Biological Molecules Flashcards
1
Q
What is a polymer
A
Monomers joined to make a larger molecules
2
Q
What is an example of a polysaccharide
A
Starch
3
Q
What is a condensation reaction
A
Joins two molecules together with formation of chemical bond, involves elimination of water molecule (polymerisation)
4
Q
What is a hydrolysis reaction
A
Breaks the chemical bond between two molecules, involves the use of water molecule
5
Q
What are organic molecules how do they form sequences
A
They contain carbon molecules
Carbon atoms very readily form bonds with other carbon atoms, allowing a sequence of carbon atoms of various lengths to join
6
Q
What are carbohydrates
A
Hydrated carbons in a 2:1 ratio of carbon and hydrogen:oxygen
7
Q
What is a saccharide
A
Basic monomer sugar unit in carbohydrates
8
Q
What is a monosaccharide and the general formula
A
Sweet tasting soluble substances General formula (CH2O)n (n can be 3-7)
9
Q
What are the two isomers of glucose
A
Alpha glucose
Beta glucose
10
Q
How are reducing sugars tested for (all monosaccharides and some disaccharides)
A
Benedicts test
- Add 2cm^3 of food sample to test tube (grind up in water is isn’t already liquid)
- Add equal volume of Benedicts reagent
- Heat mixture by boiling gently in water bath for 5 minutes
- Positive result of reducing sugar seen of solution turns brick red
11
Q
What type of test is the Benedicts test and how accurate is it
A
Semi-quantitive, estimates the approximate amount of reducing sugar in sample depends on colour solution turns
12
Q
What is a reducing sugar
A
Can donate electrons to reduce another chemical
13
Q
What is the colour change in the Benedicts test due to
A
Increasing copper (|) precipitate
14
Q
Instead of looking at the colour change in the Benedicts test what is another method of testing for a reducing sugar
A
Measure the mass of the reducing sugar, will tell us if more reducing sugar in glucose. Heavier precipitate, more reducing sugar present
15
Q
What do monosaccharides form after condensation reaction
A
Disaccharide
16
Q
What disaccharide is formed from the condensation of alpha glucose and alpha glucose
A
Maltose
17
Q
What disaccharide is formed from the condensation of alpha glucose and fructose
A
Sucrose
18
Q
What disaccharide is formed from the condensation of alpha glucose and galactose
A
Lactose
19
Q
What bond is formed between monosaccharides in a condensation reaction to form disaccharides
A
Glycosidic bond
20
Q
How would you test for a non-reducing sugar
A
- Perform Benedicts test with unknown sample, no change, know isn’t reducing sugar
- Add 2cm^3 of sample to dilute hydrochloric acid
- Heat in boiling water for 5 minutes (hydrolyse the disaccharide into monosaccharides)
- Add sodium hydrogen-carbonate solution to neutralise the acid (or would stop Benedicts test working)
- Check with pH paper that solution is neutral
- Perform Benedicts test, heat
21
Q
How do you test for starch
A
- Add iodine solution, shake
2. If present will turn blue/black
22
Q
What is the structure or starch
A
Chains of alpha glucose monosaccharides linked by glycosidic bonds by condensation
Unbranched chain wound into tight coil making molecule compact
23
Q
What is the function of starch
A
Energy storage
24
Q
Where can starch be found
A
In plants as small grains
25
What are the features of starch
Insoluble, doesn't draw water into cells by osmosis and doesn't easily diffuse out of cells easily
Compact so lots can be stored in small space
26
What happens to starch when it is hydrolysed and why is this good
Forms alpha glucose
Easily transported
Readily used in respiration
27
What is the structure of glycogen
Similar to starch but shorter chains of alpha glucose and is much more branched
28
What is the function of glycogen
Major carbohydrate storage product of animals (energy storage)
29
How is glycogen stored in animals
Small granules, mainly in muscles and liver
30
Why does the structure of glycogen suit it and how does it's chain length affect hydrolysis
Good for energy storage
| Made of smaller chains so even more readily hydrolysed to alpha glucose used in respiration
31
What is the structure of cellulose
Made of beta glucose chains (linked by glycosidic binds formed in condensation)
Beta glucose must rotate 180 degrees to neighbour to form glycosidic bonds
So CH2OH group on each beta glucose alternates above and below chain
Straight unbranched chain run parallel allowing H-bonds form cross-linkages between adjacent chains
32
What is the function of cellulose
Major plant cell wall component, provides strength support and rigidity
