3.3.3.2 Absorption of the Products of Digestion

Question 1

What does the diagram show?

Answer 1

Active transport of molecules by a carrier protein against a concentration gradient.

Question 2

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

Answer 2

They are associated with cholesterol and lipoproteins to form chylomicrons.

Question 3

What does the diagram show?

Answer 3

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

Question 4

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

Answer 4

They do not require ATP (energy)

Question 5

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

Answer 5

Glucose carrier protein

Facilitated diffusion

Question 6

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

Answer 6

• 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 7

Why does having many capillaries optimise absorption in the ileum?

Answer 7

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

Question 8

Identify the label on the diagram.

Answer 8

A capillary within a villus

Question 9

What does the diagram show?

Answer 9

The path taken by glucose/amino acids through the epithelial cells of the ileum and into the blood.

Question 10

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

Answer 10

Sodium-Glucose co-transport carrier protein

Facillitated diffusion

Question 11

Define active transport

Answer 11

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 12

What does the diagram show?

Answer 12

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

Question 13

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

Answer 13

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

Question 14

What is happening at stage 3 in the diagram?

Answer 14

Glucose is moving into the blood stream via facilitated diffusion through a carrier protein.

Question 15

How are villi adapted to optimise absorption of nutrients?

Answer 15

• 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 16

What is happening at stage 2 in the diagram?

Answer 16

• Sodium ions are moving into the epithelial cell through a cotransport carrier protein via facilitated diffusion.
• A glucose molecule is carried through the cotransport carrier protein by the sodium ion (still facilitated diffusion)
• The sodium ion moves down a concentration gradient
• Glucose moves against its concentration gradient.

Question 17

What is a lacteal?

Answer 17

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

Question 18

Describe the process of active transport.

Answer 18

• 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 19

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

Answer 19

Sodium-Potassium Pump (carrier protein)

Active Transport

Question 20

What is a protein channel?

Answer 20

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

Question 21

What is facilitated diffusion?

Answer 21

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

Question 22

Name the products of digestion

Answer 22

Monosaccharides

Amino Acids

Monoglycerides

Fatty Acids

Question 23

Where are the products of digestion absorbed?

Answer 23

Ileum (small intestine)

Question 24

Which other product of digesiton is absorbed into the blood via the same method as glucose?

Answer 24

Amino acids

Question 25

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

Answer 25

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

Question 26

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

Answer 26

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

Question 27

What does the diagram show?

Answer 27

Facillitate diffusion via a channel protein from high to low concentration

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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

Question 30

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

Answer 30

Simple diffusion

Question 31

Bile salts emulsify fatty acids into smaller structures called…

Answer 31

micelles

Question 32

Define diffusion

Answer 32

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 33

By what process is glucose absorbed from the ileum and into the blood?

Answer 33

Facilitated diffusion

Co-transport (indirect active transport)

Question 34

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

Answer 34

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

Question 35

What is happening at stage 1 in the diagram?

Answer 35

• Sodium ions are actively transported out of the epithelial cell by a sodium-potassium pump.
• Potassium ions are actively transported into the cell.
• This creates a lower sodium ion concentration in the epithelial cell than in the ileum.

Question 36

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

Answer 36

• modifies triglycerides
• combines triglycerides with proteins
• packaged for release/exocytosis

Question 37

What is meant by a chylomicron?

Answer 37

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

Question 38

What happens to chylomicrons when they enter the lymphatic system?

Answer 38

They are hydrolysed by an enzyme and enter the blood

Question 39

What is a carrier protein?

Answer 39

• 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 40

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

Answer 40

Diffusion

Question 41

Explain the advantage of lipid droplet and micelle formation

Answer 41

droplets increase SA for enzyme action so FASTER hydrolysis

micelle formation carries FA and glycerol through the intestinal membrane

Question 42

How is the golgi involved in the absorption of lipids?

Answer 42

modifies triglycerides

adds protein on/.forms lipoproteins

packages them for their release

/forms vesciles