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Transcript
Chapter 7
Membrane Structure and Function
Days
8
Objectives
-You will understand that membranes are fluid
-The structure results in a semi-permeable membrane
-Passive transport requires no energy
-Active transport requires energy
-Bulk transport of molecules either by exocytosis or by endocytosis.
Lab 1: Diffusion and Osmosis
p. 127
Cell Membranes Are Made up of Macromolecules
Lipids
-Specifically Phospholipids
-Form a bilayer with nonpolar, hydrophobic region in the middle.
Proteins
-Various proteins are embedded.
Carbohydrates
-Carbohydrates extend out and old the cell in place to the ECM
Factors That Affect The Fluidity
Of The Membrane
-
Cell membranes are mainly
held together by nonpolar
attractions --- Much weaker
then covalent bonds
-
Movement of lipids
-
Saturated
Vs
Unsaturated fats
-
Cholesterol
**Cell Membrane Sidedness
P 130
Types:
1. Integral
2. Peripheral
Functions:
Cellular Proteins
1. Transport
-Hydrophobic Channel
-Shuttle uses ATP
2. Enzymes
-Use of Active Site
-Often grouped together
3. Signal Transduction
-Acts in cellular comunication
-Uses a receptor site
4. Cell Recognition
-Glycoproteins
-Immune system
5. Inter Cellular Joining
-Used in various types of
junctions
6. Attachment proteins
-Stablize internal organelles and
cell
Membranes are Selectively Permeable
Passive Diffusion: Movement of solutes from a high concentration to
a lower concentration.
-Takes No Energy to move
-In Cell Biology we are talking
about movement across the
cell membrane
Osmosis: Passive diffusion of water.
Facilitated Diffusion: Passive diffusion of large solutes through
protein channels
Active Transport
-Takes Energy
-Increases gradient
-Gradient is used for cellular work
Passive Transport
-Takes no energy
-Common property of life
-The goal is homeostasis
Active Transport
-Na/K pump makes use of protein shape and changing
ion affinity
-ATP reacts – Phophate changes shape of protein
-Membranes can have a electronic potential based on
their electrochemical gradient
-Electrogeneic pump is a membrane protein that
increases the electrochemical gradient
Ion pump
Co-transport
-Pump creates a gradient
-Use of property of homeostasis to transport large
molecules like sucrose
Exocytosis
-Transport vesicles inside cell combine
with cell membrane and release
contents to the exterior of the cell.
-Transport occurs along microtubules
Endocytosis
1.
Phagocytosis
-
Engulf food particles into a
food vacuole for digestion
-
Ameobas and pseudopods
2.
Pinocytosis is gulping of
extracellular fluid
3.
Receptor Mediated Endocytosis
-Ligands attach to specific
-LDL (Low Density Lipoproteins)
p. 138