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Biology > Biological Molecules AS > Flashcards

Biological Molecules AS Flashcards

1
Q

Define monomer and give examples

A

small basic molecular units that can form a polymer

examples include monosaccharides, amino acids and nucleotides

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2
Q

What is the name of the reaction which forms polymers?

A

condensation reaction where a molecule of water is removed

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3
Q

Breaking down polymers by ________ reaction

A

hydrolysis = addition of water molecule

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4
Q

What are the monomer which form carbohydrates and give examples?

A

monosaccharides

examples are glucose, galactose and fructose

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5
Q

Glucose is a hexose sugar - alpha and bets glucose are the isomers - what is the difference ?

A

alpha glucose has the OH group on the BOTTOM and beta glucose has the OH group on the TOP

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6
Q

How is a disaccharide formed ?

A

2 monosaccharides are joined by a condensation reaction forming a glycosidic bond

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7
Q

Maltose + maltose =

A

alpha glucose

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8
Q

fructose + glucose =

A

sucrose

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9
Q

glucose + galactose =

A

lactose

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10
Q

The Benedicts test is used for sugars, how do you test for reducing sugars ?

A
  • Add Benedicts reagent to a sample and heat in a water bath that has been brought to a boil
  • the sample will stay blue if no reducing sugar is present
  • if positive the sample forms green –> yellow –> orange –> brick red precipitate
  • the higher the concentration of reducing sugar the further the colour change
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11
Q

What is the problem with the benedicts test?

A

qualitative data is subjective to make it objective use colorimetry to filter and measure wavelength of absorbance

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12
Q

How to test for non reducing sugars?

A
  • you need to break them down into monosaccharides to do this you get a new sample of test solution and add dilute hydrochloric acid and carefully heat in a water bath that has been brought to a boil
  • Then neutralise with sodium hydrogen-carbonate and check pH with red litmus paper
  • carry out test as normal
  • if negative sample stays blue
  • if positive sample forms green –> yellow –> orange –> brick red ppt
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13
Q

Polysaccharides are formed when ____ _____ ____ monosaccharides are joined by _____ reactions

A

more than two

condensation

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14
Q

Starch - cells get _____ from glucose, plants store excess glucose as ____

A

energy

starch

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15
Q

Starch is a mixture of two polysaccharides of alpha glucose - amylose and amylopectin - explain both

A

Amylose
- long unbranched chain of a glucose
- the 1-4 glycosidic bonds give a coiled compact structure for storage

Amylopectin
- long branched chain of a glucose
- the 1-4 and 1-6 glycosidic bonds allow for the side branched to be hydrolysed easily by enzymes for quick release of glucose/energy

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16
Q

Why is starch good for storage?

A

Starch is insoluble i water and doesn’t affect water potential

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17
Q

Glycogen - animal cells get energy from glucose too but animals store excess glucose as glycogen - another polysaccharide of alpha glucose

Explain the structure and importance of glycogen

A

structure is similar to amylopectin except it has a lot more side branches coming off it

Loads of branches means that stored glucose can be released quickly - it is also very compact for good storage

Found in muscles and packed with mitochondria

1-4 and 1-6 glycosidic bonds

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18
Q

Cellulose is made of long unbranched chains of ____ glucose

explain what happens when these bond

A

beta

When beta glucose molecules bond, they form straight cellulose chains linked together by hydrogen bonds to form strong fibres called microfibrils.

The strong fibres mean cellulose provides structural support for cells

High tensile strength so able to withstand turgor pressure and stretch

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19
Q

Describe how to test for starch

A

Add iodine dissolved in potassium iodide solution to the test sample

If positive = dark blue/black colour

If negative = orange/brown colour

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20
Q

Describe the structure of triglycerides

A

one molecule of glycerol and 3 fatty acids

fatty acid long tails made from hydrocarbons = hydrophobic

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21
Q

What are saturated fatty acids?

A

don’t have any double bonds between their carbon atoms

the fatty acid is saturated with hydrogen

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22
Q

What are unsaturated fatty acids?

A

have double bonds between carbon atoms, which cause the chain to kink

23
Q

How is a triglyceride formed and what bond is formed?

A

formed by condensation reactions - this happens 3x to form a triglyceride

an ester bond is formed

24
Q

What are the lipids found in cell membranes called?

A

phospholipids

25
Q

Explain the structure of a phospholipid

A

glycerol backbone with 2 fatty acids and one phosphate group

fatty acid tails are hydrophobic

phosphate group is hydrophilic

26
Q

Properties of triglycerides?

clue:

energy
water

A
  • Mainly used as energy storage molecules they are good for this as the long hydrocarbon tails of the fatty acids contain a lot of chemical energy - a lot of energy is released when broken down
  • insoluble in water so don’t effect water potential
  • triglycerides bundle together as insoluble droplets in cells as fatty acid tails are hydrophobic - tails face inwards shielding themselves from water with their glycerol heads
27
Q

Properties of phospholipids?

A
  • make up the bilayer of cell membranes - this controls what enters and leaves a cell

-heads are hydrophilic and tails are hydrophobic so they form a double layer with heads facing outwards

  • the centre of the bilayer is hydrophobic so water soluble substances cant easily pass through - the membrane acts as a barrier to those substances
28
Q

How to test for the presence of lipids ?

