Chapter 4- Cells Exchange Materials Flashcards
1
Q
Homeostasis
A
Body systems working together to keep the cellular environment constant
2
Q
Cell requirements
A
- for a cell to function it must be in a stable environment
- must have continual supply and removal of materials
- cell maintained at a constant temp
- concentration of fluids is kept constant
- Need oxygen and glucose for respiration
- ,
3
Q
How do substances get in and out of cells
A
- cell membrane that surrounds each cell
- separates contents from in the cell to external environment
- ## substances that leave or enter the cell must pass through the cell membrane
4
Q
Fluid mosaic model
A
- Explanation for structure of cell membrane
- membrane is fluid because the molecules around it are constantly changing position
- membrane is mosaic because it is made up of many different kinds of molecules
5
Q
Phospholipid molecules
A
Lipid molecules containing a phosphate group
6
Q
Tissue fluid or extracellular fluid
A
- The immediate environment of a cell (the fluid that surrounds it)
- ## continual exchange of materials between cell and tissue fluid
7
Q
Structure of cell membrane
A
- main structure is made of phospholipid molecules
- arranged into two layers known as a bilayer
- has a hydrophilic head and hydrophobic tail
- heads are on outside and tails are in inside
- heads and tails constantly move
- has cholesterol and protein molecules imbedded in phospholipids
- some protein molecules pass through and some are bound to the surface
- some proteins involved in movement of substances through membrane
- channel proteins form a channel that allows ions, water and other small molecules to pass through
8
Q
Functions of the cell membrane
A
- physical barrier: separates inside the cell from outside the cell
- regulation of the passage of materials: controls movement of materials into and out of the cell
- sensitivity: the cell membrane is the first things that gets affected if anything changes in the extra cellular fluid, has sense receptors
- support: supports the structure of the cell
9
Q
Membrane Proteins
A
- 2% of molecules in membrane are proteins
- only because proteins are large molecules
Membrane proteins are: - receptor proteins
- channel proteins
- cell-identity markers
10
Q
Transport across the cell membrane
A
- Cell membranes are differentially permeable (allows certain molecules to pass through and restrict others)
- materials pass through cell membrane in different ways: active and passive processes
- Active process- requires energy
- Passive process- does not require energy
Three basic types of processes are: - Diffusion
- Carrier-mediated transport
- Vesicular transport
11
Q
Diffusion
A
- Spreading out of particles so they are evenly distributed over the space available
- Occurs in gasses and liquids (constantly moving)
- Move in random directions in straight lines until they hit something
- Molecules moving away from concentrated area experience few collisions and therefore stay on straighter paths for longer than those moving to an area of high concentration
12
Q
Net diffusion
A
- movement of liquid or gas molecules from places of high concentrations to places of low concentration
13
Q
Osmosis
A
- type of diffusion
- diffusion of a solvent through a differentially permeable membrane from a region of high water concentration to low
- water is mostly considered as the solvent
- water diffuses from the more watery side to the less watery side
14
Q
Osmotic pressure
A
- Two of the same amount of liquids go through osmosis and now one of the amounts has more than the other (osmotic pressure)
- ## the higher concentration of solute, the higher the osmotic pressure
15
Q
Carrier-mediated transport
A
- Proteins in the cell, binding to molecules to be transported across the cell membrane
Important characteristics: - carrier proteins are specific and will on,y combine to a specific molecule
- carriers can become saturated (increase of molecules to be transported cannot increase rate of movement)
- carrier activity is regulated by substances such as hormones
Two types of carrier-mediated transport:
–facilitated diffusion: a passive process where substances move with the concentration gradient, from high concentration to low - attaches to binding site, changes shape and comes out the other side
–active transport: an active process because molecules are transported against the concentration gradient (low to high)
