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A level biology flashcards > Biological molecules > Flashcards

Biological molecules Flashcards

1
Q

What is the importance of water?

A
  • used as a solvent to carry water, 0xygen and sugars around body also in plants for translocation process
  • transport medium because it is such a good solvent ( ie blood plasma and transpiration stream in plants)
  • can act as an insulator when it freezes to from ice
  • high latent heat of vaporisation meaning a lot of heat energy is needed to make it evaporate, useful to cool us down when we sweat
  • support: keeping plant cels turgid
  • metabolite: involved in chemical reactions in plant/ humans such as photosynthesis, hydrolysis reactions
  • provides a stable environment as it has high specific heat capacity so large quantity of water doesn’t greatly change temp
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2
Q

What is metabolism?

A

all the chemical reactions and processes which take place in a living cell/ in the body

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3
Q

how are polymers formed

A

with condensation reactions, water formed as a by product

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4
Q

how are polymers broken apart

A

hydrolysis reactions, water is added to break bonds between monomers

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5
Q

what are reducing vs non reducing sugars

A

reducing sugars have electrons to donate usually because they have a double bond while non-reducing sugars do not have electrons to donate

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6
Q

What is a reducing agent

A

A molecule which has electrons to donate

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7
Q

What is a mole

A

a unit for measuring amount of a substance. 6.02 x 10^23 particles

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8
Q

What is a molar solution

A

solution that contain one mole of solute for each litre of solution

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9
Q

What is the formula for concentration

A

concentration = moles/ volume

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10
Q

What are the monomers of carbs

A

monosaccharides

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11
Q

What is the difference between alpha and beta glucose

A

the position of the OH groups are reversed. alpaha glucose the OH group is low and in beta glucose the OH group is higher up

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12
Q

How are two monosaccharides joined together

A

with a glycosidic bond – O–

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13
Q

What is maltose made up of

A

two alpha glucose molecules

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14
Q

What is sucrose made up of

A

glucose and fructose

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15
Q

What is lactose made up of

A

galactose and glucose

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16
Q

what is cellobiose made up of

A

two beta glucose molecules

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17
Q

Describe the benedicts’ test for reducing sugars

A
  • Add Benedict’s reagent
  • boil water and heat food sample in water bath
  • if test is positive a coloured precipitate will form
    colour change from blue to green/yellow/orange/ red
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18
Q

What is the Benedict’s test for non-reducing sugars

A
  • First check for reducing sugars
    Add dilute HCL to new food sample
  • heat in water bath
  • neutralise with sodium hydrogencarbonate
  • carry out benedict’s test for reducing sugars
  • if test is negative sample doesn’t contain any sugar
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19
Q

Benedict’s solution

A

Cu 2 + ions give the solution its blue colour. When mixture heated Cu + ions form which have a red colour in solution.

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20
Q

Why do you add HCl to test for non reducing sugars

A

If non redudicng sugars are present acid hydrolyses the glycosidic bond , releasing monosaccharides

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21
Q

Why do you add sodium hydrogen carbonate to test for non reducing sugars

A

To neutralise solution because Benedict’s solution cannot work under acidic conditions.

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22
Q

What are the two components of starch ?

A

amylose and amylopectin

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23
Q

What are the structural properties of amylose

A
  • a long unbranched chain of alpha glucose
  • coiled structure due to the angle of glycosidic bonds
    -compact molecule which makes it good for storage
  • 1,4 glycosidic bond
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24
Q

What are the structural properties of amylopectin

A
  • long branched chain of alpha glucose
  • fast release of energy due to large SA ( branches create this)
    larger SA means more access points for enzymes to break off alpha glucose molecules
  • 1, 6 glycosidic bond
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25
Q

What are the properties of glycogen

A
  • polysaccharide of alpha glucose
  • many side branches like amylopectin which allows for rapid release of glucose
  • also very compact — so good for storage
  • mostly 1,6 glycosidic bonds, some 1, 4 glycosidic bonds
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26
Q

What are the properties of cellulose ?

A
  • polysaccharide of beta glucose
  • long unbranched beta glucose chains which are linked by hydrogen bonds
  • forms microfibrils which are very strong
  • 1,4 glycosidic bonds
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27
Q

Describe and explain the roles of lipids in the body ?

A
  • source of energy, greater energy released than carbs. A high number of C_H bonds meaning a lot of energy can be stored in a small volume
  • protection: fat is stored around organs, to help protect them from injury
  • insulation: fats are slow conductors of heat, meaning they can act as insulators for cells such as nerve cells ( myelin sheath)
  • waterproofing: insoluble in water, plants and insects have waxy lipid cuticles that help conserve water
  • form cell membranes around cell organelles
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28
Q

Triglycerides structure

A
  • molecule of glycerol bonded to three fatty acid molecules
  • fomed by condensation reaction, 3 total ester bonds per triglyceride because there are three fatty acids
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29
Q

What are the different types of fatty acids ?

