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ocr a level biology > Biological molecules > Flashcards

Biological molecules Flashcards

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1
Q

what is hydrogen bonding?

A

a hydrogen bond is a weak interaction that occurs between a slightly negatively charged atom and a slightly positively charged atom

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2
Q

list 4 important functions of water inside and outside of the cells

A

reactant in most chemical reactions - hydrolysis

solvent- substances can dissolve in it as most biological reactions take place in solution

its a habitat- helps with temperature control, less dense when freezes so many organisms can survive and reproduce in it

transports substances- its a liquid and solvent so easily transports all sorts of material around animal and plant cells.

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3
Q

how is waters structure related to its functions?

A

hydrogen bonds give water a high specific heat capacity- hydrogen bonds between water molecules can absorb lots of energy so water takes a lot of energy to heat up meaning it does not experience rapid temperature changes making it a good habitat.

hydrogen bonds give it a high latent heat of evaporation- takes a lot of energy to break hydrogen bonds between water molecules, so a lot of heat is used up when water evaporates meaning waters great for cooling things as we sweat when we are hot and when sweat evaporates it cools the surface of the skin

waters polarity makes it a good solvent- ions can be be dissolved as the slightly positive end of a water molecule will be attracted to a negative ion and vice versa. (important ions can dissolve in water in blood and be transported around the body

water is less dense when it freezes- water molecules are held further apart in ice as it forms 4 H bonds with other water molecules making a lattice structure so ice floats. it forms an insulating layer on top of water so water does not freeze.

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4
Q

what is specific heat capacity?

A

is the energy needed to raise the temperature of 1 gram of a substance by 1 degree

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5
Q

what is glucose

A

it is a monosaccharide with six carbon atoms, hexose monosaccharide

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6
Q

what is a ribose

A

is a monosaccharide with five carbon atoms, pentose monosaccharide

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7
Q

what do all carbohydrates contain?

A

carbon, hydrogen and oxygen

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8
Q

what are monosaccharides joined together by?

A

glycosidic bonds

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9
Q

what is sugar a general term for

A

monosaccharides and disaccharides

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10
Q

condensation reaction

A

a hydrogen atom on one monosaccharide bonds to a hydroxyl group OH on the other, releasing a molecule of water.

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11
Q

hydrolysis reaction

A

a molecule of water reacts with the glycosidic bond, breaking it apart

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12
Q

what glucose molecules from maltose?

A

2 alpha molecules

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13
Q

what glucose molecules form sucrose?

A

alpha glucose and fructose

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14
Q

what glucose molecules form lactose?

A

either alpha glucose or beta glucose and galactose

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15
Q

name 3 polysaccharides

A

starch
glycogen
cellulose

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16
Q

what is the structure and function of starch

A

starch is a mixture of 2 polysaccharides of alpha glucose, amylose and amylopectin

starch is the main energy storage material in plants. its insoluble in water so it does not cause water to enter cells by osmosis which can make them swell ideally making them good for storage

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17
Q

what is the structure and function of amylose?

A

long, unbranched chain of alpha glucose the angles of glycosidic bonds give it a coiled structure

compact, good for storage as a lot can fit in small spaces

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18
Q

what is the structure and function of amylopectin?

A

a long, branched chain of alpha glucose.

its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily, meaning glucose can be released quickly.

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19
Q

what is the structure and function of glycogen?

A

the main energy storage material in animals

polysaccharide of alpha glucose and its structure is similar to amylopectin but has a lot more side branches, more branches=more glucose can be released quickly. very compact

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20
Q

what is the structure and function of cellulose?

A

the major component of cell walls in plants

made of long, unbranched chains of beta glucose and the cellulose chains are linked together by hydrogen bonds to from strong fibres called microfibrils, means cellulose provides structural support for cells.

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21
Q

what are triglycerides?

A

are a kinds of lipid, macromolecules

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22
Q

what bonds do triglycerides contain?

A

they contain ester bonds

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23
Q

how many molecules of glycerol and fatty acids do triglycerides have

A

1 molecule of glycerol and 3 fatty acids

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24
Q

what is the process called in which triglycerides are synthesised

A

esterification

25
Q

define saturated fatty acids

A

dont have double bonds between their carbon atoms

cnh2n+1cooh

26
Q

define unsaturated fatty acid

A

have at least one double bond between carbon atoms which cause the chain to kink

27
Q

structure of a phospholipids (macromolecule)

A

1 phosphate group attached to glycerol and 2 fatty acids

28
Q

what are the 3 lipids?

A

triglycerides, phospholipids and cholesterol

29
Q

what is the structure and function of triglycerides?

