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AS level - Biology > M2- Chapter 3 - Biological Molecules > Flashcards

M2- Chapter 3 - Biological Molecules Flashcards

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1
Q

What is an ion

A

It forms positive and negative ions that are held together by the attraction of the opposite charges.

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2
Q

What is a carbohydrate

A

Molecule that contains carbon, hydrogen and oxygen.

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3
Q

In what ratio is a carbohydrate made?

A

Cx(H20)x

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4
Q

What is a lipid (elements)

A

Molecule that contains carbon, hydrogen and oxygen.

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5
Q

What are proteins made of (elements)

A

Carbon, hydrogen, oxygen, nitrogen and sulfur

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6
Q

What are nucleic acids made of (elements)

A

Carbon, hydrogen, oxygen, nitrogen and phosphorus

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7
Q

Explain what polarity is

A

Covalent bonds occur when 2 or more atoms share an electron. Sometimes, the electron may be closer to one atom than another. This means that one atom becomes slightly negative and the other slightly positive.
Being polar is to have regions of negativity and regions of positivity.

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8
Q

Give an example of polarity

A

Oxygen and hydrogen dont share an electron equally in an OH bond. The oxygen has a much greater share of the electron than the hydrogen. Therefore, any molecules that contain the OH bond are slightly polar too.

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9
Q

How do hydrogen bonds occur?

A

It is a weak interaction between molecules containing a slightly negatively charge atom bonded to a slightly positively charged hydrogen atom.

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10
Q

Name water’s characteristics

A
  1. high boiling point
  2. it becomes less dense as a solid
  3. Cohesive and adhesive properties
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11
Q

Explain why water has a high boiling point

A

Due to the many hydrogen bonds in water, it takes a lot of energy to break the bonds.
When it evaporates, it takes a lot of heat with it too, because of its high latent heat of vaporisation.

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12
Q

Explain why water is less dense as a solid

A

When water reaches 4 degrees Celsius, the hydrogen bonds change their positions of the polar molecules slightly further apart. This pushes the oxygen atom towards the centre, meaning it becomes less dense.
As a liquid, the hydrogen bonds are constantly being broken and remade.
As a solid, it forms a crystal-like lattice where molecules are set at fixed distances.

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13
Q

Another name for sugar

A

Saccharides

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14
Q

Examples of a monosaccharide

A

Glucose, fructose, ribose

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15
Q

Example of a polysaccharide

A

Glycogen, cellulose, starch

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16
Q

Examples of a disaccharide

A

Lactose and sucrose

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17
Q

What type of sugar is glucose

A

A hexose monosaccharide (has 6 carbon atoms)

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18
Q

Explain water’s cohesiveness

A

This means that water will move as one mass because the molecules of water are physically attracted to each other. This creates surface tension

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19
Q

Explain water’s adhesivenss

A

This means that water is also attracted to other surfaces.

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20
Q

Explain the Capillary Action

A

This uses water’s adhesiveness to travel against gravity. An example is how water moves up a plant. Also how water is in a beaker. It creates a meniscus , where it curves around the edges. This is because it is attracted to the sides of the glass.

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21
Q

Name 4 reasons why water is so important

A
  1. Acts as a solvent to carry dissolved material
  2. Very efficient transport medium. It’s adhesive properties allows it to work against gravity.
  3. Acts as a coolant
  4. Stable
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22
Q

How does water act as a coolant

A

It lessens the effects of temperature changes during chemical reactions. This way any fishes that live in the sea don’t need to adapt to different weathers because the water slows down the impact of temperature changes.

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23
Q

How is water stable

A

It doesn’t change temperature or state too easily, meaning it creates a safe environment. An example is that ice floats and is made from the top down. Therefore animals in the sea actually get a thermal layer on top.

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24
Q

What is the difference between alpha- glucose and beta-glucose

A

Alpha glucose molecules have the OH functional group at the bottom at 1, and it stays that way on 4 too.
Beta glucose molecules have the OH functional group at the top at 1, and then the bottom at 4.

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25
Q

Glucose

A

They are polar and soluble in water. This is because of the hydroxyl group, that allows the glucose molecule to dissolve in the cytosol of the cell.

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26
Q

How is a glycosidic bond created

A

In a condensation reaction, because the OH groups are so close in alpha glucose molecules, the covalent bond, a glycosidic bond is created. Usually it is called a 1,4 glycosidic bond because the OH groups are on 1 and 4 of the atoms.