Prevents cell bursting when water enters - osmosis, it exerts inward pressure, prevent further water entry
Cell can be turgid, help plant semi-rigid, upright (important for photosynthesis)
33
Why are the cross links important in cellulose and what bond are they made of
Hydrogen bonds form between straight unbranched cellulose chains to increase strength and rigidity
34
What do groups of cellulose molecules form
Microfibrils which in turn are arranged in parallel groups to make fibres
35
What is a lipid made of
Carbon, hydrogen and oxygen
36
What can lipids dissolve in
Insoluble in water
| Soluble in organic solvents e.g alcohol
37
What is the main lipid groups
Triglycerides and phospholipids
38
What state are fats and oils at room temperature
Fats are solid
| Oils are liquid
39
What are the features of lipids
Energy source - when oxidised lipids provide ,ore than twice the energy as same mass of carbohydrate, release valuable water
Waterproofing - insoluble in water. Plants and insects have waxy lipid cuticles, conserve water. Mammals make oily secretion from sebaceous glands
Insulation - fats are slow conductors of heat. Electrical conductors in myelin sheath round nerve cells
Protection - fat often stored around delicate organs e.g kidneys
40
What is the function of lipids in the cell membrane
Phospholipids contribute to membrane flexibility, transfer of lipid soluble substances across them
41
What is a monomer and examples
A smaller unit
| Monosaccharides, amino acids, nucleotides
42
What bond is formed in a triglyceride
Ester bond
43
What is an unsaturated fatty acid and what state is it likely to be
Has double carbon bonds, making it more likely to be a liquid as is weaker
44
Why are triglycerides suited to energy storage role
High ratio of energy-storing carbon-hydrogen bonds to carbon atoms, good energy source
Low mass to energy ratio, good storage molecules as much energy can be stored in small volume (good for large animals reduces movement)
Is a large non-polar molecule, insoluble in water so storage doesn't effect osmosis/water potential of cell
High hydrogen:oxygen atoms, triglycerides release water when oxidised, provide water source
45
How is a glycolipid formed
When phosphate is removed and replaced with a carbohydrate group
46
Where are glycolipids often found and why are they important
Found within cell surface membrane
| Important to cells as involved in cell recognition
47
How are lipids tested for
Emulsion test
1. Dry grease free test tube
2. Add 2cm^3 sample being tested
3. Add 5cm^3 ethanol
4. Shake tube to dissolve any lipid
5. Add 5cm^3 water, gently shake
6. Cloudy white emulsion indicated lipid presence
48
Why does a lipid form a cloudy white emulsion
Tiny droplets dispersed in water form emulsion. Light passing through refracted as passes from oil to water droplets
49
How could you check the emulsion test wasn't false positive
Control could use a non fatty substance e.g water and compare to sample
50
Why are enzymes important
Involved in almost every living process
51
What is an amino acid made of
Has a central carbon atom
NH2- on left of middle carbon
-COOH- acid group on right of middle carbon
R group above (determines the amino acid)
H below
52
How many amino acids are there
20 amino acid groups
53
What bond forms between two amino acids to make a dipeptide
Peptide bond
54
What is the process when amino acid monomers join
Polymerisation
55
How do you test for a protein
Biuret test
1. Add equal volume of Biuret solution (sodium hydroxide and copper sulphate) to sample
2. Purple colour indicated peptide bonds presence, so a protein
3. If no protein remains blue
56
What is the primary structure of a protein
Order of amino acids in polypeptide
Dictated by DNA sequence of gene
Mutations can cause tiny changes, a,y have huge consequences e.g sickle cell
Peptide bonds
57
What is the secondary structure of a protein
Polypeptide chains fold and coils into secondary structure - alpha helix, beta sheet, beta turn
Held by hydrogen bonds between C=O groups of peptide bond
58
What is the tertiary structure in proteins
Alpha helices can be twisted, folded form complex, specific 3D structure
Disulphide bridges between sulphur in R groups
Ionic bonds formed between any carboxyl and amino acid not involved in peptide bonds
Hydrogen bonds easily broken between R groups
59
What is the quaternary structure of proteins
Some proteins have several subunits, two+ peptide chains attached
Some proteins have non-protein 'prosthetic group' attached
Has more than one polypeptide chain
60
What is the role of fibrous proteins and example
Structural functions
| Collagen
61
