Digestion/absorption

Question 0

What us heterotrophic nutrition?

Answer 0

Taking in complex organic molecules and breaking them down into smaller simpler molecules - digestion

Question 1

What is autotrophic nutrition?

Answer 1

Taking simple inorganic molecules and using them to form complex substances - photosynthesis

Question 2

What are the two types of digestion?

Answer 2

Physical/mechanical - e.g teeth

Chemical - e.g. Saliva

Question 3

What is the role of the oesophagus in digestion?

Answer 3

Thick muscular walled tube

Muscles in oesophagus contract to propel food and drink to the stomach

Lubricated by mucus

Question 4

What is the role of the stomach in digestion?

Answer 4

It’s a muscular sac that receives food from the oesophagus

Glands - secrete HCl, mucus, water, hormones

Optimum pH for pepsin

Muscular movements churn up food and further physically break it down

Question 5

What is the role of the small intestine in digestion?

Answer 5

Duodenum (major site of digestion)

• glands secret enzymes
• bile delivered via bile duct
• water added - hydrolysis

Ileum (major site of absorption)

• completes the digestion of proteins, carbohydrates and fats
• location of most absorption of small soluble food molecules produced by digestion

Question 6

What is the role of the large intestine in digestion?

Answer 6

Absorbs water

Remains become drier/thicker - faeces

Question 7

What is the role of the rectum in digestion?

Answer 7

Stores and compacts faeces before being egested from the body via the anus

Question 8

Where is carbohydrase made?

Answer 8

Salivary glands

Pancreas

Small intestine

Question 9

Where is protease made?

Answer 9

Stomach

Small intestine

Pancreas

Question 10

Where is lipase made?

Answer 10

Small intestine

Pancreas

Question 11

Where is amylase made?

Answer 11

Salivary glands

Pancreas

Question 12

What are villi/microvilli?

Answer 12

Villi are 1mm projections from the wall of the small intestine

Microvilli are the even small projections (0.6um) from the surface membrane of the epithelial cells that line the villi

Question 13

What are some features of villi/microvilli?

Answer 13

Huge surface area - faster diffusion

Villi can move - villi muscles contract/relax so constantly mix up contents of small intestine - conc. gradient maintained

One cell thick - short diffusion distance

Have capillaries in them - easier for diffusion of nutrients

Question 14

Why can the body not just rely on diffusion for glucose absorption and what is the solution to this?

Answer 14

Diffusion is too slow - body needs couldn’t be met. If glucose conc. gets low in the intestines it would start to diffuse back out of the epithelial cells into the lumen

Solution? Active transport/co transport

Question 15

Describe the role of co transport in the absorption of glucose

Answer 15

Sodium ions are actively transported out of epithelial cells by the Na/K pump into the blood

This causes there to be a higher conc. of sodium ions in the lumen compared to the inside of the epithelial cells

Sodium ions diffuse down their conc. gradient through a co transporter protein into the epithelial cells. Glucose is carried into the cell alongside them.

The glucose passes into the blood plasma by facilitated diffusion down a conc. gradient using another type of specific carrier

The blood is constantly moving - takes glucose with it so conc. is always higher in cell

Question 16

The epithelial cells that line the small intestine are adapted for the absorption of glucose, explain how (6 marks)

Answer 16

1. Microvilli;
2. Large/increased surface area;
3. Many mitochondria;
4. (Mitochondria/respiration) produce ATP / release or provide energy (for active transport);
5. Carrier proteins for active transport;
6. Channel / carrier proteins for facilitated diffusion;
7. Co-transport of sodium (ions) and glucose or symport / carrier protein for sodium (ions) and glucose;
8. Membrane-bound enzymes digest disaccharides / produce glucose