Chapter 7-3 Cell Boundaries 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)

Cell Wall – strong, supporting layer that surrounds some cells. Present in plants, algae, fungi, and many prokaryotes (bacteria). Layer outside the cell membrane. Function: provides support and protection to the cell. Structure: tough carbohydrate fibers (cellulose). Very porous, most substances move through easily.

Cell Wall Cell Membrane Plant, algae, fungi, and many bacteria cells

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 Example: Oxygen enters bloodstream from the lungs

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

3) Osmosis: Diffusion of water through a selectively permeable membrane until equilibrium occurs. High to low concentration Slow through phospholipids Fast through aquaporin

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

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.

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

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 channel protein.

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 material (food). 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