11) Digestive system

Question 1

Ingestion

Answer 1

Taking in of food through mouth

Question 2

Digestion

Answer 2

Break down of large insoluble molecules into small soluble ones using enzymes

Question 3

Absorption

Answer 3

Movement of small molecules from walls of small intestine into blood

Question 4

Assimilation

Answer 4

Movement of digested food molecules into cells to become part of the cell

Question 5

Egestion

Answer 5

Removal of undigested food molecules out of the rectum through anus in form of faeces

Question 6

Physical digestion

Answer 6

1.The break down of large food pieces into smaller ones
2.with no chemical change
3. To increase the surface area, for faster chemical digestion by enzymes

Question 7

Examples of physical digestion

Answer 7

1. Chewing and grinding food in mouth by teeth
2. Tongue mixes food with saliva, softening the food for easier swallowing
3. Churning action in stomach to help mix food with gastric juice
4. Emulsification by bile salts

Question 8

Chemical digestion

Answer 8

breaking down large insoluble food molecules into small soluble ones by enzymes to be absorbed into the blood

Question 9

Enzymes for chemical digestion and where they are found

Answer 9

1. Amylase: Mouth, small intestine
2. Pepsin: stomach
3. Trypsin : small intestine
4. Lipase : small intestine
5. Maltase : small intestine

Question 10

Digestion in mouth

Answer 10

Physical digestion:
1. Teeth: Premolars and molars, crush and grind large complex insoluble food pieces to smaller ones, to increase surface area for better amylase activity.
2. Tongue : mixes food with saliva

Chemical digestion:
By saliva which contains
1. Water: to soften food
2. Mucus: to facilitate swallowing
3. Amylase: breaks down starch into maltose
(food becomes a bolus)

Question 11

Digestion in stomach

Answer 11

Physical digestion:
1. Churning action: done by muscular walls of stomach to help mix the food with gastric juice

Chemical digestion:
Gastric juice which contains
1. Pepsinogen (inactive pepsin)
2. Hydrochloric acid (HCL)
3. Mucus and water
proteins are broken down into amino acids by pepsin
(Chyme forms)

Question 12

What does hydrochloric acid do

Answer 12

1. Provide optimum acidic pH for pepsin
2. Kill microorganisms as bacteria by denaturing their enzymes
3. Activates pepsinogen to active pepsin

Question 13

Digestion in duodenum

Answer 13

Physical digestion:
1. Bile produced in liver, stored in gallbladder is secreted into duodenum

Chemical digestion:
Pancreatic juice which contains
1. Mucus
2. Water
3. Amylase for breakdown of starch into maltose
4. Trypsin for breakdown of proteins into amino acids
5. Lipase for breakdown of lipids into fatty acids and glycerol
6. HCO3- : neutralizes acidity of chyme

Question 14

Bile function

Answer 14

1. Bile salts : emulsification of large fat droplets into smaller fat droplets to increase surface area for better lipase activity
2. HCO3- : Neutralises the acidity coming from stomach to make it slightly alkaline for optimum pH for enzymes
3. Bile pigment: gives colour of faeces

Question 15

Digestion in ileum

Answer 15

Chemical digestion:
Enzymes in epithelial walls of small intestine
1. Maltase for the breakdown of maltose into glucose
2. Lipase for the breakdown of lipids into fatty acids and glycerol

Absorption: movement of digested food molecules through walls of small intestine into blood
(End of digestion in ileum)

Question 16

Describe shape of ileum

Answer 16

Long and coiled with inner folding (villi) to provide large surface area for maximum absorption of digested food molecules

Question 17

Structure of villus

Answer 17

1. Thin wall (one cell thick epithelium): for shorter diffusion distance
   2.Goblet cells
2. Blood capillaries
3. Lacteal

Question 18

Goblet cells in alimentary canal

Answer 18

-Secretes sticky mucus to trap bacteria
-protects inner lining of alimentary canal from being digested by enzymes

Question 19

Blood capillaries in villus

Answer 19

Absorbs digested food molecules (e.g. glucose and amino acids) to the liver through hepatic portal vein

