Bio 2 Unit 2 Test
Which statements about the fluid mosaic structure of a membrane are correct? Select the three correct statements. 1 The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center. 2 The diverse proteins found in and attached to membranes perform many important functions. 3 The kinky tails of some proteins help keep the membrane fluid by preventing the component molecules from packing solidly together. 4 Membranes include a mosaic, or mix, of carbohydrates embedded in a phospholipid bilayer. 5 Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane.
1,2,5
Active Transport
A cell must expend energy to move a solute against its concentration gradient
Which of the following statements regarding membrane function is false? A. The plasma membrane is the control center of the cell B. The plasma membrane plays a role in transferring signals to the cells interior C. The plasma membrane has receptors for chemical messages D. The plasma membrane forms a selective barrier around the cell
A. The plasma membrane is the control center of the cell
Energy Source
ATP
Role that exocytosis has on surface area of cell membrane?
Add too the surface of the cell membrane
Transport proteins
Allow specific ions (particles with charges or molecules to enter or exit the cell)
Cells A and B are the same size and shape, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____.
B ... the diffusion gradient there is steeper
Which of the following is a difference between active transport and facilitated diffusion? A. Active transport involves transport proteins, and facilitated diffusion does not. B. Active transport requires the expenditure of cellular energy, and facilitated diffusion does not. C. Facilitated diffusion involves transport proteins, and active transport does not. D. Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot
B. Active transport requires the expenditure of cellular energy, and facilitated diffusion does not.
Which of the following statements regarding membrane protein function is false? A. Membrane proteins serve as enzymes B. Membrane proteins produce phospholipids C. Membrane proteins form junctions between cells D. Membrane proteins act as receptors to molecules like hormones
B. Membrane proteins produce phosolipids
Which of these statements is TRUE with regard to this animation? A. The cell is not expending energy. B. Potassium ions are transported down their concentration gradient. C. Sodium and potassium ions are transported against their concentration gradients. D. The cell does not expend ATP. E. Sodium ions are transported down their concentration gradient.
C. Sodium and potassium ions are transported against their concentration gradients.
Know components of plasma membrane
Cholesterol Phospholipid Protein
You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule enters the cell? A) blood or tissue type of the patient B) non-polarity of the drug molecule C) lack of charge on the drug molecule D) similarity of the drug molecule to other molecules transported by the target cells E) lipid composition of the target cellsʹ plasma membrane
D) similarity of the drug molecule to other molecules transported by the target cells
Passive Transport
Diffusion across a membrane with no energy
Facilitated diffusion
Does not require energy and relies on the concentration gradient
Concentration Gradient
Explain that things are in a higher concentration on side and a lower concentration on the other side. Higher concentration of solvent=lower concentration of solute. High solute=low solvent
Junction Proteins
Form intercellular junctions that attach adjacent cells
What is the importance of cholesterol?
Keeps the whole cell membrane fluid
Which types of molecules will actively transport?
Larger molecules, charged-polar molecules
Diffusion
Passive transport; moving from high to low concentration. Done by CO2, oxygen and glucose
Three types of endocytosis:
Phagocytosis, Pinocytosis and Receptor-mediated
Fluid Mosaic Model
Phospolid bilayer embedded with proteins
Glycoproteins
Serve as ID tags May be recognized by membrane proteins of other cells
Receptor proteins
Signaling molecules bind to receptor proteins Receptor proteins relay the message by activating other molecules inside the cell 3 stages: reception, transduction, and response of the cell
Which types of molecules will passively transport?
Small non-polar molecules; Oxygen, CO2 (by diffusion) , glucose, water (by aquaporins)
Enzymes
Some membrane proteins are enzymes Enzymes may be grouped to carry out sequential reactions
Role that endocytosis has on surface area of cell membrane?
Takes away from the surface of the cell membrane
Osmosis
The diffusion of water across a selectively permeable membrane
Hypotonic
a lower amount of solute and a greater amount of solvent.