What is the function of a globular protein and example
Carry out metabolic functions
| Enzymes, haemoglobin
62
What is the structure of fibrous proteins
Form long parallel chains linked by cross bridges, form very stable molecules
Primary - unbranched polypeptide chain
Secondary - polypeptide chain very tightly wound
Tertiary - twisted into secondary helix
Quaternary - made of three wound polypeptide chains wound together
63
Where is collagen found why is it needed there
Tendons, join muscles to bones
Muscles contracts, bone pulled in contraction direction
Individual collagen polypeptide chains in fibres held by bonds between amino acids of adjacent cells
64
Why are cross-linkages between amino acids in collagen important
Cross-linkages between amino acids in polypeptide chains prevent individual polypeptide chains sliding past each other, gain strentgh as act as single unit
65
What type of protein is an enzyme
Globular
66
What is an enzyme
A catalyst
67
What does a catalyst do
Alters the speed of chemical reaction without undergoing permanent changes
Speed up biological reactions, so can happen at body temperature
68
Where do enzymes catalyse reactions
Inside cells - intracellular
| Outside cells - extracellular
69
What causes enzymes to be specific
Globular protein has specific tertiary structure hence 3D shape so is specific to catalyse one reaction
70
What is the induced fit
```
The shape of active site and substrate molecule are complementary
Like glove (active site) and hand (substrate) both change shape slightly as bind
```
71
What is activation energy
Energy needed to start reaction - break chemical bonds in substance
72
How is activation energy lowered
When enzyme-substrate complex formed, as shale changes, enzyme puts strain on substrate molecule. Distorts bonds in substrate, lowers activation energy needed to break bond
73
How do you work out the gradient of a graph
Draw a tangent and workout y/x
74
How does temperature effect reactions
Increase in kinetic energy of molecules, move more rapidly collide more
75
What happens when an enzyme is denatured
Temperature rises causes hydrogen bonds in enzyme to break so active site is no longer complementary to specific substrate and it becomes permanently denatured
76
How do you workout pH
-log10[?]
77
What happens to the enzyme is there is extreme pH change
Denatured
78
How does pH change alter enzyme active site
Changes amino acid charges that form active site so substrate can't fit
79
How is the active site arrangement partially determined
-NH2 and COOH groups of polypeptide making up enzyme, disrupted by hydrogen ions
80
What is a competitive inhibitor
Bind to active site, but is not substrate just has a similar molecular shape so complementary, prevents enzyme-substrate complexes forming
Enzyme activity determined by concentration of substrate and inhibitor
81
What is a non-competitive inhibitor
Bind to enzyme at site other than active site, alters the active site in doing so. Substrate no longer complementary
Inhibitor and substrate not competing, increasing substrate doesn't decrease the inhibitor effect
82
What is the metabolic pathway
Series of reactions, each step catalysed by enzyme
83
How does the metabolic pathway work
Enzymes control metabolic pathway often attached to membrane of cell organelle in very precise sequence
In organelle optimum conditions for enzymes, keep steady concentration of chemical in cell, same chemical often acts as inhibitor of enzyme at reaction start
End product inhibits first enzyme, if concentration of end products increases over normal, more inhibition of the first enzyme, less product made, concentration returns to normal
84
What is DNA and what does it carry
Deoxyribosenucleic acid
Carries genetic information
Code that determines the amino acid sequence in protein (primary structure) determines how polypeptide folds up to form precise tertiary structure for protein
85
What is DNA made of
Two interlocking nucleotide chains
| Nitrogen-containing organic molecules combine form polynucleotide (3+ nucleotides)
86
What is a single nucleotide
Monomer or mono-nucleotide
87
How is a nucleotide formed and what is it made of
Pentose sugar, phosphate group, organic bases joined by condensation reactions
88
What bond is formed between nucleotide of one group and sugar of another nucleotide, what does it form
Phosphodiester bond
| Forms sugar-phosphate backbone
89
Who contributed to DNA structure work
1953 Watson and Crick published first DNA structure description following Franklins X-ray diffraction DNA patterns work
90
Which are the single-ring bases
Cytosine and thymine
91
