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Biology - paper 1 > Digestion > Flashcards

Digestion Flashcards

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1
Q

Most molecules are too…

A

large to pass through absorbing surface of gut wall

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2
Q

Function + source of CARBOHYDRATES

A

-source of energy
-glucose is main respiratory substrate
STARCH + SUGAR

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3
Q

Function + source of PROTEINS

A
  • growth and repair

- meat eggs cheese beans

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4
Q

Lipids - function and source

A

Energy - make up most of the cell membrane

butter, margarine, meat

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5
Q

Glucose

A
  • form of starch - starch is a polymer of glucose

small enough to be absorbed through walls of digestive system

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6
Q

Cellulose

A

cannot be broken down by digestive system

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7
Q

Proteins

A

proteins too big to pass through walls of digestive system

  • broken down to amino acids
  • protein synthesis, happens in ribosomes of cells
  • excess amino acids broken down in liver
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8
Q

Lipids

A

ester of fatty acids and glycerol

-used for cell membranes

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9
Q

What does qualitative mean

A

results not expressed as numbers of graphs. represented by colour or presence

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10
Q

Test for sugars ? and method ?

A

Benedictus test
-add + benedict’s solution to food
-heat in a water bath
- presence of sugar - orange or brick red
depending on how much glucose is present it will go through stages - green, yellow, orange, red

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11
Q

HAZARDS

A

wear safety goggles
benedict’s solution is an irritant
avoid contact with skin and eyes

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12
Q

test for starch ? + method

A

+ add iodine solution to food

  • food containing starch will turn blue-black
  • can use microscope to stain starch grains in plants
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13
Q

HAZARDS

A
  • safety goggles
  • Iodine solution is an irritant
  • avoid contact with skin and eyes
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14
Q

Test for proteins ? method ?

A

BIURET’S TEST

  • use biuret’s reagent A + B
  • add 1cm cubed of biurets solution A to food SOLUTION
  • mix liquids
  • add 1cm cubed of buiret’s solution B and shake
  • PURPLE colour indicates protein is presetn
  • A purple ring between layers indicates protein is present
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15
Q

HAZARDS

A

Safety goggles
Buiret’s solution A is CORROSIVE
Buiret’s solution B is an irritant
avoid contact with skin and eyes

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16
Q

TEST FOR FATS + METHOD

A

SUDAN III test
- equal amounts of food + water added to test tube
- a few drops of sudan III added and shake tube
RESULTS - Red stained layer forms above surface of water

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17
Q

The alternative test for lipids/fats

A

Emulsion test

  • ethanol added to test tube with crushed food
  • liquid poured into another test tube containing water, leaving any food residue behind
  • RESULTS - CLOUDY LIQUID INDICATES PRECENSE OF LIPIDS
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18
Q

HAZARD..

A

Ethanol is flammable

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19
Q

Human digestive system purpose ?

A

breaks down complex food substances

provides large surface area for maximum absorption

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20
Q

what is the digestive system ?

A

Organ system which breaks down food so it can be absorbed by the bloodstream

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21
Q

function of mouth

A

begins digestion of carbohydrates
saliva contains AMYLASE which begins to break down starch into sugars
saliva also contains lipase - breaks down fats

22
Q

function of stomach

A

begins digestion of protein - small molecules such as alcohol absorbed
contains AMYLASE, PROTEASE ( peptides + amino acids ), LIPASE ( fatty acids and glycerol )

23
Q

function of small intestine ?

A

completes digestion of carbohydrates and proteins into SINGLE SUGARS and AMINO ACIDS and FATTY ACIDS and GLYCEROL
-contains

24
Q

Large intestine

A

absorption of water - eggestion of undigested food

25
Q

how is villi in gut wall adapted for digestion

A

surface of wall is folded and has villi - large surface area

  • epithelial cells that cover each villus have projections called microvilli
  • network of blood capilleries - easy absorbtion, maintains concentraion gradient
  • digested food passes through epithelial cells of gut wall and carried by blood to liver
26
Q

what are enzymes

A

biological catalysts that are proteins with a complex shape. Has a region called the active site which is specific to the substrate that fits to it

27
Q

substrate ?

