biological molecules Flashcards

1
Q

what are the four key elements that make up most biological molecules

A
  • carbon (C)
  • hydrogen (H)
  • oxygen (O)
  • nitrogen (N)
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2
Q

what are two additional elements that play important roles in cell biochemistry?

A
  • phosphorus and sulfur
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3
Q

name 4 other biologival elements and their functions

A
  • sodium (Na) -nerve impulse transmission, kidney function
  • potassium (k) - nerve impulse transmission, stomotal opening
  • calcium (Ca) - muscle contraction, nerve impulse transmission
  • iron (Fe)- oxygen transport (in haemogobin)
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4
Q

what is a covelant bond

A

when two atoms share a pair of electrons

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5
Q

how many bonds can these form
- carbon
- nitrogen
- oxygen
- hydrogen

A
  • carbon- 4
  • nitrogen- 3
  • oxygen- 2
    -hygrogen-1
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6
Q

why is life referred to as carbon based

A

because carbonbcan form four bonds, making it the backbone of most biological molecules

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7
Q

what is an ion

A

an atom or molecule where the total number of electrons is NOT equal to the total number of protons

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8
Q

what is the difference between a cation and an anion

A

cation is a positively charged electron (loses electrons)
anion is negative charged ion (gains)

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9
Q

what is an ionic bond

A

when one atom donates an electron abnd the other receives it, creating oppositely charged ions that are held together by electrostatic attraction

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10
Q

whart are the functions of key cations in biological system

A
  • calcium ions (Ca2+) - nerve impulses transmission, muscle contraction
  • sodium ions (Na+) - nerve impulse transmittion, stomatal opening
  • hydrogen ions (H+) - catalysis of reactions, pH determination
  • ammonium ions (NH₄⁺): production of nuitrate ions by bacteria
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11
Q

what are the functions of key anions in biological systems

A
  • nitrate ions (NO₃⁻) - nitrogen supply to plants for amino acid and protein formation
  • hydrogen carbonate ions (HCO₃⁻): maintenance of blood pH
  • chloride ions (Cl-) - balances the positive charge of sodium and potassium ions in cells
  • phosphate ions (PO₄³⁻) cell membrane, nucleic acid, and ATP formation + bone formation
  • hydroxide ions (OH-) - catalysis of reactions, pH determination
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12
Q

what elements are found in carbohydrates and in what ration

A

carbon, oxygen, hydrogen in the ratio Cₓ(H₂O)ᵧ.

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13
Q

what elemets are found in lipids

A

carbon, hygrogen and oxygen

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14
Q

what elements are found in proteins

A

carbon, hydrogen, oxygen, nitrogen, sulfur

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15
Q

what elements are found in nucleic acids

A

carbon, hydrogen, oxygen, nitrogen, and phosphorus

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16
Q

whats a polymer

A

a long chain molecule made up of repeating units called monomers

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17
Q

what are the monomers of carbohydrates and proteins

A
  • carbohyderates : sugars (saccharides)
  • proteins: amino acids
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18
Q

what causes hydrogen bonding between water molecules

A
  • water is polar
  • the oxygen atom has a greater share of electrons, making it slightly negative
  • while hydrogens are slightly positive
  • this creates regions of positive and negative, allowingf water molecules to attract eachother and form hydrogen bonds
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19
Q

are hydrogen bonds strong or weak

A

indiviudually, hydrogen bonds are weak but they occur in high numbers, making them significant inb determining waters properties

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20
Q

what is the difference between cohesion and adhesion

A

cohesion: water moolecules stick to each other due to hydrogen bonding

adhesion: when water molecules stick to other surfaces (e.g water on your skin)

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21
Q

why does water have a high boiing point

A

due to the large number of hydorgen bonds, which require a lot of energy to break

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22
Q

why is ice less dense than liquid water

A

when water freezes, hydrogen bonds fix the molecules in a rigid open structure, creating more space between them.

