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A-Level Biology🌼 > Topic 1A: Biological Molecules > Flashcards

Topic 1A: Biological Molecules Flashcards

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1
Q

What is a monomer?

A

A monomer is a small basic molecular unit

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2
Q

What are some examples of monomers?

A

Examples of monomers: monosaccharides, amino acids and nucleotides

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3
Q

What 3 elements do ever carbohydrate contain?

A

All carbohydrates contain carbon, oxygen and hydrogen

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4
Q

What are carbohydrates made from, with examples?

A

Carbohydrates are made from monosaccharides, eg glucose, fructose and galactose

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5
Q

What is glucose?

A

Glucose is a hextose sugar, as there are six carbon atoms in each molecule

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6
Q

What are the types of glucose?

A

There is alpha glucose and beta glucose

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7
Q

What is a condensation reaction?

A

A condensation reaction is when two molecules join together with the formation of a new chemical bond

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8
Q

What happens during a condensation reaction?

A

In a condensation reaction, a new chemical bond is formed and a water molecule is released when the bond is formed

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9
Q

How do monosaccharides join together?

A

Monosaccharides join together by condensation reactions

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10
Q

What type of bond is formed in condensation reactions?

A

In condensation reactions, a glycosidic bond forms between the two monosaccharides as a water molecule is released

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11
Q

What is sucrose?

A

Sucrose is a disaccharide formed from a condesnation reaction between a glucose molecule and a fructose molecule

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12
Q

What is lactose?

A

Lactose is a disaccharide formed from a glucose and galactose molecule

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13
Q

How can polymers be broken down into monomers?

A

Polymers can be broken down into monomers by hydrolysis reactions

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14
Q

What are hydrolysis reactions?

A

Hydrolysis reactions break chemical bonds between monomers using a water molecule (opposite of condensation reactions)

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15
Q

How can carbohydrates be broken down into monosaccharides?

A

Carbohydrates can be broken down into monosaccharides by hydrolysis

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16
Q

How do you test for reducing and non-reducing sugars (practical) ?

A

Benedicts test for reducing sugars

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17
Q

What do you do during a benedicts test for reducing sugars? (practical)

A

Benedicts test:
1). Adds benedict’s reagent in excess so all reacts (it is a blue solution) and heat in a water bath at boil
2). Positive result: coloured precipitate (blue > green > yellow > orange > red)
3). Higher concentration of sugar = further colour change

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18
Q

What is the coloured precipitate change formed during a positive result in the benedict’s test for reducing sugars?

A

Coloured precipitate change in benedict’s test for reducing sugars:
Blue > green > yellow > orange

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19
Q

What happens in the benedict’s test for non-reducing sugars?

A

Benedict’s test for non-reducing sugars:
1). Add dilute hydrochloric acid to sample and heat in boiling water bath
2). Neutralise the sample with sodium hydrogencarbonate.
3). Positive result: coloured precipitate
Negative result: remains blue (contains no sugar)

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20
Q

What is a polysaccharide?

A

Polysaccharide is formed when more than two monosaccharides are joined together by condensation reactions

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21
Q

What is starch?

A

Excess glucose in plants are stored as starch, and so remains as the plant’s main energy storage materials in plants as when plants need energy, starch can be broken down back into glucose

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22
Q

What are the two polysaccharides of alpha glucose that starch is a mixture of?

A

Starch is a mixture of the two polussacharides of alpha glucose - amylose and amylopectin

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23
Q

What is amylose?

A

Amylose is long unbranched chains of alpha glucose.

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24
Q

What makes amylose good for storage?

A

The angles of the glycosidic bonds in amylose give it a coiled structure, making it more compact therefore good for storage as more can fit in a small space

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25
Q

What is amylopectin?

A

Amylopectin is long branched chains of alpha glucose

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26
Q

Why can glucose be released more quickly due to amylopectin?

A

Amylopectin has side branches which allow enzymes that break down the molecule to get to the glycosidic bonds more easily, meaning the glucose can be released quicker

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27
Q

What makes starch good for storage?

A

Starch is insoluble water and doesn’t affect water potential, meaning water does not enter the cell by osmosis. This means it does not swell meaning it’s good for storage

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28
Q

What is the test used for starch?

A

Starch uses the iodine test

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29
Q

What happens in the iodine test for starch?

