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biology paper 1 > topic 1 - biological molecules > Flashcards

topic 1 - biological molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Explain how the structure of DNA is related to its functions

A
  • DNA is strong as it has a sugar phosphate backbone which protects organic bases from chemical attack
    -It is a helical structure so is compact
    -Long molecule so can store lots of information
    -Base sequence allows information to be stored
    -Double stranded so seperate strands can act as templates to replicate DNA
    -Weak hydrogen bonds for replication
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2
Q

Where do hydrogen bonds occur between DNA molecules

A

Between deoxyribose

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3
Q

Give two differences between the structures of DNA and RNA

A

DNA contains deoxyribose, RNA contains ribose
DNA contains thymine base, RNA contains uracil base

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4
Q

Give two features of DNA and explain how each one is important in the semi conservative replication of DNA

A

-Weak hydrogen bonds mean strands can easily seperate
-Two strands so both can act as templates

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5
Q

Name the type of bond that forms between the 3rd and 5th carbons on deoxyribose and the phosphate

A

Phosphodiester

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6
Q

Describe DNA helicase’s function

A

Breaking hydrogen bonds between strands of DNA

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7
Q

Describe DNA polymerase’s function

A

Joins nucleotides

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8
Q

Describe structure of DNA

A

-Polymer of nucleotides
-Each nucleotide formed from deoxyribose, phosphate and nitrogenous base
-Phosphodiester bonds between nucleotides
-Double helix held together by weak hydrogen bonds
-Hydrogen bonds between adenine,thhmine and cytosine,guanine

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9
Q

Describe how DNA is replicated

A

1) Hydrogen bonds break and strands seperate
2) with enzyme DNA helicase
3) Each strand acts as a template
4) Free nucleotides attach
5) Complementary
6) DNA polymerase joins nucleotides
7) Hydrogen bonds reform
8) Semi conservative replication

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10
Q

Name the protein associated with DNA in a chromosome

A

Histone

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11
Q

Describe how a phosphodiester bond is formed between 2 nucleotides within a DNA molecule

A

Condensation reaction (loss of water) between deoxyribose and phosphate which is catalysed by DNA polymerase

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12
Q

what is a monomer

A

a small repeating unit that makes up a polymer

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13
Q

examples of a monomer

A

glucose, amino acids and nucleotides

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14
Q

what is a polymer

A

molecules made from a large number of monomers joined together

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15
Q

what is a condensation reaction

A

joining 2 molecules together with the formation of a chemical bond and elimination of a molecule of water

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16
Q

what is a hydrolysis reaction

A

breaks a chemical bond between 2 molecules involving the use of a water molecule

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17
Q

what is a carbohydrate

A

molecules that consist of only carbon, hydrogen and oxygen that are long chains of sugar units called saccharides

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18
Q

what bond is formed between monosaccharides

A

glycosidic

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19
Q

glucose+glucose

A

maltose

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20
Q

glucose+galactose

A

lactose

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21
Q

glucose+fructose

A

sucrose

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22
Q

is the right OH on alpha glucose at the top or bottom

A

bottom

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23
Q

properties of glycogen

A

-alpha glucose monomers
-1,4 and 1,6 glycosidic bonds
-large number of side branches
-large but compact molecule
-insoluble therefore doesn’t affect water potential of cells and cannot diffuse out

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24
Q

properties of starch (amylose and amylopectin)

A

amylose- 1,4 glycosidic bonds, unbranched therefore it is coiled so very compact

amylopectin- 1,4 and 1,6 glycosidic bonds, branched so can be broken down quickly

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25
Q

properties of cellulose

A

-beta glucose
-long unbranched chains
-microfibrils form across parallel chains (strong hydrogen bonds)

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26
Q

how does cellulose stop the cell wall from bursting

A

it exerts inwards pressure that stops the influx of water

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27
Q

reducing sugar test

A
  • add equal amounts food sample and Benedicts solution
    -heat in water bath, turns from blue-> brick red ppt
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28
Q

non reducing sugar test

A

-reducing sugar test first
-add equal parts food sample to HCl and place in water bath (hydrolyses disaccharides)
-add sodium hydrogen carbonate to neutralise (check pH with pH paper)
-redo reducing sugar test with new solution

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29
Q

test for starch

A

add iodine in potassium iodide
turns from orange/brown to blue/black

30
Q

what is a lipid

A

molecules made of only hydrogen, carbon and oxygen which are only soluble in organic solvents e.g alcohols

31
Q

what are triglycerides made up of

A

1 glycerol and 3 fatty acids

32
Q

what are the bonds in triglycerides called

A

ester

33
Q

what is a saturated lipid

A

found in animal fats - don’t contain any carbon-carbon double bonds

34
Q

what is an unsaturated lipid

A

found in plants - contain one or more carbon-carbon double bond meaning the molecule can bend (liquid at room temp)

