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Biology A Level > Biological molecules > Flashcards

Biological molecules Flashcards

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1
Q

What is a monomer?

A

A small repeat unit that forms a polymer

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2
Q

What is a polymer?

A

A long chain of repeat molecules

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3
Q

What structures can polymers have?

A

Polymers can be long, single stranded, short and / or highly branched

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4
Q

What is the backbone of most polymers made of?

A

Carbon

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5
Q

What are the three main types of biological molecule?

A

Carbohydrates
Proteins
Lipids

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6
Q

What are the two main types of sugar (from shape)

A

Hexose (6 carbon ring)
and
Pentose (5 carbon ring)

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7
Q

How do you perform the emulsion test?

A
  1. Add ethanol and shake
  2. Add water and shake
  3. If cloudly, lipids are present.
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8
Q

What are the main uses of lipids?

A 
Membrane formation
Hormone production
Electrical insulation 
Waterproofing
Thermal insulation
Protects vital organs
Buoyancy in aquatic animals
Energy storage
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9
Q

What are triglycerides made up of?

A

A hydrophilic glycerol head, ESTER BONDED to three hydrophobic fatty acid tails.

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10
Q

What are the types of bonds in:

1) Carbohydrates
2) Lipids
3) Amino acids + Proteins

A

1) Glycosidic bonds
2) Ester bonds
3) Peptide bonds

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11
Q

What are the two types of polymer in starch?

Describe them.

A

Amylose and amylopectin
Amylose - Alpha glucose joined by 1-4 glycosidic bonds. The angle means that amylose forms a helix, stabilised by hydrogen bonding, making it much less soluble than the molecules used to make it.
Amylopectin - 1-4 glycosidic bonds, but with 1-6 branching points approx every 25 glucose units.

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12
Q

Why is ice less dense than water?

A

Because when water freezes, the hydrogen bonds between the molecules fix their positions slightly further apart than the average distance

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13
Q

Why is water critical for sustaining life?

A
  1. It is a solvent in which many solutes from organisms can be dissolved. As such, water can act as a medium for important chemical reactions
  2. Water is a very efficient transport medium. Cohesion means that when water moves through a body, the molecules stay together. Adhesion means that water sticks to and is pulled along surfaces.
  3. Water acts as a coolant, and can buffer temperature changes during chemical reactions. Maintaining a constant temperature is important as enzymes only have a narrow working range.
  4. Many organisms live in water, as it is stable - does not change temp or become gas easily, and as ice floats, it forms an insulating layer on top of the water. Animals can also live on this ice or on water’s surface.
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14
Q

What is the order of the upwards molecules on alpha and beta glucose?

A

ALPHA: CH2OH, H, OH, H, H
carbon: 6,5 4 3 2 1

BETA: CH2OH, H, OH, H, OH
6, 5 4 3 2 1

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15
Q

What are the three main hexose monosaccharides?

A
  1. Glucose
  2. Fructose
  3. Galactose
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16
Q

How is the disaccharide sucrose made?

A

Glucose + Fructose

17
Q

How is lactose made?

A

Glucose + Galactose

18
Q

How does a condensation reaction occur?

A

2 hydroxyl groups react, leaving an O in the bond and “condensing” water out.

19
Q

How is cellulose formed?

A

Cellulose is formed from the glycosidic bonding of multiple beta glucose molecules, with every other one flipped so that the bonding can occur.

20
Q

How is cellulose organised into cellulose fibres?

A

Cellulose chains hydrogen bond with each other forming microfibrils.
These then group into macrofibrils
These then bundle together to form cellulose fibres, which are strong and insoluble.

21
Q

How do you test for reducing sugars?

A
  1. Place the sample in a boiling tube
  2. Add an equal volume of benedict’s reagent = Copper (II) sulfate
  3. Heat the mixture in a boiling water bath for five minutes.
    If the solution turns brick-red, there is a reducing sugar.
22
Q

How do you test for non-reducing sugars?

A

Add hydrochloric acid and boil, then perform the normal test for reducing sugars. However, results may be a range of colours so must be referred to with a chart. If precise is needed, a colorimeter may be used to calculate %absorbance

23
Q

How do you test for starch?

A

Add a dew drops of iodine dissolved in potassium iodide solution, if solution changes to dark purple/black then starch is present.

24
Q

How are phospholipids formed?

A

A phosphate group replaces one of the fatty acid tails, forming a molecule with a hydrophilic head and a hydrophobic tail.

25
Q

What does the hydrophobic/philic properties of phospholipids mean?

A

They can form a bilayer, where the tails point to the centre of the sheet whilst the hydrophilic heads protect them from the water.

26
Q

What are sterols?

A

Alcohol molecules that have the same hydrophobic/philic characteristics as phospholipids.

27
Q

What is the function of cholesterol?

A

is positioned between the phospholipid tails in cell membranes. This adds stability to the cell membranes and helps to regulate fluidity by keeping membranes fluid at lower temperatures and stopping them from becoming too fluid at high temperatures.

28
Q

How many common amino acids are there?

A

20

29
Q

How do we get amino acids?

A

From digesting what we eat

30
Q

How are amino acids bonded?

A

A peptide bond forms between the amine group on one and the carboxyl group on another

31
Q

When many amino acids join, what is the result?

A

A polypeptide chain

32
Q

What are the levels of protein structure and how are they formed? What bonds are involved in each step?

A

Primary structure - The sequence in which amino acids are joined - Peptide bonds
Secondary structure - Hydrogen bonds form in the chain. This can happen in two ways. A chain may coil and H-bond with itself to form an alpha helix, or may H-bond with another to form a beta pleated sheet. - Hydrogen bonds
Tertiary structure - Folding of the protein. This is caused from interactions in the R groups i.e.
- Hydrophobic/Philic interactions
Hydrogen bonds
Ionic bonds between oppositely charged ions
Disulfide bonds - Form between sulfur atoms
Quaternary structure - From the joining of two or more polypeptide chains - Same as tertiary structure/

33
Q

What are the main types of proteins?

A

Globular - Compact, soluble, spherical proteins.
Conjugated - Globular proteins with a prosthetic group which is a non-protein component.
Fibrous proteins - Long, insoluble, strong molecules.

34
Q

What are some examples of each type of protein:
Glolar
Conjugated
Fibrous

A

Globular - Insulin
Conjugated - Haemoglobin, Catalase
Fibrous - Keratin, Collagen, Elastin

35
Q

What does having double bonds mean in fatty acid tails of lipids?

A

Having a double bond causes the tails to kink / bend, and so they cannot pack as closely together. This increases the fluidity of a membrane with them, and can make them liquid at room temperature.

36
Q

What food test can you do to work out if a protein is present in a sample?

A

Place your liquified food sample in a test tube

Add equal volumes of potassium/sodium hydroxide and copper sulfate to the test tube to form a blue precipitate.

Heat to when it is a solution

Add egg white / milk, and if there is a protein, the blue colour will change to purple.

Biology A Level (12 decks)

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