Unit 3 iGCSE- Movement In and Out of Cells

Unit 3 iGCSE- Movement In and Out of Cells

By Robert Bailey

Multiple Choice

Which of the following is the best definition of diffusion?

• The movement of water from an area of high concentration to low.

• The movement of particles down a concentration gradient by random motion.

• The movement of particles against a concentration gradient.

• The movement of particles down a concentration using energy.

Open Ended

Define Diffusion

How many of these key words (bold) did you include?

​The Net movement of particles;

From an area of high concentration to low concentration or down a concentration;

Due to random movement;​

Multiple Choice

What provides the energy for diffusion?

• ATP

• Kinetic energy of molecules

• The cell

• Mitochondria

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Exam tip:

Diffusion

REMEMBER:

• Always high ---> low concentration

• Can occur across a cell membrane...

• BUT Is the only form of cell transport that does not require a cell membrane.

​Osmosis

Open Ended

Define Osmosis...

Osmosis​

Is the net movement of water molecules from a region of high water potential to low water potential (or down a water potential gradient) through a partially permeable membrane.

Multiple Choice

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Osmosis always occurs from an area of high to low concentration.​

​

high water potential-------> low water potential

Exam Tip:​ Always try to locate the area of high water potential first (remember that this will always be the dilute solution).

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​Boiling a piece of carrot destroys the membrane so no osmosis will occur

Remember osmosis requires a fully functional cell membrane

​

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Open Ended

Define Active transport

How many of the following did you include?

The movement of particles through a semi-permeable cell membrane;​

From a region of low concentration to high concentration;

Using ATP/energy from respiration​;

And specific protein carriers;​

​

Multiple Choice

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Explain how protein molecules move particles across a membrane during active transport. (4)

Explain how protein molecules move particles across a membrane during active transport. (4)

• Specific substance binds to the carrier protein;

• ATP binds to the protein;​

• This causes it to change its shape.

• ​Allowing it to move substances from an area of low concentration to high concentration.