this makes ice less dense than liquid water, allowing it to float

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23
Q

what is surface tension and why is it important

A
  • surface tension occurs because water molecules are more cohesive to eachother than air
  • this creates a ‘skin’ on the surface strong enough to support small insects like pond skaters
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24
Q

why is water a good solvent

A
  • its polar, allowing it to disolve many solutes, including amino acids, proteins and nucleic acids
  • this makes it a medium for chemical reactions and a transporter of dissolved compounds into and out of cells
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25
Q

how does water act as a transport medium in living organisms

A
  • cohesion allows water molecules to stick together during transport
  • adhesion causes water molecules to stick to polar surfaces, enabling capillary action (e.g water rising in plant xylem against gravity)
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26
Q

how does water act as a coolant

A
  • water buffers temp changes during chemical reactions by absorbing large amounts of energy to break hydrogen bonds
  • this helps maintain a stable environment for enzymes, which function best within a narrow temperature range (optimum)
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27
Q

why is water’s stability vital for aquatic life

A
  • water has high SHC, making it resistant to temperature changes, providing a constant environment for aquatic life
  • when ice forms on the surface of ponds and lakes, it insulates the water below, preventing the entire habitat from freezing
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28
Q

how does surface tension benefit certain organisms

A

surface tension allows small insects, like pond skaters to move across the waters surface without sinking

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29
Q

what are the three types of carbohydrates

A
  • monosaccharides: simple sugar unit (e.g glucose, fructose, ribose)

-disaccharides: two monosaccharides linked (e.g lactose, sucrose, maltose)

  • polysaccharides: many monosaccharides linked (e.g starch, glycogen cellulose)
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30
Q

what is the chemical formula of glucose

A

C₆H₁₂O₆.

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31
Q

what is glucose and its two structural forms

A
  • glucose is a hexose monosaccharides (6 carbons)

two forms:
- alpha glucose: hydroxyl group (OH) on carbon 1 points down
- beta glucose: OH group on carbon 1 points up

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32
Q

why is glucose soluble in water

A

it is polar, allowing it to form hydrogen bonds with water, making to soluble to the cytosol of cells

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33
Q

what happens during a condensation reaction

A

Two monosaccharides join by a glycosidic bond and a water molecule is removed
E.g two alpha glucose molecules form maltose via a 1’4 glycosidic bond

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34
Q

What happened during hydrolysis

A

A water molecule is added, breaking the glycosidic bond and
This releases monosaccharides, providing glucose for respiration

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35
Q

What disaccharides are formed by these monosaccharides

A

Glucose + glucose = maltose

Glucose + fructose = sucrose

Glucose + galactose = lactose

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36
Q

What is starch and what are its two forms

A

Starch is a plant energy storage polysaccharide made up of alpha glucose molecules

It’s two forms:
amylose
1’4 glycosidic bonds only
Coils into a helix (compact and less soluble)

Amylopectin
1’4 and 1’8 glycosidic bonds
Branched structure (branching every 25 subunits)

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37
Q

What is glycogen and how is it different from starch

A

Glycogen is the animal and fungal equivalent of starch
It has more branches than amylopectin making it;
- more compact (better for mobile animals)
- faster glucose release due to more free ends

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38
Q

What is cellulose made up of

A
  • beta glucose monomers linked by a 1’4 glycosidic bond and
  • alternate beta glucose molecules are flipped upside down forming a straight chain
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39
Q

How is cellulose used in plants

A
  • Cellulose chains form hydrogen bonds, creating micro fibrils
  • microfibrils bundle into macrofibrils, forming strong insoluble fibres that provide structural support in plant cell walls
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40
Q

Why is cellulose important for human diet

A

It is indigestible by humans and provides fibre, aiding digestion

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41
Q

What is a reducing sugar

A

A sugar that can donate electrons to reduce another molecule

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42
Q

What chemical is used in Benedict’s test

A

Benedict’s reagent/ alkaline copper III sulfate

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43
Q

Describe the tests for Benedict’s test

A
  1. Place the sample in a boiling tube (grind/blend if solid)
  2. Add an equal volume of Benedict’s reagent
  3. Heat the mixture gently in a boiling water bath for 5 mins
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44
Q

What colour change indicates a positive result for reducing sugars

A
  • blue = no reducing sugar
  • green/yellow = low concentration
  • orange = medium concentration
  • red = high concentration (Cu²⁺ ions reduced to Cu⁺).
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45
Q

Why does Benedict’s reagent turn red with reducing sugars

A

Reducing sugars donate electrons

Reducing blue Cu²⁺ ions to red Cu⁺ ions

Forming a brick red precipitate

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46
Q

What is a non reducing sugar

A

A sugar that cannot donate electrons (e.g sucrose)

