Humans need many different nutrients to survive. To receive these nutrients in the correct quantities, a balanced diet must be eaten.
1) State what is meant by the term Balanced Diet for Humans
- Includes all essential nutrients in the correct amounts needed for growth and repair.
Balanced diets vary between people:
- Children below 12: Require more calcium
- Teenagers: Highest calorie Intake
- Adults: Balanced meal with less calories
- Pregnant women: more iron, calcium and folic acid
- Males: Generally, require more energy
2) List the principal sources of the nutrients and describe their dietary importance
Main source of energy
Rice, potato, bread
Fats and oils
Source of energy
Protection of delicate organs
Fatty meats, butter, cheese
Growth and tissue repair
Meat, fish, egg
Maintain healthy skin and gums
Citrus fruits, tomato, guava
Helps absorb calcium from small intestine
Made in skin when exposed to sunlight. Milk, cheese
Healthy teeth and bones
Milk, cheese, fish
Formation of haemoglobin in red blood cell
Red meat, eggs, green vegetables (spinach)
Adds bulk to the undigested food in intestines, maintaining peristalsis
Vegetables, fruits, wholemeal bread
Formation of blood, cytoplasm, solvent for transport of nutrients and removal of waste
Drinks, fruits, vegetables
3) Describe the effects of Malnutrition
A condition caused by eating an unbalanced diet.
- Overnutrition: balanced diet but eating too much of everything.
- Undernutrition: having too little food, eating foods in incorrect proportions.
- Starvation: caused by eating too little food, leads to weight loss, organ damage and eventually death.
- Coronary heart disease: caused by a build-up of cholesterol in the coronary artery which limits blood flow to the heart and can cause heart attacks. Result of too much saturated fats in the diet, which comes from food such as high fat diary products and fatty meats.
- Constipation: caused by lack of fibre, leads to inability to defecate.
- Obesity: caused by eating too much food, leads to a range of health issues including diabetes, high blood pressure, strokes and heart disease.
- Scurvy: caused by lack of vitamin C, leads to bleeding under the skins and around gums, premature stopping of bone growth in children leading to stunted growth, and very dry skin and hair.
- Kwashiorkor and Marasmus: caused by protein or calorie deficiency over a long period. Kwashiorkor occurs due to severe protein deficiency and a carbohydrate based diet and is often developed by older children. Marasmus is more common with young children and babies.
4) Explain the Effects of Vitamins D and Iron Deficiencies
- Vitamin D: Rickets; weak bones and teeth
- Iron: Anaemia; Fatigue (less iron → less haemoglobin → less oxygen transported → less respiration → less energy)
5) Define Processes in the Alimentary Canal
- Ingestion: the taking of substances, e.g. food and drink, into the body through the mouth.
- Digestion: the breakdown of large, insoluble food molecules into small, water-soluble molecules using mechanical and chemical processes.
- Mechanical digestion: the breakdown of food into smaller pieces without chemical change to the food molecules.
- Chemical digestion: the breakdown of large, insoluble molecules into small, soluble molecules.
- Absorption: movement of digested food molecules through the wall of the intestine into the blood.
- Assimilation: the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells.
- Egestion: passing out of food that has not been digested, as faeces, through the anus.
* 6) Describe Diarrhoea and outline the Treatment
- Diarrhoea is the loss of watery faeces.
- Treatment of diarrhoea is oral hydration therapy. This involves drinking plenty of fluids – sipping small amounts of water at a time to rehydrate the body.
* 7) Describe Cholera
- Cholera is a disease caused by the bacterium Vibrio cholera which causes acute diarrhoea.
- When the Vibrio cholera bacteria are ingested, they multiply in the small intestine and invade its epithelial cells.
- As the bacteria become embedded, they release toxins which irritate the intestinal lining and lead to the secretion of large amounts of water and salts, including chloride ions.
- The salt decrease the osmotic potential of the gut contents, drawing more water from surrounding tissues and blood by osmosis.
- This makes the undigested food much more watery, leading to acute diarrhoea, and the loss of body fluids and salt leads to dehydration and kidney failure.
8) Identify the Main Regions of the Alimentary Canal
source: PMG biology
9) Describe the Functions of the regions of the alimentary canal
- Mouth: contains teeth used for mechanical digestion, area where food is mixed with salivary amylase & where ingestion takes place
- Salivary glands: produce saliva which contains amylase and helps food slide down oesophagus
- Oesphagus: tube-shaped organ which uses peristalsis to transport food from mouth to stomach
- Stomach: has sphincters to control movement. Food is churned to break it up by mechanical digestion. Pepsin (a protease) is secreted to break down proteins into peptides, hydrochloric acid present to maintain an optimum pH and kills bacteria by creating an extremely acidic environment.
