National 5 Biology
Unit 1: Cell Biology
Chapter 1: Cell Structure
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Mrs Smith
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National 5 Biology
Learning Intentions
By the end of this chapter, you should be able to describe cell structure
- Specifically be able to discuss - Cell ultrastructure and functions to
include: cell wall, mitochondrion, chloroplast, cell membrane, cytoplasm,
vacuole, nucleus, ribosome and plasmid.
- You should also be able to describe the ultrastructure by using examples
from typical plant, animal, fungi and bacterial cells.
- Explain fungal structure in terms of similarity to plant and animal cells but
with a different cell wall structure. (Cell wall structure in fungal and
bacterial cells is different from plant cells, ie chitin not cellulose)
- Bacterial structure description should include the absence of organelles
(no nucleus, mitochondria vacuole or chloroplasts) and a different cell wall
structure to plant and fungal cells.
-Bacterial structure should also include a description of there chromosomes
and plasmid.
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CELLS ARE THE STARTING POINT!
• All living organisms on Earth are divided
into cells. The main concept of cell theory is that
cells are the basic structural unit for all
organisms. Nothing smaller than a cell can lead to
independent life.
• Cells are small compartments that hold the
biological equipment necessary to keep an
organism alive and successful. Living things may
be single-celled or they may be very complex
such as a human being.
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Plant Cells – Can be viewed under the
microscope
• Below are examples of plant cells viewed under the microscope
• Some of a plant cells parts can be seen clearly when mounted in water (see
below)
• Other cell structures that are not so obvious can often be shown up more
clearly by the addition of a STAIN (dye). Iodine solution can be used on onion
cells to stain the nuclei.
Elodea leaf cells in
water
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Onion leaf cells in
iodine solution
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Using stains with the
microscope.
Stains can be used to make cells
more visible under the microscope,
e.g. Iodine solution.
Onion skin: 2 pieces were taken
from the bottom layer of an onion
and placed on 2 different slides.
With one, some iodine was placed n
the slide to see the different layers,
The other slide was left unstained.
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Onion Cell Lab Instructions.
• Add 2 drops of iodine to the centre of a glass slide. Be
careful! Iodine can stain your clothes.
• Take a small piece of onion. Use tweezers to peel off the
skin from the underside (the rough, white side) of the
onion. Throw the rest of the onion piece away.
• Carefully lay the onion skin flat in the centre of the slide on
top of the iodine.
• Add 2 drops of iodine to the top of the onion skin.
• Stand a thin glass cover slip on its edge near the onion skin,
next to the drop of iodine.
• Slowly lower the other side of the cover slip until it covers
the onion skin completely. If there are air bubbles, gently
tap on the glass to “chase” them out.
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Draw what you see.
Why are there
no chloroplasts
in onion cells?
Iodine Solution with
air bubbles
Chloroplasts are absent from
onion skin cells because it grows
underground in the darkness (so
what would be the point?)
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This is what our Onion cell looked like!
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Plant Cell (Pond weed).
Lab Instructions
• Tear off one small leaf/stem from
the plants in the fish tank.
• Add one drop of tap water to the
slide.
• Stand a thin glass cover slip on its
edge near the leaf, next to the
drop of water.
• Slowly lower the other side of the
cover slip until it covers the leaf
completely. Make sure there are
no air bubbles.
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Draw what you see.
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While some cells do look different, all
cells have these three basic features.
nucleus
cytoplasm
cell
membrane
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The Nucleus
Controls the cell’s
activities
Controls all the
chemical
reactions inside
the cell
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The Cell Membrane
The cell membrane
is selectively permeable
and controls what
substances may enter
and leave the cell.
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Cell
membrane
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The Cytoplasm
It is a jelly like material
All the chemical
reactions taking place
in the cell occur here
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ORGANELLES - Continued
• Organelles are tiny structures (such as
chloroplasts) that are:
– Present in a cells cytoplasm as discrete units
normally surrounded by a membrane.
– Responsible for a specialised function (such as
photosynthesis
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Ultrastructure
• Cell structure is
actually way more
complicated than we
have been teaching
you……
• There are even smaller
structures in a cell.
These minute
structures cannot be
seen with a normal
light microscope. They
can only bee seen using
a more sophisticated
piece of equipment
called the electron
microscope.
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Cooperative
activity
Cell race
20
minutes
max!
Your group will be issued with four different cell diagrams and four
different descriptions as well as your own summary sheet.
1. Read each description carefully.
2. Match up each description with the correct cell.
3. Copy each cell picture into your jotter
4. Using all of the descriptions complete your table with a general
function for each of the cell parts you have identified.
5. Complete the table by stating which of the cell parts are present in
each cell type.
You have finished the cell race only when every member of
the group has completed their own diagram and table and
this has been checked by your teacher so assign group tasks
wisely and remember to include everybody.
