BIOL 1030H Study Guide - Winter 2018, Comprehensive Midterm Notes - Gene, Dna, Meiosis

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BIOL 1030H
MIDTERM EXAM
STUDY GUIDE
Fall 2018
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Introduction To Cells
All organisms are made of either a single cell or an ensemble of cells.
Essential features of cells
1. A plasma membrane that creates a distinct boundary separating the cell interior from the
external environment
2. The ability to harness materials and energy from the environment.
3. The ability to store and transmit information
Cells are defined by membranes
Membranes:
Separate the inside of the cell from the outside.
Surround many internal structures.
Cell membranes are dynamic
Lipids associated with each other by weak interactions called van der Waals forces
Membrane lipids are able to move in the membrane (membrane is fluid) • Individual fatty
acid chains are also able to flex or bend.
Fluidity depends on the fatty acids present (e.g., double bonds, and the length of the
tails).
Saturated vs. Unsaturated
Saturated fatty acid chains lack double bonds, resulting in phospholipids with a straight
structure that favors tight packing.
Unsaturated fatty acids have one or more double bonds that introduce kinks in the
phospholipids, reducing the tightness of packing
Plasma membrane
Characteristics
Feature of all cells.
Defines the cell boundary
Separates internal contents from the surrounding environment
Critical for homeostasis
Maintenance of a constant internal environment
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Plasma membranes are selectively permeable
Certain items can move freely, while others only under certain conditions; others cannot
Reasons for limited permeability
Lipid bilayer is hydrophobic – prevents ion movement
Many macromolecules are too large
Gasses, lipids, small polar molecules can cross
Selective permeability is key to maintaining homeostasis
Active transport is movement against a concentration gradient
Passive transport works only when the concentration gradient is in the right direction.
Examples:
Nutrients: higher on the outside to lower on the inside
Waste: higher on the inside and lower on the outside
Two kinds of active transport:
Primary Active Transport
Secondary Active Transport
Cell junctions
Cells are organized into tissues, organs and organ systems
Nearby cells often adhere, interact and communicate with each other via physical contact
at cell junctions
Categories of cell junctions (based on task):
Adherens junctions; Desmosomes; Hemidesmosomes
Tight junctions
Gap junctions/Plasmodesmata (plants)
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Document Summary

All organisms are made of either a single cell or an ensemble of cells. A plasma membrane that creates a distinct boundary separating the cell interior from the external environment. The ability to harness materials and energy from the environment. 2: the ability to store and transmit information. Separate the inside of the cell from the outside. Lipids associated with each other by weak interactions called van der waals forces. Membrane lipids are able to move in the membrane (membrane is fluid) individual fatty acid chains are also able to flex or bend. Fluidity depends on the fatty acids present (e. g. , double bonds, and the length of the tails). Saturated fatty acid chains lack double bonds, resulting in phospholipids with a straight structure that favors tight packing. Unsaturated fatty acids have one or more double bonds that introduce kinks in the phospholipids, reducing the tightness of packing. Separates internal contents from the surrounding environment.

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