F4 C2 Cell Biology and Organisation

2.1 Cell Structure and Function

cell component // organelle structure function

mitochondrion  rod-shaped / - site of cellular respiration -->

mitochondria spherical
generates energy during cellular
 2 layers of
membranes respiration
 contains enzymes
- releases energy in the form of
that play a role in
cellular respiration adenosine triphosphate (ATP)

molecules

centriole  small cylindrical - forms spindle fibre during cell

components ( in
division in animal cells
pairs )
 made up of
microtubules
 does not exist in plant
cells

Golgi apparatus  a stack of parallel - processes, modifies, packs and

flattened sacs
transports chemicals such as
 new membrane is
added at one end and protein, carbohydrate and
vesicles bud off from
glycoprotein
the other end.
 plasma  outer membrane that - separates content of cell from
membrane
surrounds the entire external environment

content of cell - controls / regulates movement

 proteins + of substances into and out of

phospholipids the cell

 thin and elastic film - allows exchange of nutrients,

 selectively-permeable respiratory gases and waste

materials between cells and

their surroundings

lysosome  small spherical sac - hydrolyses / breaks down

 contains hydrolytic complex organic molecules such

enzymes as protein, nucleic acid and lipid

- breaks down bacteria and

components of damaged cells

- in certain organisms, lysosomes

combine with food vacuole to

digest food
 nucleus  largest component in - controls all cell activities
plural: nuclei
the cell - has chromosomes that contain

 spherical genetic information

 contains (deoxyribonucleic acid (DNA))

chromosomes, that determines characteristics

nucleolus, nucleoplasm and metabolic function of a cell

ribosome  protein + ribonucleic - site for protein synthesis

acid (RNA) Protein = enzymes // hormones //

 on surface of RER antibodies

 exist freely in the

cytoplasm
  a system of - rough endoplasmic reticulum
endoplasmic
interconnected transports proteins synthesised
reticulum
folded flattened sacs by ribosomes

 membrane is

continuous with

nuclear membrane

 RER : ribosomes - smooth endoplasmic reticulum

attached to the 1. synthesises and transports

surface glycerol and lipids

 SER 2. carries out the detoxification of

drugs and metabolic

by-products

 two layers of - chlorophyll absorbs sunlight and

chloroplast
membrane converts it to chemical energy

 contains chlorophyll during photosynthesis.

 vacuole  filled with liquid - maintain cell turgidity in plant

cells
(cell sap = water, organic
acids, sugars, amino acids, - in unicellular animals, vacuole
enzymes, mineral salts,
contracts during
oxygen, carbon dioxide
and metabolic osmoregulation, osmosis and
by-products)
excretion.

 young plant cells :

many small vacuoles
 mature plant cells : a
large vacuole

cytoplasm  jelly-like medium - medium for biochemical

 contains components
reactions in cells
of suspended cells
 contains organic
compounds (protein,
lipid, carbohydrate)
and inorganic
compounds (K+)
 cell wall • a strong and rigid outer - maintains the shape of plant
layer
cells
• made from cellulose
fibre - provides mechanical support to
• fully permeable
plant cells

Compare and contrast the components of animal cells and plant cells

Both cells contains nucleus, cytoplasm, plasma membrane, Golgi apparatus, mitochondrion, endoplasmic reticulum and ribosomes.

Plant cell Animal cell

Has a fixed shape Does not have a fixed shape

Has a cell wall Does not have a cell wall

Has chloroplasts Does not have chloroplasts

Has a large vacuole No vacuole/if present, it is small

Stores carbohydrate in the form of starch Stores carbohydrate in the form of glycogen

Does not have a centriole Has centrioles

 2.2 Living Processes in Unicellular Organisms
Unicellular organisms carry out all life processes: respiration, movement, nutrition, responding to stimulus, reproduction, growth and excretion.

Living processes
Growth synthesise new cytoplasm
Respiration gaseous exchange occurs by simple diffusion through plasma membrane
Response chemicals, touch or bright light --> moves away from stimuli
food --> moves towards stimuli
Movement  constantly changes its shape when it encounters obstacles moves by means of the rhythmic
beating of the cilia
 moves by extending out its pseudopodium (false feet) followed by the
flow of cytoplasm into the extended pseudopodium
Reproduction  Favourable condition : binary fission  favourable condition : carries out binary fission
  Unfavourable condition (dry conditions, low temperature and food  unfavourable condition : reproduces sexually (conjugation)
shortage) : forms spores that will only germinate when the environment
improves.

