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Biology OCR A > Chapter 3 Biological Molecules > Flashcards

Chapter 3 Biological Molecules Flashcards

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1
Q

Describe the structure of water

A

2 hydrogens and an Oxygen
Non linear shape
104.5 degree bond angle
Polar molecule

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2
Q

What are some properties of water (9) ?

A

Wide temperature as a liquid
Less dense when freezes (4 degree Celsius and above)
High latent heat of vaporisation
High Specific Heat Capacity
Polar
Cohesive
Adhesive
Solvent
Transparent
Adhesive

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3
Q

Why is water a liquid for a large range, and why does it expand when it freezes? Why is this important?

A

Hydrogen Bonds
Hydrogen bonds continually reforming and breaking, lots of energy to become a gas, and so liquid for a large range (high latent heat)
Important as allows water to be a habitat and transport

Hydrogen bonds place water molecules slightly further apart in solid than liquid as polar, meaning less dense
Important as ice as a layer of insulation

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4
Q

Why is water a solvent?

A

Polar molecule
Hydrogens (positive) would surround negative ions/ atoms
Oxygen (negative) would surround positive ions/ atoms

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5
Q

Why is water cohesive, adhesive and has surface tension? Why is it this important?

A

Polar molecule, attracted to each other so cohesive, and to other surfaces= adhesive
Helpful with capillary action (water against gravity) e.g xylem
At surface, water pulled inwards due to hydrogen bonds, surface tension= habitat

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6
Q

Why does water have a high SHC and latent heat? Why is this important ?

A

Hydrogen bonds absorb most of heat so no change in temp, and takes a lot of energy to break, so high latent
Important as high SHC means no change in temp, good habitat, stable
Latent allows water as a cooling system, absorb excess heat

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7
Q

What are the uses of water ?

A

Transport of substances e.g in plasma , as universal solvent
Coolant due to high latent, act as a buffer
Habitat due to hight SHC and more
Universal solvent

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8
Q

What are electrolytes?

A

Ions in solution

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9
Q

What are monosaccharides, disaccharides, and polysaccharides?

A

Monosaccharides- single sugars
Disaccharides- 2 sugars joined together
Polysaccharide- many sugars joined together

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10
Q

Name 3 Disaccharides and the monomers used

A

Glucose + Glucose = Maltose
Glucose + Galactose = Lactose
Glucose + Fructose= Sucrose

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11
Q

What is starch?

A

A complex polymer of alpha glucose molecules
Contains amylose- alpha glucose bonded with only 1-4 glycosidic bonds
And Amylopectin which contains both 1,4 and 1,6 (every 25 units) glycosidic bonds

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12
Q

Why is starch good for an energy store?

A

Bond angle of amylose forms a helix twisting, it is very compact- useful to allow lots of energy store in a small space
Amylopectin forms more branches allowing for hydrolysis quickly
The large size of the polymer makes it insoluble, necessary to maintain the water potential of the cell

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13
Q

What is glycogen? And why is it a good energy store?

A

The animal equivalent of starch, made of alpha glucose with 1,4 and 1,6 glycosidic bonds
It is more compact than amylopectin, requiring less space to store ideal for an energy stores, especially useful as animals are mobile
Coiling makes it compact
Many branches to quickly hydrolyse
Insoluble so does not affect cell water potential equilibrium

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14
Q

What is cellulose?

A

A straight lined polymer formed from beta glucose molecules, with alternate monomers rotated 180 degrees.
This is due to the positioning of the O-H group on the first carbon and otherwise, the O-H between monomers are too far apart to interact
Microfibres form, which form hydrogen bonds with each other to form macro fibres, then fibres.

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15
Q

What is the function of cellulose?

A

Used in cells wall
Provides strength to the cell and keeps it upright, like a Skeleton
Digestive system for humans

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16
Q

What is the test for sugars?

A

Add Benedict’s
Monosaccharides and some disaccharides are reducing sugars, act as reducing agents for Cu2+ ions
When reduced, turn to red, positive result

17
Q

What are lipids?

A

Fats/Oils, non polar
Known as macromolecules, built from repeating units

18
Q

What are triglycerides?

