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(OCR A) - A-level Biology > 2.1.2 Biological molecules > Flashcards

2.1.2 Biological molecules Flashcards

1
Q

How is water a solvent?

A

Dissolves polar molecules

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2
Q

How is water a transport medium?

A

Capillary action due to cohesion and adhesion

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3
Q

What is cohesion between?

A

Water molecules

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4
Q

What is adhesion between?

A

Water molecules and vessel wall

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5
Q

What makes water a coolent?

A

High latent heat of evaporation (high boiling point)

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6
Q

Why is ice less dense than water?

A

Due to hydrogen bonding

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7
Q

What molecules do carbohydrates contain?

A

C, H, O

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8
Q

Examples of monosaccharides?

A
  • Glucose
  • Fructose
  • Galactose
  • Ribose
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9
Q

Examples of polysaccharides?

A
  • Glycogen
  • Cellulose
  • Starch
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10
Q

What units make up the disaccharide sucrose and which bond is involved?

A
  • Fructose + glucose
  • 1,6-glycosidic
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11
Q

What units make up the disaccharide lactose and which bond is involved?

A
  • Galactose + glucose
  • 1,4-glycosidic bond
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12
Q

Where is the OH in α-glucose?

A

Below carbon-1

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13
Q

Where is the OH in β-glucose

A

Above carbon-1

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14
Q

Why is glucose soluble in water?

A

Polar molecule due to hydrogen bonds that form between OH and water

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15
Q

What reaction MAKES glycosidic bonds

A

Condensation reaction (removal of water)

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16
Q

What units make up the disaccharide maltose and which bond is involved?

A
  • α-glucose + α-glucose
  • 1,4-glycosidic bond
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17
Q

What % of amylose is present in starch?

A

20-30%

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18
Q

What % of amylopectin is present in starch?

A

70-80%

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19
Q

What is the structure of amylose?

A

Linear chain of glucose units joined by α-1,4-glycosidic bonds

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20
Q

What is the structure of amylopectin?

A

Branched chain of glucose units joined by α-1,6-glycosidic bonds and α-1,4-glycosidic bonds

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21
Q

Why is it important for amylose and amylopectin to be able to coil into a spiral shape?

A

Makes it compact and less soluble

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22
Q

What is the structure of glycogen?

A

Branched chain of glucose units joined by α-1,6-glycosidic bonds and α-1,4-glycosidic bonds (more than amylopectin)

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23
Q

Where is glycogen normally found?

A

Liver and muscle cells

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24
Q

What reaction BREAKS glycosidic bonds?

A

Hydrolysis reaction (addition of water)