Excretion /  Both live in freshwater environment

osmoregulation
 Waste products are excreted by simple diffusion through the plasma membrane.
 Water diffuses into the cell via osmosis and fills the contractile vacuole.
 When the vacuole expands to the maximum size, contraction occurs and water is excreted from time to time.
Nutrition  Amoeba sp. obtains nutrients via phagocytosis.  the beating of cilia transfers the food particles into the oral groove.
1. It moves towards food and extends its pseudopodium to trap food  the food vacuole then fuses with lysosome.
particles.  the food particles are hydrolysed by lysozyme in the lysosome.
2. A food vacuole is formed.  the nutrients are absorbed into the cytoplasm
3. The food vacuole then fuses with lysosome.  undigested food is discharged through the anus
4. The food particles are hydrolysed by lysozyme in the lysosomes.
5. The nutrients are absorbed into the cytoplasm
6. Undigested food is discharged when the Amoeba sp. moves.
 Specialised human 2.3 Living Processes in Multicellular Organisms

cells The cell structure correlates to its function, and each type of cell is specialised to carry out a specific function.

Muscle cell Sperm cell White blood cell

 Arranged as multinuclear (more than one nucleus)  Has a long tail to enable it to swim  Can change shape
striated (marked by transverse dark and light bands) towards the ovum in the Fallopian tube  Carry out phagocytosis // produce antibodies
fibres  The head carries a set of
 Contract and relax to generate movement chromosomes from the male

Epithelial cell

 Coats the surface of organs

Red blood cell 1. Provides physical protection
 does not contain a 2. helps in
nucleus (mature RBC) Nerve cell  gaseous diffusion
 allows red blood cell  absorption of nutrients
to have more sends nerve impulses  secretion
haemoglobin = more  movement
oxygen molecules it
can carry
 shaped as a biconcave
disc (allows oxygen to
diffuse into the cell
quickly)
 C T O S O

epithelial tissue muscle tissue nerve tissue connective tissue

covers surface
of mouth &
oesophagus
blood tissue

 contract and relax to

covers surface sensory
generate movement in bones
of lungs, body neurone
and limbs
cavities & blood
vessels bone

covers surface
of trachea &
bronchus
-secrete mucus
adipose
tissue

lines tubules,  enable involuntary activities relay

glands & kidney such as peristalsis neurone
ducts
cartilage

covers small
intestine loose
-secrete mucus connective
tissue

 builds walls of the heart that motor

contract to pump blood to the neurone
fibrous
whole body connective
 contraction is involuntary tissue
 Xylem

Specialised plant cells • transports water and mineral salts absorbed from roots to leaves

• walls are thickened with lignin to provide mechanical support and

strength to the plants.

 long cylindrical cells, arranged vertically and closely packed to each other
Phloem
 contains a high density of chloroplast
• transports organic substances produced during photosynthesis from
 arrangement allows maximum absorption of sunlight for photosynthesis
leaves to other parts of the plants.

 Cells are loosely

Root hair cells
arranged with lots of
have long projections which
air spaces in between increases the surface area for
the absorption of water and
 Large air spaces allows
mineral salts
gaseous exchange

between inside of the

 Modified lower epidermal cells with the thicker
leaves with the
cell wall on the inner side
palisade mesophyll
 Controls the opening and closing of the stoma
cells
 Stoma - opening that allows gaseous exchange
 Density of certain cell components and specialised cell functions

Sperm cell Requires a lot of energy to swim towards the uterus

and Fallopian tube to fertilise the secondary oocytes

Muscle cell such as flight muscle Mitochondrion Requires a lot of energy to contract and relax

cells in insects and birds to enable movement and flight

Plant meristem cell Requires a lot of energy to carry out active cell division

process to produce new cells

Palisade mesophyll cell Chloroplast Absorbs more sunlight to carry out the process of

photosynthesis

Spongy mesophyll cell

Pancreatic cell Rough endoplasmic reticulum Increases synthesis and secretion of digestive enzymes

Goblet cell in intestinal Produces mucus

epithelium and respiratory tract Golgi apparatus

Liver cell Smooth endoplasmic reticulum • Metabolises carbohydrates

• Detoxification of drugs and poisons