A

Emulsion test

  • Shake test substance with ethanol for a minute, then pour the solution into water
  • any lipid will show as a milky emulsion
  • the more lipid there is the more noticeable the milky colour will be
29
Q

what are the monomers of proteins?

A

amino acids

30
Q

A ________ is formed when two amino acids join together

A

dipeptide

31
Q

A __________ is formed when more than 2 amino acids join together

A

polypeptide

32
Q

Proteins are made up of one or more ______

A

polypeptides

33
Q

How are amino acids linked together and what is the bond formed called ?

A

condensation reactions

peptide bond

34
Q

Primary structure of a protein?

A

sequence of amino acids in the polypeptide chain

35
Q

Secondary structure of a protein?

A

Hydrogen bonds form between amino acids in the chain

This makes it automatically coil into alpha helix or beta pleated sheet

36
Q

Tertiary structure of a protein?

A

More bonds form between different parts of the polypeptide chain including hydrogen bonds and ionic bonds.

Disulfide bridges also can form

For proteins with one polypeptide chain, this is their final 3D structure

37
Q

Quaternary structure of a protein?

A

Some proteins are made of several polypeptide chains held together by bonds. The way these are held is the quaternary structure

e.g. haemoglobin, insulin and collagen

final 3D structure

38
Q

Give an example of how a proteins shape effects its function

A

Haemoglobin is compact and soluble which makes it easy for transport. This makes them good for transport of oxygen

Antibodies = two light and 2 heavy polypeptide chains - these have variable regions

Enzymes = roughly spherical in shape due to tight folding, soluble and often have roles in metabolism and other enzymes help to synthesise large molecules

39
Q

How to test for proteins?

A
  1. test solution needs to be alkaline, so first you add a few drops of sodium hydroxide solution
  2. then you add some copper (II) sulfate solution

if positive purple colour
if negative solution stays blue

40
Q

Enzymes speed up chemical reactions by acting as biological ______

A

catalysts

41
Q

Enzymes are ________

Explain the structure of an enzyme

A

proteins

Enzymes have an active site which has a specific shape. This is where the substrate molecule binds to the enzyme. Enzymes are highly specific due to tertiary structure.

42
Q

How do enzymes speed up the rate of reaction?

A

Lower the activation energy by providing an alternative pathway

43
Q

When a substrate fits into the enzymes active site it forms an enzyme substrate complex - its this that lowers the activation energy .

Give 2 reasons why

A
  • if two substrate molecules need to be joined, being attached to an enzyme holds them close together, reducing any repulsion between the molecules so they can bond more easily
  • if the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate so the substrate molecule breaks up more easily
44
Q

Explain the lock and key model

A

Substrate fits directly into the enzyme the way a key fits into a lock - the active site and substrate have a complimentary shape

45
Q

Explain the induced fit model

A

The substrate doesn’t only have to be the correct shape to sit the active site, it has to make the active site change shape as well

As the substrate binds to the active site, the active site changes shape slightly

46
Q

Each different enzyme has a different _______ structure and therefore a different shaped active site

A

tertiary

47
Q

What happens id the tertiary structure is altered and how can this happen?

A

The shape of the active site will change and the substrate will therefore not be able to fit into active site - preventing the formation of an enzyme-substrate complex and the enzyme cannot carry out the function.

The structure may be altered by pH or temperature

If there is a mutation in a gene in the primary structure it could change the tertiary structure of the enzyme produced

48
Q

How can you measure the rate of enzyme activity/rate of reaction?

A
  1. how fast the product is made - measure amount of end product present at different times in the reaction
  2. how fast the substrate is broken down - measure amount of substrate molecules present at different times in the reaction
49
Q

Explain how temperature can effect enzyme activity

A

Increased temp means more kinetic energy so the substrate molecules are more likely to collide with the enzyme active sites. The energy of these collisions also increases which means each collision is likely to result in a reaction.

If temp goes too high, the active site changes shape and the enzyme substrate can no longer fit - the enzyme is denatured and no longer can function as a catalyst

50
Q

Explain how pH can effect enzyme activity

A

All enzymes have an optimum pH value, most human enzymes work at pH 7 but others are an exception such as pepsin which is pH 2

Levels above and below the optimum pH can disrupt the ionic and hydrogen bonds that hold the enzymes tertiary structure in place

The enzyme become denatured and the active site changes

51
Q

Explain how substrate concentration can effect enzyme activity

A

The higher the substrate concentration the faster the reaction as more collisions between substrate and enzyme

After the saturation point, there is not enough enzymes to cope with all of the substrates so adding more makes no difference

52
Q

Explain how enzyme concentration effects enzyme activity

A

More enzymes = more likely a substrate will collide to form an enzyme substrate complex therefore increasing rate of reaction

If amount of substrate is limited, there aren’t enough to bind with all of the enzymes - so adding more enzyme has no further effect

53
Q

How do competitive inhibitors work?

A

Have a similar shape to the substrate molecule. They compete with the substrate molecules to bind to the active site so no reaction takes place.

They prevent substrates binding by blocking the active site

Increasing the concentration of substrate will increase the rate of reaction as the substrate will have better chance at binding with the substrate.

54
Q

How do non competitive inhibitors work?

A

Bind to the enzymes away from the active site which causes the active site to change shape so the substrate molecules can no longer bind to it.

Increasing the conc of substrate will have no effect as they don’t compete with the substrate.

Biology (11 decks)

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