Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

a-level biology. > biological molecules. > Flashcards

biological molecules. Flashcards

(59 cards)

Start Studying
1
Q

What is a polymer?

A

A polymer is a large, complex molecule composed of long chains of monomers joined together.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a monomer?

A

A monomer is a small, basic, molecular unit, like a monosaccharide or an amino acid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a carbohydrate?

A

A carbohydrate is a polymer that contains C, H, and O: formed of monosaccharides, like glucose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Which kind of reaction joins monosaccharides together to form carbohydrates? Which kind of bond does this form?

A

A condensation reaction can join two molecules together, and this forms a glycosidic bond.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a hydrolysis reaction?

A

A hydrolysis reaction breaks the chemical bond between monomers using a water molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Which kind of reaction can break a polymer apart?

A

Hydrolysis reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a polysaccharide?

A

A polysaccharide is formed when more than two monosaccharides are joined together by condensation reactions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What role does starch play in plants, and how is it adapted to this role?

A

It is the main energy storage material: plants store excess glucose as starch, and cells get energy from glucose, so whenever a plant needs more energy, starch is broken down to release the glucose.

Starch is a mixture of two polysaccharides of alpha-glucose: amylose and amylopectin. Amylose is a long, coiled, unbranching chain that makes it compact and good for storage.
Amylopectin is a long, branching chain of alpha-glucose: its branches mean that enzymes that break the molecule down can access its glycosidic bonds faster, allowing glucose to be released quickly.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the main energy storage in animals, and how is its structure related to its function?

A

Glycogen is another polysaccharide of amylopectin that animals use to store excess glucose.
It has many long, branching chains, and is very compact, so is good for fast release of glucose and storage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the test for sugars and how is it done?

A

Benedict’s test:
- add blue benedict’s reagent
- heat in a boiling water bath
- if the test is positive, a brick-red precipitate will form.
If the test is negative, the sample may contain a non-reducing sugar. To test for these, they have to be broken down into monosaccharides, by boiling it with dilute HCl and neutralising with a carbonate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are cell walls made up of, and how is it adapted to its role?

A

Cell walls are made up of long chains of betaglucose, bonded to other chains with weak hydrogen bonds to form microfibrils, which provide the cell with structural support.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the test to see if starch is present.

A

Add iodine diluted with potassium iodide solution to the starch. If it turns blue black from brown, starch is present.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is maltose made of?

A

Glucose + glucose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is sucrose made of?

A

Glucose + fructose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is lactose made of?

A

Glucose + galactose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a triglyceride composed of?

A

One glycerol molecule bonded to three fatty acids.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the structure of a fatty acid.

A

Fatty acids have a variable hydrocarbon chain, attached to a carboxyl group.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the difference between a saturated and unsaturated hydrocarbon?

A

Unsaturated contains at least one double bond between carbon atoms.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which kind of bonding forms triglycerides?

A

Ester bonds, formed by condensation reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is a phospholipid?

A

A phospholipid is a glycerol molecule bonded to two fatty acids and a phosphate group.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does the structure of a triglyceride relate to its function?

A

Triglycerides are mainly used as storage molecules. They are good for this because the long hydrocarbon tails of the fatty acids contain lots of chemical energy that is released when they are broken down.
They are also insoluble, so don’t affect the water potential of a cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does the structure of a phospholipid relate to its function?

A

Phospholipids make up the bilayer of cell membranes, which controls what enters and leaves the cell. They are good for this because the phosphate heads of a phospholipid are hydrophilic, and the tails are hydrophobic, so they form a double layer with heads facing out towards the water on each side. The centre of this bilayer is hydrophobic, so water-soluble substances can’t easily pass through it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the test for lipids, and how is it done?

A

The test for lipids is the emulsion test. This is done by mixing the sample with ethanol for about a minute until it dissolves, then pouring this solution into water. If lipids are present, a milky emulsion will be visible.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the monomers of proteins?

