Ch 4: The Living Cell - p. 68
4.1 How Cells Receive Information - p. 69
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Proteins form voltage-sensitive channels that control
the passage of ions through the cell membrane.
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Receptor proteins in the cell membrane are able to
sense chemical signals.
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Protein cell surface markers establish a cell’s identity.
4.2 Moving In and Out of Cells - p. 74
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Diffusion is the mixing of 2 substances by the random
motion of molecules.
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Osmosis is the diffusion of water through a membrane.
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Osmotic pressure is the force created by water pushing
outwards.
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Selective transport is the movement of substances
through membrane protein channels. It is selective because they allow only
a particular type of molecule or ion to pass through.
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Generally, substances move from areas with high concentration
to areas with low concentration.
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Facilitated diffusion is when a channel helps a substance
to pass through.
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Active transport is when a channel pushes a substance
from the low concentration side to the high concentration side.
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A sodium-potassium pump is an active transport system
that allows a cell to admit ions necessary for biological processes.
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A proton pump is an active transport system that sends
protons across the cell membrane.
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Chemiosmosis is the mechanism by which energy is released
by the action of proton pumps.
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Larger particles enter and exit a cell by endocytosis and
exocytosis.
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Endocytosis is the process of bringing particles into
a cell by capturing them within a sac.
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Exocytosis is the process of getting rid of material
by discharging it from sacs at the cell surface.
4.3 How Cells Divide - p. 79
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Bacteria (prokaryotic cells) reproduce by dividing themselves
in two stages.
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First the DNA is copied.
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Then the cell splits in two.
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Eukaryotic cells divide in two basic (but more complicated)
stages: mitosis and cytokinesis.
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Mitosis is the process by which the nucleus of a eukaryotic
cell divides into two nuclei.
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Each nuclei has the same number of chromosomes as the parent
cell.
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Interphase is the time period between cell divisions
when the DNA is duplicating.
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Stages of Mitosis:
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1) Prophase: chromosomes form; the nuclear membrane
dissolves
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2) Metaphase: the chromosomes line up in the middle
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3) Anaphase: the chromosomes are pulled apart
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4) Telophase: two new nuclei form and the cytoplasm
starts to separate (leading to cytokinesis)
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Chromosomes are pieces of tightly packed DNA found in the
nucleus of eukaryotic cells.
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In many cells, mitosis is followed by cytokinesis.
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Cytokinesis is cell division where the cytoplasm is
pinched in half, separates, and two separate cells are created.
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Cells have different life spans. They divided a certain number
of times and then die.
Cancer is a disease in which cells grow and divide
at an abnormally high rate.
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