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Biology: Unit 2 > 2.2 Biological molecules > Flashcards

2.2 Biological molecules Flashcards

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1
Q

What are hydrogen bonds?

A

Hydrogen bonds form between the positive and negatively charged regions of adjacent water molecules

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2
Q

What is water?

A

Water is the medium in which all metabolic reactions take place in cells

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3
Q

What are the properties of water?

A
  • Important solvent in water
  • A transport medium
    in animals it is the blood (glucose) & in plants it is the xylem (water) and the phloem (dissloved sugars)
  • A coolant
    sweat can evaporate and take away the heat on your skin surface by kinetic energy transfer therefore take away the heat and cool you down
  • Provides habitats
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4
Q

What are the water properties that hydrogen bonds contribute for?

A
  1. An excellent solvent
  2. A relatively high specifc heat capacity
  3. A relatively high latent heat of vaporisation
  4. Water is less dense when a solid
  5. Water has high surface tension and cohesion
  6. It acts as a reagent
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5
Q

What is a polar molecule?

A

When a molecule has one end that is negatively charged and one end that is positvely charged.

For example water

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6
Q

Why is the sharing of electrons uneven in water when it is electrically neutral as a whole?

A

The oxygen atom attracts the electrons more strongly than the hydrogen atoms. This results in a weak negatively charged region on the oxygen atom and a weak positively charged region on the hydrogen atoms

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7
Q

What is a dipole?

A

The seperation of charge due to the electrons in the covalent bonds being unevenly shared

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8
Q

What are the elements in each biological molecule?

A

Carbohydrates: C,H and O
Lipids: C,H and O
Proteins: C, H, O, N and P
Nucleic acids: C, H, O, N and P

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9
Q

What monosaccharides join up to make the 3 disaccharides?

A

Maltose - alpha glucose 2x
Sucrose - alpha glucose and fructose
Lactose - galactose and beta glucose

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10
Q

What are the three monosaccharides?

monomers

A

Glucose, Fructose and galactose

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11
Q

What are disaccharides?

A

They are made from two monosaccharides. They are joined together by a glycosidic bond and are formed via a condensation reaction

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12
Q

What are the three disaccharides?

dimers

A

Sucrose, maltose and lactose

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13
Q

What are the three polysaccharides?

polymers

A

Starch, cellulose and glycogen

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14
Q

What is the structure of starch?

A

It is made from 2 polymer.
It has amylose (an unbranched helix)
It has amylopectin (a branched molecule)

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15
Q

What is the structure of cellulose?

A

Polymer forms long straight chains. Chains are held parallel by many hydrogen bonds to form fibrils.
Macrofibrils combine to form a cellulose fibre

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16
Q

What are the functions of cellulose and how does the structure allow that?

A

Provides collective strength due to having many hydrogen bonds.
Won’t affect water potential because it is insoluble

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17
Q

What are the functions of starch and how does the structure allow that?

A
  • Helix can compact to fit a lot of glucose in a small space.
  • Branched stucture increases surface area for rapid hydrolysis.
  • It is insoluble so it wont affect water potential
18
Q

What is amylose?

A

A straight chain molecule
Has all 1-4 glycosidic bonds

19
Q

What is amylopectin?

A

It is a branched structure
It has 1-4 and 1-6 glycosidic bonds

20
Q

What is glycogen?

A

In animals and fungi
It is a branched stucture
Has 1-4 and 1-6 glycosidic bonds
More 1-6 because it is moree branched than amylopectin

21
Q

Why is amylopectin and glycogen good energy store compounds?

A

They both have a branched structure so they are compact. This means they are stable and don’t react easily

22
Q

What are lipids?

A
  • Macromolecules
  • Non polar
  • Insoluble in water
  • Dissolve in organic solvent like ethanol
  • hydrophobic
23
Q

How are triglycerides formed?

A

They are formed via the condensation between one glycerol and 3 molecule sof fatty acids

24
Q

What is the structure of phospholipids

A

They are made of a glycerol molecule, two fatty acid chains and a phosphate group (attached to the glycerol). The 2 fatty acids also bond to the glycerol via two condensation reactions. This forms an ester bond

25
Q

What is the phospholipid bilayer?

