Cells Chapter 3

Cells Basic organizational structure of the human body About 75 trillion cells in our bodies Can look and function quite differently

Differentiation When cells specialize Specialize in function and form

Cells https://www.youtube.com/watch?v=gFuEo2ccTPA

Typical animal cell Many organelles with distinct roles (ex: mitochondria, nucleus, etc.)

Cell (plasma) membrane Important in physiology Allows stuff in and out of the cell, so the cell can perform it’s function But, it’s selectively permeable, meaning that only certain stuff can go in and out

Cell (plasma) membrane Phospholipid bilayer Embedded proteins

http://www.youtube.com/watch?v=Qqsf_UJcfBc

Movement across cell membranes Materials must cross the membrane Metabolism of the organism occurs within the cell. Important molecules such as carbon dioxide, sugars, oxygen, and nutrients must move into and out of the cell.

Movement across the membrane Can be passive- no input of energy Simple and facilitated diffusion Osmosis Or active- necessitates energy to move stuff Active transport Endocytosis Exocytosis Transcytosis

Simple diffusion Movement of material from an area of higher to lower concentration

Simple diffusion

Simple diffusion

Simple diffusion Selectively permeable

Factors that affect the rate of diffusion Concentration Temperature Size of molecule Charge of molecule

Osmosis Same thing as simple diffusion, just with water

Osmotic pressure Force exerted on a selectively permeable membrane due to osmosis

We want the concentration of sugar and water to be equal between the two containers There’s too much sugar on the right side The only way to equalize is to move water (sugar is too big to pass through)

Tonicity Degree to which a solution’s solute concentration causes water to move into or out of cells Solution = Solvent + Solute - Hypotonic - Hypertonic - Isotonic Salt water water

Solution types

Facilitated diffusion Maybe the molecule is too big (sugars, salts) Transmembrane proteins can come to the rescue! Still moving from a higher to a lower concentration No energy required

Active transport Particles are moved against the concentration gradient Requires energy!!! Actively climbing against gravity requires energy.

Active Transport Movement of a substance against the concentration gradient Uses a carrier protein and energy (ATP) Examples: ions, amino acids, and sugars

Endocytosis Bulk transport Movement across the membrane and into the cell using vesicles Requires energy

Exocytosis Bulk transport Movement across the membrane and out of the cell using vesicles Requires energy

Transcytosis Endo, followed by exocytosis Moves substances rapidly