24
What is a dipeptide?
A dipeptide is formed when two amino acids join together.
25
What is a polypeptide?
A polypeptide is formed when more than two amino acids join together.
26
What is a protein made of?
One or more polypeptides.
27
What is the general structure of an amino acid?
A carboxyl group, an amino group, and a variable group.
28
Give four functions of proteins.
Enzymes Antibodies Transport proteins Structural proteins
29
What is an enzyme?
An enzyme is a globular protein that is roughly spherical in shape due to tight folding of polypeptide chains. They're soluble, and catalyse metabolic reactions.
30
What is an antibody?
An antibody is involved in immune response. They are made up of two light and two heavy polypeptide chains, and have variable groups.
31
What is a transport protein?
Transport proteins provide a path for substances to cross the biological membrane and use energy to move substances against the concentration gradient.
32
What is a structural protein?
A structural protein consists of long polypeptide chains that lie parallel to each other with cross-links between them to provide support to structures like hair and connective tissue.
33
What is the test for protein and how is it done?
The biuret test. First, the sample needs to be alkaline, so add a few drops of sodium hydroxide solution. Then, add some copper 2 sulphate solution. If protein is present, the solution turns purple, if it is not, it remains blue.
34
How do enzymes speed up reactions?
By lowering activation energy.
35
Explain the lock and key model.
In the lock-and-key model, the substrate fits perfectly into the enzyme's active site, forming an enzyme-substrate complex, then the substrate is broken down into products which are then released
36
Explain the induced fit model.
In the induced fit model, the enzyme's active site changes slightly around the substrate as an enzyme-substrate complex is formed. The active site then goes back to normal when the products are released.
37
Why is the induced fit model better than the lock and key model?
The induced fit model helps explain why enzymes are so specific, and only bond to one particular substrate: with this model, the substrate not only has to fit the shape of the active site, but also make it change shape in the right way too.
38
Give two factors that can influence enzyme activity.
Temperature and pH.
39
How does a competitive inhibitor work?
Competitive inhibitor molecules have a similar shape to that of the substrate. They compete with the substrate to bind to the active site, but no reaction takes place, they simply block the active site so no substrate molecules can fit. If there is a higher concentration of inhibitor, the rate of reaction will decrease because hardly any substrate will be able to bind to the enzyme. However, if the concentration of the substrate is higher, its chances of getting to an enzyme before the inhibitors increase, so increasing the concentration of substrate increases the rate of reaction up to a point.
40
How do non-competitive inhibitors work?
Non-competitive inhibitors bing to the enzyme away from its active site, and cause it to change shape so the substrate molecules can no longer bind to it. Increasing the rate of substrate will have no effect, because enzyme activity is inhibited anyway.
41
What is a nucleotide?
A nucleotide is made of a pentose sugar, a nitrogen-containing organic base, and a phosphate group. Nucleotides are the monomers that make up DNA and RNA.
42
What are the four possible bases?
Adenine, Thymine, Cytosine, and Guanine.
43
What is the sugar in DNA called?
Deoxyribose
44
What is the sugar in RNA called?
Ribose?
45
In RNA, which base replaces thymine?
Uracil.
46
Which bonds form polynucleotides?
Phosphodiester bonds.
47
Describe the structure of DNA.
Two DNA strands join by hydrogen bonding at the bases: two bonds form between A + T, and three bonds form between C + G. Two antiparallel polynucleotide strands twist to form a double helix.
48
How does DNA replicate?
1. DNA helicase breaks the hydrogen bonds between bases on the polynucleotide strands, the helix unwinds to form two separate strands. 2. Each original strand acts as a template for a new one, and complementary base pairing means that free-floating DNA nucleotides are attracted to their complementary exposed bases on each strand. 3. Condensation reactions join the nucleotides together, catalysed by DNA polymerase. Hydrogen bonds form between the bases on the original and new strands. 4. Each new DNA molecule contains one old strand and one new strand of DNA: this is semi-conservative replication.
49
Which direction does DNA polymerase move in?
DNA polymerase is only complementary to the 3' end of the newly forming DNA strand, so the DNA polymerase can only add nucleotides to the 3' end. Because the strands of a double helix are antiparallel, the polymerase working on one side moves in an opposite direction to the polymerase on the other.
50
Give 5 useful properties of water.
- It is an important metabolite - It has a high latent heat of vaporisation - It has a high specific heat capacity. - It is a good solvent - There is strong cohesion between water molecules.
51
What is the role of iron ions?
Iron ions bind to the oxygen as part of haemoglobin, helping oxygen be carried around the body
52
What is the role of hydrogen ions?
Hydrogen ions determine pH.
53
What is the role of sodium ions?
Sodium ions help transport glucose and amino acids across membranes.
54
What is the role of phosphate ions?
Phosphate ions are essential to ATP and DNA.
55
56
57
What happens when energy is needed in a cell?
ATP is broken down into ADP and Pi. Energy is released by breaking this bond. This reaction can be coupled with other energy-requiring reactions, so energy released can be used directly to make the coupled reaction happen rather than being lost as heat. ATP can then be re-synthesised, by ATP synthase.
58

a-level biology. (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions