Biological Molecules Flashcards
1
Q
what is a monomer?
A
a small, soluble molecule that can join to other similar monomers to make polymers
2
Q
what is a polymer?
A
a large, insoluble molecule made of many similar, repeating monomers.
3
Q
which monomers and polymers form carbohydrates?
A
monosaccharides and polysaccharides
4
Q
which monomers and polymers form proteins?
A
amino acids and poly-peptides
5
Q
which monomers and polymers form DNA/RNA?
A
nucleotides and polynucleotides
6
Q
why are lipids not polymers?
A
not made of similar subunits, consist of both fatty acids and glycerol.
7
Q
what is a condensation reaction?
A
one that joins 2 molecules together with he formation of a chemical bond involving the release of a water molecule.
8
Q
what is a hydrolysis reaction?
A
one that breaks down a chemical bond between 2 molecules involving the use of a water molecule
side note lol DONT SAY BREAKS DOWN SAY HYDROLYSED
9
Q
what are monosaccharides + name 3 + give their general formula
A
monosaccharides are monomers from which larger carbohydrates are made.
glucose, galactose, fructose
C6H1206 but little numbers
10
Q
which bond does a condensation reaction between 2 monosaccharides form?
A
a glycosidic bond
11
Q
draw an alpha glucose
A
12
Q
which elements are found in carbohydrates?
A
carbon, hydrogen, oxygen
13
Q
what are 2 other names for glucose?
A
a 6-carbon/ hexose sugar
14
Q
draw a beta glucose
A
15
Q
what is an isomer?
A
a molecule that has the same general formula but different structural formula.
16
Q
what is a disaccharide + name 3 with combinations + general formula
A
formed by the condensation of 2 monomers.
glucose + glucose = maltose
glucose + galactose = lactose
glucose + fructose = sucrose
C12H22O11 + H20
17
Q
how does a condensation reaction to form a disaccharide work?
A
the reaction occurs between the OH groups on carbon 4 of one monosaccharide and carbon 1 on the other, forming a 1,4 glycosydic bond
forms an H20 molecule
forms a glycosydic bond
results in a disaccharide
18
Q
draw a diagram of a condensation reaction:
A
side note lol ADD THE H20 MOLECULE OR ELSE
19
Q
when and why are disaccharides hydrolysed into monosaccharides?
A
in digestion
so they can be absorbed and assimilated (used) for processes e.g. respiration
20
Q
draw a hydrolysis reaction
A
21
Q
how does a hydrolysis reaction work?
A
the disaccaharide is hydrolysed to give 2 monosaccharides
a molecule of H20 is required
the glycosidic bond is broken
22
Q
what is a polysaccharide?
A
polysaccharides are formed by the condensation of many monosaccharide units
23
Q
name 3 polysaccharides, which type of glucose they are made from, and where they are used
A
starch- alpha glucose- storage in plants for carbohydrates
cellulose- beta glucose- plant cell wall
glycogen- alpha glucose- storage in animals as glucose, to be used in respiration
24
Q
draw how 3 molecules of alpha glucose would form starch/ glycogen
A
25
draw how 3 beta glucose molecules would form cellulose
26
name starch properties and how the properties relate to its function
insoluble- doesn't affect the cell's water potential, therefore doesn't affect osmosis
coiled into a helix- compact so many can fit in a small space for storage
1,4 and 1,6 glycosidic bonds- allows branching to occur
branched- provides many ends for rapid hydrolysis by enzymes to form an alpha glucose for respiration
large- wont diffuse out of the cell
27
name glycogen properties and how they relate to the function
insoluble- doesn't affect osmosis
coiled into a helix- compact so many can fit into a small space for storage
1,4 and 1,6 glycosidic bonds- allows branching
very highly branched with shorter chains- more ends for rapid hydrolysis by enzymes to form alpha glucose for use in respiration
large- won't diffuse out of the cell
28
name cellulose properties and how they relate to its function
only 1,4 glycosidic bonds- allows long, straight, unbranched chains of beta glucose
long,straight, unbranched chains of glucose- allows formation of many hydrogen bonds, so microfibrils are created
many microfibrils- allows formation of cellulose fibres
cellulose fibres and many hydrogen bonds- provides strength to cell wall
29
which 5 sugars are reducing?
glucose, galactose, lactose, fructose, maltose
30
which sugar is non-reducing?
sucrose
31
what is the benedict's test for reducing sugars?
