F211 Cell Membranes 1

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Role of Membranes within Cells
Control which substances enter and leave cell; Cell recognition; Cell communication
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Role of Membrane at Cell Surface
Increase SA making reactions more efficient; Form Vesicles to transport substances; Control substances leaving or entering organelles; Divide cell into compartments
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Role of Cholesterol
Phospholipids constantly moving makes the bilayer fluid; Cholesterol molecules fit between the phospholipids, binding to their tails; Causes them to pack more closely; Gives rigidity; Prevents H2O and ions passing through membrane
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Role of Glycolipids and Glycoproteins
Takes part in cell recognition by telling WBC that a cell is OWN; Glycoproteins also bind cells together in tissues
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Role of Proteins- Channel Proteins
Facilitated Diffusion; Form pores in the membrane; may be gated; Allows large molecules(Glucose), Hydrophilic molecules and Ions to cross membrane
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Role of Proteins- Carrier Proteins
Active Transport; Specific molecules fit in to be crossed through the membrane; e.g. Large molecules- glucose and amino acids
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Effect of -0 degrees; 0-45 degrees; +45 degrees on membrane structure and permeability
Membrane is rigid,phospholipid packed together,channel & carrier proteins denature, ice crystals pierce membrane; Partially permeable, phospholipid move around;Permeable, Channel & Carrier proteins denature, water expands to put pressure on membrane
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Cell Signalling Mechanism
Cell releases messenger molecule; Messenger molecule detected by another cell as it bind to complementary receptor on its cell membrane; e.g- Glucagon binds to liver cell to break stores of glycogen to produce glucose
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Membrane Bound Receptors
are sites where hormones and drugs can bind; triggering a response or blocking receptor from working
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Diffusion
Passive movement of molecules from an area of high concentration to an area of low concentration, down the concentration gradient
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Active Transport
movement of molecules or ions across membranes using ATP to drive protein "pumps" within membranes
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Protein pumps differ from proteins used in facilitated diffusion
Carry specific molecules 1 way; use ATP; carry molecules against concentration gradient; carry at a faster rate than diffusion; molecules can accumulate inside cells or organelles or outside cells
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Endocytosis- moving molecules that are too large such as Proteins, Lipids and Carbohydrates
Cell surrounds substance with section of its cell membrane; the membrane pinches off to form a vesicle around the cell containing the ingested substance; e.g. Phagocytes engulfing microorganisms
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Exocytosis- Digestive Enzymes, Hormones, Lipids
Vesicles containing these substance IN cell pinch off from the sacs of the Golgi Apparatus and move to cell membrane; Vesicles fuse with membrane and release contents outside cell; Some substances are inserted straight into cell membrane
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Osmosis
The diffusion of water molecules across a partially permeable membrane from an area of high water potential (less negative, less solute) to an area of low water potential (more negative, more solute)
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Effect of Hypotonic(higher water potential than cell), Isotonic(same water potential) and Hypertonic(lower water potential than cell) solutions on Animal Cell
1.Net water movement is into cell, it bursts/ is haemolysed; 2.Cell stays the same; 3.Net water movement is out of cell, it shrinks/ is crenated
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Effect of Hypotonic(higher water potential than cell), Isotonic(same water potential) and Hypertonic(lower water potential than cell) solutions on Plant Cell
1.Net water movement is into cell, vacuole swells and pushes against cell wall, making cell turgid; 2.Cell stays the same; 3.Net movement of water is out of cell, the cytoplasm and vacuole move away from cell wall-Plasmolysis
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Other cards in this set

Card 2

Front

Role of Membrane at Cell Surface

Back

Increase SA making reactions more efficient; Form Vesicles to transport substances; Control substances leaving or entering organelles; Divide cell into compartments

Card 3

Front

Role of Cholesterol

Back

Preview of the front of card 3

Card 4

Front

Role of Glycolipids and Glycoproteins

Back

Preview of the front of card 4

Card 5

Front

Role of Proteins- Channel Proteins

Back

Preview of the front of card 5
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