II: 6.3 - Animal nutrition

Question 1

Define

balanced diet

Answer 1

A balanced diet is a diet in which all the components needed to maintain health are present in appropriate proportions.

A balanced diet should include appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre.

Question 2

Describe a balanced diet related to age, sex and activity of an individual

Answer 2

Diet related to age/sex/activity:

• Children Below 12: Require more calcium
• Teenagers: Highest calorie Intake
• Adults: Balanced meal with less calories. The energy needs of adults go down as they age, e.g. people in their 50s need about 17% less energy in their diet than people in their 30s.
• Pregnant Women: more iron, calcium and folic acid
• Males: Generally require more energy
• People who are active tend to need more energy than sedentary people.
• In general, the greater a person’s mass, the more energy they need.

Question 3

Describe the effects of malnutrition in relation to starvation, coronary heart disease, constipation and obesity

Answer 3

Malnutrition: A condition caused by eating an unbalanced diet. Several forms:

• Overnutrition: balanced diet but eating too much of everything
• Undernutrition: having too little food
• Eating foods in incorrect proportions

1. Starvation: losing strength & finally dying because of lack of food
2. Coronary heart disease: eating too much fats which are rich in saturated fatty acids and cholesterol, may lead to heart attack
3. Constipation: lack of roughages in food causes constipation because roughages are indigestible and form bulks. Friction between bulks and walls of intestine stimulate the peristalsis
4. Obesity: Eating too much fats and carbohydrates leads to their storage in storage in the body mainly in the forms of fats and causing an increase in body weight. This can cause; heart attack, stroke, joint pain, mobility impairment, high blood pressure

Question 4

Discuss ways in which the use of modern technology has resulted in increased food production.

Answer 4

Food production has increased because:

• Improved machinery means less labor is needed
• Fertilisers help crops to grow better
• Insecticides: a type of pesticide that kills insects
• Herbicides: a type of pesticide that kills weeds
• Artificial selection and genetic modification means that yields are improved: cows produce more milk, cows are more muscular giving more meat, plant crops can resist insects and cold weather

Question 5

Discuss the problems of world food supplies

Answer 5

Not enough food available in a country to feed its people because:

• Fast increase in population
• Increasing use of crops for fuel
• Decrease of farming = Climate change/Urbanization

Question 6

Discuss the problems which contribute to famine

Answer 6

Famine: Wide spread scarcity of food
The main causes of famine:

• The rapid rate of population increase
• Long term climatic change
• Soil erosion and desertification
• Economic pressure
• Unequal distribution of food
• Drought
• Flood

Question 7

Define

ingestion

Answer 7

Taking substances (e.g. food, drink) into the body through the mouth

Question 8

Define

egestion

Answer 8

Passing out of food that has not been digested, as faeces, through the anus

Question 9

State the name and function of A

Answer 9

Mouth

Contains teeth used for mechanical digestion (chewing), area where food is mixed with salivary amylase & where ingestion takes place

i) Urvula
ii) Tongue: moves food, senses taste

Question 10

State the function of the epiglottis

Answer 10

When swallowing, the epiglottis closes the trachea so food does not go down this tube.

Swallowing is a reflex action

Question 11

State the name and function of B

Answer 11

Pharynx

Also known as the throat; the passageway leading from the mouth and nose to the esophagus and larynx

Question 12

State the name and function of C

Answer 12

Salivary glands

Produces saliva, which contains the enzyme amylase (breaks down cooked starch into maltose and glusoce), helps to lubricate the food and makes the small pieces stick together.

i) Parotid
ii) Subligual
iii) Submandibular

Question 13

State the name and function of D

Answer 13

Oesophagus

Also known as the gullet; a tube-shaped organ which uses peristalsis to transport food from mouth to stomach

Question 14

State the name and function of E

Answer 14

Stomach

• Has sphincter muscles to control movement into duodenum
• Has pepsin (a protease) to break down proteins into peptides
• Has renin which clots milk
• Kills bacteria with hydrochloric acid
• Has elastic walls
• The walls of the stomach contain muscles that contract and relax together mixing the food with the content of the stomach and turning it into liquid chyme (this process is called churning).

Question 15

State the name and function of F

Answer 15

Pancreas

Produces pancreatic juice which contains amylase, trypsin and lipase and hydrogencarbonate.

i) Pancreas duct - transport pancreatic juice to duodenum

Also involved in the regulation of glucose levels (see homeostasis)

Question 16

State the name and function of G

Answer 16

Liver

• Produces bile
• Stores glucose as glycogen, interconverting them to keep glucose concentration constant
• Carries out interconversion of amino acids (transamination), deammination and removal of old red blood cells and storage of their iron
• Site of breakdown of alcohol and other toxins.

