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Biology > 3.3.3 digestion and absorption > Flashcards

3.3.3 digestion and absorption Flashcards

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1
Q

give some examples of large biological molecules

A

starch, proteins

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2
Q

can large biological molecules cross the cell membrane and what does this mean can’t happen

A

large biological molecules in food are too big to cross cell membranes so they can’t be absorbed from the gut into the blood

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3
Q

what happens to these larger molecules during digestion

A

during digestion, these larger molecules are broken down into smaller molecules (e.g. glucose, amino acids)

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4
Q

can these smaller molecules move across cell membranes and what does this allow to happen

A

smaller molecules can move across cell membranes so they can be easily absorbed from the gut into the blood

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5
Q

what happens after these smaller molecules are absorbed from the gut into the blood

A

they can be transported around the body for use by the body cells

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6
Q

what are most large biological molecules

A

polymers

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7
Q

what are these larger molecules/polymers broken down into and by what process

A

broken down into smaller molecules (monomers) using hydrolysis reactions

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8
Q

what happens in a hydrolysis reaction (simplified)

A

hydrolysis reactions break bonds by adding water

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9
Q

during hydrolysis, what are carbohydrates broken down into

A

disaccharides then monosaccharides

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10
Q

during hydrolysis, what are fats broken down into

A

fatty acids and monoglycerides

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11
Q

during hydrolysis, what are proteins broken down into

A

amino acids

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12
Q

what are digestive enzymes used for?

A

digestive enzymes are used to break down biological molecules in food

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13
Q

where can digestive enzymes be produced

A

variety of digestive enzymes are produced by specialised cells in the digestive systems of mammals

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14
Q

what do these digestive enzymes mix with?

A

food

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15
Q

do different enzymes work with different food molecules?

A

enzymes only work with specific substrates so different enzymes are need to catalyse the breakdown of different food molecules

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16
Q

DIGESTION OF CARBOHYDRATES
what enzyme catalyses the breakdown of starch

A

amylase is the digestive enzyme that catalyses the breakdown of starch

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17
Q

DIGESTION OF CARBOHYDRATES
what is starch made of

A

starch is a mixture of 2 polysaccharides, each made from long chains of alpha glucose molecules

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18
Q

DIGESTION OF CARBOHYDRATES
how does amylase work

A

amylase works by catalysing hydrolysis reactions that break the glycosidic bonds in starch to produce maltose (disaccharide)

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19
Q

DIGESTION OF CARBOHYDRATES
where is amylase produced

A

amylase is produced by the salivary glands and the pancreas

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20
Q

DIGESTION OF CARBOHYDRATES
as a result of where amylase is produced, where is it released into

A
  • the mouth
  • the small intestine
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21
Q

DIGESTION OF CARBOHYDRATES
what are membrane-bound disaccharides

A

membrane bound disaccharides are enzymes that are attached to the cell membranes of epithelial cells lining the ileum (final part of small intestine)

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22
Q

DIGESTION OF CARBOHYDRATES
what do membrane-bound disaccharides help to do

A

they help to break down disaccharides into monosaccharides (involves hydrolysis of glycosidic bonds)

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23
Q

DIGESTION OF CARBOHYDRATES
examples of membrane bound disaccharides

A
  • sucrase
  • maltase
  • lactase
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24
Q

DIGESTION OF CARBOHYDRATES
disaccharide sucrose

A

sucrose (disaccharide) is broken down by sucrase into glucose and fructose (monosaccharides)

