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1. Movement of
substances across
the plasma
membrane
Chapter 3

2. • Many biochemical reactions take
place in a cell.
• The cells require many substances
to carry out these biochemical
reaction.
• Waste products that are formed
during biochemical reactions within
the cells must be eliminated
because they are poisonous.

3. • There is movement of substances across
the plasma membrane so that the cell can
Obtain nutrients and gases
Excrete metabolic wastes
Maintain a suitable pH and
ionic concentration with the
cell for enzyme activity

4. Red Blood Cell Near Some Body cell
Moving in Moving out
Carbon dioxide
Oxygen

5. Photosyntesising Plant Cell
Moving in Moving out
Carbon dioxide
Oxygen
Water
Glucose

6. Plant Cell With No Chloroplast
Carbon dioxide
Oxygen
Glucose
Water
Moving in Moving out

7. Liver cellCarbon dioxide
Oxygen
Glucose
Water
Amino acids
Urea
Moving in Moving out

8. The structure of the plasma membrane
The plasma
membrane has 3
components
1. Double layer of
phospholipids
molecules.
2. Pore
3. Carrier Proteins

10. A phospholipid molecule
Hydrophilic head
Hydrophobic tails

11. Phospholipid
bilayer
Outside of cell
Inside of cell Phospholipidlayer

12. • The phospholipids bilayer, proteins and other
parts are not rigid or static, but form a dynamic
and flexible structure.
• The protein molecules float about in the
phospholipid bilayer to form a mosaic pattern
that is always changing like fluid.
• Singer and Nicolson call it ‘fluid-mosaic model’

13. The plasma membrane is generally described as
semi-permeable or selectively permeable
because it only lets certain substances through.
Fat soluble molecules and
small molecules such as oxygen
are able to pass through unaided.
Water soluble substances such as
glucose and amino acids and ions
need to aided by carrier protein.
Water molecules can move
across plasma membrane.

14. Which of these substances can pass
through phospholipids layer or carrier
protein?
Na+ Sodium
ion
K+ Potassium
ion
Carrier
Protein
Channel
Protein

15. Movement Of Substances Across
The Plasma Membrane
Passive transport Active transport
Simple
diffusion
Facilitated
diffusion
Osmosis

17. The differences between PT and AT
Does not require
energy
Substances move
with concentration
gradient
Will continue until
an equilibrium is
reached
Require energy
from cell respiration
Substances move
against concentration
gradient
Process leads to
accumulation or
elimination of the
substance from the cell
Passive Transport Active Transport

18. Active TransportActive Transport
• The movement of particles across the plasma
membrane against the concentration
gradient, that is from a region of low
concentration to a region of high concentration.

19. • Active transport also requires specific carrier
proteins that bind to the substance to be
transported, enabling the substance to pass
rapidly across the plasma membrane.
• Sometimes the carrier proteins are referred to
biological pumps.
• Active transport requires an input of energy
provided by ATP. So, it can only take place in
living organism.

20. Sodium-potassium pumpSodium-potassium pump

21. Ion intake by root
hairs of a plant
Mineral ions are absorbed across the membranes of the root
hairs by active transport.

22. Facilitated DiffusionFacilitated Diffusion
• The movement of hydrophilic molecules or
ions across the plasma membrane with
the help of transport proteins.

23. • Substances that are not soluble in lipids
do not pass readily through the
phospholipid bilayer.
• Substances such as glucose, amino
acids, proteins and nucleic acids pass
through the membrane by facilitated
diffusion.

24. Facilitated Diffusion
Involves 2 types of protein
Channel proteins Carrier proteins
Provide functional pore in the
membrane for the diffusion of ions.
The pore are selective about which
ions can pass through
Pick up the diffusion molecules on
one side of the membrane and
release them on the other side

25. Absorption of certain nutrients through the villi of the small
intestine.
Carrier proteins found on the membrane of cells that line
the intestinal wall transport small molecules such as amino
acids and glucose into the blood capillaries of the villi
glucose
Ammino
acids

26. OsmosisOsmosis
The movement of water molecules from region of
their higher concentration to a region of their lower
concentration through a semi-permeable
membrane.

27. The water potential of a solution is a measure of
the tendency of water molecules to leave the
solution.
A dilute solution has a higher water potential than
a concentrated solution.
Therefore, water molecules flow from the dilute
solution to the concentrated solution.

30. How osmosis helps in the uptake of
water in plants?

31. Simple DiffusionSimple Diffusion
• The movement of particles (molecules or
solutes) within a gas or a liquid from a region of
high concentration to a region of lower
concentration.

32. Factors affecting the rate of difussion:
1. Surface area between the two region.
(The larger the surface are, the higher
the rate of diffusion)
2. Distance over which diffusion occurs.
(The shorter the distance over which
diffusion occurs, the higher the rate of
diffusion across it)

33. 3. Concentration gradient.
(The greater the difference in concentration
between the two region, the higher the rate of
diffusion)
4. Size and nature of the particles.
(Smaller particles diffuse faster than larger
particles)
5. Temperature
(At higher temperatures, the particles have more
kinetic energy and so they diffuse at a higher
rate)

34. • Diffusion of different types of particle can
take place in opposite direction. For exp,
O2
O2
CO2
CO2
When oxygen diffuses
in of the cell, at the
same time carbon
dioxide diffuses out.
• Diffusion occurs in living and non living
systems.