Biological Molecules

Question 1

What does all three biological molecules contain?

Answer 1

Carbon, hydrogen and oxygen

Question 2

What does protein also contain?

Answer 2

Nitrogen and sulfur

Question 3

What are carbohydrates consists of and what are they made up of?

Answer 3

Consists of sugars and starches

Made up of individual units called simple sugars or monosaccharides

Question 4

What are simple sugars/monosaccharides and give an example of one

Answer 4

Small molecules which are soluble in water

An example is glucose or fructose

Question 5

What would the diagram of a monosaccharide look like?

Answer 5

One hexagon with an O in top right which represents oxygen

Question 6

What do monosaccharides join together to form? Give an example of this

Answer 6

Join together to make disaccharides such as maltose and sucrose

Question 7

What would the diagram look like?

Answer 7

One hexagon with an O and then a line going down then across and then an O then a line gong across then up then another hexagon with an O.

Question 8

What do simple sugars join together to form? Give examples of this. And what are those example ps made out of

Answer 8

Polysaccharides
Examples include starch (found in plants) and glycogen (found in animals).
Examples are made up of long chains of glucose molecules

Question 9

What would the diagram look like of a polysaccharide

Answer 9

Lots of hexagon joined together with a line

Question 10

What are polysaccharides (5marks)

Answer 10

Large molecules
Act as a store of glucose
This is released when needed to be used in the process of respiration
They are insoluble so they do not upset the water balance of the cells
They are compact so can store in a small space.

Question 11

What are lipids commonly known as and what are the different between the two?

Answer 11

Fats and oils
Fats - solid at room temperature
Oils - liquids at room temperature

Question 12

What is the most common type of lipid in the body called? And what are they made up of?

Answer 12

Triglyceride

Two different sub units called glycerol and fatty acids.

Question 13

What makes the liquids different/ vary?

Answer 13

The fatty acids give them different properties

Question 14

Give two uses of lipids

Answer 14

Form cell membranes

Store of energy in fat

Question 15

What does a triglyceride look like?

Answer 15

Looks like an E shape

The I is glycerol and the stalks coming off it are fatty acids (three of them)

Question 16

What are proteins made up of? How can they be joined together?

Answer 16

Long chains of amino acids

They can be joined together in different ways to make hundreds of thousands different type of proteins

Question 17

Example of protein. What would the diagram look like?

Answer 17

Polypeptides 
See notes (coloured balls going up and down in a zig zag way and a line of balls at the top

Question 18

What do you use to test for starch and give a short method?

Answer 18

Iodine solution is used
Add a type of food to a test tube and add a bit of iodine solution you will know by the colour if it contains starch or not

Question 19

What colour is seen if it’s a positive result or negative when using iodine solution

Answer 19

Positive - blue black colour

Negative - orange colour (not changed colour)

Question 20

What do you use to test for glucose and does the solution need to be heated?

Answer 20

Benedicts solution is used

The solution needs to be heated in a water bath above 95 degrees Celsius

Question 21

Negative and Positive result for tests for glucose

If there is a lot of glucose what colour should it be?

Answer 21

Negative result stays blue
Positive result turns green or yellow if there is little glucose
If there is a lot of glucose it is shown by orange or brick red colour

Question 22

Safety for test of glucose experiment

Answer 22

Use tongs to move hot tests tubes and wear goggles to protect eyes from dangerous substances

Question 23

Do all reducing sugars give a negative or positive result with Benedicts solutions?

Answer 23

Positive result

Question 24

What are reducing sugars? What are not reducing sugars?

Answer 24

All monosaccharides are reducing sugars
So,e disaccharides are such as maltose and lactose
Sucrose is not a reducing sugar

Question 25

How can protein be tested? What does the substance consist of?

Answer 25

Biuret reagent, consists of copper sulfate and sodium hydroxide

Question 26

How is a positive or negative result shown when testing for protein?

Answer 26

Positive - purple colour

Negative - pale blue

Question 27

Test for fat what do u do?

Answer 27

Emulsion test
Add a few drops of ethanol to a sample of food and shake and leave to stand for one minute. The solution is then poured into a test tube of water

Question 28

How is a positive result shown when testing for fat?

Answer 28

Milky white colour

Question 29

Explanation for test for fat

Answer 29

The lipids have dissolved in the ethanol but they will not in water so an emulsion is formed which is seen as a cloudy white layer.

Question 30

What are enzymes?

Answer 30

Protein molecules that act as a biological catalyst to speed up the rate of metabolic reactions.

Question 31

If there were no enzymes what would happen?

Answer 31

The reactions in cells would be too slow to support life

Question 32

What do some enzymes catalyse?

Answer 32

Synthetic reactions - splitting large molecules into small soluble molecules.

Question 33

Give some examples of reactions which involves enzymes

Answer 33

The digestive system - breaking down large insoluble molecules into small soluble molecules which can be absorbed

In the ribosomes during protein synthesis

Question 34

What are enzymes made up of and what do they fold into?

Answer 34

Made up of long chains of amino acids which are folded into a specific 3D shape.

Question 35

What does this 3D result in (area)?

Answer 35

Results in the formation of a specific functional area called the active site
This is where the reactions happen.

