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Biology a level - ocr a > Chapter 3 Biological Molecules > Flashcards

Chapter 3 Biological Molecules Flashcards

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1
Q 
Elements present in: 
Carbohydrates 
Lipids 
Proteins 
Nucleic acids 
Phospholipid
A

Carbon, hydrogen, oxygen
Carbon, hydrogen, oxygen
Carbon, hydrogen, oxygen, nitrogen, sulphur
Carbon, hydrogen, oxygen, nitrogen, phosphorous
Carbon, hydrogen, oxygen, phosphorous

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2
Q

What is the structure of water?

A
  • H-O-H
  • the distribution of electrons between the covalently bonded atoms is not equal
  • causing a slightly negative charge on oxygen and slightly positive charge on hydrogen
  • the negative oxygen attracts the hydrogen of other water molecules
  • this attraction is hydrogen bonding
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3
Q

Why do hydrogen bonds give water a high specific heat capacity and latent heat?

A

The hydrogen bonds can absorb a lot of energy
It takes a lot of energy to heat the hydrogen bonds

It takes a lot of energy to break the hydrogen bonds between water
- when sweat evaporates it cools the skin

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4
Q

What is cohesion (water)?

A

Cohesion is the attraction between molecules of the same type

Water is very cohesive because it is polar
This helps water to flow - making it good for transport
Causes water to move as a mass

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5
Q

Why does waters polarity make it a good solvent?

A

Because water is polar, the slightly negative/positive ends will be attracted to the negative and positive ions
This means the ions will get totally surrounded and dissolve
Transports useful ions around the body

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6
Q

Why is water less dense when it is solid?

A

When water freezes the hydrogen bonds fix the position of polar molecules further apart in a
Giant
Open lattice structure

Allows ice to float

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7
Q

What are carbohydrates?

A

Molecules that contain oxygen, carbon and hydrogen

Can be broken down into glucose so that energy can be transferred to ATP through respiration

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8
Q

What is a monosaccharide?

A

A single sugar unit

Glucose, sucrose, galactose, ribose

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9
Q

What is a disaccharide?

A

Formed from 2 monosaccarides

G + G = maltose
G + S = fructose
G + G = lactose

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10
Q

What is a polysaccharide?

A

Polymers made of 2 or more monosaccharides

Glycogen, starch, cellulose

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11
Q

Glucose

Alpha

Beta

A

Alpha - c1 = c4
Beta - c1 / c4

CH2OH - c6

Glucose = polar and soluble in water - hydrogen bonds between hydroxyl group and water

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12
Q

Alpha glucose condensation

Glucose + glucose –> maltose + water

A

1,4 glycosidic bond

2 hydrogens and 1 oxygen is removed to form water

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13
Q

Glycosidic bonds

Amylose (poly alpha glucose)
Amylopectin
Glycogen (alpha)
Cellulose (beta)

A

1,4 (unbranched)
1,4 + 1,6
1,4 + 1,6
1,4 (unbranched)

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14
Q

What is a reducing sugar?

A

Saccharides that can donate electrons or reduce another molecule or chemical

Monosaccharides

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15
Q

Testing for carbohydrates (reducing sugars)

A

Benedicts test

  • put liquid sample in boiling tube
  • add equal volume of benedicts reagent
  • heat in a boiling water bath for 5 mins
  • reducing sugars react with copper ions - less blue colour
  • blue green yellow red precipitate colour scale
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16
Q

Testing for carbohydrates (non-reducing)

A
  • sucrose is boiled with dilute HCL
  • hydrolysed it into fructose and glucose which are reducing sugars
  • add equal volumes of Benedicts reagent
  • boiling water bath
  • colour precipitate
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17
Q

Iodine test for starch

A
  • add drops of potassium iodine into the solution

- If starch is present solution changes from yellow/brown to purple/black

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18
Q

Using the colorimeter to measure the absorbante of light by a coloured solution

A 
Filter added 
Calibrated with water 
Benedict's test 
Resulting solutions filtered 
The transmission percentage is measured 
Calibration curve plotted 
3/6 repeated for unknown solution
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19
Q

What are lipids?

