Transport in Animals and Plants

Question 1

Why do multicellular organisms need specialised transport systems?

Answer 1

• Metabolic demands are high they need lots of food and oxygen to travel long distances.
• Surface area to volume ratio get smaller as organisms grow so diffusion distances get bigger and the amount of surface area available to absorb substances become relatively smaller.
• Molecules such as hormones and enzymes may be made in one place and needed in the other.
• Food will be digested in an organ system but needs to be transported to every cell for metabolic processes to occur.

Question 2

What are the different types of circulatory systems?

Answer 2

Open and closed circulatory systems.

Single and double closed circulatory systems.

Question 3

What is a open circulatory system?

Answer 3

Contains very few vessels to contain transport medium.
Blood is pumped straight form the heart into the body cavity (called the haemocoel).
In the haemocoel the transport medium is under low pressure.
Transport medium comes into direct contact with tissues and cells.
Medium returns to heart through open - ended vessel.

Question 4

What is a open circulatory system mainly found in?

Answer 4

Insects and invertebrates.

Question 5

What is a closed circulatory system?

Answer 5

Blood is enclosed in blood vessels.
Blood does not come in direct contact with tissues and cells.
Blood is carried in high pressure.
Blood returns directly to heart.
Substances leave and enter blood by diffusion through the walls of the blood vessels.
Amount of blood flowing can be adjusted by widening/narrowing of the blood vessels.
Most of these contain blood pigment to carry the respiratory gases.

Question 6

What is a closed circulatory system mainly found in?

Answer 6

Sea urchins
Starfish
mammals
earthworms
squid

Question 7

What is a single closed circulatory system?

Answer 7

Blood flows through the heart and pumped to the body.
Blood travels once through the heart for each complete circulation of the body.
Blood passes through two sets of capillaries :
In set 1 they exchange oxygen and carbon dioxide.
In set 2 substances are exchanged between blood and cells.
Blood pressure drops as they come tot he capillaries as the capillaries are narrow.
This limits the efficiency of the exchange processes.

Question 8

What is a single closed circulatory system mainly found in?

Answer 8

Fish and worms

Question 9

What is a double closed circulatory system?

Answer 9

It involves 2 separate circulations.

Blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide and then the blood returns to the heart, the blood is them pumped through the heart and pumped around body returning to the heart again.
Blood passes through 1 capillary network.
Blood travels at high pressure and maintains a relatively fast flow of heart.

Question 10

What is a double closed circulatory system mainly found in?

Answer 10

Birds and most mammals

Question 11

Why are circulatory systems needed?

Answer 11

To supply nutrients oxygen and nutrients where they are needed and to remove waste products from cells.

Question 12

Name the different blood vessels:

Answer 12

Arteries
Arterioles
Capillaries
Veins
Venules

Question 13

Describe the structure and function of arteries?

Answer 13

Arteries carry blood away from the heart under high pressure.
Walls contain elastic fibres (helps withstand the force of blood, in between contractions the elastic fibres recoil and return to their original length), smooth muscle (lining of artery is smooth so the blood flows easily over it), and collagen (helps it stretch).

Question 14

Describe the structure and function of arterioles?

Answer 14

Arterioles link the arteries and the capillaries.
They have more smooth muscle and less elastin in their walls because they have less pulse surge.
They can constrict and dilate to control the flow of blood.

Question 15

Describe the structure and function of capillaries?

Answer 15

Microscopic blood vessels that link the arterioles with the venules.
Lumen is extremely small and the capillary walls are made up of single endothelial cells giving a thin layer for diffusion.

Blood entering the capillaries is oxygenated but by the time the blood leaves the capillaries the blood has less oxygen and more carbon dioxide.

Question 16

Describe the structure and function of veins?

Answer 16

Veins carry blood away from the cells towards the heart.
They hold a large reservoir of blood. Veins do not have a pulse the surge form the heart pumping are lost as the blood passes through the narrow capillaries.

Walls contain lots of collagen and little elastic fibre, the vessels have a wide lumen and smooth and thin lining so the blood flows easily.

Question 17

Describe the structure and function of venules?

Answer 17

Link the capillaries with the veins. Several venules join to form a vein.

They have very thin walls and little smooth muscle.

Question 18

What does the blood contain?

Answer 18

Contains plasma, proteins, amino acids, red and white blood cells and platelets.

Question 19

Name some functions of the blood.

Answer 19

To transport:
respiratory gases (oxygen and carbon dioxide).
nitrogenous waste products
hormones
food molecules from storage compounds to cells that need them
platelets to damaged cells
cells and antibodies involved in immune response.

Question 20

How is tissue fluid made?

Answer 20

1. Substances in the blood can pass through into the capillary walls apart from the large plasma protein, these proteins create an osmotic effect as they give the blood in the capillaries a high solute potential and a low water potential compared with the surrounding fluid.
2. Water has a tendency to move into the blood in the capillaries from the surrounding fluid by osmosis this is known as the oncotic pressure (3.3 Kpa).
3. As the blood flows through the arterioles into the capillaries the blood is still under pressure from the surge of blood that occurs every time the heart contracts this is known as the hydrostatic pressure.
4. The hydrostatic pressure is relatively high (4.6Kpa), at the arteriole end of the capillary forcing fluid out of the capillaries.
5. This fluid fills the spaces between the cells and is known as tissue fluid.

Question 21

How is lymph made?

Answer 21

This is made when some of the tissue fluid does not return to the capillaries. Some of the fluid drains into the lymph capillaries, where it is known as lymph.

Question 22

Compare the compositions of tissue fluid, blood and lymph.

Answer 22

Blood contains both white and red blood cells however tissue fluid and lymph only have white blood cells.
Lymph has a great amount of fatty acids in it absorbed from the villi in the small intestine.
Lymph has a similar composition to plasma but it has less oxygen and fewer nutrients.
Tissue fluid and blood are very similar because they both transport enzymes, hormones salts.

Question 23

What the name of the molecules that transports oxygen?

Answer 23

Erythrocytes

Question 24

Describe the structure of an erythrocyte.

Answer 24

biconcave shape
large surface area
contains haemoglobin (contains prosthetic group)

Question 25

What happens when oxygen binds with haemoglobin?

Give the equation.

Answer 25

Oxyhaemoglobin is formed
Hb+4O2 reversible Hb(O2)4
sign