Which are the double ring bases
Adenine and guanine
92
How many hydrogen bonds are between A-T base pairing
2
93
How many hydrogen bonds are between C-G base pairing
3
94
How are polynucleotides placed
Polynucleotide chains are antiparallel run in opposite directions
95
Why is DNA stable
Phosphodiester backbone protects more chemically reactive organic bases
Hydrogen bonds link base pairs forming bridges. As C-G have 3 hydrogen bonds more of these pairs make molecule more stable
Single H-bond not string, as many more stable
96
What are the functions of DNA
Separate strands joined by H-binds, easily broken allow strands separate for replication
Very large, lots genetic information to be stored
Very stable, passed from generations (rarely mutates)
Bases protected by sugar phosphate backbone prevents corruption by outside chemical/physical forces
Sequence bases codes for primary protein structure
Base pairing lets DNA replicate transfer information to mRNA
97
What is RNA
Ribonucleic acid
| Single, quite short polynucleotide chain, peptide sugar is ribose and organic bases
98
What is the different base in mRNA
Uracil instead of thymine
99
What types of cell division are there
Nuclear division
| Cytokinesis
100
What occurs in nuclear division
Process nucleus divides
| Two nuclear division types, mitosis, meiosis
101
What occurs in cytokinesis
Follows nuclear division process where whole cell divides
102
What must happen before nucleus divides
DNA must be replicated to ensure all daughter cells have genetic information to make enzymes and proteins they need
103
What does semi-conservative replication need
Four nucleotide types with A,C,G,T bases
Both DNA molecule strands acts as template for nucleotide attachment
Enzymes DNA helicase and RNA polymerase
Chemical energy source to drive process
104
What are the stages in the semi-conservative process
1. Representative portion of DNA undergo replication
2. Enzyme DNA helicase causes 2 DNA strands to separate, strands unwind breaking hydrogen bonds that join complementary bases
3. Once activated nucleotides bound, joined by RNA polymerase in condensation reactions form phosphodiester bonds. Remaining free bases attract to complementary nucleotides
4. All nucleotides joined form complete polynucleotide chain using RNA polymerase. Two identical strands of DNA, one original one new in each
105
What were the hypotheses of Watson and Crick
Conservative model and the semi-conservative model for DNA replication
106
What did the conservative model suggest
Originality DNA molecule remained intact, separate daughter DNA copy built from new molecules of deoxyribose, phosphate, organic bases. One entirely new material, one entirely original material
107
What did the semi-conservative model suggest
Original DNA molecule slips into two separate strands, each replicated its mirror image
Two new molecules would have one new material and one original material in one strand
108
What facts did Meselsohn and Stahl base their work to test the (semi)conservative models on
All DNA bases contain nitrogen
Nitrogen has two forms, N14 lighter than N15
Bacteria will incorporate nitrogen from growing medium into any new DNA made
109
How Meslsohn and Stahl test the (semi)conservative model
Labelled original DNA of bacteria by growing N15 medium
Transferred bacteria to medium of N14, single generation to replicate once
Mass of each 'new' DNA depend on which replication method occurred
Centrifuge extracted DNA
Lighter DNA nearer top of tube would be collected
Analyse DNA after 2 then 3 generations
Interpret results, determine which hypothesis correct
110
What is ATP made of and what does it do
```
A phosphorylated macromolecule
Adenine nitrogen-containing organic base
Ribose sugar molecule, 5-carbon ring structure (pentose sugar) acts as backbone where other parts attach
Phosphates, chain of 3 phosphate groups
Stores ATP's energy
```
111
When is energy released due to phosphate groups
Bonds between phosphate groups unstable, lower activation energy so easily broken. When break energy released
112
What is the reaction equation of ATP releasing energy
ATP+(H2O)->ADP+Pi+E
| E = energy - ATPase
113
Why is water in the reaction of ATP forming ADP
Hydrolysis reaction, catalysed by enzyme ATP hydrolase
114
What type of reaction is ATP forming ADP
Reversible reaction , energy can be used to add inorganic phosphate to ADP, reform ATP according to reverse of equation
Reaction catalysed by enzyme ATP synthase in condensation reaction
115
What ways does ATP synthesis occur to add a phosphate to ADP
In chlorophyll - containing plant cells during photosynthesis (photophosphorylation)
