Notes
The cell
- The plasma membrane is a phospholipid bilayer that is selectively permeable. Passive transport (diffusion, osmosis, filtration) needs no ATP; active transport and vesicular transport do.
- Organelles: nucleus (DNA), ribosomes (protein), rough ER, Golgi apparatus, mitochondria (ATP), lysosomes (digestion), smooth ER (lipids and detoxification).
- Gene expression: transcription (DNA to mRNA in the nucleus), translation (mRNA to protein at the ribosome). Mitosis produces two identical diploid cells.
Tissues
- Epithelial tissue covers and lines; it is avascular and sits on a basement membrane. Connective tissue has abundant matrix. Muscle tissue (skeletal, cardiac, smooth) contracts. Nervous tissue (neurons and neuroglia) conducts signals.
Membranes and repair
- Cutaneous, mucous, serous and synovial membranes cover or line body surfaces. Repair occurs by regeneration or by fibrosis (scar tissue).
Topics in this unit
Each topic has its own short notes and practice.
Practice
Water moves toward the higher solute concentration, which is outside the cell.
The Golgi apparatus receives proteins from the rough ER, modifies them and packages them in vesicles.
Translation converts mRNA codons into a chain of amino acids.
These are features of epithelium. Stratified squamous epithelium lines the mouth and covers the skin.
Scar tissue is dense collagen produced when regeneration is incomplete.
Skeletal muscle fibers are long, multinucleate cells under conscious control.
Free response
Write your answer first, then open the scoring guide.
Free-response question
A person runs a long race on a hot day. Muscle cells use large amounts of ATP and the person sweats heavily, losing water and salts. After the race the person drinks a large volume of pure water.
(a) Name the organelle that produces most of the ATP in the muscle cells and state why muscle cells have many of them.
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Mitochondria produce most ATP by cellular respiration. Muscle cells need a lot of energy for contraction, so they contain many mitochondria.
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(b) Explain how the sodium-potassium pump differs from osmosis in energy use.
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The pump is active transport. It uses ATP to move sodium and potassium against their concentration gradients. Osmosis is passive movement of water down its gradient and needs no ATP.
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(c) If red blood cells were placed in the pure water directly, predict what would happen and explain.
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The cells would swell and could burst. Pure water is hypotonic to the cytoplasm, so water moves into the cells by osmosis.
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