Cells, Tissues and Organs Notes
Plant and Animal Cells
Plant and animal cells have 3 structures in common
These structures are:
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Nucleus
Cell membrane
Cytoplasm
In addition to the previous 3 structures, a plant cell has the following:
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Cell wall
Vacuole
Chloroplasts
You studied this
in 3rd year
Cells, Tissues and Organs Notes
Cells, Tissues and Organs Notes
National 5
Multicellular Organisms
Most animals and plants are made of many cells. Such animals and plants are known as multicellular
organisms.
Multicellular organisms have more than one cell type. They are made up of tissues and organs.
Organs perform different functions e.g. stomach, lungs. The cells in organs are specialised for their
function. Groups of cells working together are called tissues. Specialisation can be applied to all
named tissues in this topic
National 5
Variety of animal cells
Smooth muscle cells
Smooth muscle cells are cells which
show no variation in a tissue. They are
spindle shaped which allow them to
contract and relax in the muscles of the
alimentary canal allowing peristalsis to
take place.
Epithelial Cells
Squamous
epithelial cells
Columnar
epithelial cells
Squamous epithelial cells are more
commonly known as cheek cells. The
cells rubbed from a cheek are identical
to each other. The function of cheek
cells is to protect the cheek lining. They
have a flat irregular shape which allows
cells to form a loose covering layer
which is constantly replaced from below
during wear and tear.
The tissue also contains columnar cells.
The columnar epithelial cells are taller
than they are wide and line the cheek.
They help protect the lining and produce
the loose covering cells.
Cells, Tissues and Organs Notes
Blood
The red blood cell is biconcave in shape. This
provides a large surface area for the uptake of
oxygen. In addition there is no nucleus. This allows it
to be filled with haemoglobin to pick up oxygen.
A phagocyte is a type of white blood cell. It has the
ability to change shape and engulf micro-organisms
in a process called phagocytosis. It contains
lysosomes which contain powerful digestive
enzymes to digest microbes.
The other type of white blood cell is a lymphocyte. A
lymphocyte can produce antibodies in response to
the surface proteins on a virus or other microbes.
The lymphocyte possesses receptor proteins which
allow them to do this.
Ciliated Epithelial Cells
Goblet cells are cup shaped and are able to
produce mucus. This traps the dirt and germs.
The ciliated epithelial cells have hair like cilia
which beat upwards sweeping dirty mucus up
away from the lungs.
Cells, Tissues and Organs Notes
Nerve Cells
There are 3 kinds of nerve cell or neurone.
The first type is the sensory neurone which
carries impulses from the sense organ to
the central nervous system (CNS). This has a
long fibre (insulated extension of
cytoplasm). This will transmit nerve
impulses long distances.
The second type of neurone is a motor
neurone which also has a long insulated
fibre to transmit electrical impulses. It
carries impulses from CNS to muscles.
The third type of neurone is a relay
neurone. It transmits impulses within the
CNS. It has many branches to make
connections with other neurones.
Cells, Tissues and Organs Notes
Variety of plant cells
Xylem Tissue
Xylem vessels are dead. They are long hollow tubes
allowing water to easily move up through the
plant. They are strengthened by rings or spirals of
lignin. This helps to support the plant.
Phloem Tissue
All phloem tissue is alive.
There are 2 types of cells
1. Cells belonging to a sieve tube
The end walls of these cells are
perforated to allow cytoplasm to move
from one cell to another carrying food.
These perforated end walls are called
sieve plates.
2. Companion cells
The companion cells contain a nucleus
which controls the sieve tube.
Cells, Tissues and Organs Notes
Root Epidermal Tissue
The epidermis cells are box like which allow cells
to fit together. This is needed for protection. The
epidermis has some of its cells elongated to
provide root hairs. This provides a large surface
area for absorption of water.
The following tissues all belong to the leaf which is an organ.
Mesophyll Tissue
There are 2 types of cell in mesophyll tissue.
The palisade mesophyll cells have chloroplasts present. They also have columnar shape which provides a
maximum surface area for absorption of light. This is where most photosynthesis takes place.
The spongy mesophyll cells have a round shape which allows moist air to be present between cells of the
tissue. These cells also have chloroplasts. More photosynthesis takes place here. In addition the moist air
spaces allow carbon dioxide to reach the cells.
Cells, Tissues and Organs Notes
Leaf Epidermal Cell
There are 2 types of epidermal tissue.
The first type is the upper epidermis tissue. These cells
are all identical to each other. They fit closely together
for protection although they allow light to pass through
to reach the mesophyll.
The second type of epidermal tissue is the lower
epidermis.
There are 2 types of lower epidermis tissue. The
epidermal cells are irregular shape allowing the cells to
fit together into a strong layer. This provides protection.
The guard cells surround the stomata. The guard cells are
sausage shaped with a thick inner cell wall facing stoma.
There are chloroplasts present.
The guard cells control gas exchange by changing shape
and opening or closing stomata.