CHAP 6 NUTRITION IN HUMANS

Question 1

State the 5 different processes in nutrition [5]

Answer 1

1) Ingestion ( intake of food )
2) Digestion ( breakdown of food )
3) absorption (breakdown of food)
4) assimilation ( movement of nutrients into blood stream
5) egestion ( removal or undigested food )

Question 2

Describe the FUNCTIONS of MOUTH [3]

Answer 2

1) teeth chew & break the food into smaller pieces to increase surface area to volume ratio for digestive enzymes to work more efficiently
2) salivary glands which secrete saliva which contains salivary amylase to break down starch into maltose (pH7)
3) tongue rolls the food into a bolus , which is then swallowed

• starch digestion is initiated by salivary amylase in the mouth -> pancreatic amylase in the small intestine

Question 3

Describe the functions of OESOPHAGUS [1]

Answer 3

• food moves along the oesophagus due to wave-like contractions of the muscular walls of the oesophagus [ peristalsis ]

Question 4

Describe Functions [1] & ADAPTATIONS of STOMACH [4]

Answer 4

1) produces protease/pepsin to digest proteins to polypeptides

Adaptations :
1) muscular bag with elastic walls
2) gastric glands secrete protease & mucus
3) mucus protects stomach walls from the acidic gastric juice
4) peristalsis in the stomach churns the food to break the food up & mix it thoroughly with gastric juice
5) Gastric juice ( acidic pH2)
- kill germs & bacteria
- stop the activity of salivary amylase by denaturing it
- provide an optimum pH for protease to work in

Question 5

Describe the Functions of SMALL INTESTINES [4]

Answer 5

1) pancreatic amylase digest starch -> maltose
2) maltase digest maltose -> glucose
3) Lipase digest fats -> fatty acids & glycerol
4) protease digest polypeptides to amino acids

Question 6

Describe the function of LARGE INTESTINE [1]

Answer 6

1) absorbs water & mineral salts

Question 7

describe what happens when CHYME enters the DUODENUM [3]

Answer 7

1) stimulates pancreatic juice which passes through the pancreatic duct into the duodenum [ lipase , amylase , protease ]
2) gall bladder to release bile [ passes through the bile duct into the duodenum ]
3) the epithelial cells in the small intestines to secrete the enzymes maltase , lipase & protease

Question 8

Describe the process of FAT digestion in the DUODENUM

Answer 8

1) The liver produces bile & is stored in the gall bladder & released into the duodenum
2) Bile emulsifies FATS by reducing the attractive forces between the fat molecules
3) Large Fat molecules -> tiny fat droplets -> increases surface area of fats
4) emulsified fats are digested by lipase produced by yeast epithelial cells into fatty acids & glycerol

• Fats (bile) -> tiny fat droplets (pancreatic lipase) -> fatty acids & glycerol

Question 9

describe process of CARBOHYDRATES digestion in MOUTH & DUODENUM [2]

Answer 9

1) Salivary amylase digest starch into maltose [ only a little can be digested as food do not remain long in the mouth ]
2) Starch is digested by pancreatic amylase into maltose , maltase secreted by epithelial cells in small intestines digest maltose into glucose into molecules that is small & soluble enough to be absorbed into blood stream

Question 10

Describe the digestion of PROTEINS in STOMACH & DUODENUM [2]

Answer 10

1) stomach protease digest some protease into polypeptides & undigested proteins enters the small intestine
2) Polypeptides further digested by protease into amino acids into small & soluble substances to be absorbed into the bloodstream

Question 11

Describe the function of Large intestines [1]

Answer 11

• absorbs 90% of the remaining water & mineral salts from the undigested food until it reaches the rectum

Question 12

Describe the process of ABSORPTION in the ILEUM ( main region of absorption in small intestine )

Answer 12

1) walls of small intestine has numerous folds

2) these folds contain villi & it has micro villi which increases surface area to volume ratio for greater rate of absorption

3) thin walls of the villi makes it easy for nutrients to pass through to the bloodstream (epithelium - one cell thick)

4) length of small intestines ( ~6m ) provides sufficient time for absorption

5) many capillaries to help carry away absorbed nutrients quickly ( the continual transport of nutrients by the capillaries maintains the concentration gradient required for absorption to take place

6) blood capillaries help to transport amino acids & glucose to the body

7) Diffusion
- glucose & amino acids diffuse into the blood capillaries
- glycerol & fatty acids diffuse into the epithelium , combined to form, minute fat globules -> enters the central lacteal

Question 13

Summary of Digestion

Answer 13

1) Mouth
- Starch (salivary amylase) -> maltose

2) Stomach
- Proteins (protease) -> polypeptides

3) Small intestines
- starch (pancreatic amylase) -> maltose
- maltose (maltase) -> glucose
- fat (lipase) -> fatty acids & glycerol
- protein (protease) -> polypeptides
- polypeptides (protease) -> amino acids

Question 14

define assimilation

Answer 14

process where some of the absorbed food substances are converted into new cytoplasm & used to provide energy

Question 15

Describe the process of what happens to Amino acids & Glucose after absorption [6]

Answer 15

1) glucose & amino acids are absorbed into blood capillaries
2) Hepatic Portal Vein ( transport nutrients from small intestines to Liver ) 3) Insulin ( hormone ) stimulates Liver to convert excess glucose to glycogen then stored in liver
4)excess amino acids are deaminated into urea
5) Hepatic Vein ( transports nutrients to the rest of the body body )
6) Body cells
- glucose is used as a substrate in cellular respiration to provide energy for the cells
- amino acids are synthesised into new cytoplasm for cell growth & repair + also used to synthesise enzymes & hormones