Question 20

Lacteal

Answer 20

Absorbs fatty acids and glycerol to be transported to lymphatic system

Question 21

Epithelial cells

Answer 21

1. Microvilli to increase surface area for faster absorption of digested food molecules into blood
2. Many mitochondria for more aerobic respiration for more energy release for absorption of some food molecules by active transport

Question 22

Diarrhoea

Answer 22

Excessive loss of water and salts in watery faeces, occurs when not enough water is absorbed back to body from faeces

Question 23

Consequences of diarrhoea

Answer 23

1. Loss of water leading to dehydration
2. Decrease in water potential of the blood
3. So water will leave cells by osmosis, less water inside cells for metabolic reactions
4. Body organs shut down
5. coma
6. death

Question 24

How cholera causes diarrhoea

Answer 24

1. Cholera bacteria in small intestine releases toxins
2. Toxins stimulate the release of chloride ions into lumen of small intestine
3. Lowering the water potential of lumen in small intestine
4. So water will move from blood to lumen by osmosis
5. Causing watery faeces diarrhoea

Question 25

Solutions to control the spread of cholera (7)

Answer 25

1. Good personal hygiene 2. Oral rehydration therapy 3. Antibiotics 4. Dont use human faeces as fertiliser 5. drink bottled water 6. good sewage treatment 7. Keep food covered from flies and store in fridge

Question 26

Incisor

Answer 26

-Biting and cutting -Chisel shaped and sharp

Question 27

Canine

Answer 27

-Tearing food -Pointed

Question 28

Premolars

Answer 28

-Crushing and chewing -2 or 3 cusps

Question 29

Molars

Answer 29

-Chewing and grinding -4 or 5 cusps

Question 30

Enamel

Answer 30

-Made of calcium and phosphate -Hardest part of the body

Question 31

Dentine

Answer 31

Less hard than enamel

Question 32

Pulp

Answer 32

Contains blood vessels and nerve cells

Question 33

Gum

Answer 33

Holds the tooth in jaw

Question 34

Cement

Answer 34

-Attaches the tooth to bones -has fibres growing out of it -Allows slight movement when chewing

Question 35

How to prevent tooth decay

Answer 35

1.Regular brushing of teeth 2.Regular visits to the dentist 3.Use fluoride in tooth paste to strengthen enamel 4. Eat less sugar 5. Use dental floss

Question 36

Role of liver in digestion

Answer 36

Produces bile juice 1. Bile salts: - which emulsify large fats droplets into smaller fat droplets, to increase surface area, for better lipase activity 2. Bicarbonate/HCO3- : Neutralises the acid coming from the stomach ,causing pH to become more alkaline, to provide optimum temp for trypsin and lipase

Question 37

Role of liver with amino acids

Answer 37

1. In case of EXCESS amino acid: - Liver carries deamination, where nitrogen containing part is removed, and amino acids are converted to ammonia, then to urea to be released in urine by kidney, carbohydrate part is stored 2. Protein synthesis: -by building up large protein molecules as fibrinogen

Question 38

Role of liver in excretion

Answer 38

1. Deamination: -Breakdown of excess amino acids producing urea to be excreted in urine 2. Destruction of old RBC: -Breakdown old RBC in liver, producing bile pigments excreted in faeces, iron is stored 3- Detoxification: - break down drugs such as alcohol 4- Breakdown of hormones: after carrying their function

Question 39

Role of liver in assimilation

Answer 39

1. Excess glucose stored in liver as glycogen 2.Glucose used in respiration 3.Amino acids used in protein synthesis to form proteins (assimilation is the process by which digested food molecules are absorbed into cells and become part of cells)

Question 40

Role of liver in case of increase in blood glucose level

Answer 40

1.Pancreas detects increase in blood level 2.Secretes insulin into blood 3. Insulin stimulates the liver to store excess glucose as glycogen 4. Returning blood glucose back to normal 5. Negative feedback mechanism

Question 41

Role of liver in case of decrease in blood glucose level

Answer 41

1. Pancreas will detect the decrease in blood glucose level 2.It will secrete glucagon into blood 3.Glucagon will stimulate the liver to break down glycogen into glucose 4.Blood glucose level will increase, returning back to normal 5.Negative feedback mechanism

Question 42

Examples of plasma proteins in blood

Answer 42

1.Enzymes 2.Antibodies 3.Insulin, glucagon 4.Fibrinogen