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BIOLOGY A LEVEL 2022 FINAL > MODULE 2 SECTION 2 - BIOLOGICAL MOLECULES > Flashcards

MODULE 2 SECTION 2 - BIOLOGICAL MOLECULES Flashcards

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1
Q

Functions of water?

A
  • Reactant in many important chemical reactions, like hydrolysis.
  • Good solvent. Good reaction medium.
  • Water transports substances around plants and animals.
  • Helps with temperature control.
  • It is a habitat.
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2
Q

Structure of water?

A
  • Polar molecule
  • Has slightly positively charge H atoms and slightly negatively charged O atoms.
  • Able to form Hydrogen bonds: The slightly negatively charged oxygen atoms attract the slightly postively charged hydrogen atoms of other water molecules.
  • Hydrogen bonding gives water some of its many properties.
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3
Q

Properties of water?

A
  • High specific heat capacity.
  • High latent heat of evaporation.
  • Very cohesive
  • Lower density when solid.
  • Good solvent.
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4
Q

High specific heat capcity of water means?

A
  • Provides a thermally stable aquatic habitat.
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5
Q

High latent heat of evaporation means?

A
  • When sweat evaporates, it helps to cool the surface of the skin.
  • This property means that water helps in temperature control of organisms.
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6
Q

Very cohesive means?

A
  • Helps water to be transported up plant stems in the transpiration stream.
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7
Q

Lower density when solid means?

A
  • Ice floats on top of liquid water.
  • Provides an insulating layer for the water underneath so that the organisms living in the water do not freeze.
  • Ice provides a habitat for some organisms such as polar bears.
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8
Q

Good solvent means?

A
  • Some substances can dissolve in it.

- Most biological reactions take place in solution, so water is essential for these reactions to occur.

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9
Q

What is a polar molecule?

A

A molecule with a slightly positively charged side and a slightly negatively charged side.

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10
Q

How does a positively charged ion dissolve in water?

A

The slightly negatively charged sides of water molecules are attracted towards the positive ion. This results in the ion being surrounded by water molecules.

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11
Q

What are macromolecules?

A 
Macromolecules are complex molecules with a relatively large molecular mass.
Includes:
- proteins
- lipids
- some carbohydrates.

Polymers are a group of macromolecules.

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12
Q

What are polymers?

A

Polymers are large complex molecules composed of long chains of monomers joined together.

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13
Q

What are monomers?

A

Small, basic molecular units.

Such as monosaccharides and amino acids.

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14
Q

How are polymers formed?

A

Most biological polymers are formed from their monomers by condensation reactions.

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15
Q

What is the result of a condensation reaction in polymerisation?

A

A condensation reaction forms a bond between monomers and also releases a water molecule.

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16
Q

How are polymers broken down?

A

Broken down by hydrolysis reactions.

A hydrolysis reaction breaks the chemical bond between monomers using a water molecule (opposite of a condensation reaction).

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17
Q

What are carbohydrates made from?

A
  • Most are polymers.
  • Elements involved are CHO.
  • Monomer is monosaccharides.

Single monosaccharides are also called carbohydrates.

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18
Q

Glucose

A

Glucose is a monosaccharide with 6 carbon atoms. It means that it is a hexose monosaccharide. 2 forms alpha and beta.

left to right OH:

alpha: down up down down
beta: down up down up.

  • Glucose is the main energy source in animals and plants.
  • It is soluble, so it can be easily transported.
  • Its chemical bonds contain a lot of energy.
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19
Q

Ribose

A

Ribose is a monosaccharide with 5 carbon atoms. It is a pentose monosaccharide.

It is the sugar component of RNA nucleotides.

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20
Q

How are polysaccharides formed?

A
  • Monosaccharides are joined together by glycosidic bonds.

- These bonds are formed in condensation reactions.

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21
Q

How are polysaccharides broken down?

A
  • By hydrolysis reactions.

- The glycosidic bond between monosaccharides is broken down using a water molecule.

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22
Q

What is a disaccharide?

A

A disaccharide is formed when two monosaccharides join together:

a glucose + a glucose = maltose
a glucose + fructose = sucrose
a/b glucose + galactose = lactose

glucose, fructose, galactose
maltose, sucrose, lactose.

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23
Q

What is a polysaccharide?

A

A polysaccharide is formed when more than 2 monosaccharides join together.

