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Chapter 7Membrane 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
Cellular ProteinsFunctions: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
Types: 1. Integral
2. Peripheral
Membranes are Selectively Permeable
What?
Water
Ions (K, Na, Ca, and C
Sugars
Amino Acids
Proteins
Why?
Cellular Respiration
To create gradients
Maintain homeostasis, balance
Protein synthesis
When?
When the cell needs anything
Constantly
Where?Aquaporins allows water to diffuse
throughChannel proteins (hydrophillic
channel)Carrier proteins are specific to what it
is moving
How? What directs movement?
Active transport needs energy
Passive transport doesn’t need
energy
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