Question 17

State the name and function of H

Answer 17

Gall bladder

Stores bile from liver

Question 18

State the name and function of I

Answer 18

Bile duct

Delivers bile to duodenum

Question 19

State the name and function of J

Answer 19

Small intestine

Tube shaped organ composed of three parts:

i) Duodenum - Fats are emulsified by bile, and 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. Intestinal juice contains carbohydrases to further break carbohydrates down:

• Maltase to digest maltose into glucose + glucose
• Sucrase to digest sucrose into glucose + fructose
• Lactase to digest lactose into glucose + galactose

ii) Jejunum
iii) Ileum - This is where absorption takes place, adapted by having villi and microvilli to increase internal surface area.

Question 20

State the name and function of K

Answer 20

Colon

Part of the large intestine; organ for absorption of minerals and vitamins, and reabsorbing water from waste to maintain body’s water levels

i) Tranverse colon
ii) Ascending colon
iii) Descending colon

Question 21

State the names and functions of L & M

Answer 21

Cecum (caecum) & appendix

Digestion of plant cell walls in herbivores.

In humans, possibly no digestive function. However, the appendix contains lymphoid tissue and so may have an immunological function.

Question 22

State the name and function of N

Answer 22

Rectum

Part of the large intestine; where faeces are temporarily stored

Question 23

State the name and function of O

Answer 23

Anus

Ring of muscle which controls when faeces is released

Question 24

Define

digestion

Answer 24

The break-down of large, insoluble food molecules into small, water-soluble molecules using mechanical and chemical processes

Question 25

Identify the types of human teeth and describe their structure and functions

Answer 25

1. Incisors: rectangular shape, sharp for cutting and biting
2. Canines: sharp-pointed for holding, cutting and ripping
3. Premolars: blunt for chewing and crushing
4. Molars: blunt chewing and crushing (have two roots)

Question 26

Label and describe parts A-J

Answer 26

• A: enamel - the strongest tissue in the body made from calcium salts
• B: dentine - calcium salts
  deposited on a framework of
  collagen fibers
• C: pulp cavity - contains tooth-producing cells, blood vessels, and nerve endings which detect pain.
• D: gums
• E: bone
• F: cementum - helps to anchor tooth
• G: nerves and blood vessels
• H: root end opening
• I: crown
• J: root

Question 27

Describe the cause of dental decay.

Answer 27

When we eat, some food particles stay in our mouth. If our teeth are not kept clean and these particles not removed, bacteria that live in our mouth feed on these food particles, respiring anaerobically and producing lactic acid. Lactic acid reacts with the enamel and dissolves it, working its way through the tooth.

Question 28

Describe the stages of tooth decay

Answer 28

1. Bacteria respire anaerobically, producing lactic acid
2. Acid starts to dissolve the enamel, letting decay enter the tooth
3. Decay reaches dentine which dissolves quite quickly as it is softer than enamel
4. Decay reaches pulp cavity, causing pain as nerves are exposed
5. The decay reaches the base of the tooth, allowing bacteria through. This forms an abscess and causes severe pain.

Question 29

Describe the proper care of teeth in order to prevent tooth decay.

Answer 29

• Eat food with low sugar content (prevents bacteria respiring)
• Brush teeth regularly and effectively to remove plaque
• Use toothpaste or water containing fluoride because it is absorbed by the teeth and helps stopping the attack by acid
• Pay regular visits to the dentist
• Don’t smoke or drink too much alcohol (This is because tobacco can interfere with production of saliva, which helps keep the surface of your teeth clean, and alcohol can contribute to the erosion of tooth enamel)

Question 30

Describe how flouride reduces tooth decay

Answer 30

• absorbs onto the surface of a tooth and promotes tooth remineralisation by attracting other minerals (e.g. calcium) to the area
• helps to make the tooth decay-resistant, as the tooth mineral that is created during the remineralization process (fluorapatite) when fluoride is present is more resistant to damage caused by acids
• inhibits production of acids by bacteria

Question 31

Explain arguments for the addition of fluoride to public water supplies

Answer 31

• Helps to strengthen tooth enamel
• Available to all
• Treats whole population
• Free (to people)
• Cheap to supply

Question 32

Explain arguments against the addition of fluoride to public water supplies

Answer 32

• Allergies such as gastric disturbance, cardiovascular problems, head ache, fits
• Bad taste
• Dosage not controlled for individuals
• No individual choice (no informed consent - considered bad medical practice)
• Discoloured teeth - fluorosis
• No benefits of swallowing fluoride, only benefits when it makes contact with the surfaces of your teeth (i.e. using fluoridated toothpaste is sufficient)

Question 33

Define

mastication

Answer 33

Also known as chewing, it is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow more efficient break down by enzymes.