A
  • saturated: single carbon n=bonds only
  • mono-unsaturated: 1 double carbon bond
  • poly- unsaturated: lots of double carbon bonds
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30
Q

Phospholipids structure

A
  • molecule of glycerol bonded to two fatty acids and one phosphate group
  • hydrophilic head and hydrophobic tail. hydrophilic head attracts water but repels fats. tails repel water but will mix with fats
  • polar molecules, so therefore soluble in water
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31
Q

What is the difference between hydrophobic and hydrophilic?

A
  • hydrophobic: water repelling
  • hydrophilic: water attracting
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32
Q

How are lipids involved in cell recognition

A
  • phospholipids and carbs form glycolipids which act as cell surface markers
  • enable us to recognise our cells from foreign ones
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33
Q

How many naturally occurring amino acids are there

A
  • 20 naturally occuring amino acids in proteins, some have to be obtained from diet as cannot be synthesised
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34
Q

What do you call two amino acids that have been bonded together

A

a dipeptide

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35
Q

What does the primary structure of a protein determine

A

The final structure which then determines the protein function

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36
Q

What are the different types of proteins ?

A
  • structural ie collagen
  • enzymes ie lipase
  • movement ie muscle proteins
  • defence ie antibodies
  • communication ie hormones
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37
Q

What are the different structures of proteins ie primary, secondary, tertiary ?

A

primary structure: initial sequence of amino acids
secondary structure : folds of the protein whether it is folded into an alpha helices or a beta pleated sheet
tertiary structure : overall 3D shape of protein held together by hydrogen bonds, disulphide and ionic bonds
quaternary structure: occurs when there is more than one polypeptide chain in a protein which are linked together by ionic bonds, disulphide nd hydrogen bonding. may also have prosphetic ( non protein group)

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38
Q

alpha helix vs beta pleated sheets

A
  • alpha helix: hydrogen bonds between NH and C double bond O
  • beta pleated sheets: hydrogen bonds between OH and C double bond O
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39
Q

What is the function of the cell membrane ?

A
  • controls the movement of substances in and out of cell
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40
Q

What is the structure of phospholipids

A
  • hydrophilic heads of phospholipid bilayer points to the outside of cell surface membrane
  • hydrophobic tails point to the centre of cell membrane
  • heads are water-attracting, tails are water repelling.
41
Q

Where are proteins found in phospholipid bilayer ?

A
  • found in surface of bilayer to give mechanical support to membrane or as cell receptors for hormones
  • some proteins extend completely across bilayer from one side to the other ie protein channels and carrier proteins
42
Q

What do carrier proteins and protein channels do ?

A
  • form water filled tubes to allow water soluble ions to diffuse across membrane
  • carrier proteins carry molecules such as glucose and amino acids across the membrane
43
Q

What are functions of proteins in membranes ?

A
  • provide structural support
  • form protein channels
  • allow active transport across membrane
  • form cell surface receptors for identifying cells
  • help cells stick together
  • act as hormone receptors
44
Q

Where is cholesterol found ?

A
  • found within phospholipid bilayer
  • adds strength to membranes and prevents water loss and dissolved ions from cells due to being hydrophobic and pull together fatty acid tails to limit their movement
45
Q

What are glycolipids made up of and what do they do ?

A

carbohydrate covalently bonded to a lipid
- act as cell surface receptors for specific chemicals
-act as recognition sites, help maintain the stability of membrane, help cells attach to one another and so form tissues

46
Q

What are the functions of glycoproteins

A
  • help cells to stick together
  • allow cells to recognise one another and distinguish from foreign cells
  • carb chains attach to proteins on outer surface of cell membrane
47
Q

Permeability of cell surface membrane

A
  • most molecules don’t freely diffuse accross cell surface membranes because they are insoluble in lipids, so can’t pass bilayer
  • also may be too large
  • could be repelled by charge on protein channels
  • may be electrically charged and so struggle to pass through non polar hydrophobic tails
48
Q

Describe fluid mosaic model of cell surface membrane

A
  • fluid because phospholipid molecules can move relative to one another , so membrane has a flexible structure that can change shape
  • mosaic because proteins embedded in bilayer vary in shape, size and pattern in the same way as tiles of a mosaic
49
Q

How can ionic bonds be split in proteins ?

A

can be split by altering the pH

50
Q

What is a disulphide bond ?

A
  • bond between two sulfur atoms of two cysteine residues ( cysteine- type of amino acid)
51
Q

What are the two types of proteins ?

