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Biology OCR > Biological Molecules > Flashcards

Biological Molecules Flashcards

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1
Q

Why is water polar ?

A

Oxygen is more electronegative than hydrogen, so electrons are more strongly attracted to oxygen. Oxygen is slightly negative and hydrogen slightly positive

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2
Q

How do hydrogen bonds form between water molecules ?

A

The slightly negative oxygen atom from one water molecule is attracted to the slightly positive hydrogen end of another water molecule

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3
Q

6 properties of water

A
  • Density based on temperature
  • High surface tension
  • Universal solvent
  • High Specific heat capacity
  • High latent heat of vaporisation
  • Cohesion and adhesion
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4
Q

Why does ice float on water ?

A

Ice is less dense than water because Hydrogen bonds hold molecules in a fixed position further away from each other
Insulates water to stop it from freezing

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5
Q

Why is the high surface tension of water important for organism ?

A

Slows water loss due to transportation in plants
Water rises unusually in narrow tubes, lowering demand on root pressure
Some insects can skim across the surface of water

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6
Q

Why is water being a universal solvent important for organisms ?

A

Many ions and covalently bonded polar substances will dissolve in it
Allows chemical reactions to occur within cells
Metabolites can be transported efficiently

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7
Q

Why is water having a high specific heat capacity important ?

A

Large amounts of energy is required to change the temperature
Water is able to maintain a constant temperature, which is vital for maintains temperatures optimal for enzyme activity

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8
Q

Why is water having a high latent heat of vaporisation important ?

A

A lot of energy is needed to change state, which means only a small amount of water is required to evaporate for the organisms to loose a lot of heat
- Provides a cooling affect A lot of energy is needed to change state, which means only a small amount of water is required to evaporate for the organisms to loose a lot of heat
- Provides a cooling affect

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9
Q

Why is water having a high cohesion and adhesion important ?

A

Cohesion - Allows water to move through the xylem of plants and through blood vessels
Adhesion - Enables water to move up the xylem

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10
Q

How are polypeptides formed?

A

Condensation reactions between amino acids forming peptide bonds
Refer to GoodNotes

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11
Q

What is the Primary Structure of Protein ?

A

Order of amino acid sequence
Formed by covalent peptide bonds

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12
Q

What is the Secondary Structure of Protein ?

A

Folding into repeat patterns (α-helix or β-pleated sheet)
By hydrogen bonds between amine and carboxyl groups

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13
Q

What is the Territary Structure of Protein ?

A

Overall three-dimensional arrangement of a polypeptide
Determined by interactions between variable side chains

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14
Q

What bonds are involved in the tertiary structure of protein ?

A

Hydrogen Bonds
Ionic Bonds - Between charged r groups
Disulphide bridges - Strong covalent bonds

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15
Q

What is the Quaternary Structure of Protein ?

A

Presence of multiple polypeptides or prosthetic groups

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16
Q

What are Conjugated Proteins ?

A

A protein that consists of a protein combined with a non-protein. The non-protein group is called a prosthetic group

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17
Q

What is the molecule shape of fibrous Proteins ?

A

Long chains running parallel to each other

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18
Q

What is the molecule shape of Globular Proteins ?

A

Compact and rounded shape

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19
Q

What is the solubIlity of Fibrous Proteins ?

A

Insoluble in Water

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20
Q

What is the solubIlity of Globular Proteins ?

A

Soluble in water

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21
Q

What is the bonding of Fibrous proteins ?

A

Chains linked by disulphide cross bridges , making proteins very strong and stable

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22
Q

What is the bonding of Globular proteins ?

A

Hydrophobic groups point into the centre of molecules away from water

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23
Q

What are the functions of Fibrous Proteins ?

A

Structural
(Keratin,Collagen)

24
Q

What are the functions of Globular Proteins ?

A

Functional
(Enzymes,Haemoglobin)

25
Q

Describe the properties of Alpha Glucose

A

Small and water soluble
- Easily transported in the bloodstream

26
Q

How do dissacharides form ?

A

When 2 monosaccharides are bonded together by glycosidic bonds

27
Q

How do polysaccharides form ?

A

When many monosaccharides are joint together by glycosidic bonds

28
Q

What are 3 examples of monosaccharides ?

A

glucose, fructose, galactose

29
Q

What are 3 examples of disaccharides ?