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47
Q

How do you test for non reducing sugars

A
  1. Perform the Benedict’s test - if no colour change, continue with the next steps
  2. Boil the sample with dilute HCl (hydrolyses the sugar into monosaccharides)
  3. Neutralise with sodium hydrogen carbonate
  4. Perform Benedict’s test again - positive result if reducing sugar is know prevent
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48
Q

What chemical is used in the iodine test

A

Iodine dissolved in potassium iodide solution

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49
Q

What indicates a positive test for starch

A

Yellow/brown into blue/black

No colour change indicates starch is absent

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50
Q

What do reagent strips test for

A

The presence of reducing sugars, most commonly glucose

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51
Q

What is the advantage of using reagent strips

A
  • fast and easy detection
  • the concentration of sugar can be determined using a colour coded chart
  • useful for diabetes management
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52
Q

What does a colorimeter measure

A

The absorbance or transmission of light through a coloured solution

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53
Q

why is colorimetry used in Benedict’s test

A

To quantitatively measure the concentration of reducing sugar

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54
Q

What are the steps for using a colorimeter

A
  1. Select the correct filter (e.g red filter for Benedict’s test)
  2. Calibrate with distilled water (zero the machine)
  3. Perform Benedict’s test on glucose of known concentrations
  4. Filter the solutions to remove the precipitate
  5. Measure the % transmission of each solution
  6. Plot the calibration curve using data
  7. Test the unknown solution and use the graph to estimate its glucose concentration
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55
Q

How do you calculate % absorbance from % transmission

A

Absorbance = 100 - transmission

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56
Q

What is a biosensor

A

A device that uses biological components to detect the presence or concentration ofg
molecules

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57
Q

What are the 3 components of a biosensor

A
  1. Molecular recognition: a protein (enzyme/antibody) or ssDNA binds to the target molecule
  2. Transduction: this interaction triggers a change in pH or produces an electrical signal
  3. Signal processing: the signal is processed and displayed as a colour change or digital reading
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58
Q

How could biosensors help in diabetes management

A
  • biosensors detect glucose in blood
  • provides a quantitative result
  • helps diabetics monitor and manage their blood sugar levels accurately
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59
Q

Is a canary in a coal mine, a biosensor

A

Yes because the birds biological response (distress or death) indicates the presence of toxic gases
Disadvantage:
- unreliable as canaries have different sensitivities to gas
- inhumane at it endangers the birds Life

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60
Q

What makes lipids insoluble in water

A

They are non polar molecules so do not interact with water molecules

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61
Q

What is the difference between fats and oils

A

Fats: solid at room temp (saturated lipids)
Oils: liquids at room temp (unsaturated lipids)

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62
Q

Why are lipids considered macromolecules

A

They are large complex molecules put not polymers as they are not made of repeating units

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63
Q

What is the structure of a triglyceride

A

1 glycerol molecule + 3 fatty acids
Formed through esterification

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64
Q

What is esterification

A

A condensation reaction forming ester bonds between glycerol and fatty acids Formed through
it producers 3 water molecules

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65
Q

How are are triglycerides broken down?

A

By hydrolysis (addition of water)
3 water molecules are needed to break the Ester bonds between glycerol

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66
Q

What is an un sature d fatty acid

A
  • Contains no double bonds between carbon atoms
  • molecules can pack closely together so are solid at room temperature (fats)
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67
Q

What is an unsaturated fatty acid

A
  • contains one or more double bonds between carbon atoms
  • the double bonds causes the chain to kink, making it harder for molecules to pack closely together so is liquid at room temp (oils)
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68
Q

What are mono saturated and poly saturated fats

A
  • monosaturated: one double bond
  • Poly saturated: two or more double bonds
69
Q

How are phospholipids different from triglycerides

A

One fatty acids chain is replaced by a phosphate group

Contains hydrogen, carbon and phosphorous

70
Q

What is the structure of a phospholipid

A

Hydrophilic head- phosphate group

Hydrophobic tails - fatty acids

71
Q

What structures do phospholipids form in water

A
  • micelles: spherical structures with hydrophobic tails inside
  • bilayers: double layered sheets with tails facing inwards and heads facing outwards — forms cell membrane
72
Q

