CELLS….. Size Structure Organisation

CELLS…..

Size

Structure Organisation

Bacteria - prokaryotes ( no nucleus or membrane-bound organelles

Protists - eukaryotes

- true nucleus, membrane bound

organelles Amoeba

Protists

Euglena (note the light- sensitive eye spot)

Paramecium (note the anal pore)and contractile vacuole

Protists

Animal Cell Structure

Animal cells are typical of the eukaryotic cell, enclosed by a plasma membrane and

containing a membrane-bound nucleus and organelles.

Unlike the cells of the two other eukaryotic

kingdoms, plants and fungi, animal cells don't have a cell wall. This feature was lost

in the distant past by the single-celled organisms that gave rise to Animalia.

Plasma Membrane - All living cells have a plasma membrane that encloses their contents. In prokaryotes, the membrane is the inner layer of protection surrounded by a rigid cell wall. Eukaryotic animal cells have only the membrane to contain and protect their contents. These membranes also regulate the passage of molecules in and out of the cells.

Mitochondria - Mitochondria are oblong shaped organelles that are found in the cytoplasm of every eukaryotic cell. In the animal cell, they are the main power generators, converting oxygen and nutrients into energy.

Ribosomes - All living cells contain ribosomes, tiny organelles composed of approximately 60 percent RNA and 40 percent protein.

Ribosomes are scattered throughout the cytoplasm and are the protein production sites for the cell.

Endoplasmic Reticulum - The endoplasmic reticulum is a network of sacs that manufactures, processes, and transports chemical compounds for use inside and outside of the cell. It is connected to the double-layered nuclear envelope, providing a connection between the nucleus and the cytoplasm

Golgi Apparatus - The Golgi apparatus is the distribution and shipping department for the cell's chemical products. It modifies proteins and fats built in the endoplasmic reticulum and prepares them for export to the outside of the cell.

Lysosomes - The main function of lysosomes is digestion. They break down cellular waste products and debris from outside the cell into simple compounds, which are transferred to the cytoplasm as new cell-building materials.

Peroxisomes - are found in the cytoplasm, roughly spherical and bound by a single membrane. Peroxisomes function to rid the cell of toxic substances, in particular, hydrogen peroxide -- a common byproduct of cellular metabolism.

Microfilaments - Microfilaments are solid rods made of globular proteins called actin. These filaments are primarily structural in function and are an important component of the cytoskeleton.

With myosin, they help in cellular contraction and basic cell movements. They enable a dividing cell to pinch off into two cells and are involved in amoeboid movements and in contractions of muscle cells.

They give structure and shape to a cell, serve as conveyor belts moving other organelles through the cytoplasm, are the major components of cilia and flagella, and participate in the formation of spindle fibers during cell division (mitosis).

Microtubules - These straight, hollow cylinders, composed of tubulin protein, are found throughout the cytoplasm of all eukaryotic cells and perform a number of functions.

Centrioles - Centrioles are self-replicating organelles made up of nine bundles of microtubules and are found only in animal cells. They appear to help in organizing cell division, but aren't essential to the process.

Cilia and Flagella - For single-celled eukaryotes, cilia and flagella are essential for the locomotion of individual organisms. In multicellular organisms, cilia function to move fluid or materials past an immobile cell as well as moving a cell or group of cells.

Nucleus - The nucleus is a highly specialized organelle that serves as the information and administrative center of the cell.

Plant cells

Plant cells have similar cell features to animal cells except that they•have cell walls•have plastids e.g. chloroplasts•a large vacuole•lack centrioles

Cell wall -

Rigid, strong, porous

made of cellulose and other

substances such as

pectin or lignin for strength,

subarin or wax for water-

proofing

Plastids - These are organelles responsible for

•starch storage (amyloplasts)

•pigment storage (chromoplasts)

•photosynthesis (chloroplasts).

Chloroplasts - can take in carbon dioxide

and water, and, with the suns energy

and chlorophyll convert these into sugar.

Note the discs ( thylakoids) stacked into

piles (grana) joined by lamellae and

found in the stroma.

Plant vacuoles

-Large, take up the whole centre of a mature plant cell.

•Acts as a fluid skeleton by inflating when full of water

and becoming flaccid when water is low - provides turgor

•Used to store organic compounds and ions

•stores enzymes that recycle “old” molecules

•stores wastes of metabolism

•stores poisons for herbivore defence