A
  • fibrous proteins which are tough and rope like, for structural function, long chains that run parallel to each other inked by cross bridges and insoluble
  • globular proteins, round and compact due to hydrophobic/ hydrophilic positioning. soluble, transported in fluid ie blood and in used in metabolic functions.
52
Q

What is the structure of haemoglobin ?

A
  • made of 4 proteins chains, two alpha and two beta chains each with a ring- like heme group which has an iron atom
  • oxygen binds to iron atoms in haemoglobin
53
Q

What is the structure of collagen

A

primary structure: unbranched polypeptide chain containing glycines
secondary structure: very tightly wound alpha helices
tertiary structure: twisting and folding into more alpha helices
quaternary structure: consists of three polypeptide chains held together by hydrogen bonds ( coiled in a triple helix)

54
Q

What are enzymes

A
  • biological catalysts
  • alter the rate of a chemical reaction without being used up by providing an alternative pathway with lower activation energy
55
Q

What is the structure of enzymes

A
  • are globular proteins
  • have a specific 3D shape
  • have a functional region ( where substrate binds) called the active site
56
Q

What is the lock and key model and give the limitation

A
  • idea that each key has a specific shape that fits into only one lock
  • applied to enzymes this means substrate will only fit into the AS of one specific enzyme
57
Q

What are the limitations of the lock and key model ?

A

Considers enzymes to be rigid when in reality they are flexible. Other molecules can bind to enzymes at other allosteric sites changes shape of AS.

58
Q

Enzyme shape is what to substrates

A

Complementary

59
Q

Applying understanding of enzyme action what happens when H2O2 was added to the liver ?

A

Liver produces catalase which binds to hydrogen peroxide substrate and breaks it down. The substrate would be complementary to the active site.

60
Q

What Are factors which affect rate of enzyme action ?

A

Concentration of substrate, concentration of enzymes, temperature and pH,and presence of inhibitors

61
Q

What is the effect of temperature on enzyme action ?

A
  • increased kinetic energy of enzyme and substrate
  • move faster and so enzyme and substrate molecules collide more
  • more frequent enzyme substrate complexes being formed
  • therefore this increases the rate of reaction. But if temp gets too high, enzyme active site distorts and eventually substrate cant bond to enzyme’s active site.
62
Q

What is the optimum temperature of enzymes

A

40 degrees

63
Q

Why does the body not maintain this temperature

A
  • more food to provide energy in respiration would be needed
  • other proteins in the body would denature at 40 degrees or higher
64
Q

How does pH affect enzymes ?

A
  • sub optimal pHs affect the charges of amino acids in active site which prevents substrate from binding
  • disrupts the interactions between NH2 and COOH groups
  • this alters the bonds of the tertiary structure which denatures active site
65
Q

How is damage to enzyme’s by sub optimal pHs avoided ?

A

pH is well buffered against changes in pH will reduce enzyme activity without stopping the activity.

66
Q

How does enzyme concentration affect the reaction ?

A

Work effectively at low concentrations because they are not used up in the reaction. If substrate is in excess there is an increase in reaction rate.

67
Q

How does substrate concentration affect enzymes

A

At low substrate concentration enzymes have limited substrate to act upon
As conc of substrate increases rate of reaction increases as more enzyme substrate complexes are formed
After certain point no more increase though ROR no longer goes up enzyme conc becomes limiting f.

68
Q

How does concentration of competitive reversible inhibitors affect rate of reaction.

A

Decreases rate of reaction of the conc increases because the AS of enzymes is blocked by inhibitors so substrates cannot bind to active site

69
Q

What do enzyme inhibitors do ?

A

inhibitors bind to enzymes and disrupt the active site, stop enzyme from functioning or alter its function.

70
Q

What are the two categories of inhibitors ?

A

competitive and non competitive

71
Q

what are competitive inhibitors and how are they affected by increasing substrate concentration ?

A

shape is similar to substrate so can occupy AS inst of substrate, competes with substrate

increase in substrate reduces effect of inhib
reaction still takes place, inhibitor eventually does leave active site.

72
Q

Describe the effect of inhibitors vs rate of reaction —- graph

inhibitors referring to both competitive and non competitive inhibs

A

Competitive inhibs
at low substrate concentrations, adding competitive inhibitor reduces rate of reaction compared to a normal enzyme . when you add more substrate however, substrate ends up outcompeting inhibitor ans so rate of reaction increases ands up reaching v max ( max rate of reaction)

Non competitive inhibs
it doesn’t matter whether you increase the substrate concentration, as non competitive inhibitors change enzyme’s active site and so substrate would no longer be able to bind anyway. so you don’t see same increase to V max as you do with competitive inhibs after you inc substrate.

