Transcript REVIEW Specialized cells ppt

Specialized Cells
In this presentation you will:
 explore how cells are specialized
 examine specialized cells of both plants and
animals
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Introduction
Plants and animals
have specialized
cells that are
designed to carry
out particular tasks.
Epidermal
layer of skin
contains
epithelial cells
Muscle cells
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The Cell
Cells are often described as the building blocks of life.
This is because all living
things are made up of
one or more cells.
All processes needed for
life, take place in cells.
Cells are microscopic, which means that they are
so tiny we cannot see them without a microscope.
Plant and animal cells are similar but not exactly
the same.
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Plant and Animal Cells
There are some features that
almost all plant and animal
cells have in common.
Plant and animal cells
both have:
Nucleus
Cytoplasm
Cell membrane
 a cell membrane – to control what goes into
and out of the cell
 cytoplasm – where chemical reactions take place
 a nucleus – to control what happens in the cell
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Plant and Animal Cells
Features only in plant cells are:
Nucleus
 chloroplasts – to
make food
 a vacuole – to keep
the cell firm
Cytoplasm
Cell membrane
Cell wall
Vacuole
 a cell wall – to
support the cell
Chloroplast
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Unicellular Organisms
Some organisms are
made up of just one
cell throughout their
whole life cycle.
They are called
unicellular or singlecelled organisms.
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Unicellular Organisms
These single cells are able
to make all the substances
needed to carry out all the
functions of life.
They are also able to divide
and copy themselves very
quickly, sometimes more
than once in an hour.
Bacteria and Amoeba are examples of unicellular
organisms.
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Multicellular Organisms
For larger, complex
organisms such as
plants and animals,
cells working alone are
not much use.
A single cell would
never be able to carry
out all the roles needed
to keep a human alive.
This is why we are made
up of so many cells.
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Multicellular Organisms
An organism that is
made up of more than
one cell is called a
multicellular organism.
Humans are made up
of billions of cells.
We do not need a
microscope to see
other humans.
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Cell Specialization
The cells that make
up a multicellular
organism are not all
the same.
For example, the cells
of the skin are not the
same as those that
make up our kidney,
and the cells of a
plant stem are not the
same as the cells of a
plant leaf.
Skin
Kidney
Stem
Leaf
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Cell Specialization
The different cells of a
multicellular organism
have very different
jobs to do.
The size and shape of
a cell depends on its
job or function.
Skin
Kidney
Stem
Leaf
We call this cell
specialization.
The cells are known as
specialized cells.
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Question 1
What is the name given to cells designed to carry
out a particular function?
A) Functional cells
B) Specialized cells
C) Designer cells
D) Worker cells
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Question 1
What is the name given to cells designed to carry
out a particular function?
A) Functional cells
B) Specialized cells
C) Designer cells
D) Worker cells
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Specialized Plant Cells
Trees and flowering
plants have a system of
roots, stems and leaves,
which support a plant
and enables it to make
food, and to transport
water and nutrients.
Leaves
Roots
Stem
They require a number
of specialized cells that
are adapted to do this.
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Specialized Plant Cells
Root hair cells are found at,
or near, to the tip of roots.
Cell Nucleus
They protrude into the
soil and have a large
surface area.
Root Hair
This feature maximizes the amount of water and
nutrients they can absorb from the soil.
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Specialized Plant Cells
As well as supporting a plant, the stem is important
for the transport of nutrients and water.
This is the vascular system.
Phloem
There are two types of
vascular tissue:
 the Xylem, which
transports water
Xylem
 the Phloem, which transports food
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Specialized Plant Cells
The phloem consists of sieve tube member cells
and companion cells.
Sieve tube member
cells carry nutrients,
such as sucrose, to
the parts of the plant
that need them.
Sieve tube
member
Nucleus
Sieve plate
Companion
cell
Phloem vascular tissue
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Specialized Plant Cells
The perforated sections in between the cells
(sieve plates), help liquid to move between them.
These cells have
no nucleus, but the
companion cells do.
