1. Nutrition and Metabolism- carbohydrates and lipids

nutrients

chemical substances supplied from environment that an organism requires for survival

macronutrients

needed in bulk (carbohydrates, fats, proteins)

micronutrients

essential in small daily doses, include vitamins and minerals

essential nutrients

human cells cannot synthesize these, must be taken in with diet

carbohydrate sources

polysaccharides, disaccharides, monosaccharides

polysaccharides

complex carbohydrates (starch from plants, glycogen from meats)

disaccharides

double sugars, milk sugar, cane sugar, beet sugar, molasses

monosaccharides

single sugars, honey and fruits → digestion breaks complex carbohydrates into these that are small enough to be absorbed

cellulose

complex carbohydrate abundant in food, not digested, provides fiber

fructose, galactose, glucose

absorbed from digestive tract

liver enzymes convert fructose and galactose into

glucose

glycogenesis

excess glucose is linked together to form glycogen, stored in liver and skeletal muscles

glycogeneolysis

glycogen broekn down to supply glucose for energy

lipogenesis

glycogen storage is limited, additional excess glucose can be converted into fat for long term energy storage

gluconeogenesis

liver and kidneys make glucose from non carbohydrate sources (lactate, glycerol, amino acids)

neurons

normally rely primarily on glucose, during prolonged fasting they can also use ketone bodies, although they still require some glucose

carbohydrate building materials

ribose in RNA and deoxyribose in DNA

glucose is

major fuel for cellular processes, especially in brain and during muscle activity

carbohydrate varies

with age, activity level, total energy requirements

recommended dietary allowance for glucose

130 grams/day

carbohydrates percent

45-65% of daily calories, 225-325 grams/day for 2,000 calorie diet

glucose sources

whole grains, fruits, veggies,, legumes

lipids

organic molecules including fats, oils, and fat-like substances such as phospholipids and cholesterol, most common are triglycerides

triglycerides

found in plant and animal based foods

saturated fat

food and animal origin

unsaturated fat

seeds, nuts, and plant oil

cholesterol

found in liver and egg yolk, smaller amounts in whole milk, butter, cheese, and meats, not in plant origin foods

lipids in foods

phospholipids, cholesterol, fats/triglycerides

lipids function

mainly supply energy, contain more than twice as much chemical energy per gram as carbohydrates or proteins, broken down to glycerol and fatty acids

glycerol and fatty acids

synthesize storage fats in adipose tissue

excess glucose or amino acids

converted into fat molecules

body digests fat from

food into glycerol, enter catabolic pathways and provide energy

beta oxidation in mitochondria

fatty acids activated, broken down by oxidases, converted to acetyl CoA, and ketone bodies

ketones produced faster than decomposed

eliminated by lungs and kidneys → fruity odor to breath and urine

lipoproteins

packages transporting lipids through blood stream, surface layer of phospholipid, cholesterol, and protein

very low density lipoproteins (VLDLs)

high concentration of triglycerides

low density lipoproteins (LDLs)

high concentration of cholesterol

high density lipoproteins (HDLs)

high concentration of protein

lipid requirements

not exceed 30% of calories from fat

dietary fats

supply required amounts of fat soluble vitamins