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25
What is the structure of cellulose?
Straight chain containing repeating units of β-glucose that alternate so OH groups are next to each other. Forms 1,4-glycosidic bonds
26
What makes cellulose suitable to be the cell wall of plants?
High tensile strength Insoluble Flexible
27
What molecules do lipids contain?
C, H, O
28
Why are lipids insoluble in water?
Non polar and hydrophobic fatty acids
29
What are triglycerides made up of?
Glycerol + 3 fatty acids
30
What bond forms between glycerol and fatty acids?
Ester bond (condensation reaction)
31
What state are saturated fats normally?
Solids
32
What state are unsaturated fats normally?
Liquids (oils)
33
What do phospholipids contain?
Hydrophilic phosphate head (PO43-) Hydrophobic fatty acid tails
34
Which parts of a phospholipid are hydrophobic and hydrophilic?
- Hydrophobic - fatty acid tail - Hydrophilic - phosphate head
35
Functions of phospholipids when interacting with water?
- Surfactant - Cell membrane bilayer
36
What are sterols?
Complex alcohol molecule with hydrophobic and hydrophilic properties
37
What is cholesterol?
A sterol which adds stability and regulates fluidity in between the phospholipids of a cell membrane
38
What can be manufactured using cholesterol?
Vitamin D, steroid hormones and bile
39
Differences between peptide hormones and steroid hormones?
Peptide hormone - Polar - Cannot pass through cell membrane - Attach to receptor Steroid hormone - Non polar - Lipid soluble - Pass through cell membrane
40
Roles of lipids?
- Membrane formation - Hormone production - Myelin sheath for electrical insulation - Thermal insulation - Cushioning
41
What molecules do proteins contain?
C, H, O, N
42
What functional groups does an amino acid contain?
Amine group Carboxyl group
43
What bond forms between amino acids?
Peptide bond (condensation reaction)
44
What is the primary structure in proteins?
Sequence in which amino acids are joined
45
What bonds are involved in the primary structure of proteins?
Peptide bonds
46
What is the secondary structure in proteins?
Amino acids pulled into either alpha helix or beta pleated sheet
47
What bonds are involved in the secondary structure of proteins?
Hydrogen bonds
48
What is the tertiary structure of proteins?
R-groups interact to fold protein into final shape
49
What bonds are involved in the tertiary structure of proteins?
- Hydrogen bonds - Hydrophilic and hydrophobic - Ionic bonds - Disulphide bonds
50
What is the quaternary structure of proteins?
Two or more proteins interact
51
What bonding is involved in quaternary structure of proteins?
- Hydrogen bonds - Hydrophilic and hydrophobic - Ionic bonds - Disulphide bonds
52
What is inulin’s quaternary structure?
Two identical subunits, disulphide bonding involved due to the presence of sulphur
53
What is haemoglobin’s quaternary structure?
Two different subunits (four in total): 2 alpha chains, 2 beta chains and haem group (Fe)
54
What are globular proteins?
Molecules which have a chemical function in living organisms and take part in specific reactions
55
What is the structure of globular proteins?
Rough spherical structure - hydrophilic groups outside and hydrophobic groups inside
56
What are the key features of globular proteins?
- Soluble in water - Compact
57
What is an example of a globular protein?
Insulin
58
What are conjugated proteins?
A globular protein that contains a prosthetic group
59
What is a prosthetic group?
Non protein component e.g. haem
60
What are examples of conjugated proteins?
Haemoglobin Catalase
61
What are fibrous proteins?
Molecules which have a structural role
62
What are the key features of fibrous proteins?
- Insoluble in water - Strong - Flexible (except in keratin)
63
What are examples of fibrous proteins?
Keratin Elastin Collagen
64
What are nitrate ions, NO3- necessary for?
Amino acid and protein formation
65
What are hydrogen carbonate ions, HCO3- necessary for?
Maintenance of blood pH
66
What are chloride ions, Cl- necessary for?
Cofactor for amylase
67
What are phosphate ions, PO43- necessary for?
- Cell membrane formation - Nucleic acid and ATP formation
68
What are hydroxide ions, OH- necessary for?
pH determination
69
What are calcium ions, Ca2+ necessary for?
- Nerve impulse transmission - Muscle contraction
70
What are sodium ions, Na+ necessary for?
- Nerve impulse transmission - Kidney function
71
What are potassium ions, K+ necessary for?
- Nerve impulse transmission - Stomatal opening
72
What are hydrogen ions, H+ necessary for?
pH determination
73
What are ammonium ions, NH4+ necessary for?
Production of nitrate ions by bacteria in the nitrogen cycle
74
What is the test for reducing sugars?
Benedict’s test - add copper II sulphate and heat
75
What are reducing sugars?
All monosaccharides and some disaccharides (maltose and lactose)
76
What is the positive result for a Benedict’s test?
Brick red precipitate
77
What is the negative result for a Benedict’s test?
Blue
78
What type of sugar is sucrose? (Non reducing or reducing)
Non reducing
79
What does a reagent strip show in the Benedict’s test to identify concentration of reducing sugars?
More reducing sugar = more precipitate so darker colour - Green - low concentration - Yellow - medium concentration - Red - high concentration
80
What is the test for starch?
Iodine test
81
What is the positive result for an iodine test?
Solution changes colour from yellow/brown to blue/black
82
What is the negative result for iodine test?
Solution remains yellow/brown
83
What is the test for lipids?
Emulsion test - mixing with ethanol and distilled water
84
What is the positive result for emulsion test?
White emulsion layer forms
85
What is the negative result for emulsion test?
Solution remains clear
86
What is the test for proteins?
Biuret test - copper ions in alkaline solution
87
What is the positive result for Biuret test?
Solution turn purple
88
What is the negative result for Biuret test?
Solution remains blue
89
What are the quantitive methods to determine concentration of a chemical substance in a solution?
Colorimeter Biosensors

(OCR A) - A-level Biology (26 decks)

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