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A Level Biology > C1- Chemical elements and biological compounds. > Flashcards

C1- Chemical elements and biological compounds. Flashcards

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1
Q

What occurs when a plant experiences magnesium deficiency?

A
  • A condition known as chlorosis.
  • Magnesium makes chlorophyll and so is essential to photosynthesis.
  • Without it leaves go yellow and the plant experiences stunted growth.
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2
Q

What is an organic molecule.

A

A molecule with a high proportion of carbon atoms found within its structure.

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3
Q

Why is water being a solvent essential?

A

It is polar so its dipoles attract charged particles and can dissolve them (e.g. glucose) and transport them.

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4
Q

Explain how water is a metabolite.

A

It is used in many chemical reactions as a reactant. e.g. within the body it is used to hydrolyse maltose to form two glucose molecules.

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5
Q

How is water’s high specific heat capacity useful?

A

It prevents large fluctuations in temperature to maintain aquatic environments so organisms don’t have to adapt to extreme temperatures. It also allows enzymes in cells to work efficiently.

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6
Q

How is water having a high latent heat of vaporisation useful to organisms?

A

A lot of energy is needed to change liquid into vapour, this is useful when cooling bodies down as the thermal energy is used to evaporate water which is known as sweat.

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7
Q

Why is water being transparent useful?

A

Allows light to pass through to plants within it.

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8
Q

Describe the destiny of water compared to ice and how this is an advantage.

A

Ice is less dense than water due to the hydrogen boding holding the molecules apart. This means ice can float of water which protects the organisms living within it.

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9
Q

Describe cohesion in water.

A

Water molecules attract to each other forming hydrogen bonds. They’re weak individually, but together they form a lattice making them strong. The fact that they stick together allows them to be drawn up in the xylem of plants.

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10
Q

What are carbohydrates composed of?

A

Carbon, oxygen and hydrogen.

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11
Q

Name one unit, two units then multiple units of carbohydrates.

A
  • monosaccharide
  • disaccharides
  • polysaccharides
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12
Q

What is the formula of hexose sugars?

A

C6H12O6

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13
Q

Describe the structure of a-glucose then explain how B-glucose differs.

A 
CH2OH
        I   \_\_\_\_\_\_O              
        /                    \
      /                        \
     I\  OH                /I
 HO \I\_\_\_\_\_\_\_\_\_/  OH
                             I
                             OH
B- glucose is the same as above except for the OH on the first C is also arrange so that is upwards like on the third C.
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14
Q

Functions of monosaccharides.

A
  • Sources of energy in respiration to allow for the production of ATP.
  • Building blocks for larger molecules.
  • Intermediates in reactions.
  • Constituents of nucleotides.
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15
Q

Name the bond found in a disaccharide.

A

Glycosidic bond.

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16
Q

Name the bond found between two a-glucose molecules.

A

a-1,4- glycosidic bond.

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17
Q

Name the monosaccharides found in the following…

  • Maltose
  • Sucrose
  • Lactose
A
  • maltose = glucose + glucose
  • sucrose = glucose + fructose
  • lactose = glucose + galactose
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18
Q

Describe how to test for reducing sugars.

A
  • Add Benedict’s solution
  • Heat to at leat 70 degrees celsius
  • If it goes from blue to brick red a reducing sugar is present.
  • It works as the sugars donate an electron to the copper ions in copper sulphate, reducing it to red copper oxide.
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19
Q

Describe how to test for non-reducing sugars.

A
  • Break down to its constituent monosaccharides by heating with hydrochloric acid.
  • Benedict’s needs alkaline conditions to work so add an alkali.
    OR
  • Use an enzyme that hydrolyses it, although they’re specific so you’d have to use the correct one.

THEN

  • Add Benedict’s solution
  • Heat to at leat 70 degrees celsius
  • If it goes from blue to brick red a reducing sugar is present.
  • It works as the sugars donate an electron to the copper ions in copper sulphate, reducing it to red copper oxide.
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20
Q

How would you gain a quantitive measure of the sugar present?

A

Use a biosensor.

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21
Q

How is glucose suitably stored and what are the advantages of storing it int this way?

A

Glucose is stored as its polysaccharide starch.
The advantages of this are…
- Is insoluble so has no osmotic effect.
- Cannot diffuse out of the cell.
- Is a compact molecule and can be stored in a small space.
- Carries a lot of energy within its bonds.

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22
Q

Name the two forms of starch found within plants.

A
  • Amylopectin

- Amylose

23
Q

Describe Amylose.

A
  • linear
  • unbranched
  • a-1,4- glycosidic bonds
  • coils in an a-helix
24
Q

Describe Amylopectin.

A
  • branched
  • chains of glucose molecules joined with a-1,4- glycosidic bonds and cross linked with a-1,6- glycosidic bonds.
  • fits inside the amylose.
25
Q

How would you test for the presence of starch?

A

Use the iodide test…

  • Add iodine solution ( dine dissolved in aqueous potassium iodide).
  • If the colour changes from orange/ town to blow/black then starch is present.
26
Q

What is glycogen used for in animals and describe how it compare to amylopectin.

A

It is used to store glucose.

It is like amylopectin, but has shorter a-1,4- glycosidic bonds so is more branched.

27
Q

Describe the structure of cellulose.

A
  • parallel chains of B-glucose.
  • joined by B-1,4- glycosidic bonds.
  • the B-link rotates adjacent glucose molecules by 180 degrees- contributes to structural stability.
  • many cellulose molecules become tightly cross linked forming microfibrils.
  • microfibrils are held in bunches called fibres.
  • Cell walls are made of many fibres that run parallel to each other, but at an angle to adjacent layers.
28
Q

Describe chitin.

