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AQA A-Level Biology > Chapter 1 - Biological Molecules > Flashcards

Chapter 1 - Biological Molecules Flashcards

1
Q

What are carbohydrates?

A

It’s an organic compounds made from carbon/hydrogen/oxygen

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2
Q

What types are there of carbohydrates? State in increasing the chain length

A
  • monosaccharides
  • Disaccharides
  • Polysaccharides
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3
Q

Describe a monosaccharide

A
  • ’simple sugar’
  • Same number of carbon as oxygen atoms
  • The general formula is (CH2O)n
  • White crystalline solids
  • dissolves in water
  • E.G glucoses, galactose and fructose
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4
Q

How are disaccharides formed?

A

By monosaccharides joining together by a condensation reaction producing 1 molecule of water with a glycosidic bond

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5
Q

Glucose + glucose ->
Glucose + fructose ->
Glucose + galactose ->

A
  • maltose
  • sucrose
  • lactose
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6
Q

How can disaccharides form monosaccharides?

A

Hydrolysis reaction - add water to disaccharides breaking the glycosidic forming monosaccharides

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7
Q

What are the two structures of glucose?

A
  • a-glucoses

* b-glucose

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8
Q

Describe what happens during hydrolysis of polysaccharide molecules

A

Water is added in suitable conditions causing the glycosidic bond to break to form the monosaccharide

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9
Q

What are all monosaccharides and some disaccharides?

A

They are reducing agents as they reduce other chemicals in the solution by gaining electrons. They can donate electrons/reduce another chemical.

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10
Q

What’s the benedicts reagent?

A

An alkaline solution of copper (II) sulfate

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11
Q

Describe how to detect a non-reducing sugar

A

1) hydrolysis into a monosaccharide
2) test with Benedict’s reagent
3) if no colour change add 2 cm³ of food sample to 2 cm³ of dilute HCL
4) then place in boiling water bath for five minutes. Slowly add sodium hydrogen carbonate solution until neutralised. Use universal indicator paper it should go from red to green
5) retest using Benedicks reagent, there should be a red precipitative of copper (I) oxide

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12
Q

Describe the test for reducing sugars

A

1) water bath should be at 70°C
2) have seven test tubes and label each one with the glucose concentration that’s going to be in them
3) add 1 cm³ of each concentration into the designated tube
4) then add 1 cm³ of Benedict solution into each tube
5) leave in the water bath for four minutes then make note of the colour change

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13
Q

What are the colour changes in the test for reducing sugars?

A

Blue to green to yellow to orange to brick-red. The more closer to red the more reducing agents present.

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14
Q

Describe the test for starch

A

1) add 1 cm³ of 1% starch to a tube
2) Then add 1 cm³ of iodine to the tube
3) The solution should turn blue/black

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15
Q

Which of the three carbohydrates are found in plant cells?

A

Starch and cellulose

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16
Q

Which of the three carbohydrates contain glycosidic bonds?

A

Starch, cellulose and glycogen

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17
Q

Which of the three carbohydrates contain beta glucose?

A

Cellulose

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18
Q

Describe lipids

A
  • they contain carbon, hydrogen and oxygen
  • they are non-polar molecules meaning they are insoluble in water
  • soluble in organic solvents
  • Generally water hating (hydrophobic)
  • Building blocks are fatty acids and glycerol
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19
Q

what are the types of lipids?

A
  • triglycerides

* phospholipids

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20
Q

Describe triglycerides lipids

A
  • reaction between fatty acid and glycerol by condensation reaction
  • glycerol molecules are always the same but fatty acids may vary
  • carboxyl group +hydroxyl group -> triglycerides + 3 molecules of water
  • Ester bond is formed
  • Hydrophobic as there are no spare oxygen molecules from water to form with hydrogen bonds
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21
Q

What is the function of triglycerides?

A
  • Energy source and the metabolic water source
  • fat as buoyancy aid (blubber is less dense than bone/muscle)
  • heat insulator
  • waterproofing
  • electrical insulation
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22
Q

Describe phospholipids

A
  • similar to triglycerides but The fatty acid molecule is replaced with a phosphate molecule
  • Phosphate molecule attracts water (hydrophilic)
  • extracellular - Hydrophilic head/hydrophobic tail
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23
Q

What is the function of phospholipids?

A
  • polar molecules formed bilayer with the surface membrane

* hydrophobic barrier between inside/outside cells

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24
Q

Describe the test for lipids (emulation test)