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27
Q

Examples of a hexose monosaccharide

A

Fructose, galactose

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28
Q

Explain amylose

A

It is formed when alpha glucose molecules join together by 1,4 glycosidic bonds. Due to the angle that the bonds are created at, a helix shape is made. The chain is further strengthened by hydrogen bonds. The coil sort of shape makes the polysaccharide a lot more compact and less soluble

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29
Q

Explain amylopectin

A

This is formed when 1,4 glycosidic bonds form as well as some 1,6 glycosidic bonds. This gives it a ‘branched’ sort of structure, with the 1,6 branching unit once every 25 subunits.
The bonding in general might become weaker though because there are chains in the way

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30
Q

Amylose- energy

A

It releases energy very slowly because the enzyme, amylase only has 2 accessible ends to start breaking down or adding glucose molecules on.

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31
Q

Amylopectin - energy

A

It releases energy much quicker in comparison to amylose because there are more accessible ends for the enzymes to work on.

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32
Q

Where are starch stores found

A

In plants, they are found in the seeds

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33
Q

Glycogen

A

It is the human sugar storage. There are a lot more 1,6 glycosidic bonds and they occur more frequently. This way, it can release more energy as there are even more accessible ends, speeding up the process entirely.
It is kept in the liver, where it is turned back into glucose using the hormone glucagon.
Here, the 1,4 glycosidic bonds are shorter, giving it a highly branched structure.

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34
Q

Hydrolysis

A

When plants or animals need to respire, the starch or glycogen undergoes hydrolysis, where water molecules are added back in, and the reaction is catalysed by enzymes.

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35
Q

Cellulose - begin

A

Beta glucose molecules cant join like alpha glucose molecules can. This is because the OH functional groups are too far away from each other (they are positioned diagonally). So, if we flip every second beta glucose molecule, then OHs come on the same side.

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36
Q

Cellulose- structure

A

Due to the flipping of the molecules, the chain can’t coil and is forced to remain straight. This means they can be positioned in parallel lines all joined by 1,4 glycosidic bonds. In the parallel lines, because the OH groups are close together, they create hydrogen bonds, which act like ‘cross-links’, making the chain strong. When they flip,the CH2OH molecule flips to the other side.

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37
Q

Cellulose- fibres

A

A cellulose chain bundled together is a mirofibril. Many microfibrils bundled together is a macrofibril.
These fibres wrap around plant cells in multiple layers and angles to provide strength. Cellulose is used to make cell walls so it needs to be able to withstand the pressure of turgid cells.
The cellulose microfibrils are embedded in other frameworks of other substances, such as pectins and hemicellulose.
There is space between the fibrils to allow water and mineral ions to get through. Sometimes they may be blocked (by suberin) to make it waterproof.

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38
Q

Breaking/ Digesting cellulose

A

It is a really strong chain, and most animals don’t have the cellulase enzyme that breaks down the 1,4 glycosidic bond. Herbivores have symbiotic bacteria that releases this enzyme, so they can gain more energy.
A lack of fibre can cause colon cancer.

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39
Q

What is breaking down polymers

A

Catabolic reaction

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40
Q

What is building up monomers

A

Anabolic reactions

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41
Q

What is a dimer

A

Units joined together

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42
Q

Starch

A

examples: glucose, amylopectin and amylose
The twisted chains gives them a compact shape, so a lot of energy can be stored. Their insolubility doesn’t allow them to diffuse outside of the cells.

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43
Q

uses of carbohydrates

A 
Cell walls 
Strengthen the digestive system
Respiration (uses glucose)
DNA (uses pentose sugar)
Energy stores
Chitin in exoskeletons
Recognition of molecules outside the cell (attached to proteins or lipids on cell surface membranes)
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44
Q

What type of sugars are monosaccharides

A

All are reducing sugars, so they can donate electrons and reduce other chemicals

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45
Q

How can you test for monosaccharides

A
  1. Place the sample in a boiling tube. If it’s not already a liquid, then blend it or grind.
  2. Add and equal volume of Benedict’s solution
  3. Heat the mixture for 5 minutes
    The reducing sugar will react with the copper ions, so they change from CU2+ to CU+ ions. This makes the mixture go from blur to red. The more reducing sgars there are, the more the precipitate will form.
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46
Q

