LECTURE 9 CYTOLOGY The Cell Membrane and Cell

LECTURE 9: CYTOLOGY The Cell Membrane and Cell Transport

�Describe the structure of cell membranes �Compare Active and Passive Transport �Explain Osmosis �Compare hypertonic, hypotonic, and isotonic solutions

Topic 1: Cell Membrane Components

Phospholipid Bilayer Phosphate head Fatty acid tails Hydrophilic = water loving Hydrophobic = water fearing

Proteins Integral found through the inner bilayer - have hydrophobic regions (towards inside of cell) Transmembrane found throughout the entire bilayer Peripheral found only “outside” bilayer

Carbohydrates Glycolipids and Glycoproteins serve as recognition sites for other cells

Topic 2: Cell Transport. Passive Transport

Cell Transport: Two types: Active and Passive processes include different types of diffusion Active processes require the input of energy

Passive Transport: Diffusion - the process of random movement toward a state of equilibrium The net movement from regions of greater concentration to regions of lesser concentration Example: Drop of ink in water

Diffusion Rate How fast can a substance diffuse? The diameter of the molecules/ions Temperature of solutions Electric charge of material diffusing Concentration gradient - change in concentration with distance in a given direction

Cell Transport Across a Membrane Permeable solutes cross membrane more easily SEMI-permeable membrane only allows certain solutes to cross membrane Impermeable solutes CANNOT cross membrane

Diffusion across cell membrane Diffusion and Facilitated Diffusion of molecules.

Osmosis is the diffusion of water across a membrane Movement of water molecules from regions of higher water potential to regions of lower water potential across a semi-permeable or selectively permeable membrane.

Carrot Demo What will happen to a carrot if place in distilled water, salt water, and sugar water? Write down your hypothesis in your notes.

Types of Solutions Hypertonic solutions cell environment has a higher concentration of solutes than inside the animal or plant cell. Hypotonic solutions cell environment has a lower concentration of solutes than inside the animal or plant cell. Isotonic solutions have equal (iso-) concentrations of substances. Water potentials are thus equal, although there will still be equal amounts of water movement in and out of the cell, the net flow is zero.

Crenation Red Blood Cells Lysis

Plant Cells

Topic 3: Cell Transport. Active Transport

Active Transport

Active Transport transport of molecules/ions across the membrane which requires energy. Transported AGAINST the concentration gradient Example: H+ ion pump and Na+ K+ pump

Transport of Large Material Endocytosis Into cell Exocytosis Out of cell

Types of Materials Transported Phagocytosis = “cell eating” Pinocytosis = “cell drinking”

Lysosomes use digestive enzymes to break down vesicle