Chapter 3 Flashcards
cell
smallest unit of life. Only come from preexisting cells
What are cells surrounded by?
A plasma membrane
What does plasma membrane do?
Contains cellular structures, regulates what enters and exits the cell
cell doctrine
- All living things are composed of cells and cell products.
- A single cell is the smallest unit that exhibits all the characteristics of life.
- All cells come only from preexisting cells.
Eukaryotes
have nucleus, cytoplasm, organelles, plasma membrane,
Human cells are…
eukaryotes
Prokaryotes
has no nucleus, no organelles, DO HAVE plasma membrane and cell wall
Understandable principle of cells #1
The total metabolic activities of a cell are proportional to its volume of cytoplasm, which is in effect its size. To support its activities, every cell needs raw materials in proportion to its size. Every cell also needs a way to get rid of its wastes
Understandable principle of cells #2
All raw materials, energy, and waste can enter or leave the cell only by crossing the plasma membrane.
Understandable principle of cells #3
As objects get larger, their volume increases more than their surface area.
microvilli
finger-like projections of the plasma membrane that increase surface area.
Plasma membrane constructed of…
2 layers of phospholipids, called a lipid bilayer, plus some cholesterol and proteins
Most animal cells have rigid or nonrigid plasma membranes?
Non-rigid
Molecules cross the plasma membrane in 3 major ways:
passive transport (diffusion and osmosis), active transport, endocytosis or exocytosis
Passive transport
transports a molecule without requiring the cell to expend any energy
Diffusion
the movement of molecules from one region to another as a result of random motion (they tend to do this from areas of high to low concentration until equilibrium is reached)
Osmosis
The net diffusion of water across a selectively permeable membrane
Three forms of passive transport across the cell membrane
diffusion through the lipid bilayer, diffusion through channels, facilitated transport
Diffusion through the lipid bilayer
Allows for the free passage of some molecules while restricting others(Must be soluble in lipids)
(o2 and CO2)
Diffusion through channels
Size and shape of channel determines who passes through. Some are gated. (Water)
Facilitated transport
Molecule attaches to a transport protein, protein changes shape, protein transfers molecule to other side of membrane, protein changes back to original shape. (Highly selective) (Glucose)
Active transport
Moves substances through the plasma membrane against the concentration gradient, requiring energy
Active Transport is like facilitated transport in that
it is accomplished by proteins that span the plasma membrane
Pumps
proteins that actively transfer molecules over the plasma membrane (mostly conver ATD to ADP for energy)