Iodine test for starch

A
  1. Add a few drops of iodine dissolved in potassium iodide solution.
  2. If the mixture changes from yellow to black or purple, starch is present
    You can also use reagent strips, except that you can determine concentration.
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47
Q

Examples of Quantitative ways

A

Colorimetry

Biosensors

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48
Q

Explain Colorimetry

A

Measures the absorbance or transmission of light by that is absorbed and less light to transmit,
Procedure:
1. A filter is placed in the colorimetry
2. Colorimeter is calibrated using distilled water
3. Benedict’s test is performed on a range of known concentrations.
4. All removed
5. The % transmission is measured coloured solution. The more concentrated the solution, the more light

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49
Q

Explain biosensors

A

They take a biological or chemical variable that can’t be easily measured and then convert that into an electrical signal. The biological component is usually immobilised and it recognises and interacts with the analyte to make a signal, which is then detected by the transducer.

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50
Q

Explain lipids

A

They are non-polar molecules. They lack positive and negative regions, and it is why they don’t dissolve. They are oils in liquid state.
Lipids are macromolecules (large complex molecules, they are not polymers)
Examples include: triglyceride, phospholipids, sterols

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51
Q

Triglyceride

A

Contains 1 glycerol (an alcohol) and 3 fatty acids (carboxylic acids). Because both have the OH group, they are bonded together in a condensation reaction. They create an ESTER BOND (COO), and the actual reaction is called Esterification.

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52
Q

what is an unsaturated molecule with 1 double bond called

A

Monounsaturated

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53
Q

what is an unsaturated molecule with 2 double bonds called

A

Polyunsaturated

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54
Q

What is an unsaturated molecule

A

Has double bonds

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55
Q

What is a saturated molecule

A

Has no double bonds

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56
Q

What does having double bonds cause?

A

They cause the molecule to bend, meaning it can’t be packed too closely together. This is why they are liquid at RTP. Oils are liquids at room temperature. This is because they are unsaturated, meaning they have double bonds and can’t be packed together, leaving them to be liquids rather than solids.

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57
Q

Explain Phospholipids

A

They contain carbon, hydrogen, oxygen and phosphorus. In the cytoplasm of every cell, there are phosphate ions. Because of their extra electrons, they become negatively charged, meaning they can be dissolved in water due to this charge. One of the fatty acids is replaced by the phosphate ions

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58
Q

Structure of phospholipids

A

The part that has the fatty acids is the non-polar side, called Hydrophobic, and the other is the polar/ charged side, called Hydrophilic.

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59
Q

Interaction of phospholipids with water

A

They Phosphate groups will stay in the water, and the fatty acids will shoot upwards. Because of this, they are called surfacants. Or in water, they will curl up to create a protective layer called a bilayer.
Because of this, they can separate an aqueous environment in which cells exist from the aqueous cytosol within the cell.

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60
Q

Explain sterols

A

They are based on a 4 carbon ring structure, with an OH group. Because they have the OH group, that makes it polar, meaning it has hydrophobic/ philic properties too.

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61
Q

Example of a sterol

A

Cholesterol
It is made in the liver and the intestine.
It is also a hydrophobic molecule, so it goes and sits inside the hydrophobic section of the bilayer.
It regulates the fluidity of the membrane

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62
Q

Roles of lipids

A 
membrane formation
hydrophobic barriers
hormone production 
electrical insulation 
waterproofing (leaves)
Energy source (broken down to release energy)
Buoyancy- the fat is less dense than water, so is used by aquatic mammals to help them stay afloat.
Thermal insulation 
Cushioning to protect vital organs
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63
Q

Identification of lipids test (emulsion test) for a liquid sample

A
  1. Sample + ethanol
  2. Mix that with water and shake

If a white precipitate is formed, this indicates the presence of a lipid.

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64
Q

what is food synergy

A

the idea that nutrients work best in unison, rather than as one.

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65
Q

Research flaws when looking at fats

A 
Not accurate info
people underestimate what they eat 
forget what they ate 
dont know the ingredients 
due to genetic makeup
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66
Q

Plants

A

Plants have unsaturated fats (healthy)

We as animals have saturated fats.

67
Q

Butter

A

Is high in saturated fats. They tried to use vegetable oils which had even more saturated fats, so instead, they used hydrogen to saturate and remove the double bond.

68
Q

transfat

A

unwanted byproducts of vegetable oils
unsaturated lipids
can cause heart diseases

69
Q

Reducing fat spreads

A

Lipids release the same amount of energy regardless if its unsaturated or saturated.