A

Iodine test for starch:
1). add iodine dissolved in potassium iodide solution to sample
2). starch present = changes from brown/orange to dark blue/black

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30
Q

What is glycogen?

A

Glycogen is stored excess glucose in animals. They are polysaccharides of beta glucose.

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31
Q

Why is glycogen good for storage and releasing glucose quickly?

A

Glycogen has lots of side branches which means stored glucose is released quickly. It is also a compact molecule, making it good for storage.

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32
Q

What is cellulose?

A

Cellulose is long unbranched chains of beta glucose, formed from bonded beta glucose, which forms the straight cellulose chains.

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33
Q

How are cellulose chains linked?

A

Cellulose chains are linked by hydrogen bonds to form microfibrils

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34
Q

Why are microfibrils good for cellulose chains?

A

Microfibrils are strong to provide good structural support for plants

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35
Q

What are the different functions of water?

A

-Water is a metabolite in lots of metabolic reactions eg hydroloysis and condensation reactions.
-Water is a solvent - substances can dissolve in it.
-Water helps with temperature control because it has a high latent heat of vaporisation and a high specific heat capacity
-Water is cohesive (they stick together) which helps water transport in plants and other organisms

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36
Q

Why is water a polar molecule?

A

Water is a polar molecule because it has a partial negative charge on one side and a partial postive charge on the other

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37
Q

Why is there hydrogen bonding in water?

A

There is hydrogen bonding in water because the slightly negatively charged oxygen atoms attract the slightly positively charged hydrogen atoms - the attraction between them is the hydrogen bond

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38
Q

Why is water an important metabolite?

A

Water is an important metabolite because many metabolic reactions involve a condensation and a hydrolysis reaction - both involve water molecules.

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39
Q

Why does water have a high latent heat of vaporisation?

A

Water has a high latent heat of vaporisation because a lot of energy is needed to break its hydrogen bonds and get water to evaporate. Lots of energy is used when it’s vaporised. This is useful as living organisms can use water loss through evaporation to cool down

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40
Q

Why does water have a high specific heat capacity and why is it important?

A

Water has a high specific heat capacity because a lot of energy is needed to heat it up, as the hydrogen bonds between water molecules can absorb a lot of energy. This is useful because it means water doesn’t experience rapid temperature changes, making it a good habitat as underwater temperature is likely to be more stable.

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41
Q

Why is water a good solvent?

A

Water is a good solvent because it can dissolve easily into substances, because water is polar. The positive end of wa ter molecule is attracted to the negative ion, and the negative end of water molecule will be attracted to the positive ion - this means the ions will get totally surrounded by water molecules and will dissolve

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42
Q

What is cohesion?

A

Cohesion is the attraction between molecules of the same type.

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43
Q

Why is it important that there is a strong cohesion between water molecules?

A

The strong cohesion helps water to flow, so it’s good for transporting substances ie xylem in plants. Strong cohesion also means that water has a high surface tension when it comes into contact with air, which is why sweat evaporates off the skin

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44
Q

Uses of carbohydrates

A

Uses of carbohydrates:
-Provides energy
-Stores energy
-Builds macromolecules

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45
Q

What are the functions of water?

A

Functions of water:
-Water is a metabolite - important for metabolic reactions such as hydrolysis and condensation
-Water is a solvent - substances can dissolve into it - lots of metabolic reactions occur in water
-Helps with temperature control - has a high latent heat of vaporisation and has a high specific heat capacity
-Water is cohesive so helps with transport in plants

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46
Q

Why is water a polar molecule?

A

Water is a polar molecule due to its partially negative oxygen atom which the electrons are pulled towards, and the slightly positive hydrogen atom

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47
Q

Why is water important for living organisms?

A

Water has a high latent heat of vaporisation, meaning lots of energy is needed to break the hydrogen bonds. This means they can use water loss through evaporation to cool down

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48
Q

What is the bonding between hydrogen and oxygen atoms in water molecules?

A

Hydrogen bonds covalently with oxygen atoms in a water molecule

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49
Q

How does electromagnegativity promote cohesion in water molecules?

A

The slightly negatively charged oxygen atom attracts to the slightly positively charged hydrogen atoms on another water molecule, hydrogen bonds occur between molecules.

