Chapter 3- Cellular level of Organization pt.2 Flashcards
Plasma membrane is SELECTIVELY PERMEABLE meaning
it allows some materials to move freely, and restricts other materials
Active transport
requires energy & ATP
Passive transport
no energy required
Diffusion (Passive)
-can be simple/channel-mediated
Always follows concentration gradient, moves “down” concent. from high to low concentration gradient which allows movement
Carrier-mediated transport (passive/active)
-of ions and organic substances
movement of molecules across cell membrane via special transport proteins that are embedded
Vesicular transport (active)
movement within a vesicle
5 factors that influence rate of diffusion in cells
- Distance particle has to move
- effective across short distances - Molecule size
- smaller is faster - Temperature
- more heat, faster motion - Concentration Gradient
- larger gradient, faster diffusion - Electrical Forces
- opposites attract, likes forces repel
Intracellular
Potassium
Extracellular
Sodium & Calcium, Chloride
Why is there a bigger concentration of amino acids inside the cell than outside?
Because amino acids are the building blocks of all cells
Simple Diffusion
Materials diffuse directly through plasma membrane w/o use of protein channel.
EX: triglycerides, lipids, steroids, testosterone, estrogen, cholesterol
Lipid soluble molecules pass into a cell by what method?
Simple diffusion
Channel-mediated diffusion
A concentration gradient drives movement of solute through a transmembrane channel protein
EX: Leak channels for Na, K, or Cl
Channel-mediated diffusion (polar & ionic molecules)
A concentration gradient drives movement of solute through a transmembrane channel protein
EX: Leak channels for Na, K, or Cl
Osmolarity
measure of solute concentration
Isotonic
A solution that does not cause osmotic flow of water in/out of cell
Hypotonic
Has less solutes and loses water through osmosis –>water flows into cell
-Ruptures (LYSING/HEMOLYSIS of red blood cells)
Hypertonic
Has more solutes and gains water by osmosis –> water moves out of cell
-Shrinks (CRENATION of red blood cells)
3 Characteristics common in carrier-mediated transport
- Specificity
- one transport protein, one set of substrates - Saturation limits
- Rate depends on the speed and number of transport proteins, not substrate - Regulation
- cofactors such as hormones play an important role in coordinating carrier protein activity
Carrier-Mediated Transport: FACILITATED DIFFUSION
Passive.
-Carrier proteins transport molecules too large to fit through channel proteins
EX: glucose, amino acids
*molecule binds to receptor site on carrier protein
*protein changes shape, molecules pass through
*receptor site is specific to certain molecules
Carrier-Mediated Transport: ACTIVE TRANSPORT **Pump (primary or secondary)
- moves substrates against concentration gradient, from an area of low concentration to high concentration
- requires energy, such as ATP
Carrier-Mediated Transport: ACTIVE TRANSPORT **Pump (primary or secondary)
-moves substrates against concentration gradient, from an area of low concentration to high concentration
*requires energy, such as ATP
ION PUMPS: move ions against concentration gradient
EXCHANGE PUMPS: exchange of molecules
Primary Active Transport
Sodium-Potassium exchange pump:
*Sodium ions out, Potassium ions in
Secondary Active Transport (another kind of facilitated diffusion)
Glucose and Sodium enter cell through facilitated diffusion. Another channel will pump Sodium out of cell.
