Cell structures.docx

Organelles of animal cell

1. CELL STRUCTURES & FUNCTIONS

Cytosol:
Jelly-like fluid portion of the cytoplasm in which particles are dispersed.

Cytoplasm:
All material within a cell, enclosed by the cell membrane, except for the
cell nucleus.

Cell Membrane:

A thin, pliable, elastic structure which envelops the cell. It is primarily
composed of phospholipid bilayer.
Selectively permeable:
Only allow certain molecules enter and exit.

Composition:
Lipids
 Phospholipids 25%
 Cholesterol 13%
 Other lipids 4%
Proteins 55%
Carbohydrates 3%

Functions:
 Regulation
 Isolation
 Communication
 Identification to body’s immune system

2. Nucleus
Control centre of the cell that determines the entire structure and
function of the cell.
Three main parts:
 Nuclear envelop:
Two bilayer membranes. It
separates nucleoplasm from
cytoplasm.
 Nucleolus:
Not membrane bound,
manufacture ribosomal RNA.
 Chromatin:
Clumped and tangled mass of nuclear chromosomes.

Cell Cytoskeleton:
Network of fibrillar proteins organized into filaments or tubules.

Components:
Microtubules, Intermediate filaments, Microfilaments

Functions:
 Maintain cell shape and structure.
 Cell motility.
 Cell reproduction.
 Transport of substances within the cell.

Ribosomes:

Serve as sites of protein synthesis,
made up of two subunits and are
not membrane enclosed.

3. Mitochondria:
“Powerhouse of cell”
A membranous organelle
composed of two lipid
bilayer membrane.
They are self-replicative and
contain DNA.
 Manufacture cellular energy in the form of ATP.


Endoplasmic Reticulum:

A network of tubular and flat
vesicular structures continuous
with the nuclear envelop,
covering the nucleus.

Two types of ER:

Granular ER: (Rough appearance)
Ribosomes attached to the outer surfaces.
 Synthesize proteins.
Agranular ER: (Smooth appearance)
Has no attached ribosome.
 Synthesize and store phospholipids, cholesterol, and steroid
hormones.
 Production of new cellular membrane.
 Perform detoxification role.

4. Golgi Apparatus:

Four or more stacked layers of
thin, flat, enclosed vesicles lying
near one side of the nucleus.


Functions:
 Additional processing of substances formed in the ER.
 Synthesizing certain carbohydrates that can’t be formed in the ER.
 Compact ER secretions into highly concentrated packets.
 Production of new intracellular organelles (lysosomes).

VESICLES
Lysosomes:
Vesicular organelles surrounded by lipid bilayer membrane.
They break off from Golgi apparatus containing hydrolytic (digestive)
enzymes and disperse through cytoplasm.

Functions:
 Digest damage cellular
structures.
 Digest food particles
ingested by the cell.
 Digest unwanted matter
(Bacteria).

5. Peroxisomes:
Vesicular organelles, break off from smooth ER or form by self
replication.
They contain oxidases.

Functions:

Detoxification role.
Catabolize long chain fatty acids.


Transport vesicles:
Composed of small envelops of smooth ER
Carries ER products to golgi apparatus.

Secretory vesicles:
A form of storage vesicle which carries compacted secretory substances
formed by ER-Golgi apparatus system.