Transcript Cell Specialisation - NCEA Level 2 Biology

Starter
Quiz:
1. What are the beating hairs for movement
of a unicellular organism called?
2. What organism uses these?
3. These structures also help with feeding by
moving food into a specialised area, what
is this called?
4. Amoeba use extensions of the flexible cell
membrane to move, what do we call this?
5. Which unicellular organisms can
photosynthesise?
Starter
Quiz:
1. What are the beating hairs for movement
of a unicellular organism called? Cilia
2. What organism uses these? Paramecium
3. These structures also help with feeding by
moving food into a specialised area, what
is this called? Cilia
4. Amoeba use extensions of the flexible cell
membrane to move, what do we call this?
Pseudopods
5. Which unicellular organisms can
photosynthesise? Euglena
4. Specialised Cells
Explain why
cells which are
specialised
contain different
organelles.
Cell
Specialisation
There are hundreds of different types of
plant and animal cells. Each focus on a
certain “job” in the organism in which
they are found. It is said that they are
specialised, or differentiated, for that
function.
https://www.youtube.com/watc
h?v=UgT5rUQ9EmQ
When a sperm and egg are
fertilised…
• The cells are unspecialised (identical)
• After several cell division cycles have
occurred, they start to differentiate.
• This occurs as some genes are
turned on in some cells only which
cause certain proteins to be made
which give the cell a particular shape
or number of organelles.
Similarities and differences in
Size of Cells.
Size:
 All cells are microscopic. When a cell gets
too big it divides, so its SA to volume ratio
goes up.
Plant cells are larger than animal cells. They
have a vacuole so cytoplasm pushed closer to
membrane for diffusion of gases and nutrients
Similarities and differences
with
Shape
Shape:
 Shape relates to function e.g. nerve cells long
and thin to carry impulses
Cells that are specialised for diffusion tend to
be long and thin to decrease the distance to
travel across a cell and to increase surface
area (root hair cell, villi cells in intestine)
Plant cells tend to be more regular in shape
as the rigid cell wall dictates shape.
Similarities and differences in
Organelles
 Number of a certain organelle can be an indicator of the
function of a cell
 Many ribosomes and rough ER- high rate of protein
synthesis, also have prominent nucleoli.
 Smooth ER – make lipids, metabolises CHO, detoxifies
other drugs, make steroids eg sex hormones so gonads rich
in smooth ER. Liver also.
 Golgi Bodies - Cells specialised for secretions
 Many mitochondria - Cells with high energy requirement –
(liver and muscles)
 Many chloroplasts – high photosynthesis rate.
Red Blood Cells
• Contain haemoglobin which transports
oxygen to other cells and around the body
• Biconcave shape for maximum surface area
to allow more oxygen to be absorbed
efficiently.
• Biconcave shape also allows for a flexible
framework which means cells can squeeze
through the thinnest of capillaries.
• Cells have a thin outer membrane allowing
oxygen to diffuse through easily.
• Have no nucleus so there is more room for
oxygen to be carried in the cell and hence
around the body.
Sperm cell
• The tail (flagella) of the sperm cell
enables it to swim to the ovum and
fertilise it.
• The head is streamlined also to aid
swimming
• The head contains genetic
information and a nucleus and has
an enzyme to help penetrate the
egg cell membrane to allow
fertilisation.
• The middle section immediately
behind the head is packed with
mitochondria to provide energy.
Nerve cell
• Transmit electrical nerve impulses
and so carry information from one
part of the body to another ie from
receptor to an effector.
• Dendrites extend from the cell body
to make connections with other
neurones.
• Have a long axon (nerve fibre) to
carry the impulse to the target
organ.
• End plate forms a synapse with an
effector (a muscle or a gland).
Muscle cells
• Long thin cells
• Have many
mitochondria due to
energy requirements
Plant cell - Xylem
• Long and tube-like hollow
vessels to carry the water
from roots to leaves.
• Cells have no end walls
between them so they form a
'pipeline' to carry the water.
• Spirals and rings of lignin in
the cell walls strengthen them
to withstand pressure of
water.
Plant cell – root hair
• Located in the root epidermis and in
direct contact with the soil
• Thin walls make up-take of water
easier.
• Wall nearest the soil has a long
'finger-like' projection with very thin
walls into the soil. This projection
increases the surface area for more
efficient absorption of water and
ions.
• no chloroplasts as no
photosynthesis occurs (no light); No
mitochondria - active transport
Plant cell – palisade
cell
• Typical plant cell
• Packed with chloroplasts which
contain the light absorbing
pigment chlorophyll.
• Regular shaped closely packed
cells forming a continuous
layer for efficient and
maximum absorption of
sunlight
Cell sort – group activity
• In groups of 4 match up the cell
names with the cell pictures with
clues underneath. Make sure
everyone in your group agrees.
There are 12 animal cells and 12
plant cells.
• You have 5 minutes then we will
mark as a class.
Compare the following cells
In terms of cell function explain why these
cells have different shape and organelles:
– Root hair cell and plant palisade cell
– Muscle cell and nerve cell