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Cells and their organelles
Achievement Standard 91160
Biology 2.8
Investigate biological material at the
microscopic level
Living cells
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Living cells are divided into two types prokaryotic and eukaryotic. This division is based
on internal complexity. Basically, a prokaryotic cell
is usually a single celled organism with no nuclear
membrane.
Cell Models
Similarities and differences
Plant Organelles
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Cell wall – semi-rigid structure outside the plasma
membrane in plant cells. Mainly cellulose. Supports
the cell and limits its volume.
Cell (plasma) membrane – Inside the cell wall, controls
entry and exist of materials.
Cytoplasm – watery solution containing dissolved
substances and enzymes.
Chloroplasts – contain the green pigment chlorophyll.
Used for photosynthesis. Mostly found in leaves.
Nuclear membrane – a double layered membrane
around the nucleus where chromosomes are found.
Vacuole – Very large in plants – filled with aqueous
solution of ions. Storage, waste disposal, growth.
Flagellum – A structure like a tail that helps
movement of a cell – found in some
reproductive plant cells.
 Mitochondria – Ovoid structures bound by a
double membrane. Cell energy converters.
 Endoplasmic reticulum – network of tubules
and flattened sacs, used for protein packaging.
 Chromosome – Found in the nucleus. Can
genes.
 Cilia – small fibres on the outside of the cell
used for movement.
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Animal cell organelles
The main organelles are mostly the same with
the same functions.
 Some differences:
1. No cell wall – the cells do not need to be
supported as animals have skeletons
2. No large water storage vacuole – they do
have small ones.
3. No chloroplasts – animals are consumers and
do not need to photosynthesis.
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Different animal cells and their
organelles
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Nerve Cell – transmits nerve impulse to and
from the brain. It has a long thin axon to
allow the nerve impulse to travel and more
mitochondria to give energy for the impulse
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Muscle cell – helps muscles contract. A
muscle cell is long and narrow so that the
cells can group together to form a long
narrow bundle of muscle tissue. They have
more mitochondria to give it more energy
to contract and provide movement.
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Sperm cell – the reproductive cell of the
male. It swims to reach the female egg and
fertilise it. It has a long tail (flagella) to do
this. The large number of mitochondria in
the tail release energy for the swimming
motion.
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White Blood cell – specialised for
engulfing harmful bacteria. The blood cell
has an irregular shape to allow it to flow
around the bacteria. The lysosomes hold
enzymes used to digest the bacteria.
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Egg cell – The egg cell is round and has
more cytoplasm than normal. The
cytoplasm acts as a food source for the
developing zygote.
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Lung cell – the cilia on the long thin lung
cell move back and forth to move dust
that has been breathed in up through the
lungs to the throat where it can be
swallowed.
Cross section of a leaf
Different plant cells and their
specialisations
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Root Hair cell- The root hair cell in a
plant has a long extension out the side
into the soil. This means the cell
membrane has a large surface area which
can absorb more water by osmosis. Also
within the root hair
cell is a larger vacuole
which allows for the
increased water
absorbed to be
stored.
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Pallisade cell – is the main
photosynthetic cell of the leaf. They are
long and thin and are close to the top of
the leaf. Pallisade cells have many
chloroplasts closely packed together.
This provides a lot of chlorophyll which
allows photosynthesis to occur.
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Xylem cell – the xylem cell carries water
from the roots, up the stem of a plant to
the leaves where it is used for
photosynthesis. The xylem cells are long,
hollow tubes with no organelles. This
allows water to move through them.
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Guard cells – guard cells are found on the
surface of leaves, usually the underneath. They
control the movement of gases and water in
and out of the leaf. They can change their shape
to close the stoma (pore) to save water. They
have chloroplasts in them to make their own
food.