A

Hydrogen, carbon, oxygen

Group of large complex molecules with a large molecular weight

GLYCEROL + FATTY ACIDS

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20
Q

Functions of lipids (7)

A 
Membrane formation 
Hormone production 
Electrical insulators 
Waterproofing 
Thermal insulation 
Cushions vital organs 
Buoyancy
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21
Q

What is a triglyceride?

A

Glycerol + 3 fatty acids

The hydroxyl groups interact creating 3 water molecules and ester bonds between the glycerol and fatty acids

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22
Q

What are saturated and unsaturated fatty acids?

A

Saturated = no double bonds - fats = solids, closer together

Unsaturated = double bonds - oils = kink so they can’t pack as close together

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23
Q

What are phospholipids?

A

Has a phosphate group covalently attached to third hydroxyl group of the glycerol replacing a fatty acid

Glycerol + phosphate group + 2 fatty acids

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24
Q

What are the qualities of phospholipids?

A

They have a hydrophilic head and hydrophobic tails
Forms a bilayer
Separates the aqueous environment
Water soluble molecules can’t pass through

Surfactants - lower the surface tension of water

25
Q

What is the structure of cholesterol?

A

Hydrophobic
Four carbon ring structure
Hydrocarbon chain

A hydrophilic hydroxyl group

26
Q

What is the role of cholesterol?

A

Maintains the fluidity of the cell membrane and integrity
Stabilises the membrane
Reduces permeability to some soultes

27
Q

Identification of lipids

A

Emulsion test

Mix sample with ethanol then with water and shake
If white emulsion forms on top a lipid is present

28
Q

What are peptides?

A

Polymers made up of amino acids - proteins are one or more polypeptides

29
Q

What are ….. amino acids?
Non essential
Essential
Conditionally essential

A

All have different R groups

  • our body can make them from other amino acids 5
  • can only be obtained from what we eat 9
  • only needed by infants 6
30
Q

Synthesis of peptides

A

Amino acids join when the amine and carboxylic acid groups react through condensation reactions
OH from carboxylic and H from amine = water

Peptide bond formed between amino acids = dipeptide

31
Q

What enzyme catalyses polypeptide synthesis?

A

Peptidyl transferase

32
Q

Separating amino acids using TLC

A

The rate the organic solvent moves depends on the interactions they form with the silica stationary phase

  • silica gel is applied to the surface
  • draw pencil line and spot the amino acids onto the line
  • place plate into a jar containing the organic solvent
  • remove plate and draw a line on the solvent front
  • plate is sprayed with NINHYDRIN SPRAY- amino acids turn brown
  • RF = component distance/ solvent front
33
Q

Levels of protein structure

Primary structure

A

The sequence in which the amino acids are joined

Bonds
- peptide

34
Q

Secondary structure

A

Local folding of the polypeptide chain into
alpha helix or
beta pleated sheet - parallel polypeptide chains

Bonds
- hydrogen bonds form within the amino acid chain

35
Q

Tertiary structure

A

The folding of the protein into its final shape
- the coiling or folding of secondary structure brings the the R groups closer together so they interact

R group interactions:

  • weak interactions = polar and non polar R groups- hydro
  • hydrogen bonds
  • ionic bonds = opposite charged R groups
  • disulfide bonds = only form between R groups that contain sulfure atoms
36
Q

Quaternary structure

A

Results from the association of two or more individual proteins called subunits

Between different protein molecules

37
Q

What enzyme catalysés the breakdown of peptides?

A

Proteases

38
Q

Identification of proteins

A

Biuret test

  • 3cm of liquid sample is mixed with equal volumes of 10% NaOH solution
  • 1% copper sulfate drops are added until the sample students blue
  • leave for 5 mins
  • if it changes lilac peptide bonds are present
39
Q

What are globular proteins?