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50
Q

Materials that water transports around the body

A

Water transports co2, o2, nutrients like glucose, urea

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51
Q

Uses of organic ions in the body

A

Uses of organic ions in the body:
-DNA
-ATP
-Muscle contraction
-Cell wall development
-Blood clotting
-Nervous impulses

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52
Q

Uses of calcium in the body

A

Uses of calcium ions in the body:
-Muscle contraction
-Cell wall development

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53
Q

How does the structure of glycogen allow it to perform its function? What’s the advantage to animals using glycogen as their energy store?

A

-Glucose released quickly due to being branched out, which is good for respiration
-Glycogen is a large polymer of alpha glucose chains
-The water potential is unaffected due to its insolubility
-Higher metabolic rate due to fast glucose release rate
-1,6 glycosidic bonds - allows glycogen to be branched - enzymes released faster

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54
Q

Structure of a triglyceride

A

Triglyceride:
One molecule of glycerol and three fatty acids

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55
Q

What makes lipids insoluble in water?

A

Lipids are insoluble in water because they have long tails made up of hydrocarbons - this tail is hydrophobic meaning they repel water molecules.

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56
Q

How does a triglyceride form?

A

A fatty acid joins to a glycerol molecule, and as ester bond is formed as a molecule of water gets released (condensation reaction). This happens twice more to form a triglyceride.

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57
Q

What is the difference between saturated and non saturated fatty acids?

A

Saturated fatty acids dont have any double bonds between their carbon atoms. The fatty acid is saturated with hydrogen.
Unsaturated fatty acids have at least one double bond between their carbon atoms, which causes the chain to kink

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58
Q

Lipids found in cell membrane

A

Phospholipids are found in the cell membrane

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59
Q

How does phospholipids differ to triglycerides?

A

Phospholipids - one of their fatty acid molecules is replaced by a phosphate group, which is hydrophilic. The fatty acid tails are hydrophobic.

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60
Q

How are the structures of triglycerides related to their functions?

A

-Long hydrocarbon tails of fatty acids contain lots of chemical energy - aload of energy is released when theyre broken down. Because of these tails, lipids contain twice as much energy per gram as carbohydrates.
-They;re insoluble. Triglycerides clump together as insoluble droplets because the fatty acid tails are hydrophobic - the tails face inwards, shielding themselves from water with their glycerol heads

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61
Q

How are the structures of phospholipids related to their functions?

A

-Heads of phospholipids are hydrophilic and the tails are hydrophobic, so they form a double layer with their heads facing out towards the water on etiher side
-Centre of the bilayer of cell membranes are hydrophobic, so water soluble substances cannot easily pass through it - membrane acts as a barrier to those substances

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62
Q

2 main types of protein

A

2 main types of proteins are globular and fibrous proteins

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63
Q

Types of globular proteins

A

Types of globular proteins:
-Insulin
-Conjugated proteins (globular proteins that contain a non-protein component called a prosthetic group)

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64
Q

Types of fibrous proteins

A

Types of fibrous proteins:
-Keratin
-Elastin
-Collagen

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65
Q

Features of globular proteins

A

Features of globular proteins:
-Compact
-Water soluble
-Spherical in shape

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66
Q

How are globular proteins formed?

A

Globular proteins are formed when proteins fold into their tertiary structure in such a way that the hydrophobic R-groups on the amino acids are kept away from the aqueous environment.

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67
Q

What makes globular proteins soluble in water?

A

Globular proteins are soluble in water because the hydrophillic R-groups are on the outside of the protein

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68
Q

Why is it important that insulin is soluble in water and have precise shapes?

A

-Insulin needs to be soluble in order to be transported in the bloodstream (for blood glucose concentration)
-Hormones such as insulin have to fit onto specific receptors on cell surface membranes and so needs a specific shape

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69
Q

What are conjugated proteins?

A

Conjugated proteins are globular proteins with a prosthetic group eg haem is a prosthetic group

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70
Q

What is haemoglobin?

A

Haemoglobin is a red oxygen-carrying pigment found in red blood cells . It is a quaternary protein formed from four polypeptides , two alpha and two beta subunits, of which each unit contains a prosthetic haem group

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71
Q

What enables haemoglobin to transport oxygen around the body?

A

The iron ions present in the prosthetic haem groups found in haemoglobin combine reversibly with an oxygen molecule which enables haemoglobin to transport oxygen around the body

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72
Q

What is catalase?