What are sterols

A

Steroid alcohols , complex lipids with a 4 carbon ring and a hydroxyl group

Cholesterol is the most common sterol

73
Q

What role does cholesterol play in the cell membranes

A

Stabilises the membraned by interacting with phospholipids

Prevents the membrane from becoming too fluid at high temperatures and too rigid at low temperatures

74
Q

What are the 8 biological roles of lipids

A
  1. Membraned formation - hydrophobic barriers
  2. Hormone production - steroid hormones
  3. Electrical insulation - e.g myelin sheath around neurons
  4. Waterproofing - e.g plant leaves, bird feathers
  5. Energy storage -long term energy reserve
  6. Thermal insulation - prevents eat loss (e.g penguins)
  7. Cushioning - protects vital organs
  8. Buoyancy - help aquatic animals float
75
Q

What is the emulsion test used for

A

To detect the presence of lipids

76
Q

Describe the steps of the emulsion test used

A
  1. Mix the sample with ethanol (lipids dissolve in ethanol)
  2. Add water and shake

Positive test = white emulations forms on surface
Negative test = the solution remains clear

77
Q

Why does the emulsion test work

A

Lipids are insoluble in water but soluble in ethanol

When mixed with water, lipids precipitate out forming a white emulsion

78
Q

Why are unsaturated fats considered healthier than saturated fats

A
  • unsaturated fats reduce LDL (bad cholesterol) levels
  • saturated fats increase LDL levels - linked to coronary heart disease
  • however evidence linking saturated fats to heart disease is inconclusive
79
Q

What are trans fats and why are they unhealthy

A
  • formed during hydrogenation of vegetable oils
  • unsaturated fats become partially saturated, making them solid
  • trans fats increase LDL and lower HDL (old cholesterol) - increasing heart disease risk
80
Q

How is margarine made from vegetable oil

A
  • vegetable oils arte hydrogenated to remove double bonds, making them solid
  • this process creates trans fats as a byproduct
  • modern spreads avoid trans fats by using mono and poly saturated oils
81
Q

What is food synergy

A

The combined effect of multiple nutrients is greater than the effect of individual nutrients

82
Q

What are the four elements found in all proteins

A

Carbon, hydrogen, oxygen and nitrogen

83
Q

What is the general structure of an amino acid

A

Carbon atom (C)
Amine group (NH₂)
Carboxyl group (COOH)
Hydrogen atom (H)
Variable R-group (side chain)

84
Q

What are the three categories of amino acids based on dietary needs

A
  • non essential: synthesised by the body
  • essential: obtained from food
  • conditionally essential: only needed by infants/growing children
85
Q

How is a peptide bond formed

A
  • through a condensation reaction
  • where the hydroxyl group (OH) from the carbonyl group of ones amino acid combines with the hydrogen group pf the amine group of another
  • water is removed
  • a peptide bond forms between the carbon and nitrogen
86
Q

What enzyme catalyses peptide bound formation in ribosomes

A

Peptidyl transferase

87
Q

What is the primary structure of a protein

A

The sequcning of am,into acids joined by peptide bonds, directed by dna

88
Q

How does the primary structure influence the final shape of the protein

A

The sequence determines folding, affecting the final shape and function

89
Q

What bonds are involved in the primary structure

A

Only peptide bonds

90
Q

What’s the secondary structure of a protein

A

The folding or coiling of the polypeptide chain due to hydrogen bonding between the backbone groups (not R groups)

91
Q

What are the two main secondary structures

A

Alpha helix: coiled structures with hydrogen bonds parallel to the helix

Beta pleated sheets: polypeptide chains running parallel, joined by hydrogen bonds, forming a sheet like shape

92
Q

Which type of bond stabilises the secondary structure

A

Hydrogen bonds

93
Q

What is the tertiary structure of a protein

A

The 3D folding of the polypeptide chain, including sections of the secondary structure

94
Q

What R group interactions stabilise the tertiary structure

A
  1. Hydrophobic/hydrophilic interactions: weak interactions between polar and non polar R groups
  2. Hydrogen bonds: weak, between polar R groups
  3. Ionic bonding: between oppositely charged R groups
  4. Disulphide bridges: covenant bonds between sulfúreo atoms in cysteine
95
Q

