Cell Structure

Revision

Animal Plant

Animal Cell

Plant Cell

Organelles

• Nucleus• Bounded by a double

membrane with pores• Chromosomes in

loosely coiled state called chromatin

• Chromosomes contain DNA

• Nucleolus – a dense body used to produce ribosomes

• 6μm in diameter

Electron micrograph of a nucleus

Endoplasmic reticulum

• Two types:

1. Rough endoplasmic reticulum (RER)

2. Smooth endoplasmic reticulum (SER)

Rough Endoplasmic Reticulum

• Parallel flattened cavities lined with thin membranes 4nm thick.

• Attached to the membrane are ribosomes.

• Used for protein transport

Smooth Endoplasmic Reticulum

• Tubes rather than flattened stacks• Synthesis and transport of lipids and steroids

Golgi Apparatus

• Stack of flattened cisternae

• Formed by fusion of vesicles from the RER

• Vesicles pinch off the trans face and move to the cell membrane.

Mitochondria

• Diameter 1.0 μm, length 2,5 μm

• Surrounded by 2 membranes

• Inner membrane folded to form cristae

• Matrix fluid inside• Used for producing

ATP in aerobic respiration

• Contains circular DNA• Contains ribosomes (70S)

Ribosomes

•They are used for protein synthesis

• There are two types of ribosomes:

• The smaller ones (70S) are found in mitochondria and chloroplasts.

• The larger ones (80S) are found in the cytoplasm and attached to the RER

Lysosomes

• Contain digestive enzymes.

• Destroys bacteria• Destroys old

organelles• Can destroy whole

cell

Chloroplasts

• Double membrane

• Inside is the stroma

• Thylakoids are membranes stacked on top of each other to form a grana.

•The membranes contain chlorophyll pigments

• Contains 70S ribosomes and small circular DNA5 – 10 μm in length

Centrioles

• A barrel shaped organelle found only in animal cells• Used in cell division. • It is a pin-wheel formation of 9 groups of 3

microtubules.

Microvilli

• Minute projections of the cell wall

• Increases surface area

• 1 μm long and 0.8 μm wide

Cell wall

• Made of cellulose• Gives plant cells

shape.• Can be lignified to

make it even stronger.

Permanent Vacuole and Tonoplast

• The tonoplast is a semi-permeable membrane surrounding the vacuole.

• The vacuole stores food, water, and wastes.

• It gives support to soft structures, such as leaves.

Plasmodesmata

• Only found in plant cells• microscopic channels

which traverse the cell walls of plant cells

• enable transport and communication between them.

Cell Membrane

• a semi-permeable membrane

Prokaryotic Cells

• Unicellular

• 1 – 5 μm diameter

• Lack membrane-bound organelles

• Naked, circular DNA

• 70S ribosomes

• Peptidoglycan cell walls

Peptidoglycan cell walls