Textbook Content (Weeks 7 - 12) Flashcards
Section 2 Weeks 7 - 12
Week 8
Water moves across cell membranes ________ its concentration gradient
down
Week 8
True or False: Water IS able to diffuse directly across the lipid bilayer
True - because they are small and uncharged, water is able to but SLOWLY
Week 8
What type of channel helps to faciliate the transport of water?
Aquaporin
Week 8
Where is aquaporin regularly found?
Mainly found in cells responsible for moving large fluids (cells in kidney)
Week 8
What is osmolarity?
The total concentraction of solute particles inside the cell
Week 8
What is osmosis?
From an area of low solute concentration (high water concentration) to an area of high solute concentration (low water concentration)
Week 7
What happens when osmosis occurs without constraint?
A cell will swell
Week 8
How does paramecium avoid swelling (via osmosis)?
It periodically ejects water that moves into the cell from a contractile vacuole. The vacuole accomplishes this feat by accumulating solutes, which causes water to enter via osmosis, pumping solutes back into the cytosol before discharging its contents at the cell surface.
Week 8
How do animal cells reduce its intracellular solute concentration?
Animal cells obtain osmotic equilibirum by using transmembrane pumps to expel solutes, nuch as Na+ ions, that draw water into the cell
Week 8
Plant cells have cell walls that allow them to take advantage of the pressure that builds up when osmosis causes the plasma membrane to push against the cell wall, what is this pressure called?
Tugor pressure
Week 8
Which type of membrane transport protein can perform both active and passive transport?
A. Channels
B. Both channels and transporters
C. Neither type of membrane transport protein can perform both active and passive transport
D. Transporters
D. Transporters - this is because only transporters can move a solute against its concentration gradient. Some transporters allow passive transportation of molecules down their concentration gradient.
Week 8
When glucose moves across a phospholipid bilayer by active transport, which factor determines the direction of its transport?
A. The charge difference across the membrane
B.The amount of energy available to fuel the transport process
C. Whether the cell is metabolically active or not
D. The concentrations of glucose on either side of the membrane
D. The concentration of glucose on either side of the membrane - this is because glucose, a large and uncharged molecule moves across the membrane throgh a glucose transporter (GLUT), not a pump. Therefore the
Week 8
Which of the following statements is true?
A. K+ is the most plentiful charged ion outside the cell while Na+ is the most plentiful inside
B. K+ and Na+ are present in the same concentration on both sides of the plasma membrane
C. K+ and Na+ are both maintained at high concentrations inside the cell compared to out
D. Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside
D. Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside - This is because cells spend a great deal of energy to maintain chemical imbalance
Week 8
The epithelial cells that line the gut have glucose-Na+ symport proteins that actively take up glucose from the lumen of the gut after a meal, creating a high glucose concentration in the cytosol. How do these cells release that glucose for use by other tissues in the body?
A. The cells run the glucose-Na+ symport proteins in reverse
B. The cells have a glucose pump that excpels the glucose needed by other tissues
C. The cells have glucose channels in their plasma membrane
D. The cells have glucose uniports in their plasma membrane
D. The cells have glusocse uniports in their plasma membrane - This is because epithelial cells have absorbed intestinal glucose release that glucose for use by other tissues in the body through glucose uniports located in parts of their plasma have membranes that do not face the gut lumen. These passive glucose uniports allow glucose to move down its concentration gradient, out of the cell
Week 8
When the glucose-Na+ symport protein is in its outward open state, which is more likely to occur?
A. Glucose binds to its binding site
B. The transporter releases Na+ into the cell
C. The transporter relseases glucose
D. Na+ binds to its binding site
D. Na+ binds to its site - This is because Na+ concentrations are high outside the cell Na+ readily binds to the trasnporter in its outward open state. The transporter must then wait for a rare glucose molecule to bind
Week 8
What is patch clamp recording?
Technique used to monitor the activity of ion channels in a membrane; involves formation of a tight seal between the tip of a glass electrode and a small region of cell membrane
Week 8
What is the cell cortex?
Specialized layer of cytoplasm on the inner face of the plasma membrane. In animal cells, it is rich in actin filaments that govern cell shape and drive cell movement.
Week 8
What is the main component of a red blood cell’s cortex?
spectrin
Week 8
What is the importance of a red blood cell’s cortex?
- Due to genetic alterations, some mice and humans produce a form of spectrin with an abnormal structure
- These individuals are anemic: fewer blood cells than normal
- The red blood cells they have are spherical instead of flattened because of this different spectrin
Week 8
If the backbone of a polypeptide is hydrophilic, how can a transmembrane alpha helix span the hydrophobic portion of the lipid bilayer?