1) add benedict's solution to sample and heat to 95 degrees
2) colour change from blue to red precipitate indicates reducing sugar
3) if there's no change, a non-reducing sugar could be present
the other colours can be used as a qualitative test on the concentration of the sugar- green = low, red = high.
if you want a quantitative measure, you could remove the liquid and measure the mass of the precipitate
32
what is the benedicts test for non-reducing sugar?
1) add benedict's solution to sample and heat to 95 degrees, if there's no colour change in the test for reducing sugar, boil a fresh sample with dilute HCl for a few minutes to hydrolyse the glycosidic bonds.
2) neutralise by adding sodium hydrogen carbonate
3) add benedict's reagant and heat to 95 degrees
4) as the sucrose has been hydrolysed to glucose and fructose, there will be a red precipitate and a colour change from blue to red.
33
what is the test for starch?
1) add iodine to potassium iodide solution to your sample
2) a colour change from orange to blue/black indicates starch
34
what are the 2 groups of lipids and where are they found?
triglycerides- found in food and used for energy storage
phospholipids- help to form cell membranes
35
how are triglycerides formed?
by the condensation of one molecule of glyerol and 3 fatty acid molecules (not a polymer)
36
which elements do triglycerides contain?
carbon, hydrogen and oxygen
37
which type of bond forms between a glycerol and a fatty acid (RCOOH)?
an ester bond (so there are 3 ester bonds in a triglyceride)
38
draw the structure of a glycerol molecule
39
fatty acids consist of a hydro______ c_____ and a carbo_______ ____ group
fatty acids consist of a hydrocarbon chain and a carboxylic acid group
R = hydrocarbon chain
COOH = carboxyl group
whole fatty acid = RCOOH
40
what is a saturated fatty acid?
all the bonds between the carbon atoms in the hydrocarbon chain are single bonds
41
what is an unsaturated fatty acid?
at least one of the bonds between the carbon atoms in the hydrocarbon chain are double bonds
42
draw 2 ways a fatty acid can be represented
RCOOH
or
O
II
HO----C----R
43
draw how 3 molecules of fatty acid join to a molecule of glycerol
for every triglyceride molecule, 3 water molecules are produced
44
fatty acid tails are hydrophobic, what does this mean?
they repel water, this is what makes lipids insoluble in water and means they form insoluble droplets.
the fatty acid tails face inwards, shielding themselves with the glycerol heads
45
how many fatty acids do phospholipids have, and if not 3, what are they replaced by?
2 fatty acids, one is replaced by a phosphate group
46
why is the phosphate head in phospholipids hydrophilic, and the fatty acid tails are hydrophobic?
the phosphate group is negatively charged (polar) and the fatty acid tails are non-polar, meaning that the phosphate head attracts water because they are oppositely charged, and the fatty acid tails repel it
47
how do phospholipids form a bilayer in water?
the fatty acid tails are arranged in the middle away from water and the hydrophilic heads are arranged on the outside in contact with water
the phospholipid bilayer forms the basis of cell membrane surface + organelle membranes
48
draw how phospholipids are arranged in a bilayer
49
name the properties of a triglyceride, and why it's useful
long, hydrocarbon fatty acid chains- contains a lot of stored chemical energy- used as an energy storage molecule
hydrophobic fatty acid tails- doesn't affect the water potential of a cell- won't dissolve and release stored energy in water
50
name the properties of a phospholipid and why it's useful
hydrophobic fatty acid tails and hydrophilic phosphate heads- forms a phospholipid bilayer with hydrophilic phosphate heads pointing towards the water and hydrophobic fatty acid tails pointing away- forms cell membranes, this means water soluble molecules can't pass easily across the membrane
51
name 2 other uses for lipids apart from storage and membranes
certain hormones (eg testosterone)
respiratory substances
52
what elements do all proteins contain?
nitrogen, carbon, hydrogen, oxygen
53
what element do some proteins contain?
sulfur
54
name roles of proteins in the body
haemoglobin- transports oxygen
antibodies- defend against infection
enzymes- biological catalysts
actin and myosin- muscle contraction
keratin- nails and hooves
collagen- tendons
55
draw the general structure of an amino acid + label the amine group, carboxyl group and R group (a carbon-containing side chain)
56
how many amino acids are there and how do they differ?
