Digestion and absorption: the non-fermentative process

Question 1

How does the small intestine increase surface area?

Answer 1

Crypts of lieberkuhn, villi, microvilli (on enterocytes), large folds (plicae circulares)

Question 2

What substances are attached to the apical surface of enterocytes and project into the glycocalyx?

Answer 2

Proteins/ digestive enzymes

Question 3

What cell contributes to the mucous layer of the glycocalyx

Answer 3

Goblet cells

Question 4

What layer must nutrients pass through before diffusing into the enterocytes?

Answer 4

Unstirred water layer + glycocalyx

Question 5

The tight junctions connecting adjacent enterocytes are permeable/ impermeable to what?

Answer 5

Permeable: ions, electrolytes
Impermeable: organic molecules

Question 6

What is the ‘lateral space’

Answer 6

The gap of space below the tight junction

Question 7

What are the two glasses of enzymes?

Answer 7

Luminal, membrane-bound

Question 8

What are the 3 types of CHO

Answer 8

Fibres: structural part of plants
Sugars: simple or complex
Starch: two main ones: amylose, amylopectin

Question 9

During the luminal phase of digestion, what is being digested?

Answer 9

CHO

Question 10

During the membranous phase of digestion, what is being digested?

Answer 10

Sugars

Question 11

What are starches digested by?

Answer 11

a-amylase

Question 12

What type of enzymes break peptide bonds?

Answer 12

Proteolytic enzymes

Question 13

Compare endopeptidases and exopeptidases

Answer 13

Endo: cleave peptide bonds from within the amino acid chain
Exo: cleave 1 peptide bones from the end

Question 14

What 3 processes must occur for lipids to be digested?

Answer 14

Emulsification (reduces size), hydrolisation (allows for packing), formation of micelles (allows lipids to diffuse through gut lumen)

Question 15

What action do lipase and co-lipase have on droplets of lipid?

Answer 15

Co-lipase clears a path for the lipid while lipase hydrolyses it into two free fatty acids (FFA) and a monoglyceride

Question 16

What active transport pump is used to keep sodium concentration low in the cell?

Answer 16

Na+/K+ pump, 3 sodium ions (out) for 2 potassium (in)

Question 17

What does secondary active transport use to power its pump?

Answer 17

Harnesses potential energy of electrochemical sodium gradient

Question 18

How does the Na+/ glucose cotransporter work?

Answer 18

Attaches 1/2 sodium ions + glucose molecule (coming from the outside of the cell), once all binding sites are filled, conformational change occurs and brings in all 2-3 molecules.

Question 19

How does the na+/ amino acid cotransporter work?

Answer 19

Attaches 1/2 sodium ions + amino acid molecule (coming from the outside of the cell), once all binding sites are filled, conformational change occurs and brings in all 2-3 molecules.

Question 20

What is an example of tertiary active transport?

Answer 20

Cl-/ HCO3- exchanger