The food is also mixed with saliva and rolled into a ball called a bolus.

This is a form of mechanical digestion.

Question 34

Define

peristalsis

Answer 34

Waves of involuntary muscle contractions and relaxations that transport food, waste matter, or other contents through a tube-shaped organ such as the intestine.

This is the process by which food travels through the alimentary canal

Question 35

Describe the role of longitudinal and circular muscles in peristalsis

Answer 35

• Circular and longitudinal muscles work antagonistically
• Circular muscles contract on either side of the bolus to push it downwards but not letting it fall
• Longitudinal muscles contract to shorten the organ

Question 36

Describe the role of bile

Answer 36

Bile emulsifies large fat droplets (i.e. separates the droplets into smaller ones), to increase the surface area for the action of enzymes

Question 37

Describe chemical digestion and state its importance

Answer 37

Chemical digestion is where enzymes are used to break down large insoluble substances (polymers) into smaller soluble substances (monomers) so that they can be absorbed by the small intestine into the bloodstream.

Question 38

State where in the alimentary canal amylase is secreted and the functions of a typical amylase, listing the substrate and end-products.

Answer 38

• Secreted by:
  
  • the salivary glands into the mouth
  • the pancreas and small intestine into the small intestine
• Substrate: starch
• End-products: maltose

Question 39

State where in the alimentary canal a protease is secreted and the functions of a typical protease listing the substrate and end-products.

Answer 39

• Secreted:
  
  • in the stomach (pepsin)
  • by the pancreas into the small intestine (trypsin)
• Substrate:
  
  • polypeptides (pepsin)
  • peptides (trypsin)
• End-products:
  
  • peptides (pepsin)
  • amino acids (trypsin)

Question 40

State where in the alimentary canal lipase is secreted and the functions of a typical lipase, listing the substrate and end-products.

Answer 40

• Secreted:
  
  • by the pancreas and small intestine into the small intestine
• Substrate: lipids
• End-products: fatty acids and glycerol

Question 41

Define

absorption

Answer 41

The movement of digested food molecules through the wall of the intestine into the blood or lymph.

The jejunum and ileum in the small intestine are the sites for absorption.

Question 42

Describe the structure of a villus

Answer 42

• A: the thin epithelium (one cell layer thick) has microvilli to further increase surface area
• B: rich capillary network which glucose and amino acids enter by active transport
• C: lacteal which fatty acids and glycerol enter by diffusion (as cell membranes are made of fat). The lacteal is connected to the lymphatic system
• D: crypt involved primarily in the secretion of intestinal juice

Question 43

State the role of the hepatic portal vein

Answer 43

The capillary networks in the small intestine combine to form the hepatic portal vein, which transports nutrient-rich blood from the small intestine to the liver.

Question 44

How is water absorbed in the alimentary canal?

Answer 44

The small intestine and the colon (large intestine) absorb water.

• The small intestine absorbs 5–10 dm³ per day
• The colon absorbs 0.3–0.5 dm³ per day

Question 45

Define

assimilation

Answer 45

The movement of digested food molecules into the cells of the body where they are used, becoming part of the cells.

Question 46

Describe the role of the liver in the metabolism of glucose

Answer 46

Excess glucose molecules are combined to make glycogen, which is a short-term energy store (this can also be stored in the muscles).

The glycogen is converted back into glucose and released from being stored in the liver when the body’s glucose level is low.

Further excess glucose may be converted into fat to be used as an energy storage substance.

Question 47

Define

deamination

Answer 47

The removal of nitrogen from excess amino acids to form urea, followed by release of energy from the remainder of the amino acid (CHO component that can be converted into glycogen or glucose).

Question 48

List some other roles of the liver

Answer 48

• Dealing with old red blood cells: changes dead red blood cells to iron and bile.
• Detoxification: breaks down alcohol and other toxins
• Generating heat: very large number of cells means a lot of metabolic reactions take place, producing energy
• Making fibrinogen: a plasma protein which helps in blood clotting when the skin is cut.