20- they differ only in their R group
57
what is the bond between amino acids called?
a peptide bond
58
how are dipeptides formed?
by the condensation of 2 amino acids, removing water in the formation of a peptide bond
59
draw a diagram of a dipeptide being formed
60
how are polypeptides formed?
by the condensation of many amino acids
61
what is primary protein structure?
the number and sequence of amino acids in a polypeptide chain- it determines the rest of the structure and most importantly the tertiary structure.
62
what is secondary protein structure?
the folding of the polypeptide into an alpha helix or a beta pleated sheet- the structure is maintained by hydrogen bonds between the amine group of one amino acid and the carboxyl group between another.
63
what is tertiary protein structure?
the folding of the polypeptide chain into a specific 3-D shape and a globular structure. it's held together by bonds between R groups of different amino acids.
64
name the 3 different types of bonds between R groups in a protein?
hydrogen bonds- weak but strong in large numbers.
ionic bonds- also weak and form between oppositely charged R groups
disulphide bonds/bridges- covalent bonds between sulpur-containing R groups.
65
why does a protein's tertiary structure/ function depend on its primary structure?
the bonds form between specific R groups. the sequence of amino acids determines where the bonds form, and if the primary structure is changed, the sequence of R groups changes, which would result in bonds in the tertiary structure forming in different places, therefore changing the shape/function of the protein
66
what is quaternary protein structure?
more than 1 polypeptide joined together
if a protein contains 1 polypeptide chain, it doesn't have a quaternary structure
67
name 3 examples of proteins that have quaternary structures
haemoglobin (4 polypeptide chains)
antibodies (4)
actin (2)
68
what is the Biuret test for proteins?
add Biuret solution to a sample, if protein is present, the solution will change from blue to lilac, and will stay blue if no protein is present
69
what happens to a protein when it's denatured?
when the hydrogen/ ionic bonds break, the tertiary structure of the protein is altered, the active site shape is altered and the protein can no longer carry out its function
70
how can we denature a protein?
increase temperature far beyond its optimum (bonds will break, loses tertiary structure etc etc)
change pH- pH= concentration of H+ ions, the charge on the R groups of the amino acids is altered and bonds break loses structure etc etc
71
what are enzymes?
biological catalysts that speed up the rate of reaction by lowering the activation energy needed for a chemical reaction
72
how do enzymes lower activation energy?
helping to align the reactants through the formation of enzyme-substrate complexes (so bonds can break and form more efficiently so less activation energy required)
73
how would you determine the presence of enzymes in a solution?
Biuret test
74
draw a sketch of the induced fit model
in this model the active site isn't fully fixed, the substrate induces a change in shape of the active site making it complementary
75
explain the induced fit model
1) the substrate enters the enzyme's active site
2) the binding of the substrate induces the change in shape of the active site
3) this puts pressure on the bonds in the substrate which causes them to break more easily, explaining how enzymes lower activation energy
4) when the substrate leaves the active site it returns to its previous shape allowing it to bind to other substrates
76
what are enzymes affected by?
temperature
pH
inhibitors
substrate concentration
enzyme concentration
77
explain the effect of temperature on an enzyme
as the temperature increases up to its optimum the enzyme and substrate molecules have more kinetic energy and are more likely to collide with sufficient energy and form enzyme substrate complexes- the rate of reaction increases.
if the temperature increases beyond optimum, the hydrogen bonds holding the tertiary structure together break and the tertiary structure changes
this changes the shape of the active site so it's no longer specific and complementary to its substrate meaning no more E-S complexes can be formed
the enzyme is denatured and can no longer catalyse reactions
78
explain the effect of pH on enzymes
changing pH means changing the concentration of H+ ions
if the pH alters from the optimum, then the charge on the R groups of the amino acids are altered and hydrogen and ionic bonds in the tertiary structure are broken so the tertiary structure changes
the active site changes shape and it's no longer specific and complementary to its substrate meaning no more E-S complexes can be formed
the enzyme is denatured and can no longer catalyse reactions
79
explain the effect of substrate concentration on enzymes
the rate of reaction is low at low substrate concentrations as not all active sites are saturated (filled)- the substrate is a limiting factor
as substrate concentration increases, the active sites are filled and the rate of reaction increases, due to more successful collisions between enzyme active sites and substrates so more E-S complexes form per second- the substrate is no longer a limiting factor
at high substrate concentrations, there is no further rise in rate for reaction since the enzymes can't form any more E-S complexes as all active sites are saturated- enzyme concentration is now the limiting factor
80
explain the effect of enzyme concentration on enzymes
the more enzyme molecules there are in a solution, the more likely they are to collide with a substrate with sufficient energy to form an E-S complex
as a result, increasing the enzyme concentration increases the rate of reaction
however, if the amount of substrate becomes limiting, increasing enzyme concentration will have no effect on the rate of reaction
81
what is an inhibitor?