Sieve tube
member
Nucleus
Sieve plate
Scientists believe the
companion cells also
control the sieve
member tubes.
Companion
cell
Phloem vascular tissue
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Specialized Plant Cells
The cells just below the
Upper side
surface of a leaf are
of leaf
called palisade cells. Palisade cells
They contain lots of
chloroplast organelles,
that hold the
chlorophyll needed to
make food via
photosynthesis.
Cross-section through a leaf
Under side
of leaf
Chloroplast
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Specialized Plant Cells
Palisade cells
are elongated.
Chloroplasts can
move up or down the
cell, toward or away
from sunlight.
Cross-section through a leaf
Upper side
of leaf
Palisade cells
By increasing or
decreasing the amount
of sunlight that reaches
the chloroplasts, the cell
is able to control the rate
of photosynthesis.
Under side
of leaf
Chloroplast
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Question 2
Which feature of the root hair cell means it is well
adapted to its job of absorption?
A) Its large surface area
B) The nucleus
C) Chloroplasts
D) Chlorophyll
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Question 2
Which feature of the root hair cell means it is well
adapted to its job of absorption?
A) Its large surface area
B) The nucleus
C) Chloroplasts
D) Chlorophyll
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Question 3
Which feature of the palisade cells enables the
control of photosynthesis?
A) They have a large surface area to maximize
absorption of water and nutrients.
B) They have perforated sections in between the
cells, to allow the movement of liquid.
C) They are elongated so that chloroplasts can move
close to, or further from the sunlight.
D) They have a large surface area so that
chloroplasts are always close to the surface to
maximize sunlight absorption.
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Question 3
Which feature of the palisade cells enables the
control of photosynthesis?
A) They have a large surface area to maximize
absorption of water and nutrients.
B) They have perforated sections in between the
cells, to allow the movement of liquid.
C) They are elongated so that chloroplasts can move
close to, or further from the sunlight.
D) They have a large surface area so that
chloroplasts are always close to the surface to
maximize sunlight absorption.
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Specialized Animal Cells
Examples of specialized cells in animals include:
 male reproductive
cells (sperm) that are
designed to swim to,
and join with, an egg
from a female
 red blood cells that
have a large surface
area to absorb
oxygen, and carry it
around the body
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Mature Sperm
The nucleus of a sperm cell is contained within the
head, and the layer of cytoplasm between the
nucleus and the cell surface membrane, is very thin.
Tail containing microtubules
Nucleus
Acrosome
Cytoplasm
Mitochondrion
Cell surface
membrane
At the tip of the head is the acrosome, which is a
membrane-bound compartment containing enzymes,
which allows the sperm to break into, and
enter, a female egg.
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Designed for Swimming
The tail of the sperm
contains microtubules,
which are responsible for
the swimming
movements of the sperm.
These are
always
arranged in a
9+2 pattern.
Cross section
of nine pairs of
microtubules
surrounding
central pair
Middle piece containing
mitochondria
Sperm obtain energy for swimming from the many
mitochondria that are closely packed together. Next >
Specialized Animal Cells
Red blood cells carry
oxygen around the body
to all of the body’s cells.
Top view
They do not contain a nucleus.
They are discs that are
narrower in the center and
wider around the edges.
Side view
This increases the surface area to maximize the
amount of oxygen they can absorb.
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Specialized Animal Cells
Red blood cells contain
a chemical called
hemoglobin that
holds the oxygen.
Hemoglobin contains iron,
and it is this that makes
the blood cells red.
Top view
Side view
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Question 4
What feature of a red blood cell helps the absorption
of oxygen?
A) It contains chloroplasts
B) It has a large surface area
C) Its tail
D) Its tube-like structure
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Question 4
What feature of a red blood cell helps the absorption
of oxygen?
A) It contains chloroplasts
B) It has a large surface area
C) Its tail
D) Its tube-like structure
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Summary
In this presentation you have seen:
 how cells are specialized
 examples of specialized cells of both plants
and animals
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