- Small Intestine: consists of the duodenum and ileum. In the duodenum, bile secreted from the gall bladder neutralized the acidity from the stomach and emulsifies fats. The emulsified fats are then digested by pancreatic lipase to form fatty acids and glycerol. Pancreatic amylase and trypsin (a protease) break down starch and peptides into maltose and amino acids. In the ileum, maltase breaks down maltose to glucose. This is where absorption takes place; adapted by having villi and microvilli.
- Pancreas: produces pancreatic juice which contains amylase, trypsin and lipase and hydrogencarbonate.
- Liver: makes bile, stores glucose as glycogen, interconverting them to keep glucose concentration constant. Also carries out interconversion of amino acids (transamination), deamination and removal of old red blood cells and storage of their iron. Also site of breakdown of alcohol and other toxins.
- Gall bladder: stores bile from liver
- Bile: produced by liver and stored in gall bladder, its role is to emulsify fats, to increase surface area for the action of enzymes.
- Large Intestine: consists of the colon and rectum. In the colon, absorption of minerals and vitamins, and water takes place. In the rectum, faeces are temporarily stored.
- Anus: ring of muscle which controls when faeces is released.
10) Identify the types of Human Teeth and Describe the Functions
11) Describe the Structure of Human Teeth
- Enamel: the strongest tissue in the body made from calcium salts.
- Cement: helps to anchor tooth.
- Pulp cavity: contains tooth-producing cells, blood vessels, and nerve endings which detect pain.
- Dentine: calcium salts deposited on a framework of collagen fibres.
12) State the Causes of Dental Decay
- Bacteria are present on the surface of our teeth. Food deposits and bacteria form a layer called plaque. Bacteria on the plaque feed on sugars, producing acid. This acid dissolves enamel, forming a hole.
- Dentine underneath the enamel is softer – it dissolves more rapidly.
- If the hole reaches the pulp cavity, bacterial infection can get to the nerve. This results in toothache and possibly, an abscess (an infection in the jaw).
13) Describe the Proper Care of Teeth
- Eating a diet with low sugar content.
- Regular and effective teeth brushing to remove plaque.
14) State the Significance of Chemical Digestion
- Allow food (large insoluble substances such as proteins) to be broken down into smaller soluble substances like amino acids so that they can be absorbed and used in the body.
15) State the functions of Enzymes and Hydrochloric Acid
- Breaks down starch to simpler sugars.
- Secreted by salivary gland in mouth and pancreas into the pancreatic juice into the duodenum.
- Breaks down protein to amino acids.
- Pepsin secreted in stomach as gastric juice.
- Breaks down fats to fatty acids and glycerol.
- Secreted by pancreas into the duodenum as pancreatic juice.
- Secreted by stomach wall as gastric juice, kill harmful microorganisms in food.
- Provide the optimum pH for pepsin activity.
* 16) Describe the Digestion of Starch in the Alimentary Canal
- Amylase is secreted from the salivary gland and pancreas, breaks down starch to maltose.
- Maltose is broken down to glucose by maltase, made by epithelium cells covering the villi.
* 17) Describe Pepsin and Trypsin
- Both pepsin and trypsin are proteases.
- Pepsin is secreted in the stomach, breaks down protein into soluble compounds called polypeptides.
- Trypsin is secreted by the pancreas in an inactive form, which is changed to an active enzyme in the duodenum, breaks down proteins to polypeptides.
- Polypeptides is broken down to amino acids by peptidase, made by epithelium cells covering the villi.
18) Outline the role of Bile
- Neutralising the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action.
- Emulsifying fats to increase the surface area for the chemical digestion of fat to fatty acids and glycerol by lipase.
19) Explain the significance of Villi and Microvilli
- Presence of many villi in the small intestine to increase the surface area for absorption.
- One villus will have tiny folds on the cells on its outside called microvilli, to further increase the surface area.
- Epithelium: only one cell thick for faster transport. The cells of the epithelium are folded to form microvilli.
20) Describe the roles of Capillaries and Lacteals
- Capillary: transports glucose and amino acids.
- Lacteal: absorbs fatty acid and glycerol.
* 21) Absorption of Water
- The small intestine absorbs most of the water in the contents of the gut.
- By the time the contents reach the end of the small intestine, most of the digested food has also been absorbed.
- The remaining material consists of: water, bacteria (living and dead), cells from the lining of the gut, indigestible substances – such as cellulose from plant cell walls.
- The colon is the first part of the large intestine. It absorbs most of the remaining water. This leaves semi-solid waste material called faeces.
- The faeces are stored in the rectum, the last part of the large intestine.
- Egestion happens when these faeces pass out of the body through the anus.