Download Week 1, Cells, Jan 17, student version

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=gFuEo2cc
TPA
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_UJcf
Bc
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
Salt
water
- Hypotonic
- Hypertonic
- Isotonic
=
Solvent + Solute
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