35
Q

triglyceride structure points to link to its properties

A

1) high ratio of energy storing carbon-hydrogen bonds to carbon atoms - good energy store
2) low mass to energy ratio meaning a lot of energy is stored in a small volume
3) large and non polar-> insoluble in water so water potential of cells not affected
4) high ratio of hydrogen-oxygen atoms so triglycerides release water when oxidised

36
Q

what is a phospholipid made up of

A

1 glycerol, 2 fatty acids and a phosphate group

37
Q

what is a micelle

A

many phospholipids in water (heads facing out and tails in)

38
Q

phospholipid structure points in relation to its properties

A

1) in an aqueous environment being polar means a bilayer can be formed
2) hydrophilic heads can be used to hold at the surface of the cell surface membrane
3)can form glycolipids with carbohydrates which are important on the cell surface membrane for cell recognition

39
Q

emulsion test

A

-add 2cm of sample and 5cm of ethanol
-shake test tube to dissolve lipid
-add 5cm water and shake gently
-cloudy white colour is positive

40
Q

what are amino acids made up of

A

amino group (NH2) carboxylic group (COOH) and R group

41
Q

what bond joins amino acids to make proteins

A

peptide

42
Q

what is the primary structure of a protein

A

order and number of amino acids in a protein (initial sequence)

43
Q

what is the secondary structure of a protein

A

shape of amino acid chain (alpha helix or beta pleated sheet) formed from weak hydrogen bonds from amine to carboxylic acid groups

44
Q

what is the tertiary structure of a protein

A

3d shape of protein formed from the twisting and folding
-disulfide bridges (if sulphur in R group)
-ionic bonds
-hydrogen bonds

45
Q

what is the quaternary structure of a protein

A

number of polypeptides

46
Q

difference between globular and fibrous proteins

A

globular- compact eg enzymes
fibrous- long to form fibres eg keratin

47
Q

biuret test for proteins

A

add equal parts sample and sodium hydroxide
add a few drops copper sulfate, mix gently
blue-> purple is positive

48
Q

how do enzymes increase rate of reaction

A

lowering activation energy of reaction they catalyse

49
Q

describe induced fit model

A

when substrate and enzyme bind the enzymes active site slightly changes shape to be complementary to substrate

50
Q

how does temp affect enzyme controlled reactions

A

rate increases up to the optimum temp as kinetic energy is increasing. after optimum temp enzymes denature so cannot form ESCs so it drops.

51
Q

how does pH affect enzyme controlled reactions

A

pH affects enzymes shape as it can disrupt the bonds in its tertiary structure, so all enzymes have different optimum pH

52
Q

how does enzyme conc affect enzyme controlled reactions

A

increases initially as more active sites for substrates to bind to but substrate conc will become a limiting factor

53
Q

how does substrate conc affect enzyme controlled reactions

A

more ESCs formed initially so rate increases however all enzymes will eventually be saturated so enzyme conc is a limiting factor

54
Q

how do competitive inhibitors affect enzyme controlled reactions

A

rate decreases as active sites become blocked by inhibitors binding to them

55
Q

how do non competitive inhibitors affect enzyme controlled reactions

A

rate decreases as enzymes active sites are changing shape due to inhibitors binding to allosteric site

56
Q

function of DNA

A

stores genetic information

57
Q

function of RNA

A

transfers genetic information to ribosomes for protein synthesis

58
Q

what is a nucleotide made up of

A

pentose sugar, nitrogenous base and phosphate

59
Q

what bonds join nucleotides together

A

phosphodiester from sugar->phosphate

60
Q

structure of ATP

A

ribose, adenine and 3 phosphate groups

61
Q

what enzyme hydrolyses ATP

A

ATP hydrolase

62
Q

properties of ATP

A

-immediate source of energy as can be broken down in one step
-isn’t stored in large quantities as it can easily be reformed by ADP
-used in metabolic processes, movement, active transport and secretion and activation of molecules

63
Q

how is water being a solvent useful

A

allows gases to readily diffuse as well as enzymes and waste products

64
Q

how does water having a high specific heat capacity make it useful

A

hydrogen bonds stick molecules close together and these bonds are hard to break, minimising temp fluctuations so it can be used as a buffer

65
Q

how does water having a large specific latent heat of vaporisation make it useful

A

evaporation of water provides a cooling effect eg sweating

66
Q

what do hydrogen ions do

A

determine the pH of substances eg blood

67
Q

what do iron ions do

A

component of haemoglobin in the blood

68
Q

what do sodium ions do

A

cotransport of glucose and amino acids

69
Q

what do phosphate ions do

A

component of ATP and DNA

70
Q

what are ribosomes made of

A

RNA and proteins

biology paper 1 (4 decks)

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