The cell
Learning objectives
To identify the function and structure of
the cell.
To describe the movement of molecule
across cell membranes.
The cell
All living organisms are
composed of cells
All new cells are derived
from other cells
Cells contain hereditary
material
All metabolic process
take place within cells
PLANT CELL VS ANIMAL CELL
Plant cell
~ Cellulose cell wall
~ Present of chloroplast
~ Central vacuole
~ Nucleus at the edge
~ No lysosome
~Starch for storage
only meristematic cells
can divide
~
~
~
~
~
~
~
Animal cell
No cell wall
No chloroplast
Small & scattering
vacuoles
Nucleus in the central
Lysosomes present
Glycogen for storage
All cells can divide
CELL MEMBRANE
Separation of internal &
external environment
Control the exchange of
substances
Form separate
compartments inside
cells
As receptor sites
ENDOPLASMIC RETICULUM內質網
Network of double membrane-bounded
sacs
Rough ER Vs Smooth ER
Functions: biosynthesis, transportation,
support, storage, detoxification,
increase surface area
GOLGI APPARATUS
A stack of membrane bounded sacs
Functions: packaging, glycosylation,
concentration, transportation, lysosome
formation, membrane differentiation,
enzyme production
LYSOSOMES
Simple spherical sac
Functions: endocytosis, exocytosis,
autolysis, autophage
Functions of lysosome
Vacuoles
Fluid-filled sac containing cell sap
Functions: Support & cell growth,
store pigments, as lysosome, temporary
stores for wastes & food
Mitochondria
Surrounded by an envelope of 2
membranes, the inner being folded to
form cristae
Functions: energy metabolism &
respiration, heat production
NUCLEUS
Largest cell organelle
Mono- nucleate, Bi- nucleate & polynucleate
Functions: contains genetic materials,
control centre, presence of DNA,
production of ribosomes & RNA, cell
division
Cellulose cell wall
Only in plant cell
Functions: support, mechanical strength,
permit movement of water, give shape
of cell
Chloroplast
Only in plant cell
Functions: photosynthesis
Movement in & out of the cell
Semi-permeable cell
membrane: the
plasma membrane
only allow some
substances to pass
through but not
others
Factors affecting permeability of cell
membrane
Chemical natures of
molecules
~ water
~ water soluble
neutral substances
~ Fat soluble neutral
substances
~ Electrolytes
Size of molecules
~ small enough
molecules
Diffusion
Diffusion: a process, the substance moves
from a region of high concentration of that
substance to a region of low concentration of
the same substance
Factors affecting the rate of diffusion:
the concentration gradient, the distance, the
area. The nature of the membrane,the size &
nature if the molecules
Process of diffusion
Osmosis
The movement of water molecules from
high water potential to a region with
lower water potential through a semipermeable membrane
Water potential
Osmotic potential
Pressure potential
Process of osmosis
Plasmolysis
Outward diffusion of water
Reduction of turgor pressure
Separation of cell wall & plasma
membrane
Decrease in size of vacuole & cytoplasm
Decrease in water potential
Active transport
An energy consuming transport of molecules
across a membrane against a concentration
gradient.
Factors affecting active transport
concentration, electrical charge & energy
available
Features of cells with active transport: many
mitochondria, ATP & a high respiratory rate
THE END
A typical animal cell
Cell wall
nucleus
Endoplasmic
reticulum
Vacuole
Golgi apparatus
A typical Plant cell