Download 1.1 Cells – structure and function

1.1 Cells – structure and function
How are we made?
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Key term
Organelles – Small structures
within cells. Each carries out a
particular function.
All living things on Earth are made of cells. Some consist of just one cell but some, like
you, are made of many cells. Cells are the building blocks of organisms. Cells are very
small but you can see them with a microscope.
cell wall
chloroplast
outer cell
membrane
cytoplasm
cytoplasm
nucleus
nucleus
mitochondrion
outer cell
membrane
ft
large fluid-filled
vacuole
The structure of a typical animal cell.
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The structure of a typical plant cell.
mitochondria
Case study
Plant and animal cells are
called eukaryotic cells.
Eukaryotic organisms have
cells with their genetic material
enclosed in a nucleus. Nearly
all of the living things on Earth,
except bacteria, are eukaryotes.
Sue is a cytology screener. She works in a hospital laboratory and has to look at
microscope slides of cells to see if any are abnormal. This could indicate that the
person whose cells they are has early stage cancer. Sue has to know about cell
structure so she can tell abnormal cells from normal ones. Cytology is the study of
cell structure.
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Did you know?
Link
Lesson 4.4 discusses how
viruses are not made of cells.
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BTEC First Principles of Applied Science
A microscope slide showing abnormal (red) and normal cells from the cervix.
Principles of Science
UNIT 1
Plant and animal cells have many components, called organelles, such as chloroplasts
and mitochondria. The table shows the different functions of the organelles found in
plant and animal cells.
Function
In plant
cells?
In animal
cells?
Outer cell
membrane
Encloses the cell and keeps it separate
from its environment. It controls how
substances enter and leave the cell.
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3
Nucleus
Contains DNA (genetic information)
arranged into chromosomes. It controls
the activities of the cell.
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3
Jelly-like substance in which the
organelles are held. Many chemical
reactions take place in the cytoplasm.
3
3
Mitochondrion
(plural:
mitochondria)
The organelle where aerobic respiration
– the release of energy from glucose or
fat in the presence of oxygen – takes
place.
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Cell wall
Made from cellulose. The cell wall is
very strong and prevents the cell from
bursting. It gives the cell shape.
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Contains chlorophyll, which absorbs
light energy for photosynthesis.
3
7
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Cytoplasm
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Chloroplast
Vacuole
ft
Cell
component
Contains cell sap and provides extra
support for the cell. The vacuole can
store nutrients and waste products.
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3
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Activity A
List the ways that animal and
plant cells are (a) similar to
each other and (b) different
from each other.
Common misconception
Many people think that plants do not have genes. Their cells contain a nucleus,
with DNA organised into chromosomes. Genes are lengths of DNA. So plants do
have genes.
Just checking
For each of the following statements, say whether it is true or false.
1 All living things are made of many eukaryotic cells.
2 Plant cells do not contain mitochondria.
3 Animal cells do not have a large vacuole.
4 The cell membrane controls which substances enter and leave a cell.
Lesson outcomes
You should know about the
basic structure and function of
some eukaryotic cells and of
some of their components.
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1.2 Specialised cells
You, like many other organisms including plants, started life as a single cell – a
fertilised egg. This divides and forms an embryo. Cells become specialised to
perform different functions. This is called differentiation (becoming different).
Some examples of specialised cells are shown below. (a) to (f) are animal cells and (g)
to (j) are plant cells. They all have the same basic components but each type has some
differences in structure. These differences enable the cells to carry out their particular
function (job). Each type of cell is adapted for its function.
(a)
(b)
Egg cell – for sexual reproduction.
outer cell membrane
Sperm cell – for sexual reproduction.
The sperm has a tail to help it move to find the egg. It
also has a large number of mitochondria to supply the
energy needed for the movement.
nucleus
very small amount
mitochondria
of cytoplasm
large amount
of cytoplasm
nucleus
mitochondria
head
ft
tail
(c) Red blood cells – small cells, packed with haemoglobin
which carriesoxygen. They have no nucleus, no mitochondria
and little cytoplasm in order to carry more oxygen.
(d) White blood cells – for defence against infection.
There are different types of white blood cell, but
they all have a nucleus, cell membrane, cytoplasm
and mitochondria.
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outer cell
membrane
(e) Sensory neurone – long fibres carry impulses from
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sensory receptors to brain and spinal cord.
cell membrane
cell body
nucleus
receptor in skin
fatty sheath
(g)
outer cell
membrane
vacuole
BTEC First Principles of Applied Science
cell body
nucleus
(h)
cell wall
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spinal cord to muscles or glands.
dendrites
Root hair cell – for absorption.
Extension of cell increases
surface area for absorption of
water and minerals from soil.
(f) Motor neurone – long fibres carry impulses from brain or
long fibre
direction of impulse
nucleus
fatty sheath
long fibre
direction of impulse
muscle fibres
Xylem – to carry water. There is no cytoplasm
or organelles.
cell wall with lignin
to make it strong
empty hollow vessel for
carrying water from roots
to rest of plant
Principles of Science
i)
UNIT 1
(j) Guard cells in epidermis of leaf – to allow carbon dioxide
Phloem – carries dissolved sugars from
leaves to other parts of plant.
to enter for photosynthesis.
cytoplasm
sieve
tube
companion cell
with organelles
cell wall
chloroplasts
nucleus
sieve
plate
nucleus
guard cells
pore open
epidermal cells
Tissues
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A tissue is a group of similar, specialised cells that work together to carry out a particular
function in the body. Some examples of animal tissues are given in the table below.
Where found in the body
Functions
Epithelial
(covering
tissues)
Outside of skin. Make up the
inside linings of heart, blood
vessels, airways and gut.
Some epithelial cells have tiny
hairs, called cilia, on them.
Protection, absorption, filtration and
excretion.
Glands are also made of
epithelial cells.
Production of useful substances,
such as saliva, hormones and mucus.
Bone
Makes up skeleton – supports you
and allows you to move.
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Connective
ra
ft
Type of
tissue
Blood
Muscle
Nervous
Transport and defence against
invading microorganisms.
Smooth muscle in walls of
blood vessels and gut
Able to contract – arteries pulsate.
Gut moves food through it.
Heart muscle
Heart beats to pump blood around
body.
Nerves, spinal cord and brain
For sensing and responding
in a coordinated way to the
environment.
Activity A
1 Draw large, clear diagrams
of one specialised animal
cell and one specialised
plant cell.
2 Label and annotate (write
notes next to the labels)
the diagrams to show how
each cell is adapted for its
function. You should also
research, using the Internet
and textbooks, to find
out more about how the
cells you have chosen are
adapted. Use a ruler to draw
the label lines.
Just checking
For each of the following statements, say whether it is true or false.
1 Red blood cells cannot carry out aerobic respiration because they do not have
mitochondria.
2 Neurones are the longest cells in your body.
3 Blood and bone are types of connective tissue.
Lesson outcomes
You should know how cells
become adapted to carry out
specific functions, and that
cells form tissues.
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