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