M O V E M E N T   T H R O U G H   C E L L  M E M B R A N E 

2008

DRAW A LABELLED DIAGRAM OF A TRANSVERSE SECTION OF A YOUNG ROOT

WATER ENTERS THE OUTERMOST CELLS OF THE ROOT BY OSMOSIS.WHAT DOES THIS TELL YOU ABOUT THE CELL SAP OF THESE OUTERMOST CELLS?

  • They have a lower water concentration

OSMOSIS HAS BEEN DESCRIBED AS A SPECIAL CASE OF DIFFUSION. EXPLAIN WHY.

Osmosis is the movement of water from where the water is in high concentration to an area where the water is in low concentration across a semi-permeable membrane.

DESCRIBE AN INVESTIGATION THAT YOU CARRIED OUT TO DEMONSTRATE OSMOSIS.

  • Put a concentrated sucrose solution into a visking tube. Find mass of the tube and note its turgidity.
  • Place the visking tube in a beaker of distilled water and leave for 30mins.
  • Remove the tube and dry and find the mass.
  • The mass and the turgidity increased.
  • As a control, put water into a visking tube.Find mass.
  • Place in a beaker of distilled water.
  • Weigh and find mass. Results: No change.

DESCRIBE HOW MINERALS SUCH AS NITRATES ENTER THE ROOT OF A PLANT FROM THE SOIL.

Diffusion.

Diffusion is the movement of particles from an area of high concentration to an area of low concentration along a concentration gradient.

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2010

WHAT IS MEANT BY SELECTIVELY PERMEABLE

They allow some molecules and prevent the passage of others.

GIVE TWO LOCATIONS IN A CELL AT WHICH THEY IS A SELECTIVELY PERMEABLE MEMBRANE.

  • Cell membrane 
  • Nucleus

WHAT IS DIFFUSION?

Diffusion is the movement of particles in a liquid or gas from an area of high concentration to an area of low concentration along a concentration gradient.diffusion will continue until equilibrium is reached. E.g Oxygen enters red blood cells from the lungs

IN THE CASE OF A NAME MOLECULE GIVE A PRECISE LOCATION AT WHICH IF DIFFUSES IN THE HUMAN BODY.

Oxygen enters the red blood cells from the lungs. Location = Alveoli

EXPLAIN THE BIOLOGICAL BASIS FOR THE USE OF HIGH SUGAR OR HIGH SALT CONCENTRATION IN THE PRESERVATION OF FOOD.

When you place food in a high salt or sugar concentration, water moves out of the cells and becomes dehydrated. As a result the bacteria cannot work or multiply. The cell becomes dehydrated as a result of osmosis.

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2011

STATE THE PRECISE LOCATION OF THE CELL MEMBRANE IN PLANT CELLS.

Immediately inside the cell wall.

WITH WHAT TYPE CELL DO YOU ASSOCIATE WITH MEMBRANE BOUND ORGANELLES.

  • Eukaryotic

WHAT CORRESPONDING TERM IS USED TO DESCRIBE BACTERIAL CELLS.

  • Prokaryotic

THE CELL MEMBRANE IS DESCRIBED AS BEING SELECTIVELY PERMEABLE. WHAT DOES THIS MEAN?

They allow the free passage of some molecules and prevent the passage of others.

WHY IS DIFFUSION ALTERNATIVELY DESCRIBED AS A PASSIVE TRANSPORT?

It does not require energy

OSMOSIS MAY BE DESCRIBED AS A “SPECIAL CASE OF DIFFUSION”. EXPLAIN WHY.

Osmosis is the movement of water from an area where water is in low concentration to an area where water is in high concentration across a semi-permeable membrane.

DESCRIBE WITH A LABELLED DIAGRAM HOW DEMONSTRATED OSMOSIS IN THE LABORATORY.

  •  Put a concentrated sucrose solution into a visking tube. Find mass of the tube and note its turgidity.
  • Place the visking tube in a beaker of distilled water and leave for 30mins.
  • Remove the tube and dry and find the mass.
  • The mass and the turgidity increased.
  • As a control, put water into a visking tube.Find mass.
  • Place in a beaker of distilled water.
  • Weigh and find mass. Results: No change

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2012

DIFFUSION: diffusion is the movement of particles in a liquid or gas from an area of high concentration to area of low concentration along a concentration gradient.Diffusion will continue until equilibrium is reached.

OSMOSIS:is the movement of water where water is in an area of high concentration to an area where water is in low concentration across a semi-permeable membrane.

ACTIVE TRANSPORT: is the movement of a substance from an area of low concentration to an area of high concentration along a concentration gradient. Energy is needed.

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2013

EXPLAIN THE TERM SELECTIVELY PERMEABLE

They allow the free passage of some molecules and prevent the passage of others.

SUGGEST AN ADVANTAGE TO THE CELL OF HAVING A SELECTIVELY PERMEABLE MEMEBRANE.

  • Substances can be kept in

TWO SUBSTANCES THAT ENTER THE HUMAN MUSCLE CELL BY DIFFUSION

  • Oxygen
  • Glucose

EXPLAIN THE TERM TURGOR

This is the pressure of cell contents against the cell wall.

GIVE A FEATURE OF A PLANT CELL THAT ALLOWS IT TO BE TURGID FOR LONG PERIODS.

Cell wall

SUGGEST A WAY WHICH TURGOR IS OF VALUE TO PLANTS

Support. Turgor allows plants to stand upright so their leaves can get more light for photosynthesis.

WHEN DEMONSTRATING OSMOSIS: 

WHAT PURPOSE DID YOU USE VISKING TUBE,POTATO TISSUE OR SOMKE SIMILAR MATERIAL?

To act as a selectively permeable membrane

HOW DID YOU CONCLUDE THAT OSMOSIS HAD OCCURED?

Change in mass. The visking tube with sucrose solution place in distilled water increased in mass.

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2015

GRAPH QUESTIONS (A)-(C)

EXPLAIN HOW PLANT CELLS REMAIN TURGID

Water is enters vacuole, swells slightly  and pushes the cytoplasm out against the cell wall. The cell wall prevents the cell from bursting because it is relatively rigid.

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2016

WHAT DO YOU UNDERSTAND BY THE TERM TURGOR IN PLANT CELLS.

Pressure of the cell contents against cell wall.

HOW DO PLANT CELLS REMAIN TURGID FOR A CONSIDERABLE PERIOD OF TIME.

Water enter the vacuole, swells slightly and pushes the cytoplasm out against the cell wall. The wall wall is relatively rigid and prevents the cell from bursting.

WHAT HAPPENS TO A PLANT IF MANY OF ITS CELLS LOSE TURGIDITY

It will fail to stay upright and wilt.

IF AN ANIMAL CELL WERE SUBJECTED TO THE CONDITIONS THAT RESULT IN A PLANT CELL BECOMING TURGID SUGGEST WHAT MIGHT HAPPEN TO THE ANIMAL CELL. EXPLAIN.

Water would enter the vacuole, swell and push the cytoplasm out, however because animal cells don’t have cell walls the cell would burst.