A

1 glycerol and 3 Fatty Acid chains
Held by ester bonds
Carboxylic acids with Alcohol

19
Q

What are saturated vs unsaturated fats?

A

Saturated= No. C=C, no linking, very compact, higher melting points, solids, so can be deposited in arteries
Unsaturated= Some C=C, kinking, less compact, liquids, oils, less likely to cause problems

20
Q

What are phospholipids?

A

One fatty acid replaced by a charged phospholipids ions.
Hydrophobic tails, Hydrophillic Head

21
Q

How do phospholipids arrange themselves in water?

A

Hydrophilic heads outwards in water as hydrophilic, charged. Tails face inwards, away from water, as hydrophobic

22
Q

What are sterols? What is the use of cholesterol?

A

Sterols are complex alcohols , with 4 carbon chains and a hydroxyl group, similar to phospholipids as they have both hydrophilic and hydrophobic regions
Cholesterol is positons between phospholipids in the cell surface membrane to prevent phospholipids grouping too close together, preventing crystallisation. Pulls membrane together with hydrophilic attracting hydrophilic and hydrophobic hydrophobic

23
Q

Role of lipids

A

Phospholipids- Membrane formation
Electrical insulation
Hormone production
Water Proofing

24
Q

Roles of triglycerides specifically

A

Thermal insulation
Cushioning of vital organs
Buoyancy

25
Q

Roles of Cations

A

Na+= Nerve impulse, Kidney
K+= Nerve Impulse, Stomatal Opening
Ca 2+ = Nerve Impulse, Muscle Contraction
NH4 + = Production of Nitrate ions by bacteria
H+ = Catalysis, pH

26
Q

Role of Anions

A

Nitrate- Amino Acids
HC03- and OH— pH
Phosphate - Cell membranes, Bones, Nucleic Acid
Cl- = Balance positive

27
Q

Why is water a good habitat?

A

High SHC and High Latent Heat of Vaporisation- provides a constant environment as lots of energy needed for temperature change and a large temperature range when liquid
Universal solvent, allowing oxygen to diffuse in

28
Q

Can shape change in haemoglobin and insulin?

A

Insulin has a fixed shape
Haemoglobin can change shape

29
Q

Why is glycogen used in human, relating to structure?

A

More branched, containing more FREE ENDS for quicker hydrolysis, glucose delivered more quickly
More coiled, so more compact, so MORE ENERGY STORE IN A GIVEN SPACE

Need all of this for 3 or 4 marks

30
Q

Why is glycogen used instead of glucose as an energy store?

A

Insoluble in water so prevents changing water potential, preventing lysis
Less METABOLICALLY active, not easily metabolised
Compact, meaning more of the energy store in a given volume

31
Q

What properties make cellulose useful as cell walls?

A

High Tensile strength
Unreactive
Flexible
Insoluble

32
Q

What are surfactants? Why are phospholipids an example of this?

A

Surface Active Agents- substances which decrease the surface tension, the phase between two mediums
The phosphate heads would be positioned into the water whilst the tails stick out

33
Q

What properties of sugars (monosaccharides) make them good energy stores?

A

High proportion of C-H bonds which contain energy, which can be broken down by respiratory enzymes into acetylcoA …
And lots of protons for chemiosmosis

Soluble so can move within the cell
Can form hydrogen bonds with water to aid with this

34
Q

What are the properties of triglycerides which make them good energy stores?

A

Highest proportion of C-H and C-C bonds (in fatty acid chains) compared to other biomolecules, which means a large amount of energy in a small space
Can be broken down into acetylCoA, enter the Kreb’s cycle and produce ATP via oxidative phosphorylation

Insoluble so does not affect water potential

Other roles in addition to storage such as cushioning and thermal insulation

35
Q

Do prokaryotes use triglycerides?

A

Some but not all
As a reserve energy store

36
Q

What is the structure of insulin?

A

Globular protein
Two long polypeptides joined by disulfide bridges
Constant shape

37
Q

How is starch broken down all the way to being absorbed?

A

First, glycosidic bonds hydrolysed forming maltose, catalysed by amylase
Then maltase catalyses hydrolysis of maltose into alpha glucose
Maltase present on the microvilli, immobilised, facilitated diffusion into blood stream

Biology OCR A (42 decks)

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