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biology aqa a-level > Biological molecules > Flashcards

Biological molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Monomer

A

the smaller units of which larger units are made

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2
Q

Polymer

A

Molecules made from a large number of molecules joined together

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3
Q

Examples of monomers

A

monsaccharides ,amino acids,nucleotides

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4
Q

Polymer examples

A

polysaccharides,polypeptide/proteins, DNA

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5
Q

Condensation reaction

A

A condensation reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.

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6
Q

Hydrolysis reaction

A

A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule. (adding water)

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7
Q

Monosaccharides

A

Monosaccharides are the monomers from which larger carbohydrates are made.

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8
Q

common monosaccharides

A

Glucose,fructose and galactose.

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9
Q

What forms during a condensation reaction between two monosaccharides?

A

A glycosidic bond.

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10
Q

How are disaccharides formed?

A

By the condensation of two monosaccharides

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11
Q

what disaccharide does the condensation of two glucose molecules form?

A

maltose

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12
Q

what disaccharide does the condensation of one glucose and one fructose molecules form?

A

sucrose

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13
Q

what disaccharide does the condensation of one glucose and one galactose molecules form?

A

lactose

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14
Q

what is an isomer?

A

Molecules with the same molecular formula but a different structure.

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15
Q

what are the isomers of glucose?

A

Alpha and beta

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16
Q

The difference between reducing and non-reducing sugars

A

Reducing sugars can donate electrons

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17
Q

what are the two groups of lipid?

A

triglycerides and phospholipids

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18
Q

how are triglycerides formed?

A

The condensation of 1 glycerol molecule and 3 fatty acid molecule.

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19
Q

how are phospholipids formed?

A

The condesnation of 1 glycerol molecule,2 fatty acid molecule and 1 phosphate-containing group molecule.

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20
Q

A condensation reaction between glycerol and a fatty acid (RCOOH) forms an _______ bond.

A

A condensation reaction between glycerol and a fatty acid (RCOOH) forms an ESTER bond.

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21
Q

the R-group of a fatty acid may be __________ or un__________.

A

the R-group of a fatty acid may be SATURATED or UNSATURATED.

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22
Q

The difference between unsaturated fatty acids and saturated.

A

unsaturated contain at least one double bond between carbons in the fatty chain. (saturated= single bonds only)

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23
Q

Properties of lipids?

A

-contain hydrogen,carbon and oxygen.
-proportion of carbon to oxygen and hydrogen much less than in carbohydrates.
-Insoluble in water
-soluble in organic solvents such as alcohols and acetone.

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24
Q

roles of lipids?

A

-contribute to flexibility of cell membranes
-source of energy
-waterproofing
-insulation
-protection

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25
Q

properties of triglycerides

A

-excellent source of energy because of high ratio of energy-storing carbon-hydrogen bonds
-good storage, low mass to energy ratio, lots of energy stored in a small volume.
-large non-polar molecules, so are insoluble in water so storage doesn’t affect osmosis or water potential of cells.
-high ratio of hydrogen to oxygen atoms means water released when oxidised, important source of water especially for animals in the desert.

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26
Q

structure of a phsopholipid

A

-charge hydrophilic head (phosphate molecules) attract water
-non-polar hydrophobic tails (fatty acid molecule repel water).

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27
Q

phospholipids are the main components of cell __________.

A

phosopholipids are the main components of CELL MEMBRANES.

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28
Q

Phospholipids are amphipathic (contain hydrophilic and hyrophobic parts) so form __________.

A

Bilayers

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29
Q

Water soluble substances can’t easily pass through phospholipid bilayer due to the _________ middle.

A

Water soluble substances can’t easily pass through phospholipid bilayer due to the HYDROPHOBIC middle

30
Q

How do you test for the presence of lipids?

A

the emulsion test

31
Q

How do you carry out the emulsion test?

A

1) add ethanol to sample and shake for 1 min
2) positive result= white/ milky emulsion

32
Q

polysaccharides are formed from the condensation of many _________ units.

A

glucose

33
Q

the condensation of what type of glucose forms starch?

A

alpha glucose

34
Q

the condensation of what type of glucose forms glycogen?

A

alpha glucose

35
Q

the condensation of what type of glucose forms cellulose?

