Unit 1 Learning Outcomes
Section A- Cell structure in relation to function
Content
Notes
A. Cell variety
The concept of variation in structure between
cells of one type of tissue and between cells Cells have a wide variation in their
of different types of tissues. The relationship structure.
of structure to function.
Structures: cell membranes, cell walls,
cytoplasm,
nucleus,
chloroplasts,
LO 1. Identify plant and animal cells from mitochondria,
vacuoles,
contractile
drawings.
vacuoles, cilia, flaggela.
Cells: epithelial, red blood cells, white
LO 2. Name the organelles in these cells and blood cells, goblet cells, xylem, phloem,
state their functions.
mesophyll.
LO3. Identify the following organelles in cell
drawings and state their functions: cell or
plasma membrane; cell wall; centriole;
cytoplasm; chloroplast; rough and smooth
endoplasmic reticulum; golgi body; lysosome;
mitochnondrion; nucleolus; nucleus; ribosome;
vacuoule and vesicle.
Extra
LO 4. Identify and explain the variations in
the structure of the cells in the following
tissues: i) blood- red blood cells, white blood
cells; ii) epithelium- glandular, ciliated and
columnar; iii) mesophyll- palisade and spongy
iv) transport tissues- cylem and phloem.
LO 5. The existence of unicellular organisms.
Some cells are complete organisms.
These cells must be able to perform all
life functions.
LO 6. Explain the relationship between cells, Cells in multicellular organisms are
tissues, organs, systems and organisms in specialised for a single function and rely
multicellular organisms.
on a variety of cells in other tissues to
perform all the other life functionsknown as “Division Of Labour”.
Specialised structure of a cell depends
on the particular function that it
performs.
Examples of specialised cells: Sperm
cells are specialised for swimming so
their structure includes a tail and they
contain lots of mitochondria for energy.
Palisade mesophyll cells that are tightly
packed and contain many chloroplasts
for photosynthesis.
B. Cell wall: reference to cellulose fibres and
permeability.
Cell walls in plant cells composed mailnly
of cellulose fibres in a criss-cross
LO 7. Describe the structure of the plant cell pattern.
wall and explain how it is involved in the Cellulose is a tough fibrous material,
movement of water through plant tissues.
classed as a structural carbohydrate.
The fibres give the cell support.
Cell walls are freely permeable.
C. Plasma membrane: reference to fluid mosaic
model.
The plasma membrane is referred to as
a ‘fluid mosaic’.
LO 8. Describe the structure of the plasma It is made of a bi-layer of phospholipids
membrane using the fluid mosaic model.
with embedded protein molecules.
The phospholipids have a hydrophilic
(water liking) head and a hydrophobic
(water hating) tail. This means that
when placed in water they arrange
themselves with the heads in the water
and the tails grouped together.
Some of the proteins that are
embedded in the plasma membrane have
channels that can transport some
substances
rapidly
through
the
membrane but can prevent other
substances from passing through.
This structure allows membranes to be
selectively permeable and to change
shape easily and quickly.
D. Absorption and secretion of materials.
Diffusion and osmosis as basic cell processes.
The role of the cell wall and plasma membrane
in relation to these processes.
Diffusion is the movement of molecules
from an area of high concentration to an
LO 9. Explain the movement of materials into area of low concentration. Osmosis is a
and out of cells by diffusion, osmosis, active special case of diffusion involving the
transport, phagocytosis and pinocytosis.
movement of water molecules.
LO 10. Define the term water potential and Osmosis occurs because water diffuses
make use of this concept to describe water through the plasma membrane quicker
movement into, out of and between cells.
than most dissolved substances.
LO 11. Correctly use the following terms: ‘High water concentration’ means a
selectively
permeable
membrane; solution with lots of water and little
concentration
gradient;
turgid;
flaccid; solute. Pure water has the highest water
plasmolysed;
hypertonic;
hypotonic
and concentration.
isotonic.
‘Low water concentration’ means a
solution with lots of solute dissolved in
it.
Hypertonic solutions have less water and
more solute than the solution they are
compared to.
Hypotonic solutions have more water and
less solute than the solution they are
compared to.
Isotonic solutions have equal water
LO 12. Predict what will happen to animal and concentrations.
plant cells when they are placed in solutions of
different solute concentrations.
Animal cells will burst if placed in
hypotonic solutions and shrink in
hypertonic solutions.
Plant cells become turgid in hypotonic
solutions and become plasmolysed in
hypertonic solutions.
E. Function of plasma membrane in relation to Plant tissues become flaccid if placed in
selective ion uptake (active transport) and hypertonic solutions.
absorption and release of chemicals.
Molecules that cross the membrane by
diffusion move down a concentration
gradient, requiring no energy.
LO 13. State the conditions under which active Some substances can be forced through
transport will occur best.
a membrane against a concentration
gradient. This requires a supply of
energy. This process is called Active
Transport.