E.g:

  • amylose
  • amylopectin
  • glycogen
  • cellulose.
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24
Q

Starch

A
  • Main energy storage material in plants.
  • Insoluble in water; doesn’t cause water to enter cells by osmosis so cells do not swell. This makes it good for storage.
  • Composed of amylose and amylopectin.

Amylose:

  • a glucose monomer.
  • long, unbranched chain of a glucose.
  • coiled structure; makes it compact, making it good for storage.
  • 1,4 glycosidic bonds.

Amylopectin:

  • a glucose monomer.
  • long, branched chain of a glucose.
  • lots of branches means that glucose can be released quickly.
  • 1,4 and 1,6 glycosidic bonds.
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25
Q

Glycogen

A
  • Main energy storage material in animals.
  • a glucose monomer.
  • long, branched chain of a glucose.
  • similar structure to amylopectin, but with many more side branches.
  • lots of branches means that glucose can be released quickly.
  • compact molecule, so good for storage.
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26
Q

What is the function of glycogen and starch?

A
  • Glycogen acts as the main energy store in animals.

- Starch acts as the main energy store in plants.

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27
Q

Cellulose

A
  • Major component in plant cell walls.
  • Strong fibres means cellulose provides structural support for plant cells.
  • b glucose monomer.
  • long, unbranched chains of b glucose.
  • beta glucose molecules join to form straight cellulose chains (each adjacent b glucose molecule is inverted).
  • cellulose chains are linked together by hydrogen bonds to form strong fibres called microfibrils.
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28
Q

What are lipids?

A
  • They are macromolecules.
  • Elements: CHO
  • Triglycerides, phospholipids, cholesterol.
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29
Q

Triglycerides structure

A
  • 1 glycerol molecule, 3 fatty acid molecules attached.
  • Made by the formation of an ester bond between each fatty acid and the glycerol molecule.
  • Process in which triglycerides are made is called esterification.
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30
Q

Ester bonds

A
  • formed in a condensation reaction, where a water molecule is released.
  • broken in a hydrolysis reaction, using a water molecule. (Triglycerides break down when the ester bonds are broken).
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31
Q

Fatty acids

A
  • Fatty acid molecules have long hydrocarbon tails (C and H only).
  • Tails are hydrophobic (repel water molecules).
  • Causes lipids to be insoluble in water.

Saturated fatty acids:
- no double bonds between C atoms in their hydrocarbon tails.

Unsaturated fatty acids:
- have at least 1 double bonds between C atoms in hydrocarbon tail, causing the chain to kink.

32
Q

Phospholipids structure

A
  • similar to triglycerides, but one fatty acid molecule is replaced by a phosphate group.
  • phosphate head is hydrophillic, fatty acid tails are hydrophobic.
33
Q

Cholesterol structure

A

Hydrocarbon ring structure attached to a hydrocarbon tail. Ring has a polar OH group attached to it.

34
Q

Triglycerides function

A
  • Mainly used as an energy storage molecule in animals and plants.
  • some bacteria use triglycerides to store both energy and carbon.
  • Good for storage because the long hydrocarbon tails of the fatty acids contain lots of chemical energy (lots of energy is released when broken down).
  • lipids contain 2x as much energy per gram as carbohydrates.
  • Insoluble, so do not cause water to enter cells by osmosis which would make them swell.
  • triglycerides bundle together as insoluble droplets with the hydrophobic fatty acid tails facing inwards and the glycerol heads facing outwards.
35
Q

Phospholipids function

A
  • Found in cell membranes of all eukaryotes and prokaryotes.
  • They make up the phospholipid bilayer.
  • Cell membranes control what enters and leaves a cell.
  • Hydrophobic fatty acid tails face inwards away from water and hydrophilic phosphate heads face out towards the water on either side, forming a bilayer.
  • Centre of bilayer is hydrophobic (fatty acid tails), so water-soluble substances cannot pass through it directly (membrane acts as a barrier to water-soluble substances).
36
Q

Cholesterol function

A
  • In eukaryotes, cholesterol helps to strengthen the cell surface membrane by interacting with the phospholipid bilayer.
  • Cholesterol has a small size and flattened shape. Allows it to fit in between the phospholipid molecules in the membrane.
  • Cholesterol molecules bind to the fatty acid tails of the phospholipids, causing them to pack more closely together. Helps to make the membrane less fluid and more rigid.
  • Regulates the fluidity of the cell surface membrane.
37
Q

What are proteins made from?