A

Catalase is an enzyme that catalyses reactions. They are quaternary proteins containing four haem prosthetic groups. The presence of the iron II ions in the prosthetic groups allow catalse to interact with hydrogen peroxide (damaging byproduct of metabolic reactions) and speed up its breakdown.

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73
Q

Features of fibrous proteins

A

Features of fibrous proteins:
-Formed from long insoluble molecules
-Repetitive amino acid sequence in primary structure > leads to organised structures
-Makes strong long molecules

74
Q

What is keratin?

A

Keratin:
-Is a group of fibrous proteins present in hair, skin and nails
-Has lots of sulfur containing amino acid called crysteine > results in many strong disulfide bonds
-Amount of disulfide bonds determines its flexibility. Fewer bonds = more flexible.
-Unpleasant smell when burnt is due to burning disulfide bonds

75
Q

What is elastin?

A

Elastin is a fibrous protein found in elastic fibres present in blood vessel walls and alveoli in lungs - they give these structure flexibility to expand when needed. Elastin is a quaternary protein made from stretchy molecules called tropoelastin.

76
Q

What is collagen?

A

Collagen is a fibrous protein, and is a connective tissue found in skin, tendons, ligaments and the nervous system. Made up of three polypeptides wound up together. It’s rope like structure gives it flexibility

77
Q

Why can molecules not pass through the phospholipid bilayer of the plasma membrane of cells?

A

Molecules cannot pass through the phospholipid bilayer because the hydrophobic tails that stick out repel water molecules

78
Q

Structural detail of polypeptide that is affected by gene mutation

A

Structural detail of polypeptide that is affected by gene mutations are the amino acids

79
Q

How may protein structures differ between animals?

A

Protein structures differ between molecules because of:
-Different primary structures due to having different amino acid sequences
-Different secondary structures where one may coil into alpha helix wheras the other may coil into a beta pleaded sheet
-Different bonds in their tertiary structure
-Different 3d shape in quaternary structure

80
Q

Why is water a good solvent?

A

A water is a good solvent because it is a polar molecule - ions attract to the negative and positive ends of the water molecules, meaning the ions get surrounded by water

81
Q

Affect of hydrogen and sodium ions on plant life

A

Hydrogen ions help regulate pH, sodium ions help regulate water potential by limiting the uptake of water

82
Q

Monomer in cellulose

A

The monomer in cellulose is beta glucose

83
Q

Alpha glucose+ alpha glucose = ?

A

Alpha glucose + Alpha glucose = Maltose

84
Q

Examples of pentose sugars and where they are found

A

Pentose sugars:
-Ribose (found in RNA)
-Deoxyribose (foundin DNA)

85
Q

Roles of lipids

A

Roles of lipids:
-Membrane formation
-Hormone production
-Electrical insulation needed for nervse impulse
-Water proofing
-Protects organs
-Themal insulation

86
Q

Esterification reac tion

A

Esterification reaction:
Alcohol + carboxylic acid > ester + water

87
Q

What are sterols?

A

Sterols are complex alcoholic molecules with 4 carbon ring structure with a hydroxide group which is polar/hydrophilic - however rest of molecule is hydrophobic

88
Q

Purpose of using an additional tube in an experiment that lacks the sample

A

Tube is used as a control

89
Q

How to modify a reducing sugar experiment to test for a non-reducing sugar

A

Add alkali/hydrogencarbonate to neutralise, carry out reducing sugar test again ensuring the boil the sample

90
Q

Elements contained within nucleic acids

A

Nucleic acids contain carbon, hydrogen, oxygen, nitrogen and phosphorus

91
Q

What are nucleic acids?

A

Nucleic acids are polymers formed from many nucleotides (monomers) linked together in a chain

92
Q

Three components that make up nucleotides

A

Three components that make up nucleotides:
-A pentose monosaccharide sugar) : contains five carbon atoms
-A phosphate group : a negatively charged inorganic molecule
-A nitrogenous base : a complex organic molecule containing one or two carbon rings in its structure as well as nitrogen

93
Q

How are nucleotides linked togethr?

A

Nucleotides are linked together by condensation reactions to form polymers called polynucleotides, where the phosphate group at the 5th carbon of the pentose sugar of one nucleotide forms a covalent bond with a hydroxyl group at the third carbon of the pentose sugar of another nucleotide.

