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Explain Transport Systems in Multi-Cellular and Single-Celled Organisms

In this worksheet. students will explain the impact of surface area to volume ratios on diffusion in organisms and the need for transport systems.

'Explain Transport Systems in Multi-Cellular and Single-Celled Organisms' worksheet

Key stage:  KS 4

Curriculum topic:  

Curriculum subtopic:  

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

To travel from A to B, we use specially designed modes of transport like cars, and multicellular and single-celled organisms move substances the same way!

 

Single-celled organisms move substances across their body surface, but when there are many cells, the volume increases while the surface area stays the same, so substances have to supply more needs and travel farther, slowing down diffusion and causing cell death.

 

To battle this, multicellular organisms increase their SURFACE AREA TO VOLUME RATIO by using specialised exchange surfaces and transport mediums to take substances in and out and around organisms.

 

1. Gas Exchange

In mammalian gas exchange, specially designed ALVEOLI increase the surface area of the lung, aiding the uptake of oxygen and the removal of carbon dioxide.

 

In plants, however, carbon dioxide diffuses into the cells to be used for photosynthesis, while the oxygen made diffuses out into the environment.

 

 

2. Urea

Diffusion also helps remove waste like urea, where blood transports it from the liver to the kidneys to be made into urine and excreted out of the body.

 

 

3. Dissolved Food

 

 

Dissolved food molecules diffuse across the wall of the small intestine and into the bloodstream using MICROVILLI that increase the gut's surface area for absorption.

                          

 

4. Water transport via OSMOSIS

Osmosis is the diffusion of water down a concentration gradient, and when plant cells are placed in a dilute solution they take water in and become TURGID, and the only thing that stops them bursting is their strong permeable cell walls.

 

But if plant cells are placed in highly concentrated solutions, meaning lots of solute but little water, cells release water and they shrink away from the cell wall, becoming PLASMOLYSED.

 

Animals cells change shape during osmosis as they don't have cell walls, sometimes affecting their function like red blood cells expanding or shrivelling up.

 

 

5. Active Transport of Mineral Ions

In plants, the uptake of MINERAL IONS by root hair cells uses active transport to pull mineral salts from the low concentration in the soil into the already highly saturated cells AGAINST the concentration gradient, using ENERGY from respiration.  

As soon as we have more than a few cells, specially designed transport systems are needed. 

What structures allow the intestines and lungs to increase their surface areas? 

How many of these different substances are transported in and out of cells and the blood using DIFFUSION?

Dissolved Foods

Water

Oxygen

Urea

Mineral Ions

Active transport is a method of substance transport across exchange surfaces, for example, root hair cells and the soil.

Dissolved Foods

Water

Oxygen

Urea

Mineral Ions

What is the journey of Urea?  

Blood ⇒ Liver ⇒ Kidneys

Liver ⇒ Blood ⇒ Kidneys

Kidneys ⇒ Blood ⇒ Liver

Both plants and mammals have very sophisticated methods of gas exchange because of the importance of effective respiration for cell survival.

Column A

Column B

In Plant Cells...
Carbon Dioxide Diffuses IN and Oxygen Diffuses OUT...
In Mammalian Lungs...
Oxygen Diffuses IN and Carbon Dioxide Diffuses OUT...

As animal cells don't have cell walls, when they gain water they sometimes threaten to...?

True or False:

 

The cell wall blocks substances from diffusing across.

When placed in different solutions, plant cells change their shape due to the effect of osmosis.

 

Diffusion, Osmosis and Active Transport all move substances down or against what phenomenon?

  • Question 1

As soon as we have more than a few cells, specially designed transport systems are needed. 

CORRECT ANSWER
EDDIE SAYS
Single-celled organisms can easily exchange substances across their surface because the thickness of one cell is a short distance, so diffusion is fast. In more complicated creatures like humans, many layers of cells mean more time is needed for substances to travel to all the cells around the body, and more cells mean a higher demand for nutrients. These two things together demonstrate the need for special transport systems to speed up the delivery of substances throughout organisms.
  • Question 2

What structures allow the intestines and lungs to increase their surface areas? 