A
  • Proteins are polymers.
  • amino acids are the monomers.
  • dipeptide forms when 2 AA join together, polypeptide when more than 2 AA.
  • Proteins are made from one or more polypeptides.
38
Q

Amino acids?

A
  • All AA have the same general structure.
  • Carboxyl group (COOH) and amino group (NH2) attached to a carbon atom.
  • Variable R group attached to same carbon atom. This is different for every AA.
  • Elements are CHONS.
39
Q

Elements in proteins?

A

CHONS

40
Q

How are dipeptides and polypeptides formed?

A
  • AA join together by peptide bonds, formed in a condensation reaction (water molecule is released).
41
Q

How are dipeptides and polypeptides broken down?

A
  • Peptide bonds between the AA are broken down in a hydrolysis reaction using a water molecule.
42
Q

Primary structure of a protein?

A

This is the sequence of amino acids in the polypeptide chain.

Bonds involved:
- peptide bonds.

43
Q

Secondary structure of a protein?

A

Alpha helix or Beta pleated sheet.

Bonds involved:
- Hydrogen bonds.

44
Q

Tertiary structure of a protein?

A

The final 3D structure of proteins made from a single polypeptide chain.

Bonds involved:

  • Hydrogen bonds
  • Ionic bonds
  • Disulfide bridges
  • Hydrophobic and hydrophilic interactions.
45
Q

Quaternary structure of a protein?

A
  • The final 3D structure of proteins made from more than one polypeptide chain.

Bonds involved:

  • Hydrogen bonds
  • Ionic bonds
  • Disulfide bridges
  • Hydrophobic and hydrophilic interactions.
46
Q

Globular proteins

A
  • round and compact
  • soluble, so they are easily transported in fluids.
  • they are fairly reactive.
47
Q

Globular protein example - Haemoglobin

A
  • Globular protein
  • Function is to carry oxygen around the body in red blood cells.
  • Also a conjugated protein. It means that it is a protein with a prosthetic group (non-protein group) attached.
  • Prosthetic group is haem group, which contains iron, which oxygen binds to.
  • Haemoglobin consists of 4 subunits - 2 alpha and 2 beta. Each subunit contains a haem prosthetic group.
48
Q

Globular protein example - Insulin

A
  • Hormone secreted by the pancreas.
  • It helps to regulate blood glucose level. (reduces blood glucose levels when they get too high).
  • soluble: it can be transported in the blood to the tissues where it acts.
  • consists of 2 polypeptide chains linked together by disulfide bonds.
49
Q

Globular protein example - Amylase

A
  • Enzyme that catalyses the breakdown of starch in digestive system.
  • Made from a single polypeptide chain.
  • Amylase’s secondary structure consists of both alpha helix and beta pleated sheet sections.
  • Most enzymes are globular proteins.
50
Q

What are the two types of proteins?

A

Globular proteins:

  • Haemoglobin (also a conjugated protein)
  • insulin
  • amylase (most enzymes are globular proteins).

Fibrous proteins:

  • Collagen
  • Keratin
  • elastin
51
Q

Fibrous protein example - Collagen

A
  • Found in animal connective tissues such as bone, skin and muscle.
  • Very strong/tough molecule with a rope-like structure.
  • Minerals can bind to collagen to increase rigidity.
52
Q

Fibrous protein example - Keratin

A
  • Found in many external structures of animals such as skin, hair, nails, feathers, horns.
  • Can be flexible, or hard and tough.
53
Q

Fibrous protein example - Elastin

A
  • Found in elastic connective tissue such as skin, large blood vessels, some ligaments.
  • Elastin is elastic so it allows tissues to return to their original shape after being stretched.
54
Q

Fibrous proteins

A
  • Tough
  • Strong
  • Insoluble
  • Rope-shaped
  • Fairly unreactive (unlike many globular proteins).
55
Q

Important cations

A
  • Ca2+
  • Na+
  • K+
  • H+
  • NH4+
56
Q

Important anions

A
  • NO3-
  • HCO3-
  • Cl-
  • PO43-
  • OH-
57
Q

What is Cl- a cofactor of?

A

Cl- is a cofactor of the enzyme amylase

58
Q

What is Zn2+ a prothetic group of?