94
Q

Bonds linked between polynucleotides

A

Polynucleotides have phosphodiester bonds, which helps form a long, strong sugar-phosphate backbone with a base attached to each sugar. These bonds can be broken down by hydrolysis

95
Q

What are the two groups that the four bases of deoxynucleotides can be split into?

A

Pyrimidines - smaller bases that contain single carbon ring structures - thymine (t) and cytosine (c)
Purines - large bases that contain double carbon ring structures - adenine )(a) and guanine (g)

96
Q

Why are the sizes of pyrimidines and purines different?

A

The sizes of pyrimidines and purines are different due to the prescence of a double or single ring structure. Complimentary pairs thymine and adenine (a and t) form two hydrogen bonds, and complimentary pair cytosine and guanine form three hydrogen bonds

97
Q

What does the base pairs allow for DNA to do?

A

Base pairs allow for DNA to to be copied and transcribed

98
Q

How is the double helix of DNA structured?

A

The double helix of DNA are held by hydrogen bonds, each strand has a phosphate and a hydroxyl group at each end, which are antiparallel to eachother as they run in opposite directions

99
Q

Why must be bases of DNA be paired complimentarily?

A

The complimentary pairing of bases means a small prymidine base always binds to a large purine base, which maintains a constant distance between the DNA backbones resulting in parallel polynucelotide chains.
It also means that DNA always has an equal amount of the bases A,T,G,C

100
Q

How are ribonucleic acids (RNA) formed?

A

RNA is formed when a short section of a long DNA molecule corresponding to a single gene is transcribed onto a similarly short rna molecule (mRNA).

101
Q

How are RNA nucleotides different to DNA nucelotides?

A

RNA nucelotides has ribose as its pentose sugar rather than deoxyribose, and the thymine based is replaced with the base uracil (T+U RATHER THAN T+A)

102
Q

How do nucleotides form polymers?

A

Nucleotides form polymers by condensation reactions with the formation of phosphodiester bonds

103
Q

What happens to RNA molecules after protein synthesis?

A

After protein synthesis, RNA molecules are degraded in the cytoplasm , where the phosphodiester bonds are hydrolysed and the RNA nucleotides are released and reused

104
Q

How can we extract DNA from plant material?

A

Extracting DNA from plant material:
-Grind sample with mortar and pestle to break down cell wall
-Mix sample with detergent to break down cell membrane and release contents
-Add salt to break down hydrogen bonds between DNA and water molecules
-Add protease enzyme - break down proteins associated with DNA in nuceli
-Add layer of alcohol - causes DNA to precipitate out solution
-DNA will be seen as white strands forming between layer of sample and layer of alcohol

105
Q

Structure of DNA that relates to its role

A

Structure of DNA allows it to carry out its function because of:
-Large polymer > lots of information
-Base sequence used as code
-Double stranded > molecule is stable
-Double stranded > accurate replication

106
Q

Difference between a purine and a DNA nucleotide that contains a base

A

Difference between purine and dna with base:
-Purine = ribose sugar, 2 phosphate
-DNA = deoxyribose sugar, 1 phosphate

107
Q

How to break down a nuclear envelope of a DNA that dissolves in water

A

Breaking down a nuclear envelope of a DNA that dissolves in water:
Add detergent to attract phospholipid bilayer and water molecules present, to break down the nuclear envelope (plasma membrane)

108
Q

What has to happen in order for DNA to replicate?

A

In order for DNA to replicate:
The double helix structure has to unwind, and so hydrogen bonds between complimentary bases must be broken

109
Q

Bonds that hold adjacent nucleotides

A

Phosphodiester bonds hold nucleotides together

110
Q

What is semi conservative replication?

A

Semi conservative replication: Free DNA nucleotides pair their bases, hydrogen bonds between them form, adjacent nucleotides join by phosphodiester bonds, so two new molecules are formed where each one consists of one old strand of DNA and one new strand of DNA

111
Q

Role of enzyme Helicase

A

Helicase unwinds strands of DNA before replication can occur. It travels along backbone and catalyses breakdown of hydrogen bonds of bases

112
Q

Role of enzyme DNA polymerase

A

DNA polymerase catalyses the formation of phosphodiester bonds between the free nucleotides that have paired their bases via hydrogen bonds

113
Q

What is a triplet code in DNA?

A

Triplet code in DNA: the code in the base sequence. It is a sequence of three bases called a codon

114
Q

What is a codon?

A

Codon is a sequence of three bases that code for a single amino acid

115
Q

What is a gene?

