Ch. 5 Cell Membrane and Transport LIPID BILAYER cytoplasm extracellular fluid

Cell Membrane—thin, flexible membrane that surrounds all cells. Selectively permeable - regulates what enters and exits the cell. Made up of a phospholipid bilayer. Double layer of phospholipids Gives cells flexible but strong barrier between itself and its surroundings.

Phospholipids are a lipid that have a Glycerol Phosphate Two fatty acid chains Phospholipids Hydrophilic head Hydrophobic tail

Hydrophilic Head Hydrophobic tail

Phospholipid Bilayer hydrophilic head hydrophobic tails hydrophilic head Water (outside of cell) Water (inside of cell)

Fluid mosaic model

Carbohydrate (of glycoprotein) Glycoprotein Fibers of extracellular matrix Microfilaments of cytoskeleton Protein Steroids (cholesterol) Phospholipid Glycolipid Phospholipid Bilayer

Membrane Proteins > 50 kinds of proteins found in human red blood cells so far Carry out many different functions Structural, external, identification tags, form junctions between cells Enzymes – catalytic teams for molecular assembly lines Receptors – receive chemical messages from other cells Message transfer is called signal transduction Help move substances across membrane

No Gradient Gradient Concentration Gradient: Difference in concentration over a distance. Cell Transport: movement of substances across the cell membrane based on concentration gradient. HIGH concentration LOW concentration

How the Cell Membrane does its thing… Two categories of cell transport: Passive transport – Requires NO energy High to low concentration Active transport – Requires energy Low to high concentration

3 types of passive transport: 1) Simple Diffusion High to low concentration Small, lipid soluble molecules like CO 2 and O 2 Example: Oxygen enters bloodstream from the lungs

2) Facilitated Diffusion Large, charged, or polar substances move across membrane in this way. Always moves from high to low concentration Requires a transport protein Transport Protein

2) Facilitated Diffusion Water can move through because it is small, but transport is slow, aquaporins allow for faster diffusion Transport Protein

3) Osmosis: Diffusion of water through a selectively permeable membrane until equilibrium occurs. High to low concentration Water will cross membrane until solute concentrations (molecules/mL) are equal on both sides of membrane

What words do you know that start with…… Iso______________ Definition: “same” Hyper___________ Definition: “above” Hypo____________ Definition: “below” Isotonic/Isosceles triangle/Isotope Hyperactive/Hyperextend Hypothermia, Hypodermic needle

Tonicity A term used to describe the tendency of a cell in a given solution to lose or gain water.

Isotonic Solution—Concentration of solutes is equal in and out of the cell. 1. No net movement of water. 2. Cell maintains shape. BEFOREAFTER

Hypertonic Solutions— Concentration of solutes is higher outside the cell. 1. Water exits the cell. 2. Animal Cell: shrinks which is known as crenation 3. Plant Cell: cell membrane collapses away from cell wall. This is known as plasmolysis.

D. Hypotonic Solution—Concentration of solutes is lower outside the cell. 1. Water enters the cell. 2. Animal cell swells and may burst which is known as Cytolysis. 3. Plant cell—cell wall prevents breaking. (Turgor Pressure)

Animal Cells in a hypertonic: CRENATION Plant Cells in a hypertonic: PLASMOLYSIS

Hypotonic Isotonic Hypertonic

Tonicity in animals Osmoregulation: or an animal to survive changes in salinity it must have a method to prevent excessive uptake of water or excessive loss of water Ex: freshwater fish live in hypotonic environment Ex: saltwater fish live in a hypertonic environment

Have evolved to have kidneys and gills that constant work to flush water out of the body Freshwater Teleost

Marine Teleost

Tonicity in plants Turgidity: When a plant cell has a net inflow of water. Plasmolysis: When a plant cell loses water, plasma membrane pulls away from cell wall. Also happens in bacteria and fungi

ISOTONIC HYPOTONIC HYPERTONIC

What type of solution is each cell in? ISOTONIC HYPERTONIC HYPOTONIC

Fig. 5.14, p. 88 2M sucrose solution 1 liter of pure water 10M sucrose solution 2M sucrose solution HYPOTONIC CONDITIONS HYPERTONIC CONDITIONS ISOTONIC CONDITIONS 1)2)3) Ticket out Quiz

Active Transport Substances move against concentration gradient -low to high concentration Requires energy (ATP) Requires a transport protein. Ex: Sodium-Potassium pumpSodium-Potassium pump in nerve cells

Sodium Potassium Pump in Nerve Cells

How do LARGE molecules enter and exit the cell? BULK TRANSPORT: Movement of particles into or out of a cell without passing through the plasma membrane. Requires energy!

Cell engulfs large materials such as macromolecules. Endocytosis – Large materials move into cell.

Phagocytosis Cell engulfs large particles, microbes, and cellular debris “Cell eating”

Pinocytosis Cells receive bulk amounts off liquid “Cell drinking”

Exocytosis - vesicle fuses with the membrane and exits the cell. Expels materials such waste and hormones.

Lorenzo’s Oil ALD Can not digest FAT Fat builds up and destroys his nerves Fat enters body in 2 ways – food and biosynthesis Oil stops biosynthesis! Oil keeps the body from building up the bad fat COMPETITIVE inhibition