Unit 2- Section 3 Variation In Biochemistry And Cell Structure

Question 0

What is haemoglobin?

Answer 0

It’s a large protein with a quaternary structure, it’s made up of four polypeptide chains. Each chain has a haem group which contains iron and gives haemoglobin the red colours. Each molecule of human haemoglobin can carry four oxygen molecules

Question 1

What is the role in haemoglobin?

Answer 1

Human haemoglobin is found in red blood cells, it’s role is to carry oxygen around the body. There are many chemically similar types of haemoglobin found in many different organisms, all of which carry out the same function. As well as being found in all vertebrates, haemoglobin is found in earthworms, starfish and some insects, some plants and in some bacteria

Question 2

How does haemoglobin turn into oxyhemoglobin?

Answer 2

In the lungs oxygen joins to haemoglobin in red blood cells to form oxyhemoglobin. This is a reversible reaction. Near the body cells, oxygen leave oxyhaemoglobin and it turns back into haemoglobin. When an oxygen molecule joins to haemoglobin it’s referred to as an association or loading. When oxygen leave oxyhaemoglobin it’s referred to as dissociation or unloading.

Question 3

What does affinity for oxygen mean? And partial pressure

Answer 3

It’s the tendency a molecule has to bind with oxygen. Haemoglobin affinity for oxygen varies depending on the conditions it’s in. One of the conditions that affects it is the partial pressure of oxygen.

Partial pressure is a measure of oxygen concentration. The greater the concentration of dissolved oxygen in cells, the higher the partial pressure. As the partial pressure increases, haemoglobins affinity for oxygen also increases

Question 4

When oxygen loads onto haemoglobin to form what? When there is a what partial pressure?

Answer 4

Forms oxyhaemoglobin where there is a higher partial pressure

Question 5

Oxyhaemoglobin unloads it’s what in a what partial pressure?

Answer 5

Unloads it’s oxygen where there is a lower partial pressure

Question 6

Where does oxygen enter the blood?

Answer 6

Enters the blood via the capillaries at the alveoli in the lungs. Alveoli have a high partial pressure, so oxygen loads onto haemoglobin to form oxyhaemoglobin. When cells respire, they use up oxygen- this lowers the partial pressure. Red blood cells deliver oxyhaemoglobin to respiring tissues, where it unloads it’s oxygen. The haemoglobin then returns to the lungs to pick up more oxygen.

Question 7

What are the characteristics of the alveoli considering partial pressure.

Answer 7

High oxygen concentration
High partial pressure
High affinity
Oxygen loads

Question 8

Characteristics of respiring tissue when considering partial pressure etc

Answer 8

Low oxygen concentration
Low partial pressure
Low affinity
Oxygen unloads

Question 9

What does a oxygen dissociation curve show?

Answer 9

How saturated the haemoglobin is with oxygen at any given partial pressure, the affinity of haemoglobin for oxygen affects how saturated the haemoglobin is

Question 10

What happens on a oxygen association graph when the partial pressure is high?

Answer 10

Haemoglobin has a high affinity (eg lungs) for oxygen, so it has a high saturation of oxygen when the partial pressure is h

Question 11

What happened on a oxygen dissociation curve when the partial pressure is low?

Answer 11

In respiring tissues the partial pressure is low. Haemoglobin has a low affinity for oxygen, so it has a low saturation of oxygen

Question 12

Why is the oxygen dissociation graph S shaped and not straight?

Answer 12

The saturation of haemoglobin can also affect the affinity. When haemoglobin combines with the first oxygen molecule, it’s shape alters in a way that makes it easier for other molecules to join too.

Question 13

What happens when the haemoglobin gets saturated?

Answer 13

It gets harder for more oxygen molecules to join. As a result, the curve has a steep bit in the middle where it is really easy for oxygen molecules to join, and shallow bits at each end where it is harder

Question 14

What happens when the curve is steep?

Answer 14

A small change in partial pressure causes a big change in the amount of oxygen carried by the haemoglobin

Question 15

What does 100% saturation mean?

Answer 15

Every haemoglobin molecule is carrying the maximum of 4 molecules of oxygen

Question 16

What does 0 saturation mean?

Answer 16

None of the haemoglobin molecules are containing any oxygen

Question 17

What is the partial pressure of carbon dioxide a measure of?

Answer 17

The concentration of carbon dioxide in a cell,

Question 18

What does the partial pressure of carbon dioxide affect?

Answer 18

Oxygen unloading. Haemoglobin gives up oxygen more readily at a higher partial pressure of carbon dioxide. It’s a cunning way of getting more oxygen to cells during activity

Question 19

What do cells produce when they respire?