A

A gene is a section of DNA that contains the complete codons to code for an entire protein

116
Q

How many codons are available in DNA?

A

There are 64 codons as there are four bases available, each in a triplet code (4x4x4)

117
Q

Why is there a single codon that signals the start of a sequence?

A

A single codon that signals the start of a sequence ensures that the codons are ‘read’ from base 1, rather than base 2 or 3, so the genetic code is non-overlapping

118
Q

Why is a genetic code degenerate?

A

The genetic code is degenerate because there are many instances in which different codons specify the same amino acid. A genetic code in which some amino acids may each be encoded by more than one codon. This is due to there being more codons than amino acids.

119
Q

Why is it more likely for there to be differences between base sequence of DNA than the amino acid sequence of proteins

A

-Triplet code makes it degenerate
-64 codons but only 20 amino acids
-So its likely there’s more differences in DNA than amino acid sequence

120
Q

Transcription in protein synthensis

A

Transcription in protein synthesis is when the base sequence of genes is copied onto an RNA strand in order for them to leave the nucleus

121
Q

What is the sense strand in DNA?

A

Sense strand contains the code for the protein to be synthesis, and runs from 5’ to 3’

122
Q

What is the antisense strand in DNA?

A

The antisense strand is the complementary copy of the sense strand that does not code for a protein, and acts as the template strand during transcription so that the complementary RNA strand formed carries the same base sequence as the sense strand, and runs from 3’ to 5’

123
Q

Transcription

A

Transcription (occurs in the nucleus):
1). Part of DNA molecule unwinds, hydrogen bonds break
2). Exposed gene transcribed
3). Complimentary copy of the code from the gene made by building mRNA molecule
4). Free RNA nucleotides pair up via hydrogen bonds
5). Sugar phosphate groups of the RNA nucletodies bond together by phosphodiester bonds by polymerase to form backbone
6). Once gene has been transcribed, hydrogen bonds form and DNA molecule re-forms
7). mRNA leaves molecule via nuclear envelope pore

124
Q

Translation

A

Translation:
1). mRNA leaves nucleus and moves towards ribosomes
2). mRNA attaches to a ribosome
3). Each tRNA has complementary anticodon to the codon on the mRNA
4). The first tRNA (which always carries the methionine amino acid) forms hydrogen bonds with the first codon on the mRNA.
5). The second tRNA (bringing the second amino acid) bonds with the next codon on the mRNA
6). A peptide bond forms between the amino acids
7). Ribosome moves along mRNA (5’ to 3’ direction) reading the next codon
8). The third tRNA (carrying the third amino acid) bonds with the complementary codon
8). The ribosome continues to read the mRNA molecule building up a polypeptide chain until it reaches a ‘stop’ codon

125
Q

Differences between mRNA and DNA

A

mRNA is:
-shorter than DNA
-only a single strand
-contains uracil instead of thymine

126
Q

Why is DNA replication described as semi-conservative?

A

In DNA replication, the DNA unwinds into 2 strands > free nucleotides pair with complimentary bases > 2 new molecules of DNA produced, each with an old strand a new strand

127
Q

Role of tRNA

A

tRNA brings the amino acids to the ribosome

128
Q

Role of rRNA

A

rRNA - formation of ribosomes

129
Q

Roles of enzymes that are found on ribosomes

A

Enzymes found on ribosomes catalyse the formation of peptide bonds between amino acids

130
Q

Why does RNA need to be present in a ribosome?

A

RNA needs to be present in a ribosome in order for complimentary base pairing to occur

131
Q

Why are there different ribosomal sites?

A

-Free floating ribosomes produces proteins that are used within the cytoplasm of the cell
-Ribosomes on the RER produces proteins that are exported outside of the cell

132
Q

Why must unnecessary base sequences be removed before DNA replication?

A

Unecessary base sequences must be removed before DNA replication because:
-Role of the protein dependant on its structure
-The shape is depended by the primary structure (the AA sequence)
-Codons on the mRNA code for the amino acids
-Codons could cause an insertion into the DNA sequence which could cause mutation as protein will have different structure

133
Q

An advantage of being able to edit mRNA

A

An advantage of being able to edit mRNA is that different proteins could be produced from one gene

134
Q

What are introns?

A

Introns are non-coding DNA sequences. They help in the regulation of transcription where it protects mRNA leading upto protein synthesis.