a substance that decreases rate of reaction
82
what is a competitive inhibitor?
competitive inhibitors have a similar structure to substrates- they fit in the enzyme but do not react
they prevent the normal substrate from binding and hence slow down the rate of reaction as LESS enzyme substrate complexes can be formed
if you add more substrate there is more chance of the enzyme binding to its substrate rather than the inhibitor, forming more e-s complexes
83
what is a non-competitive inhibitor?
they bind to a site on the enzyme other than the active site, and alter the active site so that the substrate can't fit
NO enzyme substrate complexes can be formed and the rate of reaction is decreased
you can't move away from inhibition if it's a non-competitive inhibitor
84
draw a graph showing the curves of a normal enzyme and competitive inhibitor graph with substrate concentration on the x-axis and rate of reaction on the y-axis + explain it
the competitive inhibitor curve will reach the almost same max rate of reaction as the normal curve, just slower- some of the active sites are occupied by the inhibitor, as substrate concentration increases, there will be less inhibition of the active sites so more substrates can bind to the active site, meaning max rate is almost reached
85
draw a graph showing the curves of a normal enzyme and non-competitive inhibitor graph with substrate concentration on the x-axis and rate of reaction on the y-axis + explain it
the line initially increases because there are some active sites unaltered by the inhibitor. the inhibitor changes the shape of the active site so the substrate is no longer complementary and e-s complexes can't form, so even when substrate concentration increases, the rate never reaches the maximum and the line plateaus
86
what is a nucleotide?
the monomer that forms polynucleotides, containing a phosphate group, a 5-carbon pentose sugar and a nitrogenous base
87
what is the function of DNA and what does it stand for?
deoxyribose nucleic acid- it holds genetic information and codes for amino acids
88
what is the function of RNA and what does it stand for?
ribonucleic acid- it transfers genetic information from DNA to ribosomes
89
draw and label a DNA nucleotide
always say deoxyribose sugar instead of just sugar
90
name all of the 4 bases that a dna nucleotide could contain and their complementary base pairings
adenine-thymine
cytosine-guanine
91
draw and label an RNA nucleotide
always say ribose sugar instead of just sugar
92
what are ribosomes formed from?
rRNA and proteins
93
name all of the 4 bases that an rna nucleotide could contain and their complementary base pairings
adenine-uracil
cytosine-guanine
94
what do many nucleotides join together to make?
a dna (polynucleotide) strand
95
draw the formation of a dinucleotide
96
how are nucleotides joined together?
a condensation reaction forms a phosphodiester bond between the phosphate group of one nucleotide and the pentose sugar of another- this is a covalent bond and forms the sugar-phosphate backbone, which makes the nucleic acid stable and strong
97
what is the structure of a dna molecule?
a linear double helix with 2 antiparallel polynucleotide chains held together by hydrogen bonds between specific complementary base pairs
98
why are the bonds holding the 2 dna chains together more easily broken than the phosphodiester bond of the sugar-phosphate backbone?
because hydrogen bonds are weak when there aren't many of them and the phosphodiester bond is a strong covalent bond
99
what is the structure of an rna molecule?
a relatively short linear polynucleotide chain, normally single-stranded
100
why is it important that the 2 polynucleotide chains in dna are antiparallel?