A

molecule taking part in reaction

28
Q

enzyme reaction

A
  • substrate collides with active site and attaches
  • active site has complementary shape to substrate
  • enzyme catalyses breakdown of substrate
  • enzyme molecule is unchanged and can be used again
29
Q

factors affecting enzyme action

A

low temp - molecular movement decreases
high temp - at optimum temp 37 degrees
hight temp - also disrupts shape of active site which reduces its activiity as it no longer fits with substrate and so the enzyme is denatured.

30
Q

enzyme action

A

enzymes made of folding chains of amino acids which is held together by weak forces between amino acid molecules in the chain. If temp is too high, rate of reaction will be affected because the shape has changed.

31
Q

effect of ph

A

amino acids carry a charge in an enzyme molecule - negative and positive attract
changing ph will affect the shape of the chains of folding amino acids
can become denatured

32
Q

cellular enzymes work best at ph….

A

7

33
Q

how does the stomach create the optimum ph for enzymes

A

secretion of hydrochloric acid

34
Q

optimum ph in small intestine is created by….

A

by secreting sodium hydrogen carbonate

35
Q

optimum ph for salivary amylase

A

6.8

36
Q

optimum ph for stomach protease ( pepsin )

A

1.5 - 2

37
Q

optimum ph for pancreatic protease

A

7.5 - 8

38
Q

carbohydrase

A

breaks carbohydartes into simple sugars

39
Q

amylase

A

breaks starch into glucose

40
Q

protease

A

breaks proteins down into amino acids

41
Q

lipase

A

breaks lipids down into fatty acids and glycerol

42
Q

MOUTH

A

starch - maltose ( amylase catalyst )

43
Q

small intestine

A

amylase produced in pancreas

starch - maltose ( pancreatic amylase )

44
Q

STOMACH

A

pepsin produced in gastric glands

proteins - amino acids (pepsin catalysts)

45
Q

small intestine

A

protease ( trypsin ) produced in pancreas

protein - amino acids

46
Q

small intestine ( lipases )

A

lipids - fatty acids + glycerol ( lipase produced in pancreas )

47
Q

required practical - investigate effect of ph on enzyme amylase actvity

A

buffer solutions remain at the same ph even when acids and alkalis are added
1. place one drop of iodine solution into each well of spotting tile
2. 3 test tubes
3. 1st test tube - add 3cm cubed of starch solution
4. 2nd test tube - 2cm cubed of amylase solution
5 3rd test tube - 2cm cubed of ph 5 buffer solution - controls ph
6. place all 3 test tubes in water bath at 30 degrees for 10 mins
7. combine all three test tubes into one solution - mix with a stirring rod
8. return to the water bath and start timer
9. after 30 secs, transfer one drop of solution to a spotting tile
iodine should turn blue black if starch is present
10. take a sample every thirty seconds until the iodine remains orange - starch is no longer present in solution
11. record time to see the rate of amylase at ph 5
12. repeat experiment with different ph buffers 6, 7 , 8

48
Q

problems

A

taking samples every 30 seconds - only an approximate time for reaction to complete, just an indication of rate. it is the INVERSE of the rate so we can do ONE / TIME TAKEN to work out a more accurate answer
take it every 10 seconds instead

colour change tends to be gradual
ask several people to look at spotting tile to decide if the reaction has completed

49
Q

safety

A

wear goggles
amylase may cause allergic reactions
iodine solution is an irritant

50
Q

effect of temp

A

use a water bath to maintain temps with different test tubes
breakdown of lipids by lipase - monitor ph change - as reaction proceeds, release of fatty acids would mean ph decreases

51
Q

liver and digestion

A

liver produces bile - emulsifies lipids into tiny droplets which have a bigger surface area for the lipds to work on.

contains - sodium hydrocarbonate - alkali - neutralises stomach acid - optimum ph
bile produced in liver - stored in gal bladder

Biology - paper 1 (4 decks)

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