73
Q

What are non competitive inhibitors and how does increasing substrate concentration affect rate of reaction ?

A

increasing sub concentration doesn’t affect non competitive inhibitors

this is because they attach to different binding site: different allosteric site ( binding site)

alters shape of enzyme by altering shape of AS
this means that then substrate will no longer bind, so enzyme cannot work.

74
Q

Describe how a non competitive inhibitor can reduce the rate of enzyme controlled reaction:

A
  • non competitive inhibitor binds to another binding site on the enzyme “ allosteric site”
  • changes shape of active site of the enzyme
  • so substrate is not complementary to enzyme anymore, and thus rate of reaction will decrease.
75
Q

What are metabolic pathways ?

A

reaction pathways where each step is catalysed by an enzyme

76
Q

What is end product inhibition ?

A

when the final product of a metabolic pathway inhibits an enzyme involved in the initial reactions

77
Q

What two drugs are examples of competitive inhibitors ?

A

methotrexate and penicillin are examples of comp inhibitors. methotrexate is a reversible comp inhib of an enzyme found in human cells. penicillin acts the same for an enzyme involved in synthesis of bac cell walls

key difference though: pen binds irreversibly to enzymes it inhibits. binds permanently, so its effect cannot be reduced by increasing substrate conc.

77
Q

Describe the structure of a nucleotide

A
  • pentose sugar
  • phosphate group
  • nitrogen-containing base
78
Q

What do you call one nucleotide, two nucleotides, several nucleotides ?

A
  • mononucleotide, di nucleotide, polynucleotide
79
Q

What is the bond between 1 pentose sugar and the next called. why is it so strong ?

A

phosphodiester bond. very strong because it is a covalent bond

80
Q

What is the difference between purine and pyrimidine bases

A
  • purine bases have a double ring structure ( 2 carbon ring) A and G
  • pyrimidine bases have a single ring structure C T and U
81
Q

How many bonds do C and G form when they pair together compared to A or T and U

A
  • form 3 bonds while A/t with U form 2 hydrogen bonds
82
Q

Describe the structure of RNA

A
  • single chained polynucleotide
  • pentose sugar ( ribose)
  • bases ( AUCG)
83
Q

Describe the structure of DNA

A
  • Double-chained polynucleotide
    double helix structure
  • pentose sugar ( deoxyribose)
  • bases A G C T
84
Q

How many base pairs in DNA are there per mammalian cell? What does this mean

A
  • 3 billion base pairs per mammalian cell
  • this means infinite variety of base sequences
85
Q

What protects the reactive bases ?

A

phosphodiester backbone

86
Q

What is ATP function, structure and how is it formed ?

A
  • the energy currency of the cell. plants and animals oxidise organic molecules to make ATP
  • made of adenine, ribose sugar and 3 phosphates ( bonds between phosphate groups unstable, easily broken due to low activation e)
87
Q

What is ATP used for in metabolic processes

A

needed as input for metabolic processes

88
Q

What is ATP used for in movement

A

energy for muscle contraction

89
Q

What is ATP needed for in active transport

A
  • energy needed to change the shape of carrier proteins in plasma membranes to facilitate movement of mols against conc gradient
90
Q

What is ATP required for in secretion ?

A
  • energy needed to form lysosomes( organelles which contain digestive enzymes)
91
Q

What are some important things to remember about DNA structure wise

A
  • the two polynucleotide strands in DNA run antiparallel ( opposite directions)
  • proportions of C and G are always the same as each other, as are the proportions of A and T
92
Q

What are two differences between DNA and RNA

A
  • DNA is a longer molecule RNA in contrast is shorter
  • RNA is found in the cytoplasm, and DNA is found in chromosomes in the nucleus.
93
Q

What are the functions of triglycerides in relation to their structure ?

A
  • large ratio of C- H bonds which are good at storing energy compared to number of carbo atoms increases energy storage in molecule
  • a high ratio of H to oxygen atoms, so can act as a metabolic water source. are able to release water when oxidised
  • triglycerides don’t affect water potentials and osmosis because they are large and hydrophobic so insolub in water
  • relatively low mass ie compared to muscles so a lot can be stored without inc mass of the organism and limiting movement
94
Q

How many ester bonds are made when forming a phospholipid

A

two condensation reactions, so two ester bonds, because only two fatty acids bond to glycerol

95
Q

What makes the head of a phospholipid hydrophilic ?

A

negative charge on phosphate group

96
Q

which are polar triglycerides or phospholipids?

A

phospholipids. triglycerides have no charged regions so are non polar.

97
Q
A

A level biology flashcards (15 decks)

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