because it ensures only 1 strand is read to make proteins, and in dna replication, the dna polymerase only has a complementary active site to the 3' end of the molecule (it is labelled with a 5' end and a 3' end)
101
how does the structure of dna allow it to carry out its function? (TYPICAL 6 MARK EXAM QUESTION)
1) sugar-phosphate backbone and double helix structure provides strength and stability and protects bases and hydrogen bonds between them
2) long molecule- can code for many amino acids and proteins
3) helical- compact
4) base sequence- codes for amino acids and therefore proteins
5) double stranded- allows semi-conservative replication, as each strand can act as a template
6) complementary base pairs (state the base pairs with full names of bases in the exam just cba to write them here)- allows accurate replication
7) weak hydrogen bonds between bases- allows unzipping and separating of strands for replication
8) many hydrogen bonds in the molecule- strong and stable
102
why does dna have to copy itself accurately whenever a cell divides?
so that every new daughter cell produced has exactly the same genetic information so genetically identical cells are produced
103
why is semi-conservative dna replication important?
it ensures genetic continuity between generations of cells
104
how does dna replication occur (TYPICAL 6 MARK QUESTION)?
1) the enzyme dna helicase attaches and moves along the dna molecule, unwinding the dna and breaking hydrogen bonds between complementary bases
2) the 2 strands start to separate and unzip and both strands act as a template
3) new nucleotides are attracted to the exposed complementary bases on the template strands and complementary base pairings occur, adenine to thymine, cytosine to guanine, and hydrogen bonds form between the complementary bases (HAVE TO SAY THE FULL NAMES OF THE BASES IN THE EXAM)
4) the enzyme dna polymerase joins adjacent molecules through a condensation reaction forming the sugar-phosphate backbone, joined by phosphodiester bonds
5) this is known as semi-conservative replication as each new dna molecule contains one strand from the original molecule and one new strand (HAVE TO SAY THIS LAST SENTENCE)
105
who were the 2 scientists who proposed models of dna structure and replication?
watson and crick
106
who were the 2 scientists who showed evidence for semi-conservative theory?
meselson and stahl
107
what was the experiment meselson and stahl did to prove semi-conservative theory?
they grew e.coli on a medium with the heavy isotope of 15N, as the bases are nitrogenous. the nitrogen atoms the bacteria used to make the new dna would all be of 15N kind (generation 0).
the dna made from the 15N kind was extracted and centrifuged in a test tube (heavier molecules went to the bottom)
the bacteria were then transefrred to a medium with normal 14N and after the bacteria divided once in 14N, the dna was taken and centrifuged (generation 1).
so on so forth
they were right as semi-conservative replication meant the new dna would have a mix of the og and a new strand of the new nitrogen
108
what is the function of atp?
during respiration, the energy stored in glucose isn't released directly. the energy released is used to form adenosine triphosphate (atp). it's then hydrolysed, providing energy for the cell's processes
109
draw the structure of atp
adenine, ribose, 3 phosphate groups
110
why is atp considered a nucleotide derivative?
it's a modified version of a nucleotide
111
give 4 examples of what energy is used for in a cell
1)active transport
2)synthesising molecules eg dna replication, making proteins from amino acids
3) mitosis (spindle fibre contractions)
4) muscle contraction
112
where is energy stored in atp?
in the bond between the 2nd and 3rd phosphate. when this high energy bond is hydrolysed the energy is released.
113
how is energy released from atp?
the high energy bond is broken using hydrolysis to form adenosine diphosphate (adp) and an inorganic phosphate (Pi)- this requires the enzyme atp hydrolase.
atp + water ---> adp + Pi + energy
114
what is phosphorylation?
where the released Pi from the hydrolysis of atp is added to other compounds to make them more reactive
115
name the 2 processes where atp is made
respiration and photosynthesis
116
how is atp made?
atp is made from adp and Pi via a condensation reaction- this reaction requires the enzyme atp synthase. there is a constant cycle in the cell where atp is being synthesised and hydrolysed
117
draw a diagram showing the condensation and hydrolysis of atp
118
why were bacteria used in the meselson and stahl experiment?
bacteria have no nuclei- the dna was just floating about and easier to extract than from a eukaryotic cell
119
to validate watson and cricks' dna replication model, hershey and chase experimented to show that dna is hereditary and not from proteins, what was the experiment?
