B2.1.1 Absorption of the Products of Digestion

Question 1

What happens to triglycerides which have been reformed in the endoplasmic reticulum of epithelial cells lining the ileum?

Answer 1

They are associated with cholesterol and lipoproteins to form chylomicrons.

Question 2

What does the diagram show?

Answer 2

Simple diffusion through a cell membrane from a high to low concentration

Question 3

Diffusion and facilitated diffusion are both passive processed. What is meant by this?

Answer 3

They do not require ATP (energy)

Question 4

What is the function of the endoplasmic reticulum in lipid absorption?

Answer 4

• An organelle in the epithelial cells lining the ileum where monoglyerides and fatty acids are recombined to make triglycerides.
• Triglycerides begin to associate with cholesterol and lipoproteins here also.

Question 5

Why does having many capillaries optimise absorption in the ileum?

Answer 5

Nutrients absorbed in the blood are carried away quickly which maintains the concentration gradient between the ileum and the blood.

Question 6

Define active transport

Answer 6

the movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP (energy) and carrier proteins.

Question 7

What does the diagram show?

Answer 7

Facilitated diffusion via a carrier protein from a high to low concentration

Question 8

What happens to the chylomicrons that are produced in the epithelial cells lining the ileum?

Answer 8

They exit the cells via exocytosis and enter the lymphatic system via lacteals.

Question 9

How are villi adapted to optimise absorption of nutrients?

Answer 9

• They increase the surface area for diffusion
• Very thin walls so less diffusion distance to the blood.
• Many blood capillaries- blood can carry nutrients away and maintain diffusion gradients.
• Epithelial cell lining contains microvilli increasing surface area for absorption further.
• They contain muscle so can move contents of the ileum to maintain concentration gradients.

Question 10

What is a lacteal?

Answer 10

A lymphatic capillary that is found in the centre of each villus of the small intestine.

Question 11

Describe the process of active transport.

Answer 11

• Molecule or ion binds to carrier protein.
• ATP binds to carrier protein, gives a phosphate and ADP is released.
• Carrier protein changes shape and moves molecule to opposite side of membrane.
• Phosphate is released from carrier protein and protein reverts back to start position.

Question 12

Identify the label on the diagram and the type of transport that take place.

Answer 12

Sodium-Potassium Pump (carrier protein)

Active Transport

Question 13

What is a protein channel?

Answer 13

A protein that spans a cell membrane and will only allow specific molecules to pass through. Involved in facilitated diffusion.

Question 14

What is facilitated diffusion?

Answer 14

• Diffusion of molecules or ions aided by carrier proteins or protein channels.
• Does NOT use ATP (energy),

Question 15

Name the products of digestion

Answer 15

Monosaccharides

Amino Acids

Monoglycerides

Fatty Acids

Question 16

Where are the products of digestion absorbed?

Answer 16

Ileum (small intestine)

Question 17

How is the ileum adapted to carry out the process of absorption of nutrients?

Answer 17

Its wall contains many villi, which greatly increases the area for nutrient absorption

Question 18

How does the thin wall of the ileum help to optimise absorption?

Answer 18

Less distance for nutrients to diffuse across before reaching the blood.

Question 19

What does the diagram show?

Answer 19

Facillitate diffusion via a channel protein from high to low concentration

Question 20

What happens to monoglycerides and fatty acids after they have entered the epithelial cells lining the ileum?

Answer 20

They are transported to the endoplasmic reticulum where they are recombined into triglycerides.

Question 21

Micelles are created by an asociation between bile salts and triglycerides. After lipase has acted on micelles of triglyceride we are left with…

Answer 21

Micelles of monoglycerides and fatty acids (still asociated with bile salts)

Question 22

How do monoglycerides and fatty acids enter the epithelial cells lining the ileum?

Answer 22

Simple diffusion

Question 23

Bile salts emulsify fatty acids into smaller structures called…

Answer 23

micelles

Question 24

Define diffusion

Answer 24

the net movement of molecules or ions from a region where they are highly concentrated to a region where they are less concentrated until evenly distributed.

Question 25

Why can monoglycerides and fatty acids enter the epithelial cells of the ileum via simple diffusion?

Answer 25

Because they are non polar molecules so can bypass the non polar fatty acid section of the cell membrane.

Question 26

What is the function of the golgi apparatus in lipid absorption?

Answer 26

An organelle in the epithelial cells lining the ileum where triglycerides association with cholesterol and lipoproteins takes place.

Question 27

What is meant by a chylomicron?

Answer 27

A triglyceride associated with cholesterol and a lipoprotein which aids lipid transport into the lymphatic system.

Question 28

What happens to chylomicrons when they enter the lymphatic system?

Answer 28

They are hydrolysed by an enzyme and enter the blood

Question 29

What is a carrier protein?

Answer 29

• A protein spanning a cell membrane that specific molecules or ions bind to, which causes the protein to change shape and carry the molecule onto the other side of the membrane.
• Involved in facilitated diffusion and active transport.

Question 30

How do fatty acids and glycerol molecules enter the intestinal epithetial cell?

Answer 30

Diffusion

Question 31

Explain the advantage of lipid droplet and micelle formation

Answer 31

droplets increase SA for enzyme action so FASTER hydrolysis

micelle formation carries FA and glycerol through the intestinal membrane

Question 32

How is the golgi involved in the absorption of lipids?

Answer 32

modifies triglycerides

adds protein on/.forms lipoproteins

packages them for their release

/forms vesciles