A
  • make sure completely dry and grease free test tube
  • 2 cm² of sample + 5 cm³ of ethanol
  • shake tubes to dissolve any lipid
  • Add 5 cm³ of water and shake gently
  • cloudy white colour in presence of water
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25
What does the amino acid structure contain?
* amine group * carboxyle group * variation of R group * hydrogen
26
How are proteins constructed?
• amino acid + amino acid by condensation reaction producing a protein and one molecule of water
27
Describe the primary structure of protein
• two amino acids come together by condensation reaction forming a dipeptide with a peptide bond
28
Name the two secondary structures of protein
* an alpha helix | * beta-pleated sheet
29
Describe an alpha helix protein
A polypeptide chain is twisted where a hydrogen bonds are formed between the double bonded carbon and oxygen of carboxl and the -NH of amine group
30
Describe a beta-pleated sheet protein
Several parallel chains linked together by hydrogen bonds
31
Describe a tertiary structure
Polypeptide chains folded to make a 3-D shape bond together by three types of bonds: •disulphide bridges •ionic bond •hydrogen
32
Describe a quaternary structure
Made by more than one polypeptide that may include non-protein molecules
33
Describe a globular protein
* spherical shape * hydrophilic side chains * e.g enzymes, antibodies and haemoglobin etc
34
Describe a fibrous protein
* formed by kind chains * cross links (hydrogen bonds) adding strength * insoluble * e.g keratin, collagen
35
Describe the test for proteins
A biuret test which detects peptide bonds 1) place a sample of solution to be tested in a test tube 2) add equal volume of Sodium hydroxide 3) add a few drops of dilute copper (II) sulfate 4) mix gently 5) purple colour indicates peptide bonds, hence protein
36
Describe the characteristics of an enzyme
* only changes rate of reaction * specific to one particular reaction * Biological catalysts (lowers activation energy) * enzymes are flexible
37
Describe the induced-fit hypothesis
If the Enzyme active site Is different to substrate molecule the enzyme can change slightly so that the substrate can form enzyme substrate complex. Then once the reaction is done the active site changes back to the original shape.
38
What proteins or enzymes?
Globular proteins - The active site is specific due to the tertiary structure of protein (including the three bonds)
39
An enzyme catalyse only one reaction. Explain why
Enzyme has a specific active site which only fits a specific substrate forming enzyme-substrate complex
40
What is the difference between the lock and key model and the induced fit model?
The locking key model has a specific substrate which only fits a specific active site. Whilst, the induced fit model differs as the active site can be flexible to fit the substrate
41
Define catabolic
Where the substrate is broken down
42
Describe anabolic
Where a molecule is built
43
What are the types of factors affecting enzyme action?
* Enzyme concentration * substrate concentration * temperature * pH
44
How does enzyme concentration affect the enzyme action?
The rate of reaction is directly proportional to the enzyme concentration. Assuming plenty of substrate molecules enzymes are the only limiting factor.
45
How does substrate concentration affect enzyme action?
the rate of enzyme, a controlled reaction increases substrate concentration up to certain point. V-max is the maximum rate of reaction as the enzymes become a limiting factor
46
How does temperature affect enzyme action?
* An increase in temperature, increases the kinetic energy which affects the rate of reaction. The kinetic energy increases the movement of substrate/enzyme which increases the chance of collision. Hence greater rate of this enzyme-substrate complex is formed. * IF, you increase the amount of substrate, it does not affect the rate of reaction * if temperature passes the optimum, The enzyme denatures as the vibration causes the breaking of the tertiary bonds
47
How does the pH affect the enzyme action?
The 3-D shape in enzymes have hydrogen bonds, which can be broken down by high concentrations of H+ ions which causes the shape to change meaning no enzyme-substrate complex can form
48
How can you work out the rate of reaction from a graph?
Use a tangent
49
Describe an enzyme inhibitor
* Occurs when action slowed down /stopped by another substance * Inhibitor combines an enzyme that stops it from forming enzyme-substrate complex
50
What are the two types of enzyme inhibitors?
* competitive inhibitor | * Non-competitive inhibitor
51
Describe a competitive inhibitor
The inhibitor is structurally similar to the substrate, hence competes directly with the substrate for the active site. If substrate concentration increases, it will it reduce the effects of the inhibitor
52
Describe a non-competitive inhibitor
The inhibitor binds to the enzyme with a site away from the active site. It alters the overall shape of the enzyme molecule including in the active site. Meaning the active site can no longer accommodate the substrate. If you increase the amount of substrate, it will have no effect.
53
What are the monomers of proteins?
Amino acids
54
What are the monomers of lipids?
They don’t have monomers
55
What are the monomers of carbohydrates?
Monosaccharides
56
Where is glycogen found?
Animals/bacteria
57
What are the monomers of glycogen?
Alpha glucose monosaccharides
58
What is the structure of glycogen?
* shorter chain, than starch * highly branched - more reaction (enzyme) * stores small granules in muscle/liver * insoluble * rapidly breaks down for respiration
59
What is the function of glycogen?
It’s a carbohydrate storage product
60
Where is starch found?
In plants
61
What are the monomers that form starches?
Alpha glucose monosaccharides
62
What is the structure of starch?
* made by glycosidic bonds of a condensation reaction * unbranched in to tight coils making it very compact * insoluble * large - no diffusion
63
What is the function of starch?
Energy source
64
Where is cellulose found?
In plants
65
What monomers form cellulose?
Beta glucose
66
What is the structure of cellulose?
* straight, unbranched chains running parallel to each other. * with hydrogen bonds form and cross links between adjacent chains * strong * groups together to make microfibrils * turgid - maximise surface area for photosynthesis
67
What is the function of cellulose?
cellulose cell walls prevent cell from bursting from osmosis. Exerts an inward pressure that stops influx of water
68
Define polysaccharides
Polymers formed by combining together many monosaccharide molecules
69
What is polymerisation?
Amino acid monomers being joined together in this process
70
What is a polypeptide?
The result of many hundreds of amino acid chains
71
What is an unsaturated fatty acid?
A hydrocarbon that has at least one double bond
72
What is a saturated fatty acid?
Hydrocarbon that Only has single bonds
73
What are the bonds found in carbohydrates?
Glycosidic bonds
74
What bonds are found in lipids?
Esters
75
What bonds are found in protein?
Peptide
76
Describe the structure and the adaptation to function in the cellulose molecules.
1. made from β-glucose; 2. joined by condensation / removing molecule of water / glycosidic bond; 3. 1 : 4 link specified or described; 4. “flipping over” of alternate molecules; 5. hydrogen bonds linking chains / long straight chains; 6. cellulose makes cell walls strong / cellulose fibres are strong; 7. can resist turgor pressure / osmotic pressure / pulling forces; 8. bond difficult to break; 9. resists digestion / action of microorganisms / enzymes;

AQA A-Level Biology (22 decks)

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