Question 36

What does a enzyme have what does this the same as?

Answer 36

It has a specific 3D structure

This structure of the active site is complementary(matches) to the shape of a molecule of a substrate.

Question 37

Definition of substrate

Answer 37

The molecule being acted upon by the enzyme

Question 38

What does the lock and key hypothesis suggest?

Answer 38

It suggests that just like a key fits into a lock, the substrate fits into the enzyme molecule

Question 39

What would the diagram look like for the lock and key hypothesis

Answer 39

There is A which is the substrate
And B which is the enzyme in between A and B is the active site
They are bonded together to form enzyme substrate complex.
The products are then released forming D and E where D is the enzyme which is unchanged because it is not used up in the chemical reaction and E which is the product.

Question 40

What does the lock represent? Key? Keyhole?

Answer 40

The lock is the enzyme
The key is the substrate
The keyhole is the active site
One key fits into one lock - structure is complementary to the shape of a molecule of a substrate
One key is specific for one lock - one substrate is specific for one enzyme’s active site.

Question 41

Give three properties of enzymes

Answer 41

They work very rapidly
They are specific
They are only needed in very small amounts because they can be reused.

Question 42

As temperature increases, what else increases?

Answer 42

As temperature increases, the rate of enzyme controlled reaction increases.

Question 43

However, because of the statement before, is it always true? What happens to the active site, structure of enzyme and the reaction?

Answer 43

After a specific temperature in humans, the chains of amino acids starts to unravel and the enzyme loses its specific 3D shape. This means that the shape of active site changes and the substrate can lo longer fit. We say that the enzyme has denatured and the reaction decreases dramatically until the active site becomes damaged and the enzyme cannot work at all.

Question 44

What is the optimum temperature?

Answer 44

The temperature at which the enzyme controlled reaction is working at its fastest.

Question 45

How would a graph look that would show the effect of temperature on a enzyme controlled reaction

Answer 45

The rate of reaction would be on the y axis and the temperature on the x axis. It would increase until it gets up to the optimum temperature and the enzyme starts to denature and starts to decrease.

Question 46

Why is the rate of reaction low at low temperatures. Explain in terms of movement of the enzyme and substrate molecules.

Answer 46

At lower temperatures, enzyme controlled reactions go slowly because the molecules have low kinetic energy. They move more slowly so the rate of collision between the enzyme and substrate is low. Fewer enzyme substrate complexes made means less product is made.

Question 47

Why does the rate increase as the temperature increases?

Answer 47

Because the molecules have more kinetic energy and so the move faster and so the rate of collision is higher. More enzyme substrate complexes means more product is made.

Question 48

What happens to enzymes at high temperature? How does this affect the rate of reaction?

Answer 48

After the optimum temperature, the heat causes the enzyme to denature. The enzyme changes shape as the amino acid chain unravels and so the active site no longer matches to the shape of the substrate molecule. Enzyme substrate complexes cannot form and so less product is made.

Question 49

What is the result of the specific shape of the active site?

Answer 49

The result of special bonds between different parts of the protein molecule.
These bonds hold the chains amino acids together

Question 50

How can the change in pH affect the bonds that hold the amino acids?

Answer 50

A change is pH can affect these bonds changing the shape of the protein, and therefore the shape of the active site. This means that the substrate no longer matches and rate of reaction slows down. The enzyme has been denatured and can no longer act as a catalyst

Question 51

How would a graph look if it shows the effect of pH on a enzyme controlled reaction where the enzyme has an optimum temperature of 7?

Answer 51

If rate of reaction was on the y axis and pH on x axis It would start to increase and decrease at pH 3 for pepsin and for amylase it would increase at pH 5 and decrease at pH 9.

Question 52

What does enzymes work best in? If you make the solution more acidic or alkaline what would happen?

Answer 52

Most enzymes work fastest in neutral conditions

Making the solution more acidic or alkaline it would slow down the reaction and even stop all together.

Question 53

Does pH have an effect on pepsin (enzyme) experiment

What does pepsin do to the proteins and what would we see if we did the experiment?

Answer 53

Pepsin is found it the stomach
It is a type of protease
It breaks down proteins into amino acids
Egg white contains protein when pepsin breaks it down, it goes from a cloudy solution to a colourless solution.

Question 54

Suggest errors that can happen in the pepsin experiment

Answer 54

Keeping the temperature of all the test tubes the same
Not taking the sample at exactly 10minutes
Judgement of whether the solution is clear.

Question 55

When explaining the amylase experiment….

Answer 55

Say that it won’t disappear for some temperatures (low ones) as it has a lack of temperature which gives it less kinetic energy and less successful collisions per second
For high temperatures the starch might not disappear as the temperature is too high. And denatures and so it doesn’t complement the protein molecule.

Question 56

Using the lock and key hypothesis to help you to explain…

Answer 56

Here you need to say why and not just say the lock is the enzyme etc.

You need to say that the enzyme and substrate has low kinetic energy and as temperature increases, the rate of reaction increases. If they have more kinetic energy, they collide more frequently. The active site is complementary to the substrate. After a certain temperature, the reaction slows down because it has denatured which means the active site has changed shape and is no longer complementary.