What is the quaternary structure of a protein

A

The association of two or more polypeptides (subunits) into a functional protein

96
Q

What bonds and interactions are involved in quaternary structures `

A

The same with tertiary (hydrogen bonds, hydrophobic, hydrophilic interactions, ionic bonds, disulphide bridges)
BUT between subunits rather than within a single polypeptide

97
Q

Give an example of a protein with a quaternary structure

A

Haemoglobin
- made of 4 subunits: 2 alpha and 2 beta chains
- contains prosthetic haem groups with iron that binds oxygen

98
Q

What are globular protein

A
  • compact, spherical and water soluble
  • formed when proteins fold to keep hydrophobic R groups on the inside and hydrophilic ones on the outside
99
Q

Why is the solubility of globulars proteins important

A

It allows them to dissolve in blood and bodily fluids, enabling transport and chemical reactions

100
Q

Give examples of globular proteins

A

Insulin : hormone regulating blood glucose
Catalase : enzyme that breaks down hydrogen peroxide

101
Q

What are fibrous proteins

A
  • long, insoluble and strong
  • contain many hydrophobic R groups
  • Have a repetitive amino acid sequence, making them tightly structured
102
Q

Give three examples of fibrous proteins and their functions

A
  1. Keratin: High sulfur content = disulphide bridges= strength and inflexibility
  2. Elastin: elastic fibres in lungs and blood vessels. Provides flexibility
  3. Collagen: connective tissue in skin, tendons and ligaments. Provides tensile strength
103
Q

What is thin layer chromatography used for

A

To separate and identify amino acids in a mixture

104
Q

What are the two phases in TLC

A
  1. Stationary: thin layer of silica gel or another adhesive material
  2. Mobile phase: organic solvent (e.g hexane, water, acetic acid, butanol)
105
Q

What determines how far an animo acid travels in TLC

A
  • Affinity for the stationary phase (hydrogen bonding with silica)
  • solubility in the mobile phase
  • more soluble amino acids travel further
106
Q

Why are gloves worn and the plate handles by the edges

A

To prevent contamination by skin cells

107
Q

Why is the jar sealed during the experiment

A

To prevent solvent evaporation, ensuring consistent conditions

108
Q

What is the purpose of the biuret test

A

To detect the presence of proteins by identifying peptide bonds

109
Q

What are the steps por the biuret test

A
  1. Add 3 cm^3 of Sample to the test tube
  2. Add equal volume of 10% sodium hydroxide
  3. Add a few drops of 1% copper sulfate
  4. Mix and leave to stand for 5 mins
110
Q

What colour change indicates the presence of a protein

A

Purple/ lilac : due to peptide blonds forming violet complexes with copper ions

Blue: no protein present

111
Q

Why doesn’t the biuret test quantify the amount of protein

A

It only indicates the presence/absence, not concentration

112
Q

What is a prosthetic groups

A

A non protein component permanently attached to a protein

113
Q

What type of protein contains prosthetic groups

A

Conjugated proteins

114
Q

Give an example of a conjugated protein

A

Haemoglobin with iron containing haem groups

116
Q

What are the three components of a nucleotide

A
  1. Pentose sugar (5 carbon sugar)
  2. Phosphate group (negatively charged)
  3. Nitrogenous base ( A, T, G, C)
117
Q

What type of sugar is found in DNA and RNA

A

RNA= ribose

DNA= deoxyribose (one fewer oxygen atom than ribose)

118
Q

What are the two main categories of nitrogenous bases

A
  1. Pyrimidines: smaller, single ring bases (thymine, cytosine, uracil)
  2. Purines: larger, double ring bases (adenine + guanine)
119
Q

How are nucleotides joined to form a polynucleotide

A
  • condensation reactions
  • a phosphodiester bond forms
  • between the phosphate group at the 5’ end of one carbon of a nucleotide
  • and the hydroxyl group at the 3’ end of the carbon of the adjacent nucleotide
120
Q

What are the four DNA bases and their complementary pairs

A
  1. Adenine and thymine joined by 2 hydrogen bonds
  2. Cytosine and guanine joined by 3 hydrogen bonds
121
Q

What is the structure of DNA?

