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Chapter 3. Cell Structure and Function Cells – the basic units of life.

The cell theory – How do we know about cells? Light microscopes –

Transmission electron microscopes –

Why are cells so small? Surface area to volume ratio.

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Most of what is known about cell structure has been learned using electron microscopes and chemical analysis. The typical animal (human) cell. [Figure 3.4]

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Basic cell types: Prokaryotic –

Eukaryotic – The evolution of the eukaryotic cell. [Figure 3.4]

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Getting into and out of the cell. The plasma (cell) membrane – a dynamic structure. [Figure 3.6]

Major membrane components. Protein + phospholipids. Mechanisms of movement into and out of cells. Diffusion. [Figure 3.8]

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Osmosis. A diffusion of water across a semipermeable membrane.

Isotonic, hypotonic, and hypertonic solutions. [Figure 3.9]

Facilitated transport (diffusion). [Figure 3.10]

Particles diffuse through protein carriers in a membrane.

All forms of diffusion are passive.

Active transport. [Figure 3.11]

Energy (supplied by ATP is required to move particles against a concentration gradient.

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Endocytosis and exocytosis. [Figure 3.12] An active (energy requiring) movement of “large” materials into or out of a cell.

Cellular metabolism.

Metabolism = the sum of all chemical processes occurring in a cell or an organism.

Metabolic processes are controlled and regulated by enzymes.

Most metabolic processes involve groups of enzymes – enzyme systems.

Model of how enzymes work. [Figure 3.17]

Characteristics of enzymes:

Enzymes are proteins. Enzymes are very specific.

Enzymes make it easier (less energy is required) for reactions to occur. Enzymes can be denatured. Most enzyme names end in -ase.

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Cellular respiration. The function of cellular

respiration is to produce ATP.

Aerobic respiration – Oxygen is required.

Most of the reactions associated with aerobic respiration take place in the mitochondria.

C6H12O6 + O2 + ADP + Pi* CO2 + H2O + ATP

Anaerobic respiration (fermentation) in muscle cells. Glucose + ADP + Pi Lactic acid + ATP * Pi. This symbol represents an inorganic phosphate group ultimately derived from phosphoric acid

(H3PO4 ).