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Membrane structure and function

Date post: 10-Feb-2016
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Membrane structure and function. Membranes are made of fat (lipids). Phospholipids. Hydrophilic head. Hydrophobic tails. WATER. Hydrophilic head. Hydrophobic tail. WATER. Bilayer. Bilayer. Biological membranes are fluid mosaics of lipids and proteins. Hydrophilic region - PowerPoint PPT Presentation
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Membrane structure and function
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Page 1: Membrane structure and function

Membrane structure and function

Page 2: Membrane structure and function

Phospholipids

Membranes are made of fat (lipids)

Page 3: Membrane structure and function

Hydrophilichead

Hydrophobictails

Page 4: Membrane structure and function

Hydrophilichead

Hydrophobictail

WATER

WATER

Bilayer

Page 5: Membrane structure and function

Bilayer

Page 6: Membrane structure and function

Biological membranes are fluid mosaics of lipids and proteins

Page 7: Membrane structure and function

Hydrophilic regionof protein

Hydrophobic region of protein

Phospholipidbilayer

Fluid Mosaic Model of Singer and Nicolson (1972)

Page 8: Membrane structure and function

Freeze fracture (electron microscopy)

Evidence for fluid mosaic model

Page 9: Membrane structure and function

Knife

Cytoplasmic layerExtracellular layer

Cytoplasmic layer

Plasmamembrane

Extracellular layer

Proteins

Page 10: Membrane structure and function

Lateral movement(~107 times per second)

Flip-flop(~ once per month)

Movement of phospholipids

Membrane fluidity

Page 11: Membrane structure and function

ViscousFluid

Unsaturated hydrocarbontails with kinks

Membrane fluidity

Saturated hydro-carbon tails

Page 12: Membrane structure and function

Cholesterol

Cholesterol within the animal cell membrane

Page 13: Membrane structure and function

Fibers ofextracellularmatrix (ECM)

Glycoprotein

Carbohydrate

Microfilamentsof cytoskeleton

Cholesterol

Integralprotein

Peripheralproteins

CYTOPLASMIC SIDEOF MEMBRANE

EXTRACELLULARSIDE OFMEMBRANE

Glycolipid

Membrane Proteins

Page 14: Membrane structure and function

Fibers ofextracellularmatrix (ECM)

Glycoprotein

Carbohydrate

Microfilamentsof cytoskeleton

Cholesterol

Integralprotein

Peripheralproteins

CYTOPLASMIC SIDEOF MEMBRANE

EXTRACELLULARSIDE OFMEMBRANE

Glycolipid

Membrane Proteins

Page 15: Membrane structure and function

EXTRACELLULARSIDEN-terminus

C-terminusCYTOPLASMICSIDE

Helix

Transmembrane protein

Page 16: Membrane structure and function
Page 17: Membrane structure and function

EnzymesSignal

ReceptorATP

Transport Enzymatic activity Signal transduction

Membrane Proteins: functions

Page 18: Membrane structure and function

Glyco-protein

Cell-cell recognition Intercellular joining Attachment to thecytoskeleton and extra-cellular matrix (ECM)

Membrane Proteins: functions

Page 19: Membrane structure and function

• Passive transport• Active transport• Bulk transport

Moving stuff around

Page 20: Membrane structure and function

Diffusion

Page 21: Membrane structure and function
Page 22: Membrane structure and function

Molecules of dye Membrane (cross section)

WATER

Net diffusion Net diffusion Equilibrium

Diffusion of one solute

Passive Transport

Page 23: Membrane structure and function

• Passive transport is the diffusion of a substance across a biological membrane

• No energy required

Passive Transport

Page 24: Membrane structure and function

Lowerconcentrationof solute (sugar)

Higherconcentrationof sugar

Same concentrationof sugar

Selectivelypermeable mem-brane: sugar mole-cules cannot passthrough pores, butwater molecules can

H2O

Osmosis

Osmosis

Diffusion of water across a membrane

Page 25: Membrane structure and function

Animalcell

Lysed

H2O H2O H2O

Normal

Hypotonic solution Isotonic solution Hypertonic solution

H2O

Shriveled

Page 26: Membrane structure and function

Getting across the membrane

Page 27: Membrane structure and function

Rather directly

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Exocytosis

Page 29: Membrane structure and function
Page 30: Membrane structure and function

Some material can diffuse through membranes on their own

Diffusion

Passive

Page 31: Membrane structure and function

Some materials diffuse through only with help

Diffusion

Passive

Page 32: Membrane structure and function

Some materials must be pumped through membranes

Against Diffusion

Active (not passive)

Page 33: Membrane structure and function

Diffusion Facilitated diffusion

Passive transport

ATP

Active transport


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