Bio Ch. 5
Why can't cells the size of golf-balls exist?
A cell that large would not have enough surface area to use in exchanging materials.
What is one feature all receptor proteins must share?
All receptor proteins must span the cell membrane, having a portion outside the cell and a portion inside.
Cell A has no membrane proteins at all. Cell B has aquaporin membrane proteins. Both cells are placed in hypertonic solution. What will happen?
Cell B shrivels faster than Cell A.
Patients with cystic fibrosis have a variety of symptoms, including congestion in the lungs from a thick mucous, liver blockage by thickened bile, and excessively salty sweat. Based on these symptoms, what would you guess to be the cause of cystic fibrosis?
Failure of an ion transporter causes salt imbalances. This causes problems with osmosis.
__ aid in the coordination of the activities of adjacent animal cells.
Gap (communicating) junctions
How does a freshwater Paramecium counteract osmosis?
It pumps salt into a contractile vacuole, drawing excess water in to be squeezed out of the cell.
Vibrio cholerae causes severe diarrhea in its victims. How might it cause this to occur?
It tricks the cells of the intestines into secreting ions.
Cells are rarely large enough to be visible due to restrictions of area/volume. How then can neuron cells reach lengths of up to several feet?
Neurons have more surface area than spherical cells because they are long and thin.
What causes a plant to wilt?
The cells lose turgor pressure.
How does the plasma membrane stop most substances from crossing it?
The non-polar fatty acid tails form a barrier to polar substances.
If the cytoplasmic fluid of cells in a houseplant were to become very salty, what would happen inside those cells?
The vacuoles would shrivel, but the cells would maintain turgor pressure.
What do channel proteins, aquaporins, and carrier proteins have in common?
They all perform facilitated diffusion.
What do gap junctions, tight junctions, and desmosomes have in common with each other, but not with plasmodesmata?
They are made of protein.
Which direction is water most likely to move?
Water will move out of a hypotonic solution into a hypertonic solution.
When can a cell transport a molecules across the cell membrane without expending energy?
When the molecule is more concentrated outside the cell.
Which of the following is most like a gap junction? a. a desmosome b. a vesicle c. an intermediate filament d. a plasma membrane e. a nuclear pore f. a nuclear envelope
a nuclear pore
Water crosses the plasma membrane: a. through facilitated diffusion or diffusion. b. using a process that requires energy from the cell. c. through cotransport d. through active transport e. against its concentration gradient.
a. through facilitated diffusion or diffusion.
The sodium-potassium pump uses energy from ATP to move sodium ions out of the cell, and potassium ions into the cell. This is an example of:
active transport
Which of the following would be likely to raise the concentration of calcium ions in a cell? a. blocking surface receptors b. blocking ATP binding sites c. blocking pinocytosis d. blocking aquaporins e. blocking endocytosis f. blocking exocytosis
b. blocking ATP binding sites
Which of these cell junctions form a barrier to the passage of materials? a. keratin fibers b. tight junctions c. gap (communicating) junctions d. desmosomes (anchoring junctions) e. plasmodesmata
b. tight junctions
The primary role of __ is to bind animal cells together.
desmosomes
In active transport, a. the plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. b. a vesicle inside the cell fuses with the plasma membrane and releases its contents outside the cell. c. molecules move across the plasma membrane by crossing the lipid bilayer directly, rather than by using a transport protein. d. no energy input is required from the cell. e. molecules move across the plasma membrane against their concentration gradient.
e. molecules move across the plasma membrane against their concentration gradient.
The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside of the cell. This describes the process of:
endocytosis
Which membrane proteins increase the rate of chemical reactions?
enzymatic proteins
Which of the following scenarios is most similar to desmosomes? a. short straws connecting two cups b. glue holding together plastic toy parts c. a hammock woven from nylon rope d. a tire with a slow leak e. stitching in a seam f. staples holding together two pieces of paper
f. staples holding together two pieces of paper
A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of:
facilitated diffusion
Which type of transport requires assistance from membrane proteins, but no energy?
facilitated diffusion
What is the word for membrane proteins that have carbohydrates attached to them?
glycoprotein
Endocytosis moves materials ___ a cell via __.
into....membranous vesicles
Where can the phosphate portion of the phospholipids in a membrane be found?
on the surface, facing the outside liquid or the cytoplasm inside
What name is given to the process by which water crosses a selectively permeable membrane?
osmosis
A cell has no membrane proteins at all. Which substance will diffuse across the membrane fastest?
oxygen
A white blood cell engulfing a bacterium is an example of __.
phagocytosis
Some white blood cells in the human body are able to engulf bacteria and destroy them. What should this engulfing process be called?
phagocytosis
Thermus aquaticus is a species of archaebacteria that grows in steaming hot springs. What would you expect to find in the plasma membrane of this species?
phospholipids with saturated fatty acid tails
Which of these allows hormones to pass from one plant cell to another?
plasmodesmata
What simple property causes molecules to diffuse from high concentration towards a lower concentration?
random motion of molecules
Which method of transport can a cell use to bring in molecules without allowing them to pass through the plasma membrane?
receptor-mediated endocytosis
Which type of connection would you expect to find between cells of the blood vessels?
tight junctions
Which of these would you add to a membrane to make it easier for membrane proteins to move about?
unsaturated phospholipids
As a cell gets larger, which measurement of the cell increases the fastest?
volume