In plant, animal cells in respiration (oxidative phosphorylation)
In plant, animal cells when phosphate groups transferred from donor molecules to ADP (substrate-level phosphorylation)
116
What make ATP a good energy donor
Instability of phosphate bonds
| ATP is an immediate energy source of a cell
117
What makes ATP not a good long term energy store, what are better stores
Instability of phosphate bonds
| Fats and carbohydrates e.g glycogen
118
Why is ATP a better immediate energy source than glucose
Release less energy than each glucose molecule. Energy for reactions released in smaller, manageable quantities
Hydrolysis of ATP to ADP is single reaction that releases immediate energy
119
Where is ATP made
ATP cant be stored has to continuously be made in mitochondria of cells that need energy e.g muscle fibres
120
Which processes in cells is ATP used
```
Metabolic processes
Movement
Active transport
Secretion
Activation of molecules
```
121
Why is ATP needed in metabolic processes
Provides energy needed to build up macromolecule from basic units e.g making starch from glucose
122
Why is ATP needed in movement
Provides energy for muscle contraction. In muscle contraction ATP provides energy for muscle filaments to slide past each other, often shorter muscle fibre length
123
Why is ATP needed in active transport
Energy to change carrier protein shape in plasma membranes lets molecules/ions move against concentration gradient
124
Why is ATP needed in secretion
To form lysosomes needed for cell product secretion
125
Why is ATP needed in activation of molecules
In organic phosphate released during ATP hydrolysis, can be used to phosphorylate other compounds to make them more reactive, lower activation energy in enzyme-catalysed reaction
126
What charge does a water molecule have
No overall charge
Oxygen slightly negative
Hydrogen slightly positive
Is dipolar due to positive and negative poles
127
What is the attractive force between opposite charges
Hydrogen bond
Each bond fairly weak
Form important forces cause water molecules stick together, has unusual properties
128
Why does water have a high specific heat capacity
The molecules stick together so more energy (heat) needed to separate them than if didn't bond together
129
Why is it good that water has a high specific heat capacity
Acts as a buffer against sudden temperature variations, aquatic environment is stable temperature
130
Why does water have a high latent heat
Hydrogen bonding between molecules mean lots of energy to evaporate 1 gram of water
131
How do mammals body cool itself effectively
Evaporation of water (sweat) from skin
132
What is cohesion
Tendency of molecules to stick together. Hydrogen bonding, water has large cohesive forces, allow it to be pulled up through a tube e.g xylem vessel
Force is surface tension so water surface acts like skin, strong enough to support small organisms
133
Why is water an important molecule in reactions within the body
Breaks down many complex molecules by hydrolysis and produced in condensation reactions
134
What medium does chemical reactions occur in
Aqueous medium
135
What substances does water dissolve
Gases
Wastes e.g amino acids
Inorganic ions and small hydrophilic molecules e.g ATP
Enzymes, whose reactions take place in solution
136
Why is it good that water is not easily compressed
Provides support
137
Why is it important water is transparent for plants
Transparent, aquatic plants photosynthesise, light rays can penetrate jelly-like fluid
138
What colour light does a plant reflect
Green light
139
What happens to water as it freezes why is this beneficial
Expands, density decreases so ice less dense than water
| Insulates sea underneath
140
What is specific heat capacity
Amount of energy needed to raise 1kg of water by 1 degree
141
What is specific latent heat
Amount of energy to evaporate 1 gram of water
142
Where are inorganic ions found
In organisms where occur in solution in the cytoplasmic the cytoplasm of cells and body fluids and part of larger molecules
143
What do inorganic ions do
Range of functions
Specific function a particular ion performs, related to properties e.g iron ions in haemoglobin where play a role in oxygen transport
144
Why are hydrogen ions important
They determine solution pH so enzymes functioning
145
What is a cation
Positive ion e.g sodium , iron, hydrogen
146
What is an anion
Negative ion e.g phosphate
147
What is the function of sodium ions
Help glucose, amino acid transport
148
What are iron ions important for
Part of haemoglobin
149
Why are phosphate ions important
Essential parts of DNA, RNA, ATP