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Animal Cell
Animal cells are bounded by a cell membrane that controls entry and
exit of substances. The cytoplasm is the “factory” part of the animal
cell in which chemical reactions take place to manufacture various
substances. The nucleus holds the DNA molecules (chromosomes) that
are composed of sections called genes. Gene code for the making of
proteins that control the activity of the cell. Embedded in the
cytoplasm are mitochondria- sausage shaped structures with a smooth
outer membrane and a folded inner membrane. It is in the mitochondria
that aerobic respiration (respiration that uses oxygen) takes place. Also
in the cytoplasm of animal cells free or attached to membranes are
ribosomes- small spherical structures that are where protein molecules
are created using instructions supplied from the DNA in the nucleus.
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Plant Cell
Plant cells are bounded by a cell wall made of cellulose fibres that
forms a rigid box that although permeable to all but the largest
molecules provides support for the cell and the plant as a whole. To the
inside of the cell wall is the cell membrane that controls entry and
exit of substances and is composed of proteins and phospholipids. The
cytoplasm is the “factory” part of the plant cell in which chemical
reactions take place to manufacture various substances. The nucleus
holds the DNA molecules (chromosomes) that are composed of
sections called genes. Genes code for the making of proteins that
control the activity of the cell. Embedded in the cytoplasm are
mitochondria- sausage shaped structures with a smooth outer
membrane and a folded inner membrane. It is in the mitochondria that
aerobic respiration (respiration that uses oxygen) takes place. Also in
the cytoplasm of plant cells free or attached to membranes are
ribosomes- small spherical structures that are where protein molecules
are created using instructions supplied from the DNA in the nucleus.
Chloroplasts are the site of photosynthesis in green plant cells.
Vacuoles are fluid filled sac containing cell sap which are important in
controlling water balance within the cell.
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Fungal Cell
Fungal cells are bounded by a cell wall made of chitin that forms a rigid
box that provides support for the cell. To the inside of the cell wall is
the cell membrane that controls entry and exit of substances and is
composed of proteins and phospholipids. The cytoplasm is the “factory”
part of the fungal cell in which chemical reactions take place to
manufacture various substances. The nucleus is the control centre of
the cell. It holds the DNA molecules (chromosomes) that are composed
of sections called genes. Gene codes for the making of proteins that
control the activity of the cell. Embedded in the cytoplasm are
mitochondria- sausage shaped structures with a smooth outer
membrane and a folded inner membrane. It is in the mitochondria that
aerobic respiration (respiration that uses oxygen) takes place. Also in
the cytoplasm of fungal cells free or attached to membranes are
ribosomes- small spherical structures that are where protein molecules
are created using instructions supplied from the DNA in the nucleus.
Vacuoles are fluid filled sac containing cell sap which are important in
controlling water balance within the cell.
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Bacterial Cell
Bacterial cells are bounded by a cell wall made of peptidoglycan that
forms a rigid box that provides support for the cell. To the inside of
the cell wall is the cell membrane that controls entry and exit of
substances and is composed of proteins and phospholipids. The
cytoplasm is the “factory” part of the bacterial cell in which chemical
reactions take place to manufacture various substances. In a bacterial
cell the DNA is free in the cytoplasm usually in one large mass. The
DNA is composed of sections called genes. Genes code for the making of
proteins that control the activity of the cell. In bacterial cells smaller
circles of DNA called plasmids are found. Plasmids are freely exchanged
between bacterial cells and are now used in “genetic engineering”. Also
free in the cytoplasm of bacterial cells are ribosomes- structures that
are where protein molecules are created using instructions supplied
from the DNA.
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Structure
Function
In animal
cell?
In plant
cell?
In fungal
cell?
In bacterial
cell?
cell membrane
Holds cell contents and controls entry and
exit of substances.
Yes
Yes
Yes
cytoplasm
Cell’s “factory” –chemical reactions occur
here.
Yes
Yes
Yes
Yes
Contains DNA which holds the information to
make proteins which control the activity of
the cell.
Yes
Yes
Yes
No
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes
No
Yescellulose
Yeschitin
No
Yes
Yes
nucleus
mitochondrion
ribosome
cell wall
vacuole
chloroplast
plasmid
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Site of aerobic respiration.
Manufacture of protein using instructions
from DNA.
Rigid box gives organism support.
Fluid filled sac
Site of photosynthesis where carbohydrate
is made.
Ring of DNA exchanged readily between
cells.
Mrs Smith
No
Yes
No
No
No
No
Yes
Yespeptidoglycan
No
No
Yes
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Cells have differences in structure
• Close examination of 4 types of cells sown below show they
have some features in common but also differ from one
another in other ways.