A

Maltose (Glucose + Glucose)
Sucrose (Glucose + Fructose)
Lactose (Glucose + Galactose)

30
Q

What are 3 examples of polysaccharides ?

A

starch, glycogen, cellulose

31
Q

What is the structure of starch ?

A

Constructed of two different polysaccharides
Amylose - Linear with 1-4 glycosidic bonds between alpha glucose (Compact)
Amylopectin - Branched with 1-4 and 1-6 glycosidic bonds between alpha glucose

32
Q

What is the structure of glycogen ?

A

1-4 and 1-6 glycosidic bonds between alpha glucose, Highly branched

33
Q

What is the structure of Cellulose ?

A

Linear 1-4 glycosidic bonds between Beta-Glucose molecules
Beta Molecules must rotate 180°, which causes many hydrogen bonds to form giving it strength

34
Q

What is the function of starch ?

A

Storage in plants

35
Q

What is the function of Glycogen ?

A

Storage molecule in the liver

36
Q

What is the function of Cellulose ?

A

Main structural component in cell walls

37
Q

What happens in a condensation reaction ?

A

A chemical bond forms between 2 molecules & a molecule of water is produced

38
Q

What happens in a hydrolysis reaction ?

A

A water molecule is used to break a chemical bond between 2 molecules

39
Q

What is the structure of Amino Acids ?

A

Refer to GoodNotes
-COOH carboxyl / carboxylic acid group
- R Variable side group consists of carbon chain & may include other functional groups e.g. benzene ring or -OH (alcohol)
-NH² amine/amino group

40
Q

How do triglycerides form ?

A

Condensation reaction between 1 molecule of glycerol & 3 fatty acids forms ester bonds
Refer to GoodNotes

41
Q

Describe saturated fatty acids

A

Contain only single bonds
Straight-Chain molecules have many contact points
Higher melting point = Solid at room temperature
Found in animal fats

42
Q

Describe Unsaturated fatty acids ?

A

Contain C=C double bonds
‘Kinked” molecules have fewer contact points
Lower melting point = Liquid at room temperature
Found in plant oils

43
Q

Relate the structure of triglycerides to their functions

A

Insoluble hydrocarbon chain - Used for waterproofing
Slow conductor of heat - Thermal insulation
Less dense than water - Buoyancy of aquatic animals

44
Q

Describe the structure of phospholipids

A

Glycerol backbone attached to 2 hydrophobic fatty acids tails & a hydrophilic polar phosphate head

45
Q

What is the function of phospholipids ?

A

Forms a phospholipid bilayer - Plasma Membrane
Tails can act as waterproofing

46
Q

Are phospholipids and triglycerides polymers ?

A

No, they are not made from small repeating units. They are macromolecules

47
Q

Describe the structure of cholesterol

A

Structure of 4 hydrocarbon rings.
Hydrocarbon tail on one side, hydroxyl group on the other side

48
Q

What is the function of cholesterol ?

A

Affects the fluidity and permeability of the cell membrane

49
Q

How to test for proteins ?

A

Biuret tests
- Add (equal volume) of soidum hydroxide to sample
- Add drops of dilute copper (II) sulfate solution
- Positive result: Colour changed from blue to purple
Negative result: Remains blue

50
Q

How to test for lipids ?

A

Dissolve solid samples in ethanol
Add (equal volume) water and shake
Positive result: Milky white emulsion forms

51
Q

How to test for reducing sugars ?

A
  • Add (Equal Volume) of Benedict’s reagent to a sample
  • Heat the mixture in a water bath at 100 degrees for 5 minutes
  • Positive result: Colour change from blue to orange, brick red precipitate forms
52
Q

How to test for non-reducing sugars ?

A
  • Hydrolyse non reducing sugars e.g. sucrose into their monomers by adding 1cm3 of hydrochloride acid. Heat in a boiling water bath for 5 minutes
  • Neutralise the mixture using sodium carbonate solution
  • Proceed with normal Benedict’s test
    Negative result: Benedict’s reagent remains blue
53
Q

What is the test for starch ?

A
  • Add iodine solution
  • Positive result: Colour change to Blue-Black
54
Q

Draw the structure of Alpha and Beta Glucose

A

Both hexose monosaccharides (6C) with ring structure
Refer to GoodNotes

55
Q

Draw the structure of ribose

A

Pentose monosaccharides (5C)

Refer to good notes

Biology OCR (25 decks)

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