70
Q

How many different amino acids are there?

A

20

71
Q

Explain the different types of amino acids

A

5- non-essential (your body makes them from other amino acids)
9- essential (can only get from food)
6- conditionally essential (only infants need them)

72
Q

How do amino acids join

A

They join when amine and carboxylic acids groups connect. When they connect, the OH from carboxylic acids and the H from the amine group bond to create a water molecule (through a condensation reaction). Then, when the 2 particles join a peptide bond is made (O=C-H-N), to create a dipeptide.

73
Q

What is the enzyme that allows a polypeptide to be made

A

Peptidyl Transferase, which is present in the ribosomes

74
Q

Method for separating amino acids using TLC

A
  1. Wearing gloves, draw a pencil line 2cm from the bottom and hold the plate by its edges only
  2. Draw equal points along the line
  3. Amino acids are dropped onto the points. (1 unknown and all others known)
  4. Place the plate in a jar containing the solvent (organic or mobile phase) no more than 1 cm deep. Leave it there.
  5. Remove the plate when the solvent has reached 2 cm from the top. Draw a line along the solvent front.
  6. Spray with (in a fume cupboard) ninhydrin, to see the marks
75
Q

How can you calculate Rf

A

Distance component / distance solvent

76
Q

Primary structure - levels of protein

A

The sequence in which the amino acids are joined, which is controlled by the DNA. Essentially it decides the protein’s final shape. They bases are held together by hydrogen bonds.

77
Q

Secondary structure- levels of protein

A

This is the shapes that can be formed because of the hydrogen bonds between the backbone of the polypeptide. This is when all the different atoms of the repeating structure of the amino acids interact. The types of bonds that form can create 2 different shapes: alpha helix
and beta pleated sheet

78
Q

what is a micelle

A

The structure that phospholipids form in water where thy create tiny balls, with the hydrophilic head on the outside, and the hydrophobic tails on the inside.

79
Q

What is a bilayer

A

Phospholipids are used in cell membranes. They create 2 different layers, where the hydrophilic heads are on the outside of the membrane, with the hydrophobic tails on the inside, tucked away. This is called a phospholipid bilayer.

80
Q

more cholesterol means?

A

it means less movement.
More cholesterol inside the bilayer of the cell membrane means that the membrane can’t be as fluid because there is cholesterol there to stop it from doing so.
This is quite important, because even at higher temperatures, it allows the cells to retain structure and not become too liquidy.

81
Q

what else is made from cholesterol

A

testosterone
oestrogen
vitamin D
they are all hydrophobic, and they can pass through the hydrophobic part of the membrane.

82
Q

functions of proteins

A

enzymes
antibodies
antigens
hormones

83
Q

what is the name of the most basic amino acid

A

Glycine

84
Q

What is an amine group

A

NH2

85
Q

What is a carboxylic group

A

COOH

86
Q

alpha- helix secondary structure

A

The hydrogen bonds that form between the amino acids pulls it into a coil shape, called an alpha helix structure. The bonds are held between the NH of the amino acids and the CO from the carboxylic acids, which is 4 places ahead of it.

87
Q

beta- pleated sheet

A

the R groups alternate pointing up and down
the pleats is the alpha carbon.
the H-bonds are perpendicular to the direction of the polypeptide.
hydrogen bonds will be formed between the oxygen and the hydrogen atoms.
beta-bends allow the change of direction of peptide chain to the get this structure

88
Q

Tertiary Structure

A

When the coils and the pleats fold together, they form tertiary structures. These are held together by:
H bonds
Ionic bonds (between oppositely charged R-groups)
Disulphide bridges
Bonding between the Hydrophobic/ philic :
weak interactions between polar and non-polar R-groups which gives rise to the 3D shape.

89
Q

Tertiary structure as the temperature increases

A

they can be denatured with higher temperatures. Increasing KE, means increasing the vibrations, meaning that bonds are broken and they unravel. This is quite important, because many proteins are used to make enzymes, which need to maintain their active site.

90
Q

Quaternary structure

A

the interaction of 2 or more subunits (individual proteins).
This is the same as the tertiary structure, except that it is between different molecules.