A

beta-glucose

36
Q

what is the structure of starch?

A

Mixture of two polysaccharides of alpha-glucose,called amylose and amlyopectin.

amylose-long unbranched chain of a-glucose. The angles of the glycosidic bond gives a coiled structure.

amylopectin-long branched chain of a-glucose.

37
Q

function of starch?

A

Plants store excess glucose as starts, when plants require more energy they can breakdown starch to release glucose.

Amylose-unbranched coiled chain of a-glucose that is one of the two polysaccharide s that make up starch is very compacted due to coiled structure so is great for storage, more can fit in one space.

Amylopectin-the second polysaccharide making up starch. Is a long branched chain of a-glucose , the branches allow enzymes that break down the molecule to get at the glycosidic bonds more easily meaning energy can be released more quickly.

38
Q

structure of glycogen?

A

Polysaccharide of a-glucose, long chain with lots of branches coming off it.

39
Q

function of glycogen?

A

used in animals to store excess glucose. Very compact so good for storage as more can be fit into one space. Lots of branches mean glucose stored can be released quickly good for energy release in animals.

40
Q

cellulose structure

A

made of long unbranched polysaccharide of beta-glucose, When beta-glucose molecules bind the form straught cellulose chains. The straight celluslose chains linked together by hydrogen bonds forming microfibrils.

41
Q

function of cellulose

A

structural support of cells. The cellulose chains (made of bonded b-glucose), bond together forming strong fibres called microfibrils these fibrils provide structural support.

42
Q

functions of proteins

A

enzymes-catalyse chemical reactions
antibodies-fight pathogens as part of the immune systems.
transport proteins-transport ions and molecules across cell membranes
structural proteins-strong proteins found in hair,nails and connective tissues.

43
Q

what are Amino acids, how many are there and how do they differ?

A

amino acids are the monomers from which proteins are made up.
The twenty amino acids that are common in all organisms differ only in their side group.

44
Q

structure of amino acids?

A

consists of carbon, an amine/amino group NH2, carboxyl group COOH and a side chain (R).

45
Q

A condensation reaction between two amino acids forms a ________ bond.

A

A condensation reaction between two amino acids forms a PEPTIDE bond.

46
Q

How are dipeptides formed?

A

Dipeptides are formed by the condensation of two amino acids.

47
Q

How are polypeptide formed?

A

polypeptides are formed by the condensation of many amino acids.

48
Q

A _______ protein may contain one or more polypeptides.

A

A functional protein may contain one or more poly peptides.

49
Q

Primary structure

A

Order of the amino acids in a polypeptide chain.

50
Q

Secondary structure

A

Initial 3D shape the polypeptide chain forms.

Either and alpha-helix or a beta-sheet.

The NH group has a positive charge and the c=o a negative charge these group form hydrogen bonds which holds the polypeptide chain in shape.

51
Q

Tertiary structure

A

secondary structure can be twisted and folded even more.
Kept in shape by hydrogen bonds, ionic bonds and disulfide bridges .

52
Q

Bonds in tertiary structure

A

Hydrogen bonds-between slightly positive hydrogen and a slightly negative atom e.g oxygen.-weak but are lots of them

Ionic bonds-between negative carboxyl groups and positive amino groups that aren’t involved in peptide bonds-stronger than hydrogen bonds but easily broken by changes in PH.

Disulfide bridges-between sulphur atoms- stronger than ionic, not easily broken.

53
Q

Quaternary structure

A

large proteins can be made up of multiple polypeptide chains linked together in various ways.

54
Q

properties of proteins

A

.structure and shape of proteins enable them to carry out functions
.fibrous proteins have structural functions e.g collagen
.globular proteins have metabolic functions e.g enzymes.

55
Q

what is the test for proteins?

A

Biuret test
biuret solution is mad eup of sodium hydroxide and copper (ll) sulfate.
Put test solution in test tube with biuret solution if protein is present will turn purple.

56
Q

how do enzymes speed up reaction?

A

By lowering the activation energy.

57
Q

What are two ways in which enzymes lower activation energy?

A

If two substrates need to join together, being attached by enzymes holds them close together reducing any repulsion between the molecules meaning they can bond more easily.

