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A-level Biology > 2.2 Biological Molecules > Flashcards

2.2 Biological Molecules Flashcards

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1
Q

What type of molecule is water?

A

A polar molecule
It has a partially negative O atom and two partially positive H atoms

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2
Q

What is meant by Universal solvent?

A

Polar and charged molecules can dissolve in water meaning water can be used as a transport medium

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3
Q

What is meant by Cohesion?

A

The cohesive hydrogen bonds between molecules

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4
Q

What is meant by Adhesion?

A

The ability of dissimilar molecules to stick together

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5
Q

Why are cohesive forces important?

A

Surface tension between molecules allows small organisms to move along the surface
Allows columns of water to move through xylem vessels of plants and blood vessels of animals

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6
Q

Why is adhesion important?

A

Allows Capillary action: Hydrogen bonds with cellulose allows water to be transported up plant stems via a transpiration stream

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7
Q

What are proteins made of?

A

Amino acids

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8
Q

What are amino acids?

A

Monomer units

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9
Q

What is a condensation reaction?

A

When water is removed when two molecules/monomers join together

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10
Q

What is a hydrolysis reaction?

A

Water is added to split molecules apart

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11
Q

How is a dipeptide formed?

A

A peptide bond is formed between 2 amino acids, water is released (Condensation reaction)

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12
Q

Where is a peptide bond located?

A

Between two amino acids -
the C of the first amino acid and N of the second amino acid

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13
Q

What are the levels to protein structure?

A
  1. Primary structure: Amino Acid sequence
  2. Secondary structure: Polypeptide chain twists or folds
  3. Tertiary structure: More folding to form a complex shape
  4. Quaternary structure: More than one polypeptide chain joins together
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14
Q

Describe the secondary structure of a protein:

A
  1. Alpha Helix
  2. Beta Pleated sheet
    –> weak Hydrogen bonds maintains the structure
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15
Q

Describe the tertiary structure of a protein

A

Bonds between R-groups maintain structure
–> e.g. Ionic, Hydrogen, disulphide bridges

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16
Q

What is the structure and function of globular proteins?

A

Compact and soluble in water

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17
Q

What is the structure and function of fibrous proteins?

A

Long strands of polypeptide chains that have cross-linkages due to hydrogen bonds
These proteins have little or no tertiary structure
Insoluble
e.g. Keratin, Elastin, Collagen

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17
Q

What are conjugated proteins?

A

Proteins which contain an additional prosthetic group. Prosthetic groups assist proteins, for example in their structure or bonding.
e.g. Haemoglobin

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18
Q

What are the 3 types of lipids?

A

Triglycerides
Phospholipids
Steroids

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19
Q

Which elements make up lipids?

A

C,H,O

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20
Q

Are lipids soluble?

A

They are non-polar molecules so insoluble in water

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21
Q

What is the structure of a triglyceride?

A

1 molecule of glycerol
3 fatty acid chains

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22
Q

What bonds are found in a triglyceride?

A

Ester bonds

23
Q

What is the difference between saturated and unsaturated fatty acids?

A

Saturated fatty acids have single bonds between C atoms

Unsaturated fatty acids may have one or more sets of double bonds between carbon atoms

24
Q

What are the functions of triglycerides?

A

Energy source - stores more energy per gram than carbs or proteins
Insulation - blubber
Buoyancy
Protection

25
Q

What is the structure of a phospholipid?

A

Hydrophilic phosphate head
Diglyceride: Hydrophobic fatty acid tails

26
Q

What is the structure/functions of steroid alcohols?

A

4 carbon ring structure
Cholesterol

27
Q

What is the function of cholesterol?

A

Binds to hydrophobic tails of phospholipids, causing them to pack more closely together
Restricts the movement of phospholipids so makes the membrane less fluid - increases structure
Prevents solidification at low temps and melting at high temps

28
Q

What are the 3 types of carbohydrate?

A

Monosaccharides
Disaccharides
Polysaccharides

29
Q

What is the general formula for monosaccharides?

A

Cx
H2x
Ox

30
Q

What are the features of glucose?

A

Polar and soluble in water
Energy source

31
Q

What is the difference between alpha and beta glucose?

A

Alpha: C1 has the H on the top and OH on the bottom
Beta: C1 has OH on the top and H on the bottom

32
Q

What bond is formed between glucose molecules?

A

1,4-glycosidic bonds

33
Q

Which monomers make up maltose?

A

Glucose + Glucose

34
Q

Which monomers make up sucrose?

A

Glucose + Fructose

35
Q

Which monomers make up lactose?

A

Glucose + Galactose

36
Q

What is starch made from?

A

Amylose and amylopectin

37
Q

What are key features of starch?

A

1,4 and 1,6 glycosidic bonds
Highly branched
Insoluble so doesnt affect water potential
Storage molecule in plants

38
Q

What is the structure of amylose?

A

Long straight chain molecules
1,4-glycosidic bonds between alpha glucose molecules

39
Q

What is the structure of amylopectin?

A

Branched
1,4 and 1,6 glycosidic bonds

40
Q

What is the structure of cellulose?

A

Made of beta glucose
every other glucose molecule is flipped 180 to allow OH on C1 and C4 to be next to each other
No branching
Parallel strands form hydrogen bonds
Used in plants to form the cell wall

41
Q

What is the structure of Glycogen?

A

Alpha glucose
Branched chain
storage in animals
More dense than starch
Insoluble
Lots of 1,4 and 1,6 glycosidic bonds

42
Q

What is the test for starch?

A

Addition of iodine. Iodine turns blue-black when in contact with starch

43
Q

What is the test for proteins?

A

Biurets test

44
Q

What is the test for lipids?

A

Emulsion test

45
Q

What is the test for reducing sugars / non-reducing sugars?

A

Benedict’s solution
Blue copper 2+ ions are reduced to red copper 1+ ions in the presence of a reducing sugar e.g. glucose
Copper 1+ ions are insoluble and form a red precipitate

46
Q

What is the difference between hexose and pentose sugars and give examples of each

A

Hexose: Glucose - 6 C

Pentose: Ribose - 5 C

47
Q

What is the charge on a calcium ion and where is it used?

A

Cu2+
Transmission of impulses
Stimulation of muscle contraction
Regulates protein channels

48
Q

What is the charge on an iron ion and where is it used?

A

Fe2+ or Fe3+
Binds to oxygen in haemoglobin
Transfers electrons during photosynthesis/respiration

49
Q

What is the charge on a sodium ion and where is it used?

A

Na2+
Transport of glucose and amino acids
Transmission of nerve impulses

50
Q

What is the charge on a potassium ion and where is it used?

A

K+
Nerve transmission

51
Q

What is the charge on an ammonium ion and where is it used?

A

NH4 +
The intermediate ion that forms during the deamination of proteins in the liver and kidneys

52
Q

What is the charge on a nitrate ion and where is it used?

A

NO3 -
Provides an essential source of nitrogen for protein synthesis

53
Q

What is the charge on a hydrogencarbonate ion and where is it used?

A

HCO3 -
Transport of carbon dioxide in the blood

54
Q

What is the charge on a chloride ion and where is it used?

A

Cl-
Chloride-shift, maintaining the charge and pH balance in the blood

55
Q

What is the charge on a phosphate ion and where is it used?

A

PO4 3-
Stores energy in ATP

56
Q

What is the charge on a hydroxide ion and where is it used?

A

OH-
Bonding between molecules

A-level Biology (16 decks)

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