1) proteins from phages are radioactively labelled with 38S (sulfur is found in proteins not dna)
2) the phages infect the bacteria with genetic material
3) no radioactivity entered the cell (no protein passed on)
1) dna from phages radioactively labelled with 32P (found in dna not proteins)
2) phages infect bacteria with genetic material
3) radioactivity enters cell showing dna must be hereditary
120
to validate watson and cricks' dna replication model, griffith experimented to show that dna is hereditary, what was the experiment?
he used mice and bacteria that cause pneumonia
1) one mouse was injected with a safe strain of the virus- lived
2) the second was injected with a harmful strain- died
3) the 3rd was injected with a harmful strain that was heat-killed- lived
4) the 4th was injected with both the heat-killed harmful strain and the safe one- died
121
what does the energy released from respiration that is stored in glucose form?
atp (adenosine triphosphate)
122
what does atp release when it is hydrolysed?
energy for processes in the cell
123
draw a flow diagram to represent formation and hydrolysis of atp
respiration hydrolysis
glucose --------------> atp--------------> energy
124
atp is a nucleotide derivative, what does this mean?
it is a modified version of a nucleotide
125
give 3 differences between a dna nucleotide and atp
1) atp has a ribose sugar, a dna nucleotide has deoxyribose
2) atp has 3 phosphates, a dna nucleotide has 1
3) atp always has adenine as the base but a dna nucleotide can have adenine, thymine, cytosine or guanine
EXAM TIP: always write the bases out in full, and always say "a dna nucleotide" instead of just "dna" bc dna is made of loads of polymers and such
125
why is atp useful?
1) it's an immediate source of energy which is released in small, usable amounts
2) it involves a single-step reaction to release energy
3) phosphorylation
4) it can be resynthesised
5) it's soluble (this ones not rlly that important tho)
126
where are various inorganic ions present?
in cell cytoplasm and body fluids- some are at high concentrations and some low
127
what does inorganic mean?
without carbon
128
explain how iron ions (Fe2+) are important in the body
they are found in the protein haemoglobin, in red blood cells. the oxygen binds to the Fe2+ and transports the oxygen to respiring cells.
haemoglobin has a quaternary structure with 4 polypeptide chains, each with 1 Fe2+ so haemoglobin can carry 4 oxygen molecules
129
explain how hydrogen ions (H+) are important in the body
H+ ions determine the pH of a solution- the higher the concentration of hydrogen ions, the lower the pH. a high or low concentration of H+ ions can denature proteins including enzymes and affect enzyme rate of reaction.
H+ ions are also used in photosynthesis and respiration, along with atp synthase, in the formation of adp + Pi
130
explain how sodium ions (Na+) are important in the body
sodium ions are involved in the absorption of glucose into the blood. Na+ are co-transported along with glucose into the epithelial cells of the small intestine down a Na+ concentration gradient.
Na+ are also involved in the production of electrical impulses in neurones.
Na+ are also involved in water reabsorption in the kidneys
131
explain how phosphate ions (PO4 3-) are important in the body
PO4 3- (Pi) are added to adp to produce atp in a condensation reaction during photosynthesis and respiration.
PO4 3- also phosphorylates other molecules
PO4 3- also joins dna and rna nucleotides via phosphodiester bonds in the sugar phosphate backbone
PO4 3- makes up the hydrophilic part of the phospholipid bilayer
132
how is a water molecule polar (opposite charges at either end)?
the oxygen atom is slightly negative and the hydrogen atoms are slightly positive
133
where do hydrogen bonds form between water molecules?
where the negative oxygen on one molecule is attracted to the positive hydrogen on another
134
name and explain the 5 properties of water (COMMON EXAM QUESTION)
1) cohesion due to hydrogen bonding- allows water to be pulled up in a continuous column in the xylem and allows surface tension to support small organisms like pond skaters + droplets on skin for sweating
2) a metabolite in: photosynthesis, respiration, hydrolysis (eg breaking of glycosidic bonds), condensation (eg formation of peptide bond)
3) a solvent- allows chemical reactions to occur in a solution and transport of substances
4) cooling body temperature- water has a large latent heat of vaporisation (to turn to gas hydrogen bonds must be broke, lots of energy), useful in cooling down with sweat/panting as when it evaporates, lots of energy removed, reducing dehydration
5) preventing large changes in body temperature- water has high specific heat capacity (lots of energy to increase temp, hydrogen bonds must be broke) so it buffers change in body temp (keeps optimum temp for eg enzymes) and makes water a reliable habitat
