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OCR ALEVEL BIOLOGY > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

What elements do carbohydrates contain

A

Carbon
Hydrogen
Oxygen

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2
Q

What elements do lipids contain

A

Carbon
Hydrogen
Oxygen
(in a different proportion to carbohydrates)

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3
Q

What elements do proteins contain

A

Carbon
Hydrogen
Oxygen
Nitrogen
(Sometimes) Sulphur

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4
Q

What elements do nucleic acids contain

A

Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus

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5
Q

Examples and functions of cations

A

Calcium ions-
Muscle contraction and nerve impulse transmission
Sodium ions-
Co-transport, reabsorption of water in the kidney and nerve impulse transmission
Potassium ions-
Involved in stomatal opening and nerve impulse transmission
Hydrogen ions-
Involved in chemiosmosis, pH determination and catalysis of reactions
Ammonium ions-
Involved in nitrogen cycle (bacteria convert ammonium ions into nitrate ions)

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6
Q

Examples and functions of anions

A

Nitrates-
Mineral ion absorbed by plants to provide a source of nitrogen to make amino acids
Hydrogencarbonate-
Maintains the pH of the blood
Chloride-
Provide a negative charge to balance the positive sodium ions and potassium ions in cells
Phosphate-
Involved in the formation of phospholipids for cell membranes, nucleic acids, ATP formation and in making bones
Hydroxide

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7
Q

Describe the structure of water

A

Polar molecule due to unevenly distributed charge
Hydrogen bonds form between the oxygen and a hydrogen atom as the positive and negative regions interact with each other. Individual hydrogen bonds are weak but collectively provide strength

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8
Q

4 Key Properties of Water

A

Solvent in reactions
Transport medium
Coolant
Provides habitat

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9
Q

Describe how water is used as a solvent

A

Polar (hydrophilic) or charged molecules dissolve in water due to the fact that water is polar
The slight positive charge on hydrogen atoms will attract any negative solutes and the slight negative charge on the oxygen atoms will attract any positive ions in solutes
Non polar (hydrophobic) molecules cannot dissolve in water and are repelled by water
The cytosine in cells is mainly water so many solutes can dissolve within the cell and be easily transported

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10
Q

Describe how water is used as a transport medium

A

Polar substances dissolve and are easily transported in water around animals and plants either in the blood of animals or the xylem of plants.

Cohesion is when water molecules stick together by hydrogen bonds, this allows water to move up the xylem as a continuous column of water which makes it easier to draw up

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11
Q

Describe how water is used as a coolant

A

Water has a high specific heat capacity (which means a lot of energy is required to raise the temperature) due to energy required to break the hydrogen bonds
Can be used advantageously to keep internal temperatures of animals and plants relatively constant (so enzymes do not denature of become less productive)
Water has a large latent heat of vaporisation (a lot of energy is required to convert water from a liquid to a gas)
Can be used advantageously because it provides a cooling effect (e.g. sweat)

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12
Q

Describe how water is used as a habitat

A

Water buffers temperature so it provides a stable environment for aquatic organisms
Cohesion causes surface tension which lets small invertebrates to move and live on the surface which provides them with a habitat away from the predators in the water
Ice is less dense than liquid water due to hydrogen bonds therefore it floats on top, providing a surface habitat for animals

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13
Q

What is a monomer

A

Smaller units which can create larger molecules

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14
Q

What is a polymer

A

Made of lots of monomers bonded together

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15
Q

What are polymers made from glucose

A

Starch
Cellulose
Glycogen

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16
Q

What is the polymer made from amino acids

A

Protein

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17
Q

What are the polymers made from nucleotides

A

DNA and RNA

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18
Q

What are the 3 monosaccharides

A

Glucose
Fructose
Galactose

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19
Q

What are the 3 disaccharides

A

Sucrose (glucose+fructose)
Maltose (glucose+glucose)
Lactose (glucose+galactose)

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20
Q

Difference between alpha and beta glucose

A

in alpha glucose, at carbon 2, H is at the top whereas in beta glucose OH is at the top

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21
Q

Structure of disaccharides

A

made of two monomers joined together by a glycosidic bond formed via a condensation reaction

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22
Q

What is a condensation reaction

A

Joining two molecules together by removing water

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23
Q

What is a hydrolysis reaction

A

Splitting apart molecules through the addition of water

24
Q

Function of the polysaccharide starch

A

Store of glucose in plants

25
Q

Function of the polysaccharide cellulose

A

Structural strength in plants

26
Q

Function of the polysaccharide glycogen

A

Store of glucose in animals

27
Q

Structure of starch

A

Monomer is alpha glucose
Made of the 2 polymers amylose (unbranched due to 1-4 bonds) and amylopectin (branched due to 1-4 and 1-6 bonds)

28
Q

How does the structure of starch relate to its function

A

Helix can compact to fit a lot of glucose in a small space
Branched structure increases surface area for rapid hydrolysis back to glucose
Insoluble so won’t affect water potential

29
Q

Structure of cellulose

A

Monomer is beta glucose
1-4 glycosidic bonds
Polymer forms long straight chains which are held in parallels by many hydrogen bonds to form fibrils
Macrofibrils join together to form a cellulose fibre

30
Q

How does the structure of cellulose relate to its function

A

Many hydrogen bonds provide collective strength
Insoluble so wont affect the water potential

31
Q

Structure of glycogen

A

Monomer is alpha glucose
1-4 and 1-6 bonds (highly branched)

32
Q

How does the structure of glycogen relate to its function

A

Branched structure increases surface area for rapid hydrolysis back to glucose
Insoluble so won’t affect water potential

33
Q

Features of lipids

A

Macromolecules (not polymers)
Non- polar
Insoluble in water
Dissolve in organic solvents (e.g. ethanol)
Hydrophobic
Made of fatty acids and glycerol.