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Animal Cell Structure
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Animal Cell Structure
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Example animal cells
nerve cell
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ciliated
epithelial cells
blood cells
sperm and egg cells
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Plant Cell Ultrastructure
Cellulose
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Plant Cell Structure
THEY ALSO HAVE MITOCHONDRIA AND RIBOSOMES
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Example Plant Cells
root hair cells
onion epidermal cells
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leaf cells
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xylem cells phloem cells
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Fungal Cell Ultrastructure
chitin
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Fungal Cell Ultrastructure
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Example fungal Cells
yeast cells
mushroom mycelial cellsMrs Smith
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Penicillium notatum
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Fusarium mycelial cells
Bacterial Cell Ultrastructure
Peptoglycan
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Bacterial Cell Ultrastructure
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Example Bacterial Cells
Eschericia coli
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Rhizobium
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Cholera
bacteria
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Cell Rap
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The Cell Song
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Cell Structure Notes
cells
All living things are composed of one or more _______
, the basic unit
of life.
The cells of green plants, animals and fungi have several structures in
common, including a ________,
and mitochondria.
nucleus
Bacterial
___________
cells lack a cell wall and store genetic material within
plasmids
_________.
chloroplasts but all cells contain
Only green plants contain __________,
ribosomes, a cell membrane and cytoplasm.
The cell’s activities are controlled by the nucleus. A plant cell is
supported by the cell wall and its cell _____
sap is stored in its
__________
vacuole.
Bacterial
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Cells
Plasmids
Supported
Chloroplasts
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Nucleus
Sap
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Activity – Measuring cell sizes
• Cells cannot be seen without the aid of a
microscope.
• They are so small that we used units
called micrometers (μm) or microns to
measure them
• There are 1000 microns in 1 millimetre.
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YOU MUST BE ABLE TO MOVE
BETWEEN THESE DIFFERENT
UNITS> MAKE SURE YOU
PRACTISE
CONVERTING ONE TO
Mrs Smith
THE OTHER.
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Measuring cell sizes
We can estimate the sizes of cells by knowing the diameter of the
field of view.
e.g. If the field of view is 2mm which is 2000μm and there are 8
cells streching from one side to the other, then each cell must be
250μm (2000/8)
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Activity – Measuring cell sizes
2mm (field of view)/ 5 (no. of cells lengthwise across field of view) = 0.4mm
2mm (field of view)/ 10 (no. of cells up and down in field of view) = 0.2mm
0.4
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0.2
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Activity – Measuring cell sizes
This cell is 25mm in the diagram.
What is the actual size of the cell?
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0.0625mm
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Activity – Measuring cell sizes
This cell is 20mm in the diagram.
What is the actual size of the cell?
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0.05mm
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Task TYK
• Complete questions 1 – 4. Torrance p5
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Task TYK
• Complete questions 1 – 4. Torrance p5
1.
2.
2.
3.
Cells (1)
A) Cell membrane, mitochondria, nucleus, ribosome's. (4)
B) Cell wall, chloroplasts, large central vacuole (3).
Chloroplast for photosynthesis, nucleus for control of cell activities, cell membrane
for control of movement of substances onto and out of cell, mitochondrion for
aerobic respiration (4).
4.
A) 1 millimetre = 1000 micrometers (1)
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4. B) 1 micrometer = 0.001 millimetres (1).
Quick test
1. How is the cell wall of a plant cell different
from that of a yeast cell?
2. Name two cell structures that cannot be seen
with a light microscope.
3. What features do yeast and p[lant cells have
in common?
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Answers
1. How is the cell wall of a plant cell different from
that of a yeast cell?
1. Plant cell wall is made of cellulose, yeast cell wall is
made of chitin.
2. Name two cell structures that cannot be seen
with a light microscope.
2. Ribosomes and mitochondria.
3. What features do yeast and plant cells have in
common?
3. Cell wall, nucleus, cytoplasm, cell membrane,
ribosomes, mitochondria and vacuole.
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National 5 Biology
Have we achieve our learning
Intentions
By the end of this chapter, you should be able to describe cell structure
- Specifically be able to discuss - Cell ultrastructure and functions to
include: cell wall, mitochondrion, chloroplast, cell membrane, cytoplasm,
vacuole, nucleus, ribosome and plasmid.
- You should also be able to describe the ultrastructure by using examples
from typical plant, animal, fungi and bacterial cells.
- Explain fungal structure in terms of similarity to plant and animal cells but
with a different cell wall structure. (Cell wall structure in fungal and
bacterial cells is different from plant cells, ie chitin not cellulose)
- Bacterial structure description should include the absence of organelles
(no nucleus, mitochondria vacuole or chloroplasts) and a different cell wall
structure to plant and fungal cells.
-Bacterial structure should also include a description of there chromosomes
and plasmid.
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Mrs Smith
48