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Unit 8 Test Guide
Terms in this set (28)
Why are cells typically small?
The ratio of surface area to volume
Surface area dictates what?
Amount of exchange across the cell membrane.
-More surface area, more exchange of nutrients and gasses into the cell and wastes out via the membrane.
-In: glucose, O2
Out: CO2, Urea
Volume dictates what?
The amount of materials that are needed or produced in the cytoplasm.
-More volume; more nutrients and gasses needed inside cell for metabolic reactions.
-More volume; more waste that is produced and must leave.
What happens as a cell becomes too large?
S:V ratio becomes too small.
-Amount of surface area for exchange of materials through the cell is too little for metabolic demands of the volume and cell will not function properly.
Some cells increase S:V ratio by what?
-Long cellular extensions that increase S, but not V.
-Thin, flat shapes that increase S, without V.
-Extensions of membrane for S, but not V.
The net movement of molecules from areas of higher concentration to areas of lower concentration.
Diffusion is _______.
-Cell does not use energy.
In diffusion, the phospholipid bilayer must be ______________.
-Small, non-charged particles like oxygen and carbon dioxide.
Rates of diffusion depend on what?
-Concentration of the diffusing molecule: greater difference=greater rate.
-Temperature: greater temperature=greater rate of diffusion because temperature increases rate of movement.
-Pressure: greater pressure=greater rate of diffusion because pressure increases rate of movement.
Movement of water by diffusion across a membrane; passive transport.
Osmosis depends on the following:
The amount of solutes in solutions in relation to each other.
-hypertonic, hypotonic, and isotonic.
Water moves from what?
Hypotonic to hypertonic
-cell has higher solute than the solution.
-SOLUTION IS HYPOTONIC
-Water must move into the cell (swell).
-Cell has same solute concentration as solution.
-No net water movement.
-Cell has lower solute concentration than solution.
-Solution is hypertonic.
-Water will move OUT of the cell.
Passive transport with protein channels.
-High to low concentration.
Why is facilitated diffusion different than simple diffusion?
-Molecules move through channel protein into membrane.
-Used for small, charged molecules (ions).
The phospholipid bilayer must be ________________ for facilitated diffusion.
Studded with channel proteins.
-Movement of substances from low concentration to high concentration with protein pumps.
What is energy in the form of?
1. Molecule to be transported enters the pump.
2. Energy from ATP changes the shape of protein.
3. Molecule can now pass through.
Proton pump in cellular respiration and photosynthesis
-H+ ions must be pumped across inner membranes of mitochondria or chloroplast.
Bulk transport in cells
Transport of many molecules into (endo) or out of (exo) the cell at once.
Process by which cells take in molecules (proteins) or smaller cells by engulfing them.
Examples of endocytosis are what?
1. White blood cells engulf bacteria during infection.
2. Single-celled organisms like amoeba engulf bacteria as food.
Cell directs the contents of the secretory vesicles out of the cell membrane and into the extracellular space (outside/between cells).
Examples of exocytosis are what?
1. Secretion of neurotransmitter proteins to send signals between neurons.
2. Secretion of salvia from salivary glands in the mouth.
Why are membranes fluid?
-Fluid is not liquid.
-Phospholipids can move in the membrane because:
-no bonding between phospholipid tails.
-kinks in phospholipid tails prevent close packing.
-Cholesterol keeps phospholipids from packing too close or drifting too far apart.
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