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

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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

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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)

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