91
Q

Hydrophobic or philic interactions

A

the shape of the molecule can often also depend on whether the R-groups are hydrophobic or hydrophilic. If they are hydrophilic, they will remain on the outside of the protein, but on the inside, if they are hydrophobic.
Essentially, this causes the twisting of the amino acids, changing the shape of the entire protein, to form globular protein. This means that protein is water soluble.

92
Q

Disulfide bonds

A

strong covalent bonds
less effected by temperature
formed between the R- groups
Made of 2 cysteines (contains sulphur)

93
Q

Ionic Bonds

A

Formed between the NH3 + and the COO- groups that are part of the R Groups.

94
Q 
Examples of:
enzymes
transport
movement
cell recognition 
channels 
structure 
hormones 
protection
A 
enzymes- amylase
transport - haemoglobin
movement - actin and myosin
cell recognition  - antigens 
channels -membrane proteins 
structure - collagen or keratin 
hormones - insulin (for glucoregulation)
protection - antibodies
95
Q

What are the 2 types of 3D Tertiary and Quaternary structures

A

Fibrous and globular

96
Q

Explain fibrous proteins

A

they have a repetitive sequence of amino acids. They usually contain non-polar R groups, which makes the entire molecule of protein non polar. Therefore, it is insoluble in water. It is a structural protein.

97
Q

Explain globular proteins

A

They are round in shape
They have hydrophilic/ phobic properties, and the hydrophobic R-groups usually go to the inside, and the hydrophilic groupd to the outside. This gives it the spherical shape. Therefore, they are soluble in water.

98
Q

examples of fibrous proteins

A

keratin (hair, skin, nails)
elastin (vessels)
collagen (skin, tendons, ligaments)

99
Q

Keratin

A

They have a lot of sulphur- containing amino acids (cysteine). This makes many strong disulfide bonds, and therefore it is strong, inflexible and insoluble. The degree of disulfide bonds determines the flexibility.

100
Q

Elastin

A

Found in elastic fibres, which are present in the walls of blood vessels and the alveoli of lungs. They have cross-linking and coiling, which makes the structure strong and flexible. They can expand and also return to their normal shape. Elastin is made from tropoelastin.

101
Q

Collagen

A

A structural protein
Found in artery walls, bones and tendons
It is a repeating structure of amino acids. They are all made up of amino acids that create a strong rope-like structure. It is also quite flexible.

102
Q

What is the shape of a globular protein

A

It is highly specific/ 3D, allowing them to carry out very specific functions. Examples include enzymes.

103
Q

Examples of globular proteins

A

Haemoglobin
Insulin
Pepsin

104
Q

Explain haemoglobin

A

2 alpha-globin and 2 beta-globin polypeptide chains are used.
It includes 4 ‘haem’ groups (prosthetic), which contain a iron ion. Each haem group carries 1 oxygen molecule, which means 1 red blood cell can carry 4 oxygen molecules.

105
Q

What is a conjugated protein

A

They are globular protein that contain a non-protein component, which is called a prosthetic group. The group is necessary for the protein to carry out its functions

106
Q

Insulin

A

Composed of 2 polypeptide chains, one alpha-helix and another beta-pleat. A- Chain begins with a-helix and the B-Chain ends with a B-pleat. Both the chains are joined by a disulfide bond in the R-groups. It has hydrophilic R groups on the outside, again making it soluble on the outside. This is good because it can dissolve in the blood and be easily transported.

107
Q

Explain pepsin

A

It catalyses the digestion of proteins. It can break down peptides into smaller peptides, such as meat. It is found in the stomach, which is highly acidic. They don’t denature here because because they have very little R- groups for the H+ ions to add on to, preventing the tertiary structure from being affected.

108
Q

Why does a low pH cause enzymes to denature

A

Low pH means more H+ ions. These H+ ions go and join the enzymes, which changes their structure. Eventually, as more H+ ions keep adding on,the entire enzyme will denature.

