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AQA Biology A-Level > Biological molecules > Flashcards

Biological molecules Flashcards

1
Q

Hydrolysis reaction

A

Reaction which uses water to break down a polymer (incl. disaccharide or polysaccharide) into its constituent monomers by breaking glycocidic bonds

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2
Q

Condensation reaction

A

Reaction between monomer units to form polymers held together by glycosidic bonds, also forming small molecules of H20

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3
Q

Metabolism

A

The sum of all reaction in a cell or organism

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4
Q

Isotopes

A

Atoms of the same element with the same number of protons but different number of neutrons

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5
Q

General formula of a monosaccharide

A

(CH20)n where n=any number between 3 and 7

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6
Q

Isomer

A

Molecules with the same molecular formula but with atoms connected differently

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7
Q

Isomers of glucose

A

ALPHA glucose: on carbon 1 has H on top the OH

BETA glucose: on carbon 1 has OH on top then H

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8
Q

Glucose + glucose =

A

maltose

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9
Q

Glucose + fructose =

A

sucrose

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10
Q

Glucose + galactose =

A

lactose

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11
Q

Test for reducing sugars

A
  • add benedict’s solution (copper (ii) suplfate) to food sample
  • heat
  • an insoluble red precipitate of copper (ii) oxide will form
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12
Q

Test for non-reducing sugars

A
  • add Benedict’s solution to to foood sample
  • heat
  • if remains blue = no reducing sugar present
  • add HCl + heat (HCl hydrolyses any disaccharides)
  • add sodium hydrogencarbonate solution to neutralise
  • check pH
  • test with Benedict’s again
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13
Q

Test for starch

A
  • add iodine

- if present = blue/black

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14
Q

which sugars are reducing?

A

all monosacharrides and some disaccharides

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15
Q

which sugars are non-reducing?

A

some disaccharides

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16
Q

3 main functions of starch in relation to structure

A

1) insoluble in water = good storage material and doesn’t affect water potential
2) amylose helixs forms compact shape = allows tight packing
3) amylopectine has many protruding ends which can be hydrolysed rapidly = allows rapid release of glucose

17
Q

what is starch made up of?

A 
made of two polymers of alpha glucose:
- amylose
- amylopectin
monomers connected by glycosidic bonds formed in condensation reactions
can be branched or unbranched
18
Q

what is the structure of amylose?

A
  • polysaccharide
  • unbranched = coils
  • glucose linked linearly with alpha 1-4 linkage
19
Q

what is the structure of amylopectin?

A

-branched

20
Q

structure of glycogen

A
  • polymer of alpha glucose
  • has more branches + shorter branches than starch
  • more compact than amylopectin
21
Q

function of glycogen

A
  • compact structure allows faster hydrolysis than starch = faster release of glucose in animals/bacteria (higher surface area for enzymes to work)
  • insoluble = doesn’t affect osmosis + doesn’t diffuse out cells
22
Q

where is glycogen stored in animals

A

muscles and liver as small granules

23
Q

what is cellulose made up of?

A
  • alpha AND beta glucose (different to starch + glycogen)
  • forms straight, unbranched chains (not coiled) which run parallel to each other with hydrogen bonds forming cross linkages
  • cellulose molecules grouped together to form microfibrils then fibres
24
Q

how is the structure of cellulose suited to its function?

A
  • hydrogen bond cross links in thr long, unbranched fibrous structure gives great physical strenght - good for cell walls
  • hydrogen bonds prevent water entering molecule so molecules are resistant to enzyme hydrolysis = strong
25
Q

what are lipids made up of?

A

carbon, oxygen, hydrogen

the proportion of carbon to oxygen and hydrogen is smaller than in carbohydrates

26
Q

are lipids insoluble or soluble?

A

insoluble in water

soluble in organic solvents, e.g. acetone or alcohols

27
Q

what are the four roles of lipids?

A
  • insulation
  • energy source (when oxidised, more than carbs)
  • waterproofing
  • protection
28
Q

what is the structure of a triglyceride?

A
  • consists of : 3 fatty acids and 1 glycerol
  • each fatty acid forms an ester bond with glycerol in a condensation reaction
  • the difference between different lipids is due to the varying structure of fatty acids
29
Q

whats the difference between a saturated, mono-unsaturated and a polyunsaturated fatty acid?

A
  • saturated = no double bonds
  • monounsaturated = a single double bond
  • polyunsaturated = more than 1 double bond
30
Q

functions of triglycerides related to their structure

A
  • have a high ratio of energy-strong carbon-hydrogen bonds to carbon atoms = good energy source
  • low mass to energy ratio = lots of energy in small area
  • insoluble: doesn’t affect cell water potential
  • when oxidised release water due to lots of hydrogen/oxygen
31
Q

whats the difference between a triglyceride and a phopholipid

A

one fatty acid molecule is swapped for a phosphate group

32
Q

where are phopholipids used and why?

A

cell membranes because they have:
- a hydrophobic tail (repel water)
- a hydrophillic head (attracts water)
so they form a bilayer, controlling what can enter/exit the cell (water-soluble substances can’t easily pass through)

33
Q

steps in the emulsion test for lipids

A
  • place test substance in test tube w/ ethanol + shake
  • add distilled water
  • any lipid = milky emulsion

AQA Biology A-Level (2 decks)

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