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
When in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. This molecule rapidly enters the cell regardless of whether its concentration is higher inside or outside the cell. Using this information, which transport mechanism is most likely to be responsible for the movement of the molecule across a plasma membrane?
active transport
Utah's Great Salt Lake has an average salinity seven times higher than that of the oceans. Very few multicellular organisms live in this harsh environment. An example is the brine shrimp, which must devote a large portion of its metabolic energy to osmoregulation. These brine shrimp must _____.
actively pump water back into their cells to counter its loss due to osmosis
Membrane phospholipids _____________.
are able to drift about in the plasma membrane since they remain fluid due to cholesterol
attachment proteins
attach to extracellular matrix and cytoskeleton Help support the membrane Can coordinate external and internal changes
Which type of proteins help support the membrane and can coordinate external and internal changes?
attachment proteins
Lysed
burst open
Pinocytosis
cell-drinking, or engulfment of extracellular liquid
Tonicity
describes the ability of a surrounding solution to cause a cell to gain or lose water
The first mosaic model describes the plasma membrane as consisting of what?
diverse proteins embedded in a phosolipid bilayer
A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via __________.
endocytosis
The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of __________.
endocytosis
Isotonic
equal amount of concentration.
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 proteins serve as ID tags and aid in cell to cell recognition?
glycoproteins
The cholesertrol associated with animal cell membranes ____________.
helps to keep phospholipids from being too close to one another, thus remaining fluid
A plant cell placed in a(n) _______________solution will lose water and plasmolyze.
hypertonic
There is a net diffusion of water out of an animal cell when it is placed in a(n) ___________solution.
hypertonic
An animal cell placed in a(n) __________solution will gain water, swell, and possibly burst.
hypotonic
The ideal osmotic environment for a plant cell is a(n) ________ environment.
hypotonic
Plant Cells optimal solution type
hypotonic; in hyper, plasmolysis happens cell membrane separates from cell wall
Endocytosis moves materials _____ a cell via _____.
into ... membranous vesicles
Endocytosis
is used to take in large molecules.
A plant cell surrounded by a(n) _____________ solution will be flaccid (limp).
isotonic
Animal Cells optimal solution type
isotonic
The ideal osmotic environment for an animal cell is a(n) _____________environment.
isotonic
In active transport, _____________________.
molecules move across the plasma membrane against their concentration gradient.
When molecules move down their concentration gradient, they move from where they are ____________ to where they are ________________.
more concentrated; less concentrated
What name is given to the process by which water crosses a selectively permeable membrane?
osmosis
Diffusion across a biological membrane is called ______________________.
passive transport
Facilitated diffusion is a type of _____.
passive transport
A white blood cell engulfing a bacterium is an example of _____.
phagocytosis
In the fluid mosaic model, where are the kinky tails?
phosolipid bilayer
Most of the function of a cell membrane, including transport and enzymatic fucntion are _______.
proteins
What molecules are responsible in phospholipid bilayer for cellular transport
proteins
Which type of proteins binds with a ligand?
receptor proteins
Hypertonic
solution has more solute and less solvent (water) than the cell.
Osmosis is often viewed incorrectly as a process driven directly by differences in solute concentration across a selectively permeable membrane. What really drives osmosis?
the difference in water concentration across a selectively permeable membrane
Phagocytosis
the engulfment of a particle by the cell wrapping cell membrane around it, forming a vacuole
How would fatty acids get through the membrane and why?
they travel by passive transport, specfically diffusion. the tails are fatty-acids which allows them to pass through
Water crosses the plasma membrane.
through facilitated diffusion or diffusion.
Which proteins allows specific ions or molecules to enter or exit the cell?
transport proteins
Receptor-mediated
used membrane receptors for specific solutes.
Exocytosis
used to export bulky molecules, such as proteins or polysaccharides.
Aquaporins
very rapid diffusion of water into and out of certain cells is made possible by a protein channel
Aquaporins are proteins that facilitate the transport of __________ across the membrane
water
In the figure below, working from the inside out, what would be the order of components observed?
water, hydrophilic head, hydrophobic tail, hydrophobic tail, hydrophilic head, water