A

energy storage molecules

they long hydrocarbon tails of the fatty acids contain lots of chemical energy so a lot of energy is released when they are broken down.lipids contain 2x more energy in g than carbohydrates

insoluble- dont cause water to enter cells by osmosis

30
Q

what is the structure and function of phospholipids?

A

found in cell membranes

phospholipid tails are hydrophobic and head is hydrophilic so water soluble substances cant easily pass though it

31
Q

what is the structure and function of cholesterol

A

helps strengthen the cell membrane by interacting with the phospholipid bilayer

small and flattened shape (fits in between phospholipid molecules in membrane, bind to hydrophobic tails making them more rigid and less fluid

32
Q

which elements do amino acids contain?

A

carbon, oxygen, nitrogen and hydrocarbon and some contain sulfur

33
Q

what are amino acids linked together by?

A

peptide bonds

34
Q

what is the primary structure of a protein?

A

sequence of amino acids in a polypeptide chain

35
Q

what is the secondary structure of a protein

A

hydrogen bonds form between nearby amino acids in the chain, this makes them coil into alpha helix or beta pleated sheet

36
Q

what is the tertiary structure of a protein

A

the coiled or folded chain of amino acid coils and folds further, more bonds form between different parts of the polypeptide chain, 3d structure

37
Q

what is the quaternary structure of a protein?

A

some proteins are made of different polypeptide chains held together by bonds, this forms their final 3d structure. the quaternary structure is how these polypeptide chains are assembled together.

38
Q

what bonds hold the primary structure?

A

peptide bonds between amino acids

39
Q

what bonds hold the secondary structure?

A

hydrogen bonds

40
Q

what bonds hold the tertiary structure?

A

ionic, disulphide, hydrophobic/phillic interactions, hydrogen bonds

41
Q

what bonds hold the quaternary structure?

A

all bonds

42
Q

what is the structure and properties of a globular protein?

A

round and compact

soluble

43
Q

3 globular proteins and their functions

A

haemoglobin- carries oxygen around the body in red blood cells, known as a conjugated protein as it has a non protein group attached (prosthetic group-haem) has 4 in each polypeptide chain which has iron in it which oxygen binds too

insulin-hormone secreted by pancreas and helps to regulate blood glucose level, 2 polypeptide bonds held by disulphide bonds

amylase-enzyme that catalyses the breakdown of starch in the digestive system

44
Q

what is the structure and properties of a fibrous protein?

A

tough and rod shaped, unreactive

45
Q

3 fibrous proteins and their functions

A

collagen-connective tissues of animals, strong

keratin-skin, hair, nails. flexible or hard and tough

elastin-elastic connective tissue such as skin and large blood vessels, allows tissues to return to their original shape after being stretched

46
Q

name 5 cations

A

calcium (ca2+)
sodium (na2+)
potassium (k+)
hydrogen (H+)
ammonium (NH4+)

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47
Q

name 5 anions

A

nitrate (no3-)
hydrogen carbonate (HCO3-)
chloride (cl-)
phosphate (po43-)
hydroxide (oh-)

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48
Q

what is the test for sugars

A

benedict’s test
reducing sugars-add benedict’s reagent (blue) to sample and heat it in water bath to boil, if its positive a coloured precipitate forms (yellow-orange-red). the higher the conc= the further colour change, filter and weigh the precipitate

non reducing sugars-new sample, add dilute HCL and carefully heat in water bath, neutralise with sodium hydrogen carbonate then carry out benedict’s test, coloured precipitate forms

49
Q

test for starch

A

iodine test
add iodine dissolved in potassium iodide solution

browny orange to blue black

50
Q

test for proteins

A

biuret test
add few drops of sodium hydroxide to make test solution alkaline, add copper sulfate solution

blue to purple

51
Q

test for lipids

A

emulsion test

shake test with ethanol for a min then pour solution into water

clear to milky

more milky=more lipid

52
Q

what is colorimetry used to determine?

A

concentration of a glucose solution

53
Q

what are biosensors?

A

a device that uses a biological molecule such as an enzyme to detect a chemical. the biological molecule produces a signal which is converted into an electrical signal by a transducer. the electrical signal is then processed and can be used to work out other information

54
Q

what is a mobile phase?

A

a liquid solvent such as ethanol or water

where the molecules can move

55
Q

what is a stationary phase?

A

paper C-piece of chromatography paper

TLC-layer of solid, silica gel,glass or plastic plate

where the molecules cant move

56
Q

what is a chromatogram?

A

the patterns of spots u end up with in paper C

57
Q

RF value equation

A

distance travelled by solute/distance travelled by solvent

58
Q
A

ocr a level biology (17 decks)

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