A

Zn2+ is a prosthetic group for carbonic anhydrase

59
Q

What is a source of coenzymes?

A

Vitamins are a source of coenzymes.

60
Q

Name an ion that acts as a buffer in the blood

A

HCO3- Hydrogencarbonate.

61
Q

The biuret test

A
  • Test for proteins.
  • Add a few drops of sodium hydroxide solution to the test sample.
  • Add some copper(II) sulfate solution.
  • If protein is present, solution turns purple. If no protein is present, solution remains blue.
62
Q

The iodine test

A
  • Test for starch
  • Add iodine dissolved in potassium iodide solution to test sample.
  • If starch present, colour changes to orange-brown to blue-black. If no starch present, colour remains orange-brown.
63
Q

Emulsion test for lipids

A
  • Test for lipids.
  • Add ethanol to test sample and shake test tube.
  • Add water to the resulting solution.
  • If lipid is present, solution turns milky. If no lipids is present, solution remains clear.
64
Q

What are reducing sugars?

A
  • Includes all monosaccharides and some disaccharides.
65
Q

What are non-reducing sugars?

A
  • E.g sucrose
66
Q

The Benedict’s test for reducing sugars

A
  • Add benedict’s reagent to test sample and heat in a water bath.
  • If reducing sugar is present, there is a change from blue solution to brick-red precipitate.
67
Q

The Benedict’s test

A
  • If reducing sugars test is negative, non-reducing sugars may be present.
  • Add Hydrochloric acid to a new sample of test solution and heat in a water bath.
  • the purpose of the hydrochloric acid is to break the reducing sugars down into monosaccharides.
  • After, neutralise the solution with sodium hydrogencarbonate.
  • Then carry out the bendict’s test like before.
  • Add benedict’s reagent to test solution and heat in a water bath.
  • If solution remains blue, no non-reducing or reducing sugar present.
  • If solution turns from blue solution to brick-red precipitate, non-reducing sugar is present.
68
Q

Test strips for glucose

A

Glucose can also be tested using glucose test strips.

  • The strips are dipped in a test solution, and change colour if glucose is present.
  • The colour change can be compared to a colour chart to indicate the concentration of glucose present.
  • These strips are useful for testing urine for presence of glucose, which may indicate that the person has diabetes.
69
Q

Qualitative testing

A

You use qualitative testing to determine whether a substance is present in a sample or not.

70
Q

Quantitative testing

A

Quantitative testing tells you the concentration of a substance present in a sample.

  • colorimetry
  • biosensors
71
Q

Colorimetry and benedict’s reagent

A

You can use Benedict’s reagent and a colorimeter to get a quantitative estimate of the concentration of glucose in a solution.

  • A colorimeter is a device that measures strength of a coloured solution by seeing how much light passes through it.
  • It measures absorbance.
  • The more concentrated the colour of the solution, the higher the absorbance is.
72
Q

How to find the glucose concentration of an unknown solution?

A
  • Make up several solutions of known glucose concentrations (using serial dilution technique).
  • Measure the absorbance of each of these solutions.
  • Plot a graph of absorbance against glucose concentration to make a calibration curve.
  • The curve can be used to estimate the concentration of the unknown solution.
  • It is the easiest to measure the concentration of the blue Benedict’s solution that is left after the test.
  • The more glucose present, the paler the solution since more glucose reacted with the benedict’s solution to form the brick red precipitate which is removed.
  • Therefore, the higher the glucose concentration, the lower the absorbance of the solution.
73
Q

Biosensors

A

A biosensor is a device that uses a biological molecule, such as an enzyme, to detect a chemical.

  • The bio molecule produces a chemical signal, which is converted to an electrical signal by a transducer.
  • the electrical signal is then processed and used to work out other information.
74
Q

What is chromatography used for?

A

It is used to separate substances in a mixture. After separation, you can often identify the components.

Can often be used to separate out and identify:

  • amino acids
  • carbohydrates
  • vitamins
  • nucleic acids.
  • paper chromatography
  • thin layer chromatography.
75
Q

How do you calculate Rf values?

A

Rf = distance moved by solute / distance moved by solvent.

76
Q

How can you use Rf values to identify substances?

A

You can identify the substances in the mixture by comparing the calculated Rf values with known Rf values of the solutes in a database, or table of known values.

BIOLOGY A LEVEL 2022 FINAL (5 decks)

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