2e: Nutrition (Humans)

• to supply us with fuel for energy

• to provide materials for growth and repair of tissues

• to help fight diseases and keep our body healthy

a diet that contains all the main nutrients in the correct amount to maintain good health

lack of proper nutrition due to various factors

carbohydrates, lipids, proteins, minerals, vitamins, dietary fibre, water

sources: bread, pasta, rice, potatoes function: provides and stores energy

sources: meat, fish, egg, pulses, nuts function: growth and repair

sources: butter, oil, nuts function: insulation and energy storage

sources: vegetables, whole grains function: provides roughage for the intestine to push through

sources: water, juice, milk, fruits, vegetables function: needed for cellular chemical reaction

sources: milk, cheese, eggs function: strong teeth and bones, blood clotting

sources: meat, liver, dairy, leafy green veggies function: pigment in the retina for vision

sources: oily fish, dairy products, sunlight function: absorption of calcium, strong bones

sources: citrus fruits, green vegetables function: collagen protein formation

source: meat, liver, leafy greens function: makes haemoglobin

starvation, coronary heart disease, constipation, obesity

cause: taking in less energy than needed effect: weight loss, heart damage, immune system damage

cause: saturated fat and increased cholestrol effect: heart attack, death

cause: lack of dietary fibre effect: increased risk of diseases such as bowel cancer

cause: taking in more energy than used effect: development of many diseases such as heart failure, diabetes

age, activity levels, pregnancy

chemical and mechanical breakdown of food where large, insoluble molecules of food are broken down into smaller, soluble molecules to be absorbed and delivered to cells in the body.

provide cells with energy or with materials to help build, grow and repair other molecules.

channel through which food flows around the body starting: mouth ending: anus

digestion occurs within the alimentary canal

produce substances needed for digestion to occur

1. ingestion

2. mechanical digestion

3. chemical digestion

4. absorption

5. assimilation

6. egestion

taking in of substances through the mouth

breakdown of food without chemical change

breakdown of large molecules into smaller ones

movement of small molecules and ions through the wall of the intestine into the build

movement of digested food molecules into the cells of the body where they are used

passing out of food that hasn't been digested, through the anus

mechanism that helps food move along the alimentary canal.

1. muscles in the wall of the oesophagus create waves of contractions, forcing the bolus along.

2. the bolus has churned into chyme by the time it reaches the stomach.

3. it continues onto the small intestine.

circular and longitudinal

contract to reduce the diameter of the lumen of the oeosphagus or the small intestine

contract to reduce the length of that section of the oesophagus or the small intestine

produced to lubricate food mass and reduce friction

provides roughage required for muscles to push against

chemical digestion is controlled by enzymes produced in different areas of the digestive system. enzymes are biological catalysts.

1. carbohydrases

2. proteases

3. lipases

breaks down carbohydrates to simple sugars (amylase, maltase)

a carbohydrase that breaks down starch into maltose made in: salivary glands, pancreas, small intestine

breaks down maltose into glucose acts in: mouth, small intestine

break down proteins into amino acids (pepsin, trypsin, peptidases) acts in: stomach, small intestine

a protease that breaks down proteins into small polypeptide chains made in: stomach

made in: pancreas, small intestine

break down lipids to glycerol and fatty acids (lipase)

produced in: pancreas secreted in: small intestine

an alkaline substance produced by cells in the liver

stored in the gallbladder before being released into the small intestine

it contains bile salts which emulsify fats

1. neutralised hydrochloric acid from the stomach

2. emulsification

neutralisation is essential as enzymes in the small intestine have a higher optimum ph (more alkaline) than those in the stomach. the alkaline properties of bile allow this to occur.

breaking apart large drops of fat into smaller ones (and so increasing their surface area)

• very long

• has a highly folded surface

• surface has millions of villi

it helps by mixing together food and enzymes and keeping things moving along the alimentary canal

tiny finger-like projections on the surface of the small intestine

• large surface area

• short diffusion distance

• steep concentration gradient

microvilli further increase the surface available for absorption

one cell thick wall of villus

• network of blood capillaries for transportation of glucose and amino acids

• lacteal running through the center of the villus to transport fatty acid and glycerol

• enzymes assist with chemical digestion

• movement of villi helps move food along and mix it with enzymes

• boiling tube

• boiling tube holder

• bunsen burner

• mounted needle

• measuring cylinder

• balance

• thermometer

• water

• food samples

• pour 25cm of water into the boiling tube

• record starting temperature

• weight initial mass of the food sample

• set fire to the food sample using the bunsen burner and hold near water until completely burnt

• record final temperature of water

• recordd the mass of the food sample once cooled

• repeat with different samples

a larger increase in water temperature indicates a larger amount of energy contained by the sample

(mass of water x temperature increase) / mass of food

• incomplete burning

• heat energy loss

C - type of food R - repeat for different samples M1 - change in temperature of water M2 - mass of food S - volume of water, distance between food sample and boiling tube