bio chapter 7

why do we need food?

-for growth

-source of energy

-replacement of worn and damaged tissues

how does food help with growth?

-provides substances needed for making new cells and tissues

how does food act as a source of energy?

-energy is needed for chemical reactions that take place in living organisms to keep them alive

-food is broken down during respiration to provide energy

how does food help to replace worn and damaged tissues

-substances from food are used to replace worn away skin, dead red blood cells and repair wounds

what is the meaning of a balanced diet

-contains all essential nutrients in the correct proportion to maintain good health.

-carbohydrate, fat, protein, vitamin, minerals, fiber and water

7 food classes

-fats, oils and confectionery

-meat, fish and alternatives

-milk, cheese and dairy

-fruit and vegetables

-bread, cereals and potatoes

uses of carbohydrates

-source of energy

source of carbohydrates

-rice, potato, sweet potato, cassava, bread, millet, sugary foods

uses of fats/oils

-source of energy

-heat insulation

-part of hormones

-in cell membranes

-insulation of nerve fibres

sources of fats/oils

-butter, milk, cheese, egg yolk, animal fat, groundnuts

uses of protein

-growth

-tissue repair

-helps body make enzymes

-some hormones

-hair, nails

-can be broken down to release energy

sources of protein

meat, fish, eggs, soya, ground nuts, milk, cowpeas

what are the uses of fibre

-is cellulose

-adds bulk to undigested food passing through the intestines to maintain peristalsis (muscle contractions that move food through the digestive tract)

sources of fibre

-vegetables, fruit, wholemeal bread

what is the use of water in the body?

-formation of blood, cytoplasm

-solvent for transport of nutrients and removal of wastes (urine)

-enzymes only work in a solution (water helps move substrates to enzymes)

source of water in the body

drinks, fruit, vegetables

what is the use of vitamin c?

prevents scurvy

what are sources of vitamin c?

-oranges, lemons, grapefruit, tomato, green vegetables

vitamin c deficiency effects

-scurvy: fibres in connective tissue of skin and blood vessels do not form properly.

leads to:

-bleeding gums

-bleeding under the skin

-poor healing of wounds

what are the uses of vitamin d?

-prevents rickets

-helps absorb calcium from intestine and deposition of calcium in bones

good source of calcium

-butter, milk, cheese, egg yolk, liver, fish-liver oil

what are vitamin d deficiency effects

-rickets: bones become soft and deformed

-osteo-malacia: fractures are likely

what are vitamins?

-not digested or broken down for energy

-mostly not built into body structures

-essential in small quantities for health

-needed for chemical reactions in cells

what is the use of calcium?

-form healthy bones and teeth

-normal blood clotting

-help in muscle contraction and nerve impulse transmission

good sources of calcium

milk, cheese, fish

calcium deficiency effects

osteoporosis in older people (inner structure of the bone becomes spongy and loses mass, making it brittle and break easily)

what is the use of iron?

-formation of haemoglobin in the red blood cells

-needed by muscles and enzyme systems in cells

what are good sources of iron

-red meat, liver, kidney, eggs, green vegetables (spinach, cabbage) and chocolate

what are iron deficiency effects

-it is the decrease in red blood cells

symptoms: feeling weak, tired and irritable

(red blood cells break down in the liver after about 3 months)

what is ingestion

-taking of substances (eg: food and drink) into the body through the mouth

what is mechanical digestion

-breakdown of food into smaller pieces without chemical change to the food molecules

what is chemical digestion

-breakdown of large, insoluble molecules into small, soluble molecules

what is absorption

-the movement of digested food molecules through the wall of the intestine into the blood

what is assimilation?

uptake and use of nutrients by cells

what is egestion

passing out of food that has not been digested or absorbed as faeces passing through the anus

what is mastication?

-a form of mechanical digestion in the mouth, chewing.

-done by the teeth

memorise this diagram:

features of the incisor

-at the front

-chisel-shaped (sharp edge)

-bite off pieces of food

features of the canine

-either side of incisors

-slightly more pointed than incisors

-bite off pieces of food

features of the premolar

-behind canines

-have to points (cusps0 and one or two roots

-tears off and grinds food

features of the molar

-at the back

-have 4 or 5 cusps, have 2-3 roots

-chewing and grinding food

memorise the tooth structure

features of the crown

-the part visible above the gum line

features of the gum

-tissue that overlays the jaws and anchor your teeth

features of the root

-other structures that are embedded in the jaw bone

features of the enamel

-covers the surface of the crown, very hard

features of the cement

-in the root, cement replaces enamel

-enables tooth to grip its bony socket in the jaw

features of the dentine

-below enamel

-softer than enamel

-contains pulp cavity

features of the pulp cavity

-contains nerves and blood vessels which enters the tooth through a small hole at the base of the root

alimentary canal: memorise this

what is the function of the mouth?

ingesting food, mechanical digestion by teeth and chemical digestion of starch by amylase, formation of a bolus for swallowng

what is the function of salivary glands?

contains amylase for chemical digestion of starch in food, and liquid to lubricate food and make small pieces stick together

what is the function of the oesophagus?

transfers food from the mouth to the stomach by peristalsis

what is the use of the stomach

-produces gastric juice containing pepsin for chemical digestion of protein

-has hydrochloric acid to kill bacteria

-peristalsis churns up food into liquid

what is the use of duodenum

-first part of the small intenstine, receives pancreatic juice for chemical digestion of proteins, fats and starch and neutralising acid from the stomach

-receives bile to emulsify fats (physical digestion)

what is the use of the ileum

-second part of the small intestine

-enzymes in the epithelial lining carry out chemical digesting of peptides and maltose

-very long and has villi to increase surface area to absorb digested food molecules

what is the use of the pancreas

secrets pancreatic juice into the duodenum via pancreatic duct for chemical digesting of protein, fat and starch

what is the use of the liver

-makes bile containing salts to emulsify fats (physical digestion)

-assimilation of digested food such as glucose

-deamination of excess amino acids

what is the use of the gallbladder

-stores bile made in the liver

-secrets bile into the duodenum via bile ducts

what is the use of colon?

-first part of the large intenstine

-absorption of water from undigested food

-absorption of bile salts to pass back into the liver

what is the use of the rectum?

-second part of the large intestine that stores faeces

what is the use of the anus?

-egestion of faeces

process of chemical digestion

-chemical digestion functions to break down large molecules into smaller, soluble molecules.

process that takes place in the mouth

-food in the mouth stimulates the salivary glands to secrete saliva

-mucus in saliva helps to soften food.

-enzyme called salivary amylase, which digest starch to maltose

-tongue rolls food into bolus (slippery round masses)

-boli is pushed down the oesophagus into the stomach from peristalsis

-presence of food stimulates gastric glands to secrete gastric juice.

-peristalsis churns, mixes and breaks up the food

-

chemical digestion in the mouth

-digested by salivary glands

-secrest saliva

-ph7

-salivary amylase

-starch → maltose

chemical digestion in the stomach

-digested by gastric glands

-secretes gastric juice

-enzyme: pepsin

-ph1-2

-proteins → peptides

chemical digestion in the small intestine (duodenum)

-digested by pancreas

-secretes pancreatic

-ph8-9

-enzyme: trypsin, pancreatic amylase and lipase

-proteins → amino acids, starch → maltose, fats → fatty acids & glycerol

chemical digestion in the small intestine (ileum)

-digested by the epithelial cells of intestine

-secrets intestinal enzymes

-ph8-9

-enzyme: protease, maltase, lipase

-proteins→amino acids, maltose→ glucose, fats → fatty acids and glycerol