135
Q

What are the three main activities cells require energy for?

A

Cells require energy for synthesis, transport and movement

136
Q

What does ATP stand for?

A

ATP = adenosine triphosphate

137
Q

ATP structure

A

ATP structure: 3 phosphates, nitrogenous base, pentose sugar. The base of ATP is always adenine

138
Q

How does ATP release energy?

A

ATP releases energy when the bonds between phosphate groups are broken in a hydrolysis reaction, where water is added

139
Q

ATP hydrolysis reaction

A

ATP hydrolysis reaction:
ATP + H20 > ADP (adenosine diphosphate) + P (inorganic phosphate) + energy

140
Q

What is ATP hydrolysed into?

A

ATP is hydrolysed into ADP (adenosine diphosphate) and a phosphate ion, as well as releasing energy

141
Q

Why is ATP not a good long-term energy store?

A

ATP is not a good long-term energy store because of the instability of the phosphate bonds

142
Q

How is ATP created?

A

ATP is created through a process called phosphorylation where a phosphate group is reattatched to an ADP molecule (adenosine diphosphate). The energy for this process comes from cellular respiration via breakdown of fats and carbohydrates. This is a condensation reaction as water is removed.

143
Q

Properties of ATP

A

Properties of ATP:
-Small = moves easily in and out of cells
-Water soluble = energy-requiring processes happen in aqueous environments
-Contains bonds between phosphates with intermediate energy: large enough to be useful for cellular respiration but not large enough that energy is wasted as heat
-Releases energy in small quantities: suitable for cellular needs and not wasted as heat energy
-Easily regenerated: can be easily recharged

144
Q

What is splicing?

A

Splicing is removing introns from pre-mRNA so exons ramain

145
Q

What are exons?

A

Exons are sections of DNA that code for proteins

146
Q

Result of changing shape of DNA polymerase on DNA replication

A

Change to amino acid sequence > tertiary structure altered > active site changes shape > no longer complementary to substrate (nucleotide) > cannot catalyse condensation reaction that forms phosphodiester bonds between nucleotides

147
Q

Non-reducing sugars test

A

Test for non-reducing sugars:
Hydrochloric acid added to sample > heat with sodium hydrogencarbonate > add benedicts reagent > heat

148
Q

Starch test

A

Test for starch:
Iodine in potassium iodide solution

149
Q

Test for proteins

A

Biuret - sodium hydroxide + copper II sulfate

150
Q

Test for lipids

A

Test for lipids:
Ethanol water add to sample + shake
-Positive result = cloudy white precipitate / emulsion layer

151
Q

Bonds found in cellulose, and amylose

A

Cellulose and amylose has 1-4 bonds between glucose molecules

152
Q

Bonds found in amylopectin, and glycogen

A

Amylopectin + glycogen has both 1-4 and 1-6 bonds between glucose molecules

153
Q

Why are condensation reactions important?

A

Condensation reactions are important in the build up of large molecules eg glucose into glycogen for storage

154
Q

Why is hydrolysis important?

A

Hydrolysis is important in the breakdown of large insoluble molecules into smaller soluble molecules eg glycogen into glucose for respiration

155
Q

Reactions that occur in the disaccharides sucrose, lactose and maltose

A

Condensation reactions occur in disacharides to form glycosidic bonds

156
Q

How is a triglyceride formed?

A

Triglyceride formed from condensation reactions : fatty acid + glycerol with an ester (water released), occurs twice more to form triglyceride

157
Q

Difference between saturated and unsaturated fatty acids

A

Saturated fatty acids have no double bonds between carbon atoms. wheras unsaturated fatty acids has at least one double bond between carbon atoms

158
Q

Esterification reaction

A

Esterification reaction:
Carboxylic acid + Alcohol > Ester + Water

159
Q

What is a colorimeter?

A

A colorimeter quantitativelty measures the absorbance/transmission of light by a coloured solution. More concentrated solution = more light will be absorbed = less light will be transmitted. Can be used to calculate reducing sugar concentration in benedits test.