109
Q

2 types of nucleic acids

A

RNA and DNA

110
Q

what are the 3 things in a nucleotide

A

Pentose sugar
Phosphate group
Organic base

111
Q

Pentose Sugar

A

contains 5 carbons

112
Q

Phosphate group

A

Inorganic molecule
acidic
negatively charged

113
Q

What is the bond that hold 2 bases together

A

hydrogen bonds

114
Q

Bases

A

A complex organic molecule that contains 1 or 2 carbon rings in its structure along with nitrogen

115
Q

What is the name of the bond that connects nucleotides together

A

Phosphodiester
During a condensation reaction
Happens between a carbon 5 and a carbon 3
Usually, there is an OH on carbon 3, but it forms a covalent bond with the phosphate group

116
Q

What is different about a RNA and a DNA

A

a DNA contains 1 less oxygen (usually on carbon 3)

117
Q

What are the 2 structures that bases can be

A

Either a pyrimidines or a purine

118
Q

Pyrimidine

A

They are the smaller bases. They contain single carbon ring structures.
Thymine and Cytosine

119
Q

Purine

A

They are the larger bases. They contain double carbon ring structures. Guanine and Adenine

120
Q

Thymine and adenine create what

A

2 hydrogen bonds

121
Q

Guanine and cytosine create what

A

3 hydrogen bonds

122
Q

Double helix structure

A

The 2 strands actually run in opposite direction, therefore they are called antiparallel.

123
Q

How is RNA made

A

Because the DNA cant leave the cell, an mRNA is made by a short section of the DNA is transcribed into an mRNA. It has uracil, which is also a pyrimidine, to bond with adenine.

124
Q

Semi conservative replication

A

double helix opens up
free nucleotides join up
creates 2 strands with 1 old strand each

125
Q

enzymes used in DNA replication

A

DNA helicase- break bonds

DNA polymerase- join up bonds

126
Q

What is an ion

A

Atom or molecule in which the total number of electrons is not equal to the total number of protons is called an ion

127
Q

Calcium ions Ca2+

A

Muscle contraction

Bone formation

128
Q

Sodium ions Na+

A

Nerve impulse

Affects absorption of carbohydrate in the intestine

129
Q

Potassium ions K+

A

Nerve impulse

Stomatal opening

130
Q

Hydrogen ions H+

A 
Production of ATP
pH determination(more H+ ions than OH- ions in solutions creates an acid)
131
Q

Ammonium ions NH4+

A

Production of nitrate ions by bacteria

132
Q

Nitrate ions NO3-

A

Component of nucleic acids

A component of the nitrogen cycle

133
Q

Hydrogencarbonate ions HCO3-

A

Involved in the transport of CO2

134
Q

Chloride ions Cl-

A

Involved in the transport of CO2

Regulates affinity of haemoglobin to oxygen

135
Q

Phosphate ions PO43-

A

Component of phospholipid, ATP and nucleic acids

Helps root growth

136
Q

Hydroxide ions OH-

A

Involved in regulation of blood pH(more OH- ions than H+ ions in solutions creates an alkali)

137
Q

What is a non-reducing sugar

A

A sugar that doesm’t have an open chain

138
Q

Emulsion test for a solid sample

A

Crush the food sample and place it in a dry test tube
Add ethanol and shake thoroughly
Allow the solid to settle
Decant the ethanol into another test tube
Add 2cm3 of water to the second test tube

139
Q

Give the explanation behind the ethanol emulsion test

A

Because lipids are non-polar to begin with, they are soluble in organic solvents such as ethanol, but they are insoluble in water.
As there is no change seen when ethanol is added to lipids, but when water is added, all the lipids create micelles. this creates a layer at the top because lipids are less dense than water.

140
Q

Precaution taken during the emulsion test

A
  1. clean apparatus
  2. wash hands between testing different foods
  3. keep food samples away from each other.
141
Q

Testing for proteins

A

Add a couple drops of dilute copper sulphate solution
then some sodium hydroxide solution
If there is a colour change from blue to lilac, protein is present

142
Q

Explanation behind testing for proteins

A

The colour is formed by a complex between nitrogen atoms in a peptide chain and the Cu+2 ions.

143
Q

Difficulties with Chromatography

A

may not be able to see colourless molecules. you can try:
UV lights
Ninhydrin bonds which makes amino acids easier to see
Iodine gas binds to each molecule.

144
Q

Explanation behind chromatography

A

the height moved is dependant on the molecules’ solubility and polarity. If there are exposed OH groups of the paper allow hydrogen bonds with the molecules.
A highly polar solute will stick to the surface and move very slowly. A non-polar will move very quickly up the plate.

145
Q

What is the leading strand

A

The DNA polymerase enzyme only binds to 3’ ends, it travels in a 3’ to 5’ direction. The strand that is unzipped from the 3’ end can be continuously replicated and this is called the leading strand.

146
Q

What is the lagging strand

A

The strand that is 5’ to 3’. This is where the DNA needs to be made in sections , which later have to be joined (called the ozaki fragments)

147
Q

What is degenerate coding

A

The whole idea that 1 amino acid can be coded for by many codons.