A. The hydrophobic amino acid side chains in a transmembrane helix interact with the hydrophobic interior of the bilayer
B. Lipids in a fluid membrane can bend inwards to their polar heads interact with the transmembrane helix
C. The hydrophobic backbone cloaks itself in a shall of water molecules
D. Transmembrane alpha helices only occur in sets in which the helices interact to neutralize the hydrophilic backbones
A. The hydrophobic amino acid side chains in a transmembrane helix interact with the hydrophobic interior of the bilayer - Although the backbone is hydrophilic, the amino acid side chains of an alhe helix stick out from the helix. If those amino acid sie chains are hydrophobic, they will interact with the hydrophobic tails in the bilayer and shield the hydrophobic backbone from unfavourable interactions
Week 8
In a patch of animal cell membrane, about 10pm^2 in area, which will be true?
A. There will be more protein mols than lipid mols
B. There will be an equal number of proteins and lipids
C. Because the lipid bilayer acts as two dimensional fluid, there is no way to predict the relative numbers of proteins and lipids in any patch of the cell membrane
D. There will be more lipids than proteins
D. There will be more lipids than proteins - This is because proteins make up about half of the mass of an animal cell membrane. In terms of mass, lipids and proteins are equal share. However, lipids are much smaller than proteins, so a cell membrane contains 50 times more lipids mols than protein mols.
Week 9
In a typical secretory cell, which of the following membranes has the largest surface area
A. Plasma membrane
B. Smooth ER
C. Nuclear inner membrane
D. Rough ER
D. Rough ER - this organelle can compose about half of the total membrane present in the cell
Week 9
How do the interiors of the ER, GA, endosomes, and lysosomes exchange contents with each other?
A. By open pores that allow ions to exit and enter the organelles
B. By secreting hormones and other small signaling molecules
C. By fusing with another
D. By small vesicles that bud off one organelle and fuse with another
D. By small vesicles that bud off one organelle an dfuse with another
Week 9
What are Rab proteins?
One of a family of cmall GTP-binding proteins present on the surfaces of transport vesicles and organelles that serves as a molecular marker to help ensure that transport vesicles fuse only with the correct membrane
Week 9
What are tethering proteins?
Filamentous transmembrane protein involved in the docking of transport vesicles to target membranes
Week 9
What is a SNARE?
One of a family of membrane proteins responsible for the selective fusion of vesicles with
Week 9
Vesicle budding is driven by which of the following?
A. Assembly of a protein coat
B. Binding of a cargo molecule
C. Hydrolysis of GTP by domains
D. Interactions of v and t SNAREs
A. Assembly of a protein coat - this is because after budding from its parent’s organelle, the vesicle sheds this coat, allowing its membrane to interact with the target membrane with which it will fuse
Week 9
What is phagocytosis?
the process by which particulate material is engulfed (eaten) by a cell. Prominent in predatory cells, such as Amoeba proteus and in cells of the vertebrate immune system, such as macrophages
Week 9
What is a phagocytotic cell?
A cell such as a macrophage or a neutrophil that is specialized to take up particles and microorganisms by phagocytosis
Week 9
What is the endosomal compartment?
The endosomal compartment has a function similar to that of the Golgi network in which is serves as the main sorting station in the inward endocytotic pathway
Week 9
What is autophagy?
It is a mechanism by which a cell “eats itself”, digesting molecules or organelles that are damage or obsolete
Week 11
Which of the following determines the direction in which cellulose microfibrils are laid down in the extracellular space of a plant cell?
A. Amount of tugor pressure within a cell
B. Availability of sugar monmers for a cellulose microfibril elongation
C. Orientation of microtubules in the cell wall
D. Orientation of microtubules on the cytoplasmic side of the plasma membrane
D. Orientation of microtubules on the cytoplasmic side of the plasma membrane - this is because microtubules beneat the cell wall serve as tracks that guide the movement of the enzyme complexes that synthesize the cellulose microfibrils
Week 11
Fibroblasts are the major cell component in which tissues?
A. Epithelial
B. Nervous
C. Muscle
D. Connective
D. Connective - Fibroblasts are the major cellular component in connective tissues. Fibroblasts manufacture and inhabit the extracellular matrix in skin, tendon and many other connective tissues.
Week 11
Which of the following most likely describes a protein that will become a proteoglycan? A protein that contains:
A. ECM signal sequence
B. N terminal ER signal sequence
C. Collagen binding domain
D. Transmembrane domain
B. N terminal ER signal sequence