CORRECT ANSWER
EDDIE SAYS
The alveoli look like cotton plants or grapes, having a bumpy formation rather than being smooth spheres, increasing the amount of surface that has contact with the blood for optimal diffusion. Microvilli also increase the surface area for dissolved food molecules to diffuse into the blood, creating peaks and troughs in the lumen of the small intestine instead of a regular circular tunnel.
  • Question 3

How many of these different substances are transported in and out of cells and the blood using DIFFUSION?

CORRECT ANSWER
Dissolved Foods
Oxygen
Urea
EDDIE SAYS
How did you get on with this question? Diffusion is used in gas exchange with oxygen and carbon dioxide in both plants and animals, but also with dissolved foods across the small intestine wall and waste products like urea. Osmosis is simply the diffusion of WATER and is important in determining cell shape. And finally, active transport is necessary for mineral ions to be transported into root hair cells in plants.
  • Question 4

Active transport is a method of substance transport across exchange surfaces, for example, root hair cells and the soil.

CORRECT ANSWER
EDDIE SAYS
Active transport is a type of diffusion, but it's trying to fight natural concentration gradients in living beings. When substances need to move substances into an already saturated area, simple diffusion won't work, so cells RESPIRE and use the ENERGY gained to push substances AGAINST the concentration gradient from an area with little to an area with a lot.
  • Question 5

What is the journey of Urea?  

CORRECT ANSWER
Liver ⇒ Blood ⇒ Kidneys
EDDIE SAYS
When excess amino acids from protein breakdown are converted into fat and carbohydrate stores, the liver makes toxic ammonia as an unwanted byproduct which has to be made into urea so it can be safely removed. Urea is therefore made by the LIVER and then diffuses into the BLOOD to be transported into the KIDNEYS to be made into urine and excreted out of the body.
  • Question 6

Both plants and mammals have very sophisticated methods of gas exchange because of the importance of effective respiration for cell survival.

CORRECT ANSWER

Column A

Column B

In Plant Cells...
Carbon Dioxide Diffuses IN and Ox...
In Mammalian Lungs...
Oxygen Diffuses IN and Carbon Dio...
EDDIE SAYS
Plant cells take in carbon dioxide for photosynthesis, creating oxygen which diffuses out of the cells. But in the alveoli, oxygen is needed for respiration while carbon dioxide waste is gathered in the blood from cells, escorted to the lungs, diffused across the alveoli and breathed out.
  • Question 7

As animal cells don't have cell walls, when they gain water they sometimes threaten to...?

CORRECT ANSWER
BURST
EDDIE SAYS
The additional support provided by the cell wall gives plant cells strength so when they take up water by osmosis they don't burst, which is a problem in humans cells like red blood cells.
  • Question 8

True or False:

 

The cell wall blocks substances from diffusing across.

CORRECT ANSWER
EDDIE SAYS
The cell wall is permeable, meaning it lets everything through for the partially permeable cell membrane to sort through. Remember: the role of the cell wall is to provide support for the cell! Well done on making it through this activity and remember to jot down any useful phrases or explanations that have helped you wrap your head around this topic!
  • Question 9

When placed in different solutions, plant cells change their shape due to the effect of osmosis.

 

CORRECT ANSWER
EDDIE SAYS
TURGID means the plant cell is full of water and the cell wall stops it bursting like human cells. This happens when there is a lot of water around the cell like a low solute or a dilute solution, as the cell takes up water across the concentration gradient through the permeable cell wall and cell membrane. PLASMOLYSED is when the cell vacuole and cytoplasm have lost so much water that the cell membrane starts peeling off the cell wall as the cell shrinks. A cell loses water when osmosis takes water across a concentration gradient into an area with little water like highly concentrated solutions (meaning concentrated in SOLUTE NOT WATER- this is called a dilute solution!) In animal cells, this causes shrinkage.
  • Question 10

Diffusion, Osmosis and Active Transport all move substances down or against what phenomenon?

CORRECT ANSWER
CONCENTRATION GRADIENTS
A CONCENTRATION GRADIENT
THE CONCENTRATION GRADIENT
EDDIE SAYS
The movement of substances is often dependent on whether the outside environment has more or less of the desired molecule than what's inside the cell, creating a natural shift in particles to create an equal balance on both sides. Active transport takes this one step farther and uses energy to go against this natural desire for equilibrium.
---- OR ----

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