A
  • compact, water soluble and spherical
  • the tertiary structure is folded so that the hydrophilic r groups are on the outside of the protein and the hydrophobic r groups are kept away from the aqueous environment

Soluble in water

40
Q

Examples of globular proteins… (insulin)

A

Insulin - hormone - regulation of blood glucose levels

Need to be soluble because are transported in the bloodstream
Fit in receptors on the cell membrane so need to be a specific shape
2 polypeptide chains with disulfide bonds

41
Q

What are conjugated proteins?

A

Globular proteins that contain a non protein component called prosthetic group

42
Q

Examples of conjugated proteins (haemoglobin)

A

Haemoglobin

Red oxygen carrying pigment found in blood cells
Quaternary protein made from 2 alpha and 2 beta subunits
prosthetic groups is called haem
each haem contains iron
oxygen binds to iron

43
Q

Examples of conjugated proteins (catalase)

A

Enzyme
Quaternary group containing 4 haem groups
The presence of iron II ions allow it to interact with hydrogen peroxide and speed up its breakdown

*Hp- byproduct of metabolism that is damaging to cells

44
Q

What are fibrous proteins?

A

Formed from long insoluble molecules - have a lot of hydrophobic r groups of amino acids in primary structure

Amino acid sequence is repetitive = organised structures

Contain a limited range of amino acids with small r groups

Not folded into complex 3D shapes unlike globular

45
Q

Examples of fibrous proteins

Collage

A

Collagen
- made up of 3 polypeptides wound together in a rope structure

connective tissue
- bone, skin, muscle

46
Q

How are nucleotides linked together?

A
  • condensation reactions
  • phosphodiester bonds formed when phosphate group on the 5th carbon of the pentose sugar forms a covalent bond with the hydroxyl group on the 3rd carbon of the adjacent sugar
47
Q

DNA EXTRACTION

A

1) use blender to break up the sample
2) mix the sample with detergent - break the cell membrane
3) add salt - break the hydrogen bonds between DNA and water
4) incubate the solution in a water bath
5) cool down and filter
6) add protease enzymes to mixture = break down proteins bound to DNA
7) add a layer of cold ethanol
* DNA white precipitation removed with rod

48
Q 
Glycosidic 
Ester 
Peptide 
Hydrogen 
Phosphodiester
A 
Disaccharides 
Glycerol + fatty acids 
Between amino acids 
Between water molecules 
Between nucleotides
49
Q

What is the role of rRNA?

A

Plays a biochemical role in catalysing the reaction

Maintains the structural stability of the protein synthesis sequence

50
Q

What is the role of tRNA?

A

Transfer RNA

A strand of RNA folded in a way that 3 bases are exposed (anticodon)
They carry an amino acid corresponding to that codon to form the amino sequence chain that forms the primary structure of the protein

51
Q

What is mRNA?

A

Carries mRNA to the site of protein synthesis

52
Q

What are the steps of translation?

A

The mRNA binds to the small sub unit of ribosome
The tRNA with the complementary anticodon binds to the mRNA and carries the amino acid
Another tRNA binds to and carries the next codon
The first amino acid is transferred to the second amino acid by the formation of peptide bonds which is catalysed by peptidyl transferase , which is an rRNA component

53
Q

Why do cells require energy?

A

For synthesis
For movement
For transport

54
Q

Atp

A

Nitrogenous base (always adenine)
Pentose sugar
3 phosphate groups

55
Q

How atp releases energy

A

Hydrolysed into adp - supplies energy

56
Q

Properties of ATP

A

Small
Water soluble
Releases energy
Easily regenerated

57
Q

Example of fibrous proteins

Keratin

A

Keratin
- large portion of sulfur containing amino acid
= disulfide bonds = strong

can be either flexible or hard
- hair , nails

58
Q

Example of fibrous protein

Elastin

A

Elastin

  • quaternary protein made from stretchy tropoelastin molecules
  • gives flexibility to vessel walls

found in elastic connective tissue
- skin, vessels

Biology a level - ocr a (11 decks)

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