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Cells
Cell Structure
Structure of eukaryotic cells
Organelle
Ribosomes
Rough endoplasmic
reticulum (rER)
Golgi apparatus

Mitochondria

Lysosomes
Smooth endoplasmic
reticulum (sER)
Cell surface membrane
Nucleus

Nucleolus
Chloroplasts (found in
plants and algae only)

Vacuole (in plants)
Cell wall (in plants, algae
and fungi)

The functions of organelles in a eukaryotic cell
Structure
Function
Very small organelle, made of RNA and protein
Carry out protein synthesis
They are not surrounded by a membrane
Layers of membranes that form flattened, interconnected Synthesise proteins and transport them to the
tubes through the cytoplasm
Golgi apparatus
The outer face is covered in ribosomes
Stacks of flattened, membrane-bound sacs
Modify proteins made at the rER, for example,
Vesicles are constantly pinched off the ends of these sacs adding carbohydrate to form glycoproteins
These are secreted from the cell in Golgi
vesicles, pinched off from the cisternae
Bean-shaped organelles that have a double membrane
Aerobic respiration
around them
The inner membrane is folded into cristae, and the matrix
in the middle contains enzymes
Membrane-bound vesicles containing hydrolytic
Digest unwanted materials in the cell, for
enzymes (lysozymes) produced by the Golgi apparatus
example, worn-out mitochondria
Similar to rER but the cavities are more tubular and the
Synthesis of lipids
membranes do not have ribosomes
Made of phospholipids and proteins
Controls the passage of substances into and
Surrounds the cell
out of the cell
This is the largest organelle in the cell
Contains DNA, which holds the genetic
It is surrounded by a double membrane called the
information necessary to control the cell
nuclear envelope, which have many holes in it called
The DNA is in the form of linear chromosomes,
nuclear pores
made of DNA wound around proteins
A dark, granular area inside the nucleus that contains
Synthesises ribosomes
DNA and proteins
Surrounded by a double membrane
Carry out photosynthesis
Contains stacks of membranes that contain chlorophyll
and other pigments, surrounded by the liquid stroma,
which contains enzymes
A space surrounded by a membrane called the tonoplast Keeps cells turgid
and containing cell sap
In plants, the cell wall is made of cellulose fibres and
The cell wall surrounds the cell membrane and
surrounds the cell surface membrane
stops the cell bursting wen it takes in water by
Algal cell walls are typically made of glycoproteins and
osmosis
polysaccharides, and the fungal cell walls are usually
made of the carbohydrate chitin

Tissues, organs and systems
Many organisms are multicellular
...
g
...
g
...
, and stomach contains smooth muscle tissue, blood tissue etc
...
(e
...
heart veins, arteries and capillaries all work together in the circulatory system)

Structure of prokaryotic cells and of viruses
Prokaryotic cells
Prokaryotic cells are much smaller than eukaryotic cells
...

Have a cell wall surrounding the cell-surface membrane, but it is made of a glycoprotein called murein
Have ribosomes that synthesise proteins, but these are smaller than the ribosomes in eukaryotic cells

In addition, some prokaryotic cells:
-

Contain plasmids
Have flagella that enable the cell to move
Have a slimy capsule surrounding the cell, which stops the cell drying out, helps to protect the cell from being engulfed by white
blood cells, and stores toxins

Viruses
Viruses contain genetic material, either DNA or RNA
...
Once inside, it ‘hijacks’ the cell’s organelles which start to make new viral proteins and the cell starts making many new viruses,
which are then released from the host cell, destroying the host cell in the process
...
This means
that the specimen needs to be quite thin
...

Magnification – is making things larger
Resolution – is the ability to see two objects that are close together as separate objects
...
Optical microscopes cannot be used to study the tiny organelles within the cells or the structure of prokaryotic cells
...




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