digestion and absorption Flashcards

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1
Q

What three things can be digested in mammals?

A
  1. carbohydrates
  2. proteins
  3. Lipids
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2
Q

What is the process of the digestion of carbohydrates?

A
  • It begins in the mouth
  • Continues in the duodenum
  • Completed in the ileum.
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3
Q

How many enzymes does carbohydrates need to hydrolyses them into monosaccharides?

A

Carbohydrates required more than one enzyme to hydrolyze them into monosaccharides such as amylase and membrane - bound disaccharidases.

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4
Q

What is the function of amylase in the digestion of carbohydrates?

A

Amylase is produced by the pancreas and salivary glands. It hydrolyses polysaccharides into the disaccharide maltose by hydrolysing the glycosidic bonds.

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5
Q

What are the membrane - bound disaccharides that are involved in the digestion of carbohydrates and what is their function?

A

Sucrase and lactase are the membrane - bound enzymes that hydrolyse sucrose and lactose into monosaccharides.

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6
Q

How many enzymes are involved in the digestion of proteins?

A

Three enzymes that can be used to hydrolyse proteins ( large polymer molecules) are :
- endopeptidases
- exopeptidases
- membrane -bound dipeptidases

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7
Q

What is the function of endopeptidases?

A

An enzyme that is involved in the digestion of proteins - it hydrolyses peptide bonds between amino acids in the middle of a polymer chain).

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8
Q

What is the function of exopeptidases?

A

An enzyme that is involved in the digestion of proteins - it hydrolyses peptide bonds between amino acids at the end of a polymer chain.

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9
Q

What is the function of a membrane - bound dipeptidases?

A

An enzyme involved in the digestion of proteins - it hydrolyses peptide bonds between two amino acids.

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10
Q

What is the process for the digestion of proteins?

A

Protein digestion starts in the stomach, continues in the duodenum and is fully digested in the ileum.

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11
Q

What are lipids digested by?

A

They are digested by lipase and the action of bile salts.

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12
Q

Where is lipase produced and what is its function?

A

Lipase is produced in the pancreas and it can hydrolyse the ester bond in triglycerides to form the monosaccharides and fatty acids.

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13
Q

Where is bile salts are produced and what is its function?

A

Bile salts are produced in the liver and can emulsify lipids to form tiny droplets, micelles. This increases the surface area for lipase to act on.

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14
Q

What 2 stages does digestion lipids involve?

A
  1. Physical ( emulsification and micelle formation )
  2. Chemical ( lipase )
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15
Q

What is the physical stage that involves the digestion of lipids?

A

Physical ( emulsification and micelle formation).
- Lipids are coated in bile salts to create an emulsion
- Many small droplets of liquid provides a larger surface area to enable the faster hydrolysis action by lipase

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16
Q

What is the chemical stage that involves the digestion of lipids?

A

Chemical ( lipase )
- Lipase hydrolyses lipids into glycerol and fatty acids ( some monoglycerides ).

17
Q

What are micelles ?

A

They are water soluble vesicles formed of the fatty acids , glycerol, monoglycerides and bile salts.

18
Q

What do micelles deliver?

A

Micelles deliver fatty acids, glycerol and monoglycerides to the epitheilal cells of the ileum for absorption.

19
Q

Where are the products of digestion absorbed at?

A

They are absorbed across the cells lining the ileum.

20
Q

Describe the features of the ileum.

A

The ileum wall is covered in villi, which have thin walls surrounded by a network of capillaries and epithelial cells have even smaller micro villi.

21
Q

How do the features of ileum maximise absorption.

A

This happens by increasing surface area, decreasing the diffusion distance and maintaining a concentration gradient.

22
Q

What needs to be required for glucose and amino acids to be absorbed?

A
  • To absorb glucose and amino acids from the lumen to the gut there must be a higher concentration in the lumen compared to the epithelial cells ( for facilitated diffusion ).
23
Q

Why is active transport and co - transport required for the absorption of glucose and amino acids ?

A

As there is a higher concentration of glucose and amino acids in the epithelial cells rather than in the lumen.

24
Q

Where are lipids digested?

A

Lipids are digested into monoglycerides and fatty acids by the action of lipase and bile salts.

25
Q

What happens when micelles encounter the ileum epithelial cells?

A

When they encounter the ileum epithelial cells, they diffuse across the cell-surface membrane to enter the cells of the epithelial cells due to the non-polar nature of the fatty acids and monoglycerides.
once in the cell, these will be modified into triglycerides in the endoplasmic reticulum and Golgi body.

26
Q
A