If enzymes is catalysing a breakdown reaction, fitting substrate in active site puts strain on the bonds in the substrate so molecules break up more easily.

58
Q

The ____________ structure of an enzyme determine the shape of it’s active site.

A

The tertiary structure of any enzyme determines the structure of it’s active site.

59
Q

The active sight binds to _____________ substrate.

A

the active site binds to a complementary substrate.

60
Q

When an enzyme ____________ the substrate can no longer bind to the active site.

A

When the enzyme denatures the substrate can no longer bind to the active site.

61
Q

What are the models of enzyme action?

A

lock and key model
Induce fit model

62
Q

explain the lock and key model

A

The substrate fits exactly into the active site,to form and enzyme-substrate complex, the enzyme does not change shape/remains unchanged after the reaction.

63
Q

explain the induced fit model

A

Substrate does not fit perfectly into the active site as the substrate binds the active site changes shape slightly, form the enzyme-substrate complex.

64
Q

Factors which effect enzyme activity

A

-temperature
-pH
-enzyme concentration
-substrate concentration

65
Q

How does temperature affect rate of enzyme-controlled reactions

A

As the temperature increases the rate of reaction increase,as the enzymes and substrate molecules gain more kinetic energy so move more, which increases the number of collisions so more enzyme-substrate complexes are formed. The optimum temperature is the temperature at which the enzymes works fastest, after this point the rate of reaction decreases. As the temperature increases the enzymes vibrates more so some bonds that hold its shape (tertiary structure) break so the enzyme changes shape (denatured) the substrate no longer fits in the active site.

66
Q

How does pH affect the rate of an enzyme-controlled reaction.

A

All enzymes have an optimum pH where they work fastest. Below the optimum pH in acidic conditions the H+ ions can disrupt the ionic and hydrogen bonds that hold the enzymes tertiary structure together. The enzyme becomes denature the active site changes change and substrate can no longer fit.,the reaction will stop .above the optimum pH in alkali conditions the OH- ions can disrupt the ionic and hydrogen bonds that hold the enzymes tertiary structure together. The enzyme becomes denature the active site changes change and substrate can no longer fit.

67
Q

How can substrate concentration affect the rate of enzyme-controlled reactions?

A

Increasing the substrate concentration increases rate of reaction as collisions between substrate and enzyme are more frequent so more enzyme-substrate complexes form. This is only true up to the saturation point, at this point all active sites are full so adding more substrate will not increase the rate of reaction any further rate plateaus.

68
Q

How does enzyme concentration affect the rate of enzyme-controlled reactions?

A

Increasing the enzyme concentration increases the rate of reaction as enzymes and substrate are more likely to collide form enzyme-substrate complexes. If substrate molecules are limited comes a point where increasing enzyme concentration will have no further effect, as all substrate will be acted upon, the substrate concentration becomes a limiting factor, the rate plateaus.

69
Q

How do competitive inhibitors work?

A

-The inhibitor enters the enzymes environment
-the shape of the inhibitor matches the shape of the substrate.
-due to kinetic energy molecules move
-sometimes the inhibitor binds with the enzymes active site, preventing the substrate from binding
-other enzyme active sites still available so reaction can still occur, just at a slower rate.
-increased amount of inhibitor= decreased rate

70
Q

In the presence of a competitive inhibitor how will increasing the substrate concentration affect the rate of reaction?

A

Increasing the substrate concentration will increase the rate of reaction.

71
Q

How do non-competitive inhibitors work?

A

-The inhibitor enter the enzymes environment
-the shape of the inhibitor is different to the shape of the substrate.
-Inhibitor shape does match with different part of enzyme-called allosteric site
-inhibitor binds to allosteric site causing a reaction altering tertiary structure (shape of the active site)
-Substrate can no longer fit in the active site
(if the inhibitor is reversible it can dissociate with the enzyme allowing enzyme to regain tertiary structure).

72
Q

In the presence of a non-competitive inhibitor how will increasing the substrate concentration affect the rate of reaction?

A

Increasing the substrate concentration won’t increase the rate of reaction because the active sites of the enzymes will have changed shape so the substrate can’t bind.

biology aqa a-level (5 decks)

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