A
  • Similar structure to cellulose but has groups derived from amino acids.
  • strong
  • waterproof
  • lightweight
  • found in the exoskeleton of insects and fungal cell walls.
29
Q

What do lipids contain?

A

Oxygen, hydrogen and carbon.

In proportion to the carbon and hydrogen the levels of oxygen are much lower.

30
Q

Describe the structure of triglycerides.

A
  • One glycerol molecule and three molecules of fatty acids.
  • The fatty acid component can vary, but the glycerol is always the same.
  • The fatty acids are joined to the glycerol by a condensation reaction producing three water molecules. The bond formed between the two is called an ester bond.
31
Q

Describe the structure of phospholipids.

A
  • one end is soluble in water the other is not.
  • The end of the molecule with the glycerol group and phosphate is hydrophilic and called the polar head.
  • The end of the molecule with the two fatty acids and containing no oxygen molecules is hydrophobic so is non-polar.
32
Q

Describe the properties of waxes.

A
  • melt above 45 degrees celsius

- have a waterproofing role

33
Q

How does the structure of fats differ from that of oils?

A
  • The hydrogen carbon chain of fats is fully saturated with hydrogen atoms (saturated fatty acids). It is a straight zigzag. Remains solid at body temperature so is used for storage.
  • The hydrocarbon chain of oils is unsaturated and the chain gets a kink at the point of the double bond. Hence they remain liquid at rom temperature. On double bond means it’s monounsaturated, two or more means it’s polyunsaturated.
34
Q

Describe the roles of phospholipids.

A
  • In biological membranes.

- Electrical insulation- myelin sheath that surrounds nerve cells.

35
Q

Describe the roles of triglycerides.

A
  • energy reserves in plants and animals as contains more carbon and hydrogen bonds.
  • thermal insulation when stored under the skin.
  • protection- surrounds internal organs to protect against physical damage.
  • produces metabolic water when oxidised.
36
Q

How do you test for fats and oils.

A
  • The emulsions test.
  • The sample tested is mixed with absolute ethanol to dissolve lipids present.
  • It is shaken with an equal volume of water which causes the insoluble lipids to come out of the solution.
  • They form an emulsion, making the sample cloudy white.
37
Q

Fatty deposit in the coronary arteries is called…

A

atherosclerosis

38
Q

high blood pressure is called…

A

hypertension

39
Q

What occurs if a diet is high in saturated fats?

A
  • low-density lipoproteins (LDL) build up.
  • atheroma builds up in the coronary arteries.
  • this restricts blood flow to the heart.
  • can result in angina, myocardial infarction or a heart attack.
40
Q

What occurs if a diet is high in unsaturated fats?

A
  • high-density lipoproteins (HDL) build up.

- they carry harmful fats to the liver for disposal

41
Q

What are proteins composed of?

A

Hydrogen, carbon, oxygen and nitrogen.

42
Q

What are the monomers that form a polymer that make proteins?

A

Amino acids.

43
Q

Describe the basic structure of amino acids.

A
  • NH2 at the end of the molecule- amino group
  • COOH at the other end of the molecule- carboxyl group
  • a hydrogen atom off the central carbon
  • the R group which is different on each amino acid
44
Q

What occurs to amino acids at pH7.

A
  • They become zwitterions.
  • The amino group gains a H and becomes positively charged.
  • The carboxyl group loses a H and becomes negatively charged.
45
Q

What is the bond formed between two amino acids?

What is the new compound formed?

A

A peptide bond forms between two amino acids, the resulting compound is a dipeptide, a molecule of water is also produced.

46
Q

What is the primary structure of a protein?

A
  • This is the order of amino acids in the polypeptide chain.

- It is determined by the base sequence on one strand of DNA molecule.

47
Q

What is the secondary structure of a protein?

A
  • The shape the polypeptide chain forms as a result of hydrogen bonding between =O and -CO groups and -H and -NH groups.
  • This causes it to twist into a 3D shape.
  • This could be a-helix or B-pleated.
48
Q

What is the tertiary structure of a protein?

A
  • The secondary protein structure can be further folded and twisted to give a more complex, compact 3D structure.
  • The shape is maintained by hydrogen, ionic and disulphide bonds as well as hydrophobic interactions.
  • They’re important in giving globular proteins shape.
49
Q

What is the quaternary structure of proteins?

A
  • Some polypeptide chains are only functional in combination.
  • They can combine with another polypeptide chain or be associated with non-protein groups.
50
Q

Describe fibrous proteins.

A
  • long, thin molecules.
  • insoluble in water due to their shape
  • polypeptides in parallel sheets with many cross linkages.
  • form long fibres.
  • fibrous so strong and tough.
51
Q

Describe the structure of collagen.

A
  • a fibrous protein.
  • strong and tough- needed in tendons.
  • a single fibre (tropocollagen)- three identical polypeptide chains wound around each other like a rope- linked by hydrogen bonds so stable.
52
Q

Describe globular proteins.

A
  • folded into spherical molecules.
  • soluble in water
  • functions include antibodies, plasma proteins and hormones.
53
Q

Describe the structure of haemoglobin.

A
  • globular protein
  • four folded polypeptide chains
  • at the centre has an iron-containing group (heam).
54
Q

How can you test for protein?

A
  • add a few drops of biuret reagent (sodium hydroxide and copper sulphate).
  • sodium hydroxide and copper sulphate react to produce blue copper hydroxide.
  • this interacts with the peptide bonds in the protein to make biuret which is purple.
  • the darker the purple the more protein present.
  • to determine a more accurate result from a test use a colorimeter to determine the concentration or a biosensor.

A Level Biology (10 decks)

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