A
  • double helix: two polynucleotide strands twisted into a spiral
  • anti parallel strands : one strand runs 5’-3’ but the other 3’-5’ \
  • sugar phosphate backbone: with bases projecting inwards
122
Q

What maintains the stability of the DNA double helix

A
  • hydrogen bonding between complementary base pairs
  • base pairing riles maintain a constant distance between the sugar phosphate backbones
123
Q

What is complementary base pairing

A
  • purine always pairs with pyrimidine
  • this maintains a consistent distance between the two DNA strands
  • ensures equal amounts of complementary bases (A-T, G-C)
124
Q

Why is complementary base pairing important

A
  • ensure accurate replication of genetic information
  • allows for efficient transcription into mRNA
125
Q

What are the key differences between RNA and DNA

A
  1. Sugar; dna contains deoxyribose, rna contains ribose
  2. Bases: dna uses thymine, rna uses uracil
  3. Strand: dna is double stranded, rna is single stranded
  4. Size: dna is larger than rna
  5. Function: dna is for the long term storage of gentic information, rna is for temporary copies of gentic information
126
Q

what are the roles of RNA in the cell

A
  1. mRNA - transfers gentic information from dna to ribosomes
  2. tRNA - carries amino acids for protein synthesis
  3. rRNA - component of ribosomes aiding in translation
127
Q

What is the purpose of dna extraction

A

To isolate and purify DNA from plant cells

128
Q

What are thesteps in DNA extraction

A
  1. Grind the sample (using a mortar and pestle) - breaks down cell walls
  2. Mix with detergent -breaks down the cell membrane, releasing cell contents
  3. Add salt - disrupts hydrogen bonds between dna and water molecules
  4. Add protease enzyme - breaks down proteins associated with dna
  5. Add ethanol (alcohol) - precipitates the dna out of solute
129
Q

Why does dna precipitate in ethanol

A
  • dna is insoluble in alcohol
  • it appears as white strands between the aqueous layer and ethanol
130
Q

Why is it important to keep the temperature low during dna extraction

A

To prevent the degradation of the dna by enzymes

131
Q

How are polynucleotides broken down

A
  • by hydrolysis reactions
  • water breaks down the phosphodiester bonds
  • which releases individual nucleotides
132
Q

What is a polynucleotide

A

A long chain of nucleotides linked by a phosphodiester bond

133
Q

What is the sugar phosphate backbone

A

The repeating chain of sugars and phosphates that form the structural framework of rna and dna

134
Q

What is a phosphodiester bond

A

A covenant bond between the phosphate group of one nucleotide and the hydroxyl group of another

135
Q

What does anti parallel mean in dna structure

A

The two DNA strands run in opposite directions:
• One strand → 5’ → 3’
• The other strand → 3’ → 5’

136
Q

Why is dna ideal for storing genetic information

A
  • stable double helix structure protects genetic code
  • complementary base pairing ensures accurate replication
  • long molecule stores large amounts of information
  • hydrogen bonds allow the strands to separarte easily for replication and transcription
137
Q

How is the dna sequence bases linked to protein synthesis

A
  • the sequence of bases carriers the genetic code
  • this code is transcribed into mRNA and translated into proteins
138
Q

Why do cells divide in mitosis

A

To produce more cells needed for growth or repair

The daughter cells produced are genetically identical to each other and the parent cell

Their dna has identical base sequencing

139
Q

What is the process of dna replication called

A

Semi conservative replication

Where each new dna molecule consists of one old strand and one new strand

140
Q

What are the steps of semi conservative replication

A
  1. DNA helicase unwinds the double helix and breaks the hydrogen bonds allow
  2. Free dna nucleotides pair with complementary bases
  3. Dna polymerase forms phosphodiester bonds between adjacent nucleotides
  4. Two identical dna molecules are produced with each with one original and one new strand
141
Q

What is the role of dna helicase in replication

A

DNA helicase unwinds the double helix and catalyses the breaking of hydrogen bonds between complementary base pairs

142
Q

What does dna polymerase do

A

It catalyses the formation of phosphodiester bonds between free nucleotides, synthesising the new dna strand

143
Q

What is continuous replication

A

The leading strand (unzipped from the 3’ end) is replicated continuously as dna unwinds, since dna polymerase moves in the same direction

144
Q

What is discontinuous replication

A

The lagging strand (unzipped from the 5’ end) is replicated in short Okazaki fragments because DNA polymerase moves in the opposite direction

