The Cell_Part III

8/7/2019 The Cell_Part III

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The Cell

Part III - The Specialised Cells


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Overview Specialised cells:

Red blood cell

Xylem vessel Root hair cell


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What does it mean by

specialised cellspecialised cell?

Specialised cell is the cell that

performs specific functions.


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Examples of specialised cells

Animal cells:

Type of Cells Function

Red blood cells Transport oxygen

Nerve cellsCarry nerve impulses or

information

Muscle cells For body movement

Sperm cells Reproduction


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Examples of specialised cells

Plant cells:

Type of Cells Function

Xylem vessel

Transport water and dissolved

mineral salts from the root to

various parts of the plant

Root hair cellsTo absorb water and mineral salts

from the soil

Mesophyll cellsTrap energy from the Sun to make

food during photosynthesis


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Where do specialised cells

come from? New cells are produced through cell division.

The new cell may develop special structures

or lose certain structures to enable them to

carry out specific function.

This process is known as differentiation,which is a process by which a cell becomes

specialised for a specific function.


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DifferentiationDifferentiation


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Types of Specialised Cells

Specialised cells

Redblood

cell

Xylem

vessel

Roothair

cell


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Red Blood Cell (RBC)

Also known as erythrocyte.

Appears red because RBC contains

red pigment called haemoglobin

which can bind to oxygen.

Mission of RBC: Transport oxygen from the lungs to

the tissues throughout the body.


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Red pigment

Combines easily with oxygen to

transport oxygen throughout the

body.

1. Presence of

haemoglobin

Relationship between Structure

and Function of Red Blood Cell

The human red blood cell is able to carry out its

function efficiently because:


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How does the structure of the human redblood cell help it carry oxygen efficiently?

The frog is normally inactive. How could this

behavior be attributed to the structure of its

red blood cell?

Red Blood Cell (RBC)

RBC in human RBC in a frog


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Enable RBC to carry more haemoglobin

Hence,more oxygen can be carried.

2. Nuclues isabsent(anucleated)

This increases the surface area to

volume ratio of the cell.

Oxygen can diffuse in and out at a

faster rate.

3. Circularbiconcaveshape

Provide flexibility so that cell can

change its shape while squeezing

through narrow capillaries.

4. Thin andelastic plasmamembrane

Relationship between Structure

and Function of Red Blood Cell


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Circular biconcave shape of RBC


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Students

Activity (10 mins) Refer to your textbook

pg. 25.

Complete the GraphicOrganiser Worksheet

given to you for

another 2 types of

specialised cells: Xylem vessel

Root hair cell

You have to relate the

structure of the

specialised cells to

their functions.

(Ques: How does this

structure aids the cell

to carry out a

particular function?)


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Types of Specialised Cells

Specialised cells

Redblood

cell

Xylem

vessel

Roothair

cell


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Increase the diffusion rate

of oxygen into the cell.

4. Thin andelastic plasma

membrane

Relationship between Structure and

Function of Red Blood Cell

Amendment:


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Recap

Adaptations Effect of the adaptation

Circular biconcave shape

Increase the surface area to

volume ratio to increase the

diffusion rate of oxygen

Has no nucleusTo have more space to carry

oxygen

Haemoglobin To carry oxygen

Thin plasma membraneTo allow oxygen to diffuse in

and out easily

Adaptations of red blood cell:


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Root Hair Cell

Fig 11. Root hair is a tubular

outgrowth of an epidermal cell.


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Root Hair Cell

Mission to absorb water and mineral salt

from soil

Adaptation Long, narrow extension of the

cell

Cell wall

NucleusCytoplasm

Vacuole

Plasma membrane


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Root Hair Cell

Advantages of having long, narrow

extensions:

It increases the surface area to volume

ratio of the root hair cell.

Hence,absorption of water and mineral

salts increase.


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Xylem Vessel

Cut


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Xylem Vessel

Mission Transport water and dissolved

mineral salts from root to various parts of a

plant.


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Xylem Vessel

Adaptations:

1) Form long hollow tubes laid end to end

2) Lignin is deposited on xylem walls

3) Do not have cross walls or protoplasm


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Xylem Vessel

Adaptation 1:

Form long hollow tubes laid

end to end Advantage: provides a

pathway for transportation

of water and mineral salts


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Xylem Vessel

Adaptation 2:

Lignin is deposited on xylem walls

What is Lignin?

-Polymer found in wood-Binds to cell wall to strengthen cell wall

-The more lignin a plant has, the woodier it

becomes

Advantage: To strengthen the wall (make the

vessel hard and rigid), hence prevent it fromcollapsing; provide mechanical support


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Xylem Vessel

Adaptation 3:

Do not have cross walls or protoplasm

Adv

antage:E

nables water to mov

e easilythrough the central space or lumen


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Xylem Vessel

How does these adaptations help xylem vessel

to carry out the function more efficiently?

Adaptation How does it help the function?

Long hollow tubes

laid end to end

Lignin is deposited on

xylem walls

Do not have cross

walls or protoplasm

Provides a pathway for transportation

of water and mineral salt

To strengthen the wall and prevent it

from collapsing; provide mechanicalsupport

Enables water to move easily through

the central space or lumen


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Closure

Specialised cells

Redblood

cell

Xylem

vessel

Roothair

cell


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Homework

Comparison between the animal cell and

plant cell (Essay)

W

orkbook (pg. 2 to 7)

Cell Structure and Organisation The week after term-break

Class Test


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Animal cells versus Plant cells

Features Animal cells Plant cells

1. Cell wall

2. Chloroplasts

3. Centrioles

4. Vacuole

5. Shape

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