Transport Processes Passive processes Active processes Diffusion of solutes Diffusion of water (called osmosis) Facilitated diffusion (requires a specific channel or a carrier molecule, but no energy is used) Active processes Various types of transporters are used, and energy is required.

Passive Transport Processes Diffusion is the passive spread of particles through random motion, from areas of high concentration to areas of low concentration. It is affected by the amount of substance and the steepness of the concentration gradient. Temperature Surface area Diffusion distance

Passive Transport Processes Channel-Mediated Facilitated Diffusion Carrier-Mediated Facilitated Diffusion

Passive Transport Processes An example of Channel-Mediated Facilitated Diffusion is the passage of potassium ions through a gated K+ Channel An example of Carrier-Mediated Facilitated Diffusion is the passage of glucose across the cell membrane.

Passive Transport Processes Osmosis is the net movement of water through a selectively permeable membrane from an area of high water concentration to one of lower water concentration. Water can pass through plasma membrane in 2 ways: through lipid bilayer by simple diffusion through aquaporins (integral membrane proteins)

Passive Transport Processes In the third tube, the force generated by the movement of water from the left to the right side is called osmotic pressure.

Passive Transport Processes In the body, tonicity refers to the concentration of salt solutions in the blood and elsewhere. Since semipermeable membranes separate these fluid compartments, osmosis of water is free to occur between any fluid space and another. The effect of changing tonicity is demonstrated in this graphic, as water moves in and out of red blood cells.

Active Transport Processes Solutes can also be actively transported across a plasma membrane against their concentration gradient ([low] to [high]) by using energy (usually in the form of ATP). The sodium-potassium pump is found in all cells.

Secondary Active Transport Mechanisms Antiporters carry two substances across the membrane in opposite directions. Symporters carry two substances across the membrane in the same direction.

Transport in Vesicles Vesicle - a small spherical sac formed by budding off from a membrane Endocytosis - materials move into a cell in a vesicle formed from the plasma membrane three types: receptor-mediated endocytosis phagocytosis bulk-phase endocytosis (pinocytosis) Exocytosis - vesicles fuse with the plasma membrane, releasing their contents into the extracellular fluid Transcytosis - a combination of endocytosis and exocytosis

Receptor-Mediated Endocytosis

Phagocytosis

Bulk-phase Endocytosis

Interactions Animation Transport Transport Across the Plasma Membrane Interactions Animation You must be connected to the internet to run this animation.

Transport Interactions Animations Transport Across the Plasma Membrane You must be connected to the internet to run this animation.

Cytoplasm - 2 Components 1. Cytosol - intracellular fluid, surrounding the organelles - The site of many chemical reactions - Energy is usually released by these reactions. - Reactions provide the building blocks for cell maintenance, structure, function and growth. 2. Organelles - Specialized structures within the cell

The Cytoskeleton Network of protein filaments throughout the cytosol Provides structural support for the cell

The Cytoskeleton Types Microfilaments Intermediate filaments Microtubules

Organelles Centrosome - located near the nucleus, consists of two centrioles and pericentriolar material

Organelles Cilia - short, hair-like projections from the cell surface, move fluids along a cell surface Flagella - longer than cilia, move an entire cell; only example is the sperm cell’s tail

Organelles

Organelles Ribosomes - sites of protein synthesis

Organelles Endoplasmic reticulum - network of membranes in the shape of flattened sacs or tubules - Rough ER - connected to the nuclear envelope, a series of flattened sacs, surface is studded with ribosomes, produces various proteins -Smooth ER - a network of membrane tubules, does not have ribosomes, synthesizes fatty acids and steroids, detoxifies certain drugs