160
Q

How to callibrate a colorimeter

A

Callibrate a colorimeter by using distilled water inbetween samples

161
Q

How to extract DNA

A

Extracting DNA:
-Grind sample with pestle and mortor to destroy cell wall
-Add detergent to dissolve cell membrane
-Add salt to break hydrogen bonds
-Add protease to break down any proteins associated with DNA
-Add layer of alcohol/ethanol so DNA precipitates out of solution
-DNA will appear as white strands inbetween ethanol layer and sample layer, remove with rod

162
Q

Purine bases (double carbon ring structures)

A

Purine bases are adenine and guanine

163
Q

Pyrimidine bases (single carbon ring structures)

A

Pyrimidine bases are thymine and cytosine

164
Q

Phosphodiester bonds

A

Phosphodiester bonds occur when the phosphate group at the fifth carbon of the pentose sugar forms a covalent bond with the OH group at the third carbon of the pentose sugar on the adjacent nuclEotide

165
Q

Peptide bonds

A

Peptide bonds occur between amino acids, when the OH from the carboxylic group of one amino acid, and the hydrogen bond from the amine group of the other amino acid, is lost and the carbon atom then bonds to the nitrogen atom of the other amino acid

166
Q

Why can you use chromatography for amino acids?

A

Chromatography can be used to seperate and identify amino acids in a solution

167
Q

Rf value

A

Rf value = (distance travelled by component) / (distance travelled by solvent)

168
Q

Positive inorganic ions important in human metabolism

A

Positive inorganic ions that are important in human metabolism: K+, Na+, Ca2+, H+

169
Q

Negative inorganic ions available to plant roots in soil

A

Negative inorganic ions that are available to plant roots in soil: NO3-, P0(4)3-

170
Q

Structural differences between secondary and tertiary folding of proteins

A

Structural differences between secondary and tertiary folding of proteins:
Secondary structure - involves H bonds only, forms fibrous structures, bonds form between the chemical
groups either side of peptide bonds (–C=0 and
–N–H groups)
Tertiary structure: involves other bonds like ionic and disulfide, forms globular structures, tertiary bonds form between
the side-chains of amino acid residues

171
Q

Functions of lipids

A

Functions of lipids:
-Thermal insulation
-Electrical impulses
-Long term energy store
-Source of metabolic water

172
Q

Functions of carbohydrates

A

Functions of carbohydrates:
-Cell signalling
-Cell walls
-Short term energy store
-Antigens

173
Q

Difference between DNA polymerase and RNA polymerase

A

DNA polymerase is involved with DNA replication wheras RNA polymerase is involved with transcription

174
Q

Functional differences between collagen and elastin

A

Elastin - stretchy, in ligaments, lungs and bladder
Collagen - inflexible, in tendons and bone

175
Q

How can you investigate into carbohydrates other than reducing sugar tests under the microscope?

A

Iodine in potassium iodide solution to find carbs other than the reducing sugar test

176
Q

Type of nucleic acid that holds the sequence of bases during protein synthesis

A

mRNA is the nucleic acid that holds sequences of bases during protein synthesis

177
Q

Why is sucrose so sweet?

A

Sucrose is sweet because it is usually found as table sugar used in baking

178
Q

How do colorimeters work to give us concentration of glucose in a benedicts solution?

A

Red filter is placed on colorimeter, and red colour will either be absorbed or transmitted by the solution. The less right red light absorbed (more transmitted) the higher the glucose concentration

179
Q

How to create callibration curve in colorimeter pracical?

A

1) Use standard solutions of reducing sugar concentration to 6 tubes along with distilled water
2) Carry out benedicts test on each tube and boil them to form red precipitate
3) Filter out the red precipitate so only the blue benedicts solution remains

180
Q

How to create callibration curve in colorimeter practical?

A

1) Use standard solutions of reducing sugar concentration to 6 tubes along with distilled water
2) Carry out benedicts test on each tube and boil them to form red precipitate
3) Filter out the red precipitate so only the blue benedicts solution remains

181
Q

How to use colorimeter to measure concentration of glucose?

A

1) Add solutions into cuvettes (so light passes through their transparent walls)
2) Use red filter
3) Set colorimeter to measure absorption of red light
4) Place cuvette with distilled water into colorimeter and set to 0
5) Use colorimeter to find absorptions of each solution
6) Find glucose concentration of unknown sample by plotting on a graph its absorption of red light

182
Q

Difference between polypeptides and proteins?

A

In order to be classed as a protein, polypeptide has to fold into a complex 3d-shape, and then they can carry out its function as a protein eg an eznymes or hormones

A-Level Biology🌼 (25 decks)

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