Chapter 3 - Cellular Form & Function Flashcards
What are the different cell sizes?
1) Most human cells are about 10-15um wide.
2) Nerve cells can be over a 1 m long and muscle cells can be up to 30 cm.
What are the different cell shapes?
1) Squamous - thin, flat, scaly shape.
2) Cuboidal - squarish looking
3) Columnar - taller than wide
4) Polygonal - having irregular angular shape
5) Stellate - having multiple pointed processes projecting from the cell body
6) Spheroidal to ovoid - round to oval
7) Discoid - disc-shaped
8) Fusiform - elongated with a thick middle and tapered ends
9) Fibrous - long, slender, and threadlike
What is the plasma membrane?
The membrane at the cell surface that prevents escape of cell contents, regulates exchange of materials between cytoplasm and ECF, and is involved in intercellular communication
What percentage of the molecules in the membrane are lipids?
98%
What percentage of the lipids are phospholipids?
78%
How are phospholipids arranged?
Phospholipids arrange into a bilayer, with the hydrophilic heads facing out and the hydrophobic tails directed toward the center
What are the two classes of membrane proteins?
a) Integral proteins penetrate into or through the membrane.
b) Peripheral proteins adhere to one surface of the membrane.
What are the functions of membrane proteins?
Receptors Second-messenger system Enzymes Channel proteins Carriers Cell-identity markers Cell-adhesion molecules
What are Receptors?
Surface proteins where chemical signals from other cells bind
What does the Second-Messenger System do?
A chemical messenger binds to an EC receptor triggering an IC peripheral protein to relay the message to an enzyme which converts a molecule to a second messenger
What do Enzymes do?
Digest nutrients, help produce second messengers, and breakdown signaling molecules
What are Channel Proteins?
Passageways that allow water and hydrophilic solutes to move through the membrane
What are Carriers?
Transmembrane proteins that transfer solutes to the other side of the membrane
What are Cell-Identity Markers?
Glycoprotein acting as “identification tags”
What are Cell-Adhesion Molecules?
Membrane proteins that bind one cell to another or to extra cellular material
What are microvilli?
Extensions of the plasma membrane that serve to increase absorptive surface area and play some sensory roles
How are microvilli best developed?
In cells specialized for absorption
What is brush border?
Dense microvilli at the apical cell surface
What are cilia?
Hair-like processes on the surface of a cell
What are flagellum?
Tail of sperm for motility
The membrane is..?
Selectively permeable - it allows some things through but prevents other things from entering or leaving the cell
What are the methods of moving substances through the membrane?
a) Passive mechanisms require no energy.
b) Active mechanisms consume ATP.
c) Carrier-mediated mechanisms use a membrane protein to transport the substance.
What is filtration?
A process in which pressure forces fluid through a membrane
What is simple diffusion?
The movement of particles from a place of high concentration to a place of lower concentration
What is concentration gradient?
The concentration of a substance differs from one point to another
What are the different types of concentration gradients?
a) Down or with the gradient - particles move from a region of high concentration to a region of lower.
b) Up or against the gradient - particles move from a region of low concentration to a region of higher.