34
Q

What bond joins the glycerol and the three fatty acids in triglycerides

A

An ester bond (formed by a condensation reaction)

35
Q

What is an R group

A

A fatty acid which may be saturated or unsaturated

36
Q

Difference between saturated and unsaturated fatty acids

A

In saturated fatty acids, the hydrocarbon chain has only single bonds between carbons whereas in unsaturated fatty acids there is at least one double bond between the carbons

37
Q

How does the properties of a triglyceride link to the structure

A

Can transfer energy due to the large ratio of energy storing carbon-hydrogen bonds compared to the number of carbon atoms, a lot of energy can be transferred when it is broken down
Can act as a metabolic water source due to the high ratio of hydrogen to oxygen atoms, triglycerides release water if oxidised (essential for desert animals like camels)
Low mass so a lot can be stored without the animal increasing in mass and preventing movement.

38
Q

Structure of phospholipids

A

Made of glycerol, two fatty acid chains and a phosphate group (attached to the glycerol)
Two fatty acids bond to the glycerol via two condensation reactions resulting in two ester bonds
Hydrophilic (charged) head
Hydrophobic (not charged) tail

39
Q

Structure of cholesterol

A

A sterol (4 carbon rings and a hydroxyl group at one end and they have both hydrophobic and hydrophilic regions)

40
Q

Function of cholesterol

A

Embedded within cell membranes to impact fluidity
Help reduce fluidity of membranes at high temps and increase fluidity at low temps
Help control movement across cell membrane

41
Q

Structure of proteins

A

Made up of one or more large polymer creating a macromolecule
Four levels of structure primary
secondary
tertiary
quaternary

42
Q

What is the primary level of structure of a protein

A

The order of the amino acids in the polypeptide chain (this is a polymer)
The order is vital!!!

43
Q

What is the secondary level of structure of a protein

A

The sequence of amino acids causes parts of a protein molecule to bend into alpha helix shapes or beta pleated sheets
Secondary structure is held by hydrogen bonds

44
Q

What is the tertiary level structure of a protein

A

The secondary structure is folded to form a unique 3D shape.
This is held together by 4 bonds
Hydrophobic and hydrophilic interactions (weak)
Hydrogen bonds (weak)
Ionic bonds (strong bonds between R groups)
Disulphide bonds (strong covalent bonds which forms between R groups of two sulphur containing amino acids)
Disulphide bonds will only occur when there is a sulphur is the R group

45
Q

What is the quaternary structure of a protein

A

A protein made up of more than one polypeptide chain.
E.g. Haemoglobin is made up of 4 polypeptide chains
Haemoglobin has a prosthetic group attached to each polypeptide chain, these groups are not made of amino acids but instead contain iron.

46
Q

What is a conjugated protein

A

A non-protein (e.g. a prosthetic group) is added to a protein

47
Q

Features of a fibrous protein

A

Long rope like shape
Polypeptide chains form long twisted strands together
Stable structure
Insoluble in water
Strength gives structural function
e.g. collagen in bone and keratin in hair

48
Q

Features of a globular protein

A

Spherical shape
Polypeptide chains roll up into a spherical shape
Relatively unstable structure
Soluble
Metabolic functions
e.g. all enzymes, antibodies, some hormones (insulin), haemoglobin

49
Q

Main inorganic ions

A

H+ and OH- ions impact pH, can denature enzymes and proteins, increase heart rate and Bohr effect
Cl- ions have an inhibitory effect at a synapse
Na+ and K+ ions play roles in the co-transport of glucose and important in the nervous system.
Phosphate ions as components of DNA and ATP
Ammonium ions in the decay of amino acids in decomposition and deamination
Nitrate ions are essential for the creation of proteins and nucleic acids
Calcium ions are involved in synaptic transmission and muscle contractions

50
Q

Test for starch

A

Iodine
Turns from orange to blue/black if starch is present

51
Q

Test for reducing sugars

A

Benedict’s reagent and heat
Turns from blue to green/yellow/orange/brick red (the more red the higher the conc) if there are reducing sugars

52
Q

Test for non reducing sugars

A

(Following a negative benedict’s test)
Add acid and boil (acid hydrolysis)
Cool solution and add alkali to neutralise
Add benedict’s reagent and heat
Change from blue to green/yellow/orange/brick red (the more red the higher the conc of reducing sugar)

53
Q

Test for proteins

A

Biuret
Change from blue to purple if protein is detected.

54
Q

Test for lipids

A

Dissolve sample in ethanol
Add distilled water
If lipids are detected, a white emulsion will form.

55
Q

How to use colorimeter

A

Set filter
Calibrate using distilled water
Insert samples
Measure percentage transmission of light
A calibration curve can be created

56
Q

How to use biosensors

A

A single strand of DNA or protein (complementary to the test sample) is immobilised
When the sample is added, it will bind to the immobilised DNA/protein
This binding causes a change in a transducer and as a result, a current is released
The current is processed to determine the concentration of the sample present

57
Q

What is thin layer chromatography

A

A method to separate proteins, carbohydrates, vitamins or nucleic acids
To identify the biological molecules present use the equation distance moved by the solute/ distance moved the solvent to find the Rf value.

OCR ALEVEL BIOLOGY (18 decks)

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