatty acids from the bloodstream.

Anaerobic metabolism

the metabolic pathway that does not require oxygen

before an amino acid can be used for ATP production what must occur?

the nitrogen group must be removed by deamination or transamination.

liver and muscle

the primary sites for glycogen storage and degradation

Aerobic metabolism:

the production of ATP that occurs in the presence of oxygen

gluconeogenesis

the synthesis of glucose from non carbohydrate precursors ex: glycerol, lactate, pyruvate, most amino acids

what happens when liver cells become insulin resistant? what can occur as a result?

their ability to regulate synthesis and gluconogenesis becomes altered. metabolic syndrome

Acetyl CoA

two-carbon segments derived from fatty acid molecules are cleaved during beta-oxidation