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25
DIGESTION OF CARBOHYDRATES disaccharide maltose
maltose (disaccharide) is broken down by maltase into glucose and glucose (monosaccharides)
26
DIGESTION OF CARBOHYDRATES disaccharide lactose
lactose (disaccharide) is broken down by lactase into glucose and galactose (monosaccharides)
27
DIGESTION OF CARBOHYDRATES what happens to the monosaccharides
monosaccharides can be transported across the epithelial cell membranes in the ileum via specific transporter proteins
28
DIGESTION OF LIPIDS what enzyme catalyses the breakdown of lipids
lipase enzymes catalyse the breakdown of lipids
29
DIGESTION OF LIPIDS what are lipids broken down into
monoglycerides and fatty acids
30
DIGESTION OF LIPIDS what does the breakdown of lipids involve
involves the hydrolysis of the ester bonds in lipids
31
DIGESTION OF LIPIDS where is lipase made
lipases are mainly made in the pancreas
32
DIGESTION OF LIPIDS where are lipases secreted
they are then secreted into the small intestine where they act
33
DIGESTION OF LIPIDS what do bile salts do
bile salts emulsify lipids - cause the lipids to form small droplets
34
DIGESTION OF LIPIDS what are bile salts produced by
bile salts are produced by the liver
35
DIGESTION OF LIPIDS are bile salts enzymes
no
36
DIGESTION OF LIPIDS how do bile salts affect surface area
several small lipid droplets have a bigger surface area than a single large droplet
37
DIGESTION OF LIPIDS how does increased surface area as a result of bile salts give an advantage
formation of small droplets increases the surface area of lipid that's available for lipases to work on
38
DIGESTION OF LIPIDS micelles
once lipid has been broken down by lipase, the monoglycerides and fatty acids stick with the bile salts to form tiny structures called micelles
39
DIGESTION OF LIPIDS what do micelles help do
micelles help the products of lipid digestion to be absorbed
40
DIGESTION OF PROTEINS what are proteins broken down by
proteins are broken down by a combination of different peptidases
41
DIGESTION OF PROTEINS what are peptidases
enzymes that catalyse the conversion of proteins into amino acids by hydrolysing the peptide bonds between amino acids
42
DIGESTION OF PROTEINS what peptidases do you need to know about
endopeptidases and exopeptidases (including dipeptidases)
43
DIGESTION OF PROTEINS what do endopeptidases do?
endopeptidases act to hydrolyse peptide bonds within a protein
44
DIGESTION OF PROTEINS examples of endopeptidases synthesised in the pancreas
trypsin and chymotrypsin, synthesised in the pancreas and secreted into the small intestine
45
DIGESTION OF PROTEINS example of endopeptidase released into the stomach
pepsin, released into the stomach by cells in the stomach lining
46
DIGESTION OF PROTEINS what conditions does pepsin work in
pepsin only works in acidic conditions (HCl in the stomach)
47
DIGESTION OF PROTEINS what do exopeptidases do
exopeptidases act to hydrolyse peptide bonds at the ends of protein molecules
48
DIGESTION OF PROTEINS what do exopeptidases remove
they remove single amino acids from proteins
49
DIGESTION OF PROTEINS what are dipeptidases
dipeptidases are exopeptidases that work specifically on dipeptides
50
DIGESTION OF PROTEINS how do dipeptidases act
they act to separate the 2 amino acids that make up a dipeptide by hydrolysing the peptide bond between them
51
DIGESTION OF PROTEINS where are dipeptidases often located
dipeptidases are often located in the cell-surface membrane of epithelial cells in the small intestine
52
what are the products of digestion absorbed across?
products of digestion are absorbed across the ileum epithelium into the bloodstream
53
ABSORBTION OF THE PRODUCTS OF DIGESTION: MONOSACCHARIDES how is glucose absorbed
glucose is absorbed by active transport with sodium ions via a co-transporter protein
54
ABSORBTION OF THE PRODUCTS OF DIGESTION: MONOSACCHARIDES how is galactose absorbed
galactose is absorbed in the same way as glucose using the same co transporter protein
55
ABSORBTION OF THE PRODUCTS OF DIGESTION: MONOSACCHARIDES how is fructose absorbed
fructose is absorbed via facilitated diffusion through a different transporter protein
56
ABSORBTION OF THE PRODUCTS OF DIGESTION: MONOGLYCERIDES AND FATTY ACIDS what do micelles help to do
micelles help to move monoglycerides and fatty acids towards the epithelium
57
ABSORBTION OF THE PRODUCTS OF DIGESTION: MONOGLYCERIDES AND FATTY ACIDS what do micelles constantly do which allow monoglycerides and fatty acids to be absorbed
as micelles constantly break up and reform they can 'release' monoglycerides and fatty acids, allowing them to be absorbed
58
ABSORBTION OF THE PRODUCTS OF DIGESTION: MONOGLYCERIDES AND FATTY ACIDS are whole micelles taken up across the epithelium
whole micelles are not taken up across the epithelium
59
ABSORBTION OF THE PRODUCTS OF DIGESTION: MONOGLYCERIDES AND FATTY ACIDS what do monoglycerides/fatty acids diffuse across
monoglycerides and fatty acids are lipid soluble, so they can diffuse directly across the epithelial cell membrane
60
ABSORBTION OF THE PRODUCTS OF DIGESTION: AMINO ACIDS how are amino acids absorbed
amino acids are absorbed via co-transport, in a similar way to glucose/galactose
61
ABSORBTION OF THE PRODUCTS OF DIGESTION: sodium ions step 1
sodium ions are actively transported out of the ileum epithelial cells into the blood which creates a sodium ion concentration gradient
62
ABSORBTION OF THE PRODUCTS OF DIGESTION: sodium ions step 2
sodium ions can then diffuse from the lumen of the ileum into the epithelial cells through sodium dependent transporter proteins, carrying the amino acids with them

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