Chapter 2 Cell Membranes

Slide 1: Biology 10 Cell Membranes

Slide 2: Cell Membranes

Slide 3: Cell Membranes  Prokaryotic cells have outer cell membrane only  Eukaryotic cells have outer cell membrane and membranes surrounding organelles  Allows separation and specialization  More complex and successful  Ex: chloroplasts, nucleus, vacuole, etc.  Mitochondria have outer membrane and inner folded membrane to allow high surface area for respiration

Slide 5: Advantages of Membranes  Membranes control what goes in/out  Separate organelles to keep reactants for processes inside to allow faster reactions  Isolate harmful substances from rest of cell  Folds in membrane create villi and microvilli for high surface area for diffusion/osmosis

Slide 6: Structure of Membranes  All membranes (inner and outer) same  Made of phospholipids with proteins  Phosphate “heads” and fatty acid “tails”  Surface is phosphate heads and proteins.

Slide 7: Phospholipids in Membrane  Phosphate is attracted to water – hydrophilic  Head turns towards water solutions  Fatty acids are repelled by water – hydrophobic  Tails turn away from water  In water, phospholipid heads group together on the outside and tails group together inside  Called a bilayer

Slide 8: Phospholipids in Membrane

Slide 9: Phospholipids in Membrane  Hydrophobic centre prevents free diffusion  Controls movement by protein carriers and channels -> selectively permeable

Slide 10: Cell Membrane - TEM

Slide 11: Proteins in Membrane  Proteins “float” in cell membrane  Provide support  Transport across membrane  Protein's are shape specific  Molecules with matching shape will be transported  Carry molecules from high conc. to low conc.  Facilitated diffusion  Carry molecules from low conc. to high conc.  Active transport

Slide 12: Proteins in Membrane  Carbohydrates stick up like “antennae”  Allows cells to recognize each other to form tissues  Enzymes (also proteins) float in cell membrane  Speed up reactions along membrane  Channel protein's span membrane  Allow some substances to avoid hydrophobic centre  Some are open, some are gated (door)  Open channels allow fast diffusion (water)  Gated provide selective permeability (sodium)  Receptor proteins allow molecules outside cell to start reaction inside cell

Slide 13: Transport Across Membranes  Diffusion  Active transport  Simple  Osmosis  Facilitated  Cytosis

Slide 14: Transport Across Membranes

Slide 15: Diffusion  Liquids and gases have kinetic energy and move  Passive process (no energy)  Factors affecting rate:  Surface area  Concentration gradient  Thickness of membrane  Size and type of molecule  Temperature

Slide 16: Villi  Create more surface area  Villi are folds in layers of cells  Microvilli are folds along one cell

Slide 17: Simple Diffusion  Molecules pass between the phospholipids  Oxygen and carbon dioxide  Must be soluble in both lipids and water

Slide 18: Facilitated Diffusion  Protein carriers needed to transport molecules past lipid layer of membrane  Glucose and amino acids  Carriers have matching shape for specific molecule  Molecule binds and protein passes them into cell  No energy required – High conc. to low conc.

Slide 19: Facilitated Diffusion

Slide 20: Active Transport  Move molecules low conc. to high conc. like a pump  Molecule binds protein  ATP provides energy for movement  Protein changes shape to pass molecule  Protein return to shape

Slide 21: Osmosis  Hypotonic solution – solution surrounding cell has higher water potential than cell  Water flows into cell  Hypertonic solution – solution surrounding cell has lower water potential than cell  Water flows out of cell  Isotonic solution – solution surrounding cell has same water potential as cell  Water remains in dynamic equilibrium

Slide 22: Water Potential  Measure of the kinetic energy of the water molecules  The more they hit the membrane, the higher the potential  Solutes reduce ability to hit membrane -> reduce water potential  0 kPa – Highest water potential  -100 kPa – Dilute sugar solution  -350 kPa – More concentrated solution  Lower water potential  Water will flow from 0 -> -350

Slide 23: Cytosis  Membrane surrounds molecules, breaks from bilayer and forms vesicle around molecules  Endocytosis: substances taken in of cell  Phagocytosis  Pinocytosis  Exocytosis: substances taken out of cell  Cytosis relies on the ability of phospholipids to move around within the membrane

Slide 24: Endocytosis  Phagocytosis  Cytosines

Slide 25: Exocytosis