145
Q

What enzyme joins Okazaki fragments

A

DNA ligase joined them into a continuous strand

146
Q

What is the genetic code

A

The genetic code is the sequence of DNA bases that determines the sequence of amino acids in a protein

147
Q

What is a codon

A

A codon is a triplet of 3 bases on mRNA that codes for one amino acid

148
Q

Why is the genetic code described as universal

A

The same codon codes for the same amino acids in across all species

149
Q

What does it mean that the genetic code is degenerate

A

Multiple variations of codons can code for the same amino acids

E.g GGU, GGC, GGA, GGG all code for glycine

150
Q

What are start and stop codons

A

Start codons: signals the start of protein synthesis ( AUG, coding for methionine)

Stop codons: signals the end of translation and does not code for any amino acid

151
Q

What is transciption

A

The process where the evens dna sequence is copied into mRNA

152
Q

What’s enzyme catalyses transcription

A

RNA polymerase

153
Q

What are the steps of transcription

A
  1. DNA helicase unwinds and unzips the double helix
  2. One strand (the antisense strand) acts as a template
  3. Free RNA nucleotides base pair with complementary bases on the template strand
  4. RNA polymerase catalyses the formation of phosphodiester bonds between rna nucleotides
  5. mRNA detaches and leaves the nucleus through the nuclear pore
154
Q

What base is used in RNA instead of thymine

155
Q

What is translation

A

The process where mRNA is decoded by a ribosome to produce a polypeptide (protein)

156
Q

What are the temps of translation

A
  1. mRNA binds to the small subunit of the ribosome
  2. A tRNA molecule with a complementary anticodon binds to the start codon on the mRNA, carrying the corresponding amino acid
  3. The ribosome catalyses the formation of peptide bonds between the amino acids
  4. The process continues until a stop codon is reached
157
Q

What is the role of tRNA in translation

A
  • it carries a specific amino acid
  • it has an anticodon that pairs with a complementary codon on mRNA
158
Q

What enzyme catalyses peptide bonds between the formation during translation

A

Peptidyl transferase, which is part of the ribosome rRNA

159
Q

What is a mutation

A

A random spontaneous change in the DNA’s base sequence during replication

160
Q

How do replication errors occur

A

When complementary bases do not match correctly
Causing base substitutions, insertions or deletions

161
Q

What are the 3 main types of activity that cells require energy for

A
  1. Synthesis: e.g large molecules like proteins
  2. Transport- e.g pumping ions or molecules across cell membranes by active transport
  3. Movement - e.g protein figures in muscle cells causing muscle contraction
162
Q

What is the universal currency in all living cells

A

Adenosine triphosphate (ATP)

163
Q

What is the structure of an ATP molecule

A
  • Adenine ( nitrogenous base)
  • ribose (pentose sugar)
  • 3 phosphate groups
164
Q

How is the structure of ATP similar to the structure of DNA and RNA nucleotides

A
  • ATP contains adenine, like nucleotides in DNA/RNA
  • ATP is a ribose sugar like RNA
  • ATP has three phosphate groups instead of one
165
Q

How does ATP release energy

A
  • ATP is hydrolysed into adenosine diphosphate (ADP) and an inorganic phosphate (pi)
  • this releases energy for cellular processes
  • it is a hydrolysis reaction, using a water molecule
  • it is catalysed by atp hydrolase
166
Q

Why is ATP not a good long term energy store

A
  • the phosphate bonds in ATP are unstable
  • fats and carbohydrates are better for long term energy storage
  • ATP is more suited as an immediate energy source
167
Q

What process reforms atp from ADP

A

Phosphorylation.
ADP + Pi = ATP (+water)
This is a condensation reaction
Catalysed by ATP synthase
During respiration and photosynthesis

168
Q

What are the key properties of ATP that make it suitable for energy transfer

A
  1. small: moves easily into, out of and within cells
  2. Water soluble: suited for aqueous environments where reactions occur
  3. Inorganic phosphate can be used to phosphorylase other compounds, making them more reactive
  4. Intermediate energy bonds: releases enough energy for cellular reactions but not too much to avoid heat wastage
  5. Releases energy in small quantities: preventing energy waste
  6. Easily regenerated: quickly reformed by ADP