Biology 2.4
Cellular Life Processes
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Bio 2.4 Cell Bits
Biological ideas, as they relate to each of
the life processes at the cellular level, are
selected from:
• reasons for similarities and differences
between cells such as cell size and
shape,
• type and number of organelles present.
Limited to plant and animal cells
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Cell wall
A rigid structure made of cellulose
surrounding plant cells. This provides
shape and strength.
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Cell membrane
A layer that
encloses the
cell contents.
Plant cell
Controls what
enters and
exits the cell.
Animal cell
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Cell membrane
Is made of two
layers of lipid
(fat) molecules
with proteins for
cell
identification,
active transport
and
communication.
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Cytoplasm
fills the interior of the cell. It
consists of a liquid (called the
cytosol that contains water,
proteins and dissolved ions) and
cell organelles.
It is used to transport substances
throughout the cell and create
internal pressure and is where
most chemical reactions occur.
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Nucleus
Contains the
genetic
material which
controls the
cells activities.
nucleoplasm
Nucleolus: round structure
inside nucleus: produces the
ribosomal RNA
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Nuclear membrane
Separates the
contents of the
nucleus from the
cytoplasm.
Perforated by
pores and
continuous with
ER.
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Chromosomes
Structures
made of DNA
and protein
containing
genes for
protein
synthesis.
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Mitochondria
Organelles
within the
cytoplasm for
cell respiration
- where food
molecules are
broken down
to release
energy.
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Chloroplast
Starch granule
Stroma
Membrane
Grana
Organelles in plant cells
containing chlorophyll for
photosynthesis.
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Centriole
Mostly present
in animal cells
for cell division.
Produces
spindle fibres
for separating
chromosomes.
Centrioles
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Vacuole
Liquid-filled
organelle in
cytoplasm
for creating
pressure
and storing
water and
dissolved
substances.
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Ribosome
Organelle<> found <>
free in the
cytoplasm or
attached to
ER.
Used for protein
synthesis.
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Endoplasmic reticulum
Is a system of membranes and
connecting tubes that provide a
surface for chemical reactions and a
pathway for moving material within
the cell.
Rough
ER
Smooth
ER
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RER vs SER
• RER
– Produces proteins (both secreted & part of cell
membrane)
• SER
– Produces lipids, steroids
– Metabolises carbohydrates
– Regulates calcium levels
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Lysosome
Membrane-bound sac containing
digestive enzymes.
Breaks down food and worn out
cell parts.
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Golgi body
a series of membrane-bound sacs
for producing and releasing
secretions.
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Plant Cells
have:
- rigid cell walls giving the plant
cells a geometric shape;
- chloroplasts (usually);
- starch granules
- large central vacuole
They are usually larger than animal
cells.
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Become specialised to perform
support, absorption of water,
conduct liquids, allow gases
in and out, manufacture food,
form protective surfaces and
reproduction.
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Animal Cells
don’t have a cell wall and have
centrioles and an irregular
shape. Become specialised to
perform specific tasks.
Humans have over 200
different kinds of cells.
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Similarities and
differences
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Cell size
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Cell size is limited by the rate
at which essential nutrients
and oxygen can diffuse into a
cell and waste products can
be removed.
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Cell shape
is determined by the role of the
cell.
Nerve cells are long and thin to
conduct neural messages
around the body.
Intestinal cells have frilly edges
to increase surface area for
rapid diffusion.
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Egg cells are spherical and
large to contain organelles
and nutrients for the zygote.
Sperm cells have a long
flagellum and many
mitochondria for fast
movement.
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RBC’s are disc-shaped with
rounded edges for easy
passage through blood
vessels.
Many cells are flat to increase
the surface area, reduce
travelling distance and
increase diffusion rates
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Relative numbers of
organelles present
Secretory cells (e.g. glands)
have large numbers of golgi
bodies.
Highly active cells (e.g.
muscle) have larger numbers
of mitochondria.
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Leaf cells contain large
numbers of chloroplasts.
Root cells have a large surface
area for efficient water
absorption.
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