Cell Structure

The improvement of the microscope and microscopic techniques in the last four centuries has allowed scientists to observe cells better and develop the cell theory.

(MODERN CELL THEORY)

1. The cell is the unit of structure and function in living things.

2. All cells arise from preexisting cells.

3. The cells of all living things carry on similar chemical activities.

4. All cells carry on their metabolic activities in organelles.

Metric System--used extensively in science

1 meter(m) = 100 centimeters = 1,000 millimeters = 1,000,000 micrometers (microns)

1,000 micrometers = 1 millimeter

organelles- little organs of the cell

Organelles in BOTH plants and animals

1. Nucleus

--cellular control center

--contains hereditary material (DNA in chromosomes)

--self duplicating structure--divides when the cell divides

2. Nuclear membrane

--surrounds nucleus allowing certain materials to enter and leave

3. Nucleolus

--round organelle in the nucleus--usually a pair

--involved with the synthesis of RNA in the ribosomes

4. Ribosomes

--sites of protein synthesis in the cytoplasm

--may be free in the cytoplasm or attached to the endoplasmic reticulum

5. Endoplasmic reticulum

-- cytoplasmic channels from the cell membrane to the nuclear membrane

--associated with the storage, synthesis, and transport of materials within the cell

6. Cytoplasm (protoplasm)

--fluid like material between the cell membrane and the nucleus

--over 80 % water

--site of most organelles and cellular chemical reactions

7. Vacuole

--membrane bound cytoplasmic spaces containing materials

** Vacuoles are crucial in one celled organisms.

Food vacuole--store and digest ingested food

Contractile vacuole-pumps excess water from cells maintaining homeostasis

8. Lysosome

-- pouch containing digestive enzymes

-- digest bacteria and some foods entering the cell

-- important in the work of some white blood cells

-- breakdown worn out cell organelles

9. Mitochondrion

-- "Powerhouse of the cell"

--carries on cellular respiration (contains respiratory enzymes that make ATP) (energy molecule)

-- may contain DNA--is self duplicating-- divides when the cell divides

-- found in greater nos. in active cells

10. Golgi apparatus (complex)

--usually located near the nucleus

--synthesizes, packages, and secretes cellular products

11. Plasma (cell) membrane

--surrounds the cell

--is semi-permeable--selectively regulates the flow of materials to and from the cell--thus maintaining chemical homeostasis within the cell

--consists of two layers of fat or lipid--an outer and an inner layer--and an inner layer of protein with globular proteins found throughout the "Fat sandwich"

--transport through the plasma membrane likely occurs through these globular proteins (Fluid mosaic model)

This is a graphic of a plasma membrane. The blue and purple illustrate the two layers of lipids, while the green depicts the protein within the membrane.

ANIMAL CELL ORGANELLES ONLY

1. Centriole- a cylindrical structure found in the cytoplasm which appears to function during the division of certain animal cells (usually near the nucleus)

PLANT CELL ORGANELLES ONLY

1. Cell Wall- a nonliving structure which surrounds and supports the cell - composed mostly of cellulose

2. Chloroplasts- green in color-double membrane - contain the green pigment chlorophyll which carries on photosynthesis

-- is self replicating like the mitochondrion

photosynthesis- the conversion of light energy to chemical energy by chlorophyll in chloroplasts

Overall Net eq'n for photosynthesis

6 Water + 6 Carbon dioxide yields glucose + 6 oxygen (when catalyzed by chlorophyll in the presence of sunlight)

Levels of Tissue Organization

cell -- unit of structure of all life

tissue -- composed of groups of similar cells

organs -- composed of groups of tissues functioning together

organ systems -- composed of groups of organs functioning together

Organ systems function together in higher organisms to produce the structure and functioning of the entire organism.