Biology Unit 4.3 Animal Nutrition

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Unit 4.3 Animal Nutrition

1. State what is meant by the term balanced diet and describe a balanced diet related to age, sex and activity of an individual.

A balanced diet is a diet that includes all the necessary nutrients needed for an individual to maintain their health. A balanced diet should include carbohydrates, fats, proteins, vitamins, minerals, fibre and water.

Typically, older individuals need more food than the young; males need more food than females; more active individuals need more food than less active individuals. Of course, this doesn't factor in lifestyles, activity and such, so this is not all set in stone. It depends on the individual.

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

Malnutrition can mean the lack of food, resulting in starvation. It can also refer to the lack of important nutrients. If your diet contains too much fat, coronary heart disease and obesity could be a result. The lack of fibre will result in constipation, as the role of fibre is to help bowel movement.

3. Define ingestion as taking substances (e.g. food, drink) into the body through the mouth.

4. Define egestion as passing out of food that has not been digested, as faeces, through the anus.

5. Identify the main regions of the alimentary canal and associated organs including mouth, salivary glands, oesophagus, stomach, small intestine: duodenum and ileum, pancreas, liver, gall bladder, large intestine: colon and rectum, anus.

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6. Describe the functions of the regions of the alimentary canal listed above, in relation to ingestion, digestion, absorption, assimilation and egestion of food.

Mouth: where food enters the alimentary canal

Salivary glands: produce saliva containing amylase to help break down the food 

Oesophagus: a muscular tube where ingested food is led down to the stomach

Liver: produces bile to emulsify fats

Stomach: where part of digestion occurs; the muscles in the stomach break down the food

Gall bladder: where bile is stored

Pancreas: produces digestive enzymes to break down food

Small intestine (duodenum): where food is mixed with digestive enzymes and bile

Small intestine (ileum): where digested food is absorbed by the blood (assimilation)

Large intestine (colon): where water is absorbed

Large intestine (rectum): where faeces is stored

Anus: egested substances (i.e. faeces) are removed

7. Define digestion as the break-down of large, insoluble food molecules into small, water-soluble molecules using mechanical and chemical processes.

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

Tooth type	Quantity	Role
Incisor	8	Biting and cutting
Canine	4	Piercing and cutting
Premolar	8	Crushing and chewing
Molar	12	Crushing and chewing

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9. State the causes of dental decay and describe the proper care of teeth.

Dental decay occurs when the hard enamel of the tooth is damaged. This happens when bacteria enters the mouth and converts sugars into acid. The acid essentially eats its way through the enamel and can enter the soft dentine inside the tooth.

To avoid dental decay, cut down on food and drink high in sugar content, consistently and properly brush your teeth, and use toothpaste with fluorine in it so plaque can be removed. 

10. State the significance of chemical digestion in the alimentary canal in producing small, soluble molecules that can be absorbed. 

Our bodies can't absorb food molecules if they are too big; they won't be able to pass through the walls of the villi. This is why the body produces bile and enzymes to chemically digest food, so the particles are small enough to be dissolved and assimilated. 

11. Outline the role of bile in emulsifying fats, to increase the surface area for the action of enzymes.

Lipase is the enzyme that breaks down fats, but it can't do so unless the fat is broken down into smaller portions. The role of bile is to break down fats, called emulsifying, so that it gives the lipase a bigger surface area to work on. 

12. State where, in the alimentary canal, amylase, protease and lipase enzymes are secreted.

Amylase: pancreas and salivary glands

Protease: stomach and pancreas

Lipase: pancreas

13. State the functions of a typical amylase, a protease and a lipase, listing the substrate and end-products. 

Enzyme	Substrate (what the enzyme works on)	End product(s)
Amylase	Starch	Glucose
Protease	Proteins	Long chains of amino acids
Lipase	Lipids (fats)	Glycerol and fatty acids

14. Define absorption as movement of digested food molecules through the wall of the intestine into the blood.

15. Describe the significance of villi in increasing the internal surface area of the small intestine.

If you consider the shape of villi, you will see that they are like small, skinny mountains. This increases the internal surface area of the small intestine, maximising assimilation of food molecules. 

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16. Identify the small intestine as the region for the absorption of digested food.

As briefly mentioned above, the small intestine is split into two: the duodenum and the ileum. The ileum (second half of the small intestine) is where digested food is absorbed.

17. Describe the structure of a villus, including the role of capillaries and lacteals. 

The walls of the villi are very thin so that molecules can be absorbed easily. Villi contain blood capillaries in them so that when the molecules diffuse through the walls, they go into the bloodstream. The concentration of food is lower in the blood so diffusion happens quickly. 

The lacteal is in between the blood capillaries. Its function is to transport glycerol and fatty acids away form the small intestine. 

18. Describe the role of the liver in the metabolism of glucose (glucose → glycogen).

This process is called glucoregulation. You will come across this again in the hormones unit, but here is what it is: when glucose levels in the body are too high, the pancreas secretes insulin, a hormone that regulates your body's glucose levels, into the bloodstream. This allows the liver to convert the glucose into glycogen, which is stored. When the glucose levels are too low, insulin will not be secreted, allowing the stored glycogen to break down into glucose that is then used by the body. 

19. Describe the role of fat as an energy storage substance.

Lipids are broken down into glycerol and fatty acids. The liver can convert glycerol into glucose for the body to use as energy.