Answer 19

They produce carbon dioxide, which raises the partial pressure of carbon dioxide. This increases the rate of oxygen unloading, the dissociation curve ‘shifts’ right. The saturation of blood with oxygen is lower for a given partial pressure of carbon dioxide meaning that more oxygen is being released. This is called the Bohr effect

Question 20

How can low oxygen environments have different types of haemoglobin?

Answer 20

Organisms that live in environments with a low concentration of oxygen have haemoglobin with a higher affinity for oxygen than human haemoglobin. This is because there isn’t much oxygen available,so the haemoglobin has to be very good at loading any available oxygen. The dissociation curve of their haemoglobin is to the LEFT of ours

Question 21

What happens it the haemoglobin of an organism with high activity levels?

Answer 21

Organisms that are very active and have a high oxygen demand have haemoglobin with a lower affinity for oxygen than human haemoglobin. This is because they need their haemoglobin to easily unload oxygen, so that it’s available for them to use. The dissociation curve of their haemoglobin is to the RIGHT of the human one.

Question 22

How can the size of an animal affect haemoglobin?

Answer 22

Small mammals tend to have a higher surface area to volume ratio than larger mammals. This means they lose heat quickly, so they have a high metabolic rate to help them keep warm which means they have a high oxygen demand. Mammals that are smaller than humans have haemoglobin with a lower affinity for oxygen than human haemoglobin, because they need their haemoglobin to easily unload oxygen to meet their high oxygen demand. The dissociation curve of their haemoglobin is to the RIGHT of the human one

Question 23

What is the structure of an animal cell?

Answer 23

Plasma membrane- holds the cell wall together and controls entry and exit of cell
Cytoplasm- gel like substance where most of the chemical reactions occur
Mitochondria- where most of the reactions for respiration take place. Respiration releases energy that the cell needs to work
Robosomes- protein synthesis
Nucleus- contains genetic information and controls activities within the cell

Question 24

What is the structure of a plant cell?

Answer 24

Rigid cell wall- made of cellulose and supports and strengthens the cell
Permanent vacuole- contains cell sap, a weak solution of sugars and salts
Chloroplasts- where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll

Question 25

What are chloroplast and what do they do?

Answer 25

Chloroplasts are surrounded by a double membrane, they also have membranes inside called thylakoids membranes. The membranes are stacked up in the chloroplasts to form grana. Grana are linked together by lamellae- thin, flat pieces of thylakoids membrane. Some parts of photosynthesis happen in the grana, and other parts happen in the stroma.

Question 26

What is the variation in plant cells?

Answer 26

If it’s exposed to more light then it will have lots of chloroplasts to photosynthesis

If the cell uses lots of energy then it will have lots of mitochondria

If the cell uses lots of proteins then it will have lots of ribosomes

Question 27

What are polysaccharides?

Answer 27

They are made up of lots of monosaccharides joined together.

Question 28

What is cellulose?

Answer 28

It’s a major component of cell walls in plants. It’s made up of long unbranched chains of beta-glucose

Question 29

What is beta glucose?

Answer 29

Glucose is a monosaccharide with two forms alpha and beta. They are basically the same but the OH and H are swapped round on the right hand side .

H O. OH

HO. H

Question 30

What is a condensation reaction?

Answer 30

When monosaccharides join, a molecule of water is released. This is called a condensation reaction. The bonds that join monosaccharides together are called glycosidic bonds.

Cellulose is formed when beta glucose is linked by condensation

Question 31

What is the structure of cellulose?

Answer 31

The bonds between the sugars are straight, so the cellulose chains are straight. The cellulose chains are linked together by hydrogen bonds to form strong fibres called microfibrils. The strong fibres mean cellulose provides structural support for cells

Question 32

What is starch and what is it used for?

Answer 32

Starch is the main energy stage material plants. Cells get energy from glucose, and plants store excess glucose as starch. (When a plant needs more glucose for energy it breaks down starch to release the glucose) starch is insoluble in water so it doesn’t cause water to enter cells by osmosis,which would make them swell. This makes it good for storage. Starch is a mixture of two polysaccharides of alpha-glucose and amylose and amylopectin

Question 33

What is amylose?

Answer 33

It is a long unbranched chain of alpha glucose, the angles of the glycosidic bonds are different between two alpha glucose molecules than they are between beta glucose molecules. This gives amylose a coiled structure,almost like a cylinder, this makes it compact so it is very good for storage because you can fit more into a small space.

Question 34

What is amylopectin?

Answer 34

It is a long branched chain of alpha glucose. It side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily. This means that glucose can be released quickly

Question 35

What is glycogen and it’s function?

Answer 35

It is the main energy storage material in animals. Animal cells get energy from glucose too, but animals store excess glucose as glycogen- another polysaccharide of alpha glucose. It’s structure is very similar to amylopectin, except that it has lots more side branches coming off it. Loads of branches means that stored glucose can be released quickly, which is important for energy release in animals. It is also very compact molecule so is good for storage