MitochondriaThese are 0.5 -1.5 µm x 3-10µmThey can be seen under a good light microscopeMitochondria are the site of aerobic respirationThey are found in all cells

There arehigh numbersIn Metabolicallyactive cells

They are surrounded by a double membrane

The outer membrane is smooth and the inner is folded into cristae

These folds increase the surface area for the enzymes involved in ATP synthesis

The matrix contains enzymes used in the Krebs cycle of respiration

In the matrix are 70S ribosomes and circular strands of DNA

The ATPsynthse enzymes are called stalked particles because they look like stalks

Vacuoles

• These are only found in plant cells

• They are membrane bound and filled with cell sap

• The membrane is called the tonoplast

• Cell sap contains water, ions, waste, pigments, and hydrolytic enzymes

• Younger cells have many smaller vacuoles

• In older cells these fuse to form a large, permanent, central vacuole

• Animal cells have small, temporary vesicles

Chloroplasts

These are the site of photosynthesis

They are 4-10 x 2-3µm

They are a type of Plastid, that is an organelle containing pigment

They are biconvex discs

There is a double membrane

The inner membrane is formed

into ling flat sacks called thylakoids

Some of these form stacks called granum thylakoids

Plural = grana

Those going between the grana

are called stroma or inter-lammelae thylakoids

The thylakoids contain the photosystems made of chlorophyll pigments – light energy is trapped here

The fluid filled centre is the stroma

The stroma contains the enzymes needed for the Calvin Cycle which converts carbon dioxide into a carbohydrate

There are 70S ribosomes

And circular DNA

Sometime there are starch

granules or lipid droplets

Microtubules• These are hollow cylinders made of

protein• They are 24nm in diameter

They occur throughout the cytoplasm and bring about movement of cell contents, such as lysosomes

• Microtubules are also found in cilia and flagella and centrioles

• Misrotubules in the cytoplasm form the structure of the cell, they are said to from the cytoskeleton

MicrofilamentsThese are single stranded proteins They are involved in cytoplasmic

movement

Centrioles• These are only found in animal cells• They consist of two hollow cylinders at

right angles• They are about 0.3-0.5µm long and 0.2 µm

wide• Centrioles contain microtubules in the

same structure as seen in cilia and flagella basal bodies

• The Centrioles move to opposite poles during cell division

Centrioles• These are only found in animal cells• They consist of two hollow cylinders at

right angles

• They are about 0.3-0.5µm long and 0.2 µm wide

• Centrioles contain microtubules in the same structure as seen in cilia and flagella basal bodies

• The Centrioles move to opposite poles during cell division

Cilia and FlagellaCilia are many short cytoplasmic projectionsFlagella are one or a few much longer

cytoplasmic projections

In cross section under the EM they are seen to contain 9 peripheral pairs of microtubules and 2 central microtubules (9+2)

These are connected to a different system of microtubules inside the cytoplasm, the basal body

The microtubules slide over each other to bring about movement