A

The phospholipids are positioned in a way that the hydrophilic head is exposed to the water and the tails are not.
This forms a phospholipid bilayer membrane structure which makes up the plasma membrane around cells.

26
Q

What is cholesterol?

What is s sterol?

A
  • It is a sterol
    Sterols have 4 carbon rings and a hydroxyl group at one end and they have both hydrophobic and hydrophilic regions
27
Q

What is the function of cholesterol?

A

It is embedded within cell membranes to impact fluidity
They help reduce the fluidity of membranes at high temperatures and increase fluidity at low temperatures

28
Q

What is primary structure?

A

The sequence of amino acids in the polypeptide chain

29
Q

What is secondary structure?

A

the sequence of amino acids causes parts of a protein molecule to bend into alpha helix or beta pleated sheets
* Held in place by hydrogen bonds
* Forms between the c=o groups of the carboxyl group of one amino acid and the H in the amine group of another amino acid

30
Q

What is a globular protein?

A
  • Polypeptide chains “roll up” into a spherical shape
  • Relatively unstable structure
  • soluble
  • metabolic functions

e.g all enzymes like haemoglobin

31
Q

What is tertiary structure?

A

The further folding of the secondary structure to form a unique 3D shape
* Held in place by ionic bonds. hydrogen bonds and disulphide bridges
* The ionic bonds and disulphide bridges form between the R groups of different ammino acids
* Disulphide bonds only sometimes occur, as there must be a sulfur in the R groups for this bond to occur

32
Q

What is the quarternary structure?

A

A protein made up of more than one polypeptide chain

for example, haemoglobin

33
Q

What is the importance of primary structure?

A

If even one amino acid in the sequence is different then it will cause the ionic/hydrogen/disulphide bonds to form in different locations
- Enzymes willl have a different shaped active site
- Carrier proteins will have different shaped binding site

34
Q

What happens if a protein is denatured?

A

This means that bonds that hold the tertiary and secondary stucture in shape break and therefore the unique 3D shape is lost. (e.g enzymes losee their unique active site shape)
- Ionic and hydrogen bonds break

35
Q

What is a fibrous protein?

A
  • polyeptide chains form long twisted strands lined together
  • Stable structure
  • Insoluble in water
  • Strength gives structural function

e.g collagen in the bone, keratin in the hair

36
Q

What is the test for starch?

A

Iodine solution
Goes from brown to blue-black

37
Q

What is the test for reducing sugars?

A

Benedict’s solution
1. Mix the sample with Benedict’s solution
2. Heat it with a water bath
Goes from blue to:
* Green at a low concentration of reducing sugars
* Yellow at a medium concentration of reducing sugars
* Brick red at a high concentration of reducing sugars

This is because the Cu2+ will be reduced to Cu+

38
Q

What is the test for non reducing sugars?

A
  1. Boil is with hydrochloric acid
    Hydrolyses sucrose to glucose and fructose which are reducing sugars
  2. Use Benedict’s solution
  3. Heat it with a water bath

It will go from blue to:
* Green at a low concentration of reducing sugars
* Yellow at a medium concentration of reducing sugars
* Brick red at a high concentration of reducing sugars

39
Q

What is the test for lipids?

A

Emulsion test
1. Mix ethanol with your sample and mix it with water
Dissolves the lipids in ethanol
* Positive test = white layer formed

40
Q

What is the test for proteins?

A

Biuret’s solution
1. Mix sample with your solution for a few minutes
* Changes from blue to purple

41
Q

What is the method for using a colorimeter?

A
  1. Set the filter in the colorimeter (picking the colour)
  2. Calibrate the machine using distilled water and seeing what absorbance of light there is
  3. Insert sample from biochemical test
  4. It measures the percentage transmission of light going through your sample
  5. Create a calibration curve using the results from known concentrations of glucose
42
Q

What is the method for biosensors?

A
  1. A single strand of DNA or protein, which is complementary to the test sample, is immobilised. When the sample is added, it will bind to the immobilised DNA/Protein
  2. This binding causes a change in a tranducer and as a result, an electronic current is released
  3. This current is processed to determine the concentration of the sample present

Biology: Unit 2 (12 decks)

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