Anatomy Exam 3 - Nutrients and Metabolism

Macronutrients

major nutrients that make up the bulk of ingested food; carbohydrates, lipids, proteins

Micronutrients

required in small amounts; vitamins and minerals

Carbohydrates

totally digestible; complex carbohydrates (starches); simple carbohydrates (sugar); glucose is the fuel used by most cells to make ATP, excess is converted to glycogen or fat, then stored

Lipids

protection, insulation, concentrated fuel storage; phospholipids, precursor of bile salts, steroids; total are animal sources and plant sources

Proteins

structural materials, functional molecules; amino acids are used to make proteins or as fuel; complete are eggs, milk, milk products, meat; incomplete are legumes, nuts and seeds, grains and cereals, and vegetables

Vitamins

organic compounds that help the body use nutrients; most function as coenzyme, some are important antioxidants; most must be ingested

Water-Soluble Vitamins

B complex and C, not stored in the body, any not used within 1 hour are excreted

Fat-Soluble Vitamins

A,D,E, and K are absorbed with lipid digestion products; stored in body except for vitamin K

Minerals

work with nutrients for proper body function; uptake and excretion are balanced to prevent toxic overload; some are required in moderate amounts; greater than 200mg per day; others are required in trace amounts

Metabolism

sum of all biochemical reactions involving nutrients

Anabolism

synthesis of large molecules from small ones

Catabolism

hydrolysis of complex structures to simpler ones involves breaking down molecules to release energy

Substrate-Level Phosphorylation

high-energy phosphate group is transferred directly from a substrate to ADP to form ATP; occurs in the cytosol and mitochondrial matrix

Oxidative-Phosphorylation

electron transport proteins “pump” protons creating a proton gradient; ATP synthase uses the energy of the proton gradient to bind phosphate groups to ADP; occurs only in the mitochondrial matrix

Chemiosmotic Processes

couple the movement of substances across membranes to chemical reactions

Cellular Respiration

catabolic breakdown of food fuels whereby energy from food is captured to form ATP

Carbohydrate Metabolism

rising intracellular levels of ATP inhibit glucose catabolism and promote glycogen or fat formation; if no oxygen is present, pyruvic acid is reduced to lactic acid to regenerate NAD (fermentation)

Glycogenesis

glycogen formed with excess glucose; mostly occurs in liver and skeletal muscle cells; occurs when glucose supplies exceed demand for ATP

Glycogenolysis

breakdown of glycogen to release glucose; stimulated by low blood glucose

Gluconeogenesis

forming new glucose from non-carbohydrate sources; glucose can be formed from glycerol and amino acids when blood glucose levels drop; protects against damaging effects of low blood glucose levels and maintains adequate energy supply for the brain and other tissues.

Lipid Metabolism

glycerol is broken down into glyceraldehyde 3-phosphate; lipolysis is the breakdown of stored fats into glycerol and fatty acids; fatty acids undergo beta-oxidation where they are broken into acetic acid fragments which form acetyl CoAs; fatty acids are preferred by liver, cardiac muscle, and resting skeletal muscles as fuel; acetyl coa can enter citric acid cycle only if enough intermediates are available; if not acetyl coa can accumulate and be converted by ketogenesis to ketone bodies

Ketogeneis

ketone bodies can be converted to acetyl coa and used as an anergy source for the heart, muscle, and brain

Protein Metabolism

proteins deteriorate, so they need to be continually broken down and replaced; when dietary proteins are in excess, amino acids are oxidized for energy or converted for fat storage (proteins are not stored)

Absorptive (Feeding) State

lasts for about 4 hours after eating, when absorption of nutrients occurs; anabolism exceeds catabolism; excess nutrients are stored as fats if not used; insulin directs nearly all events of this state; also inhibits glucose release from the liver and gluconeogenesis

Post-Absorptive (Fasting) State

when GI tract is empty and energy sources are supplied by breakdown of body’s reserves; catabolism exceeds anabolism; goal is maintain blood glucose; sympathetic nervous system interacts with several hormones to control events; glucagon is a hyperglycemic hormone that stimulates a rise in blood glucose levels

Cholesterol

not used as an energy source; structural basis of bile salts, steroid hormone, major component of plasma membrane; 15% is ingested, the rest is made in the body, primarily by the liver; lost from the body when catabolized or secreted in bile salts that are lost in feces

High-Density Lipoprotein

cholesterol at liver is broken down and secreted into bile; also provide cholesterol to steroid-producing organs

Saturated Fatty Acids

stimulate liver synthesis of cholesterol and inhibit cholesterol excretion from the body

Unsaturated Fatty Acids

enhance excretion of cholesterol into bile salts

Energy Intake

energy liberated during good oxidation

Energy Output

includes energy lost as heat, used to do work driven by ATP, or stored as fat or glycogen.

Metabolic Rate

total heat produced by body’s chemical reactions and mechanical work

Basal Metabolic Rate

energy needed to perform essential activities

Total Metabolic Rate

rate of kilocalorie consumption to fuel all ongoing activities; increases with skeletal muscle activity and food ingestion

Metabolic Syndrom

increase waist circumference, increase blood pressure, increase blood glucose, increase triglycerides, decrease blood HDL; presented of these factors can double chance of heart disease and increase risk of diabetes five times

Heat Production

basal metabolism; muscular activity (shivering); thyroxine and epinephrine (stimulating effects on metabolic rate); temperature effect (warmer cells metabolize faster, producing more heat)

Heat Loss

radiation, conduction/convection, evaporation

Regulation of Body Temperature

thermoregulatory centers of hypothalamus - heat promoting and heat loss center; hypothalamus received input from peripheral thermoreceptors in shell and central thermoreceptors in core

Hypothermia

low body temperature from cold exposure; shivering stops at core temp of 30-32C, can progress to coma and cardiac arrest at 21C

Hyperthermia

elevated body temperature; positive-feedback mechanism (heat stroke) beings at core temp 41C; skin becomes hot and dry, organs can be damaged, can be fatal, fever is controlled hyperthermia

Heat Exhaustion

heat-associated collapse after vigorous exercise; due to dehydration and low blood pressure; heat-loss mechanisms are still functional; may progress to heat stroke if body is not cooled and rehydrated properly