148
Q

Transcription

A

The DNA strand opens up because of the DNA helicase. The strand of DNA that runs 5’ to 3’ is the strand that needs to replicated and is called the ‘sense strand’. Therefore, the free RNA nucleotides that are in the nucleus join up with the other strand (called the antisense strand). The RNA polymerase enzyme comes and creates phosphodiester bonds between the complementary bases, and it creates an mRNA strand.

149
Q

Translation stage 1

A

In the ribosomes (which have a smaller and larger subunit), the mRNA goes in between. As each codon is read, it is assigned to a tRNA, which contains an anticodon. This is highly specific and it only bonds to a specific codon that it contains the anticodon for. It attaches an amino acid to that codon.

150
Q

Translation stage 2

A

Once the next codon has a tRNA attached to it, the amino acid before it will bond with it (by a peptidyl transferase enzyme). The tRNA will leave it and the amino acids start adding up as they move to the amino acid in front of itself. Eventually, the amino acid will get big enough to leave the ribosome. Here it is in the cytoplasm, where there is mainly a lot of water. Here, the hydrophobic/ philic properties of the amino acids come into play and it can create the primary, secondary, tertiary structures.

151
Q

What is the start codon

A

AUG - methionine

152
Q

What do cells require energy for

A

Synthesis
Movement
Transport

153
Q

What is in a ATP molecule

A

3 phosphates
1 adenine
1 ribose (sugar)
It is basically a nucleotide

154
Q

How can you release energy from ATP

A

Essentially, you have to break down the last phophate bond (hydrolysis), using energy but this also gives back a lot of energy. It creates ADP, which is adenosine Diphosphate. Because this reaction needs energy to occur, it happen simultaneously as the reaction is given energy.

155
Q

Why is ATP a short-term energy store

A

The phosphate bonds in the ATP are quite unstable and therefore, the energy gained from respiration is used to create ATP. This is when phosphate groups are added back (during phosphorylation). Because you can invert between the two, most cells don’t have a lot of ATP.

156
Q

Properties of ATP

A

small
water soluble (can happen in aqueous solutions)
it contains bonds that release enough energy so it isn’t wasted.
it releases energy is small quantities (no waste)
easily regenerated

157
Q

how can you test for non-reducing sugars

A

non-reducing sugars are usually polysaccharides. So if you break them down (hydrolyse them), into monosaccharides (which are reducing sugars), and then test this for reducing sugars you can prove that the substance was a non-reducing sugar. The steps are:
1. test the non-reducing sugar for reducing sugar by adding some drops of Benedict’s Reagant to it and then put into a water bath for 5 minutes. It should result in no change and it should remain blue.
2. Then, get some more of that substance and now we have to hydrolyse it. This can be done by adding 1cm3 of dilute HCl to 2cm3 of the sample. Put into a water bath for 2-3 minutes (100 degrees).
3. Since the solution is now quite acidic, you can neutralise it by adding NaHCO3 until the solution is slightly alkaline.
Benedict’s test only works in alkaline environment so check it using a blue litmus paper.
4. Perform the Benedict’s test again and if it does test positive for reducing sugars, then the substance indeed was a non-reducing sugar.

158
Q

Reagent test strips for reducing sugars

A

They can also be used to test for reducing sugars, most commonly glucose. The advantage of that is that, with the use of a colour-coded chart, the concentration of sugar can also be determined.

159
Q

DNA extraction by purification

A
  1. Grind sample
  2. Add detergent (1cm3)
  3. Add salt (solution)
  4. Add protease enzyme
  5. Add a layer of ice-cold ethanol by holding the test tube at an angle and dropping the ethanol down the side.
  6. DNA should be seen as white strands in between layers. You can take it out using a spool.
160
Q

Why do you grind the sample

A

To break down cell walls (if a plant)

161
Q

Why do we add detergent to DNA extraction

A

Breaks down the cell membranes

162
Q

Why do we add salt solution to DNA extraction

A

It breaks down the hydrogen bonds between the DNA and the water molecules

163
Q

Why do we add protease enzyme to DNA extraction

A

It breaks down proteins associated with the DNA in the nuclei.

164
Q

Why do we add the ethanol to DNA extraction

A

It causes the DNA to precipitate out of the solution.

AS level - Biology (12 decks)

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