Unit 2: Cell Structure and Function
If you examine side A in the figure after three days, the contraptions of glucose and NaCl should be
0.4 M glucose, 0.45 M NaCl
Which line in the graph represents the bag with the highest initial concentration of sucrose?
A
If you examine side A after three days, you should find
A decrease in the concentration of NaCl and a decrease in the water level.
Which of these can rapidly pass directly through the phospholipids of the plasma membrane, without the help of a transport protein?
A only (Small, non-polar, lipid-soluble molecules can pass rapidly through the phospholipids of the plasma membrane. Ions, such as hydrogen ions, and hydrophilic;lic molecules, such as water and glucose, cannot rapidly pass directly through the phospholipids of the membrane. To move rapidly through the membrane, they must pass through membrane transport proteins.)
In the diagram of the plasma membranes of two adjoining cells, identify the protein indicated by the white arrow, including its function
A receptor proteins that binds with a signaling molecule and relays the message into the cell by activating other molecules inside the cell. (Signaling proteins are part of signal transduction pathways that transmit external chemical signals into the cell.)
Active and passive transport of solutes across a membrane typically differ in which of the following ways?
Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy. (Active and passive transport can be distinguished by whether or not they use cellular energy.)
What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?
Amphipathic nature (Detergents form micelles around the grease, which are then washed away because the polar head groups facing outward on the micelle are water-soluble.
A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from
Any eukaryotic organism
Which component in the figure is a glycolipid?
B
Which component in the figure plays an important role in cell-cell recognition?
B
Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes?
B
Which of the following are common traits of chloroplasts and mitochondria?
Both have their own DNA (Mitochondria and chloroplasts contain their own DNA and ribosomes)
Which of the following statements is true with regard to this animation?
Both sodium and potassium ions are transported against they concentration gradients. (Both ions are transported from where their concentration is low to where their concentration is high, and the cell expands energy in the form of ATP to do it.
Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?
C
The structure that regulates the passage of material information and out of this bacterial cell is indicated by the letter ______.
C (The plasma membrane is selectively permeable)
What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell?
Cell wall (The cell wall is a rigid supporting structure)
Plant cell only
Cellulose cell wall, chloroplast, central vacuole
Which of the following correctly matches an organelle with its function
Central vacuole ... storage (But remember, plant cells have a central vacuole, where as most animal cells have several smaller vacuoles located throughout the cytoplasm)
Animal cell only
Centriole
Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a ______ attached to phosphate.
Choline group
In a liver cell detoxifying alcohol and some other poisons, the enzymes of the peroxisome remove hydrogen from these molecules and
Combine the hydrogen with oxygen molecules to generate hydrogen peroxide
The fluid mosaic model of the membrane proposed that membranes
Consist of protein molecules embedded in a fluid bilayer of phospholipids.
The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane-more acidic outside the cell than inside the cell. Phosphate transport is an example of
Cotransport
The movement of glucose into a cell against a concentration gradient is most likely to be accomplished by which of the following?
Cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis (Movement of most solutes against their concentration gradient couples the movement of one solute down its concentration gradient to the movement of another (glucose in this case) against its concentration gradient.)
Drag each solution to the appropriate bin.
Crenation: A (3.21% (m/v) NaCl, D (6.97% (m/v) glucose, E (5.0% (m/v) glucose and 0.9% (m/v) NaCl Hemolysis: B (1.65% (m/v) glucose, C (distilled H2O)
Which component in the figure is a peripheral protein?
D
The DNA containing region of the bacterial cell is indicated by the letter ______
D (The nucleoid region contains DNA)
Which of the following statements concerning cells of bacteria and archaea is correct?
DNA is present in both archaea and bacteria
The movement of the hydrophobic gas nitrous oxide (N2O) (laughing gas) into a cell is an example of
Diffusion through the lipid bilayer
A cell has formed a food vacuole as it ingested a food particle. Which of the following events is associated with the breakdown of that food particle?
Digestion of the food particle occurs in a vesicle enclosed by a membrane that separates the digestion from the cytoplasm (Digestion occurs within a vesicle. If the digestive enzymes were in the cytosol, they might degrade essential components of the cell)
Which component in the figure helps membranes resist changes in fluidity at high and low temperatures?
E
Which component in the figure is cholesterol?
E
A primary function of cholesterol in the plasma membranes of some animals is to
Enable the membrane to stay fluid more easily when the temperature drops
Which of the following may be found in eukaryotic cells, but not in bacteria?
Endoplasmic reticulum
Transport of potassium ions into an animal cell by the sodium-potassium pump requires
Energy from ATP
Which of the following correctly describes some aspect of exocytosis or endocytosis?
Exocytosis and endocytosis change the surface area of the plasma membrane. (The fusion or budding of transport vesicles at the plasma membrane either acids or remove proteins and phospholipids, thus changing the surface area.)
A phospholipid also has two "tails" made up of two ______ molecules, which consist of a carboxyl group with a long hydrocarbon chain attached.
Fatty acid
______ are surface appendages that allow a bacterium to stick to a surface.
Fimbriae (Fimbriae enable bacterial cells to stick to a surface)
Identify Structure A
Glycoprotein (Structure A is composed of both a carbohydrate and a protein.)
Which of the following produces and modifies polysaccharides that will be secreted?
Golgi apparatus
Because the phosphate group and its attachments are either charged or polar, the phospholipid head is ______, which means it has an affinity for water.
Hydrophilic
Ions
Hydrophilic, have difficulty crossing the hydrophobic part, transport protein required to cross efficiently
Polar molecules
Hydrophilic, have difficulty crossing the hydrophobic part, transport protein required to cross efficiently
Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are ______, which means they are excluded from water.
Hydrophobic
Nonpolar molecules
Hydrophobic, can cross easily, no transport protein required
The cell is a(n) ______ solution
Hypertonic (There is a greater concentration of solute outside the cell.)
You know that this cell is in a(n) _____ solution because it _____.
Hypertonic solution ... lost water (A cell will lose water when placed in a hypertonic solution.)
If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?
Hypotonic (The salt concentration in the solution is lower than it is in the cell, so water enters the cell, causing it to burst.)
You know that this cell is in a(n) _____ solution because it _____.
Hypotonic ... swelled (A cell will gain water when placed in a hypotonic solution.)
Many cell organelles, most notably the nucleus, are anchored by ______, which are assembled from a diverse class of proteins.
Intermediate filaments
The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the ______.
Intermediate filaments
At the beginning of the experiment, side A
Is hypotonic to side B
Initially, in terms of tonicity in the figure, the solution in side A with respect to that in side B is
Isotonic
Which of the following is a characteristic feature of a carrier protein in a plasma membrane?
It exhibits a specificity for a particular type of molecules
Which of the following statements about diffusion is correct?
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration
Why isn't the mitochondrion classified as part of the endomembrane system?
It is not derived from the endoplasmic reticulum or Golgi
Water passes quickly through cell membranes because
It moves through aquaporin channel proteins
The sodium-potassium pump generates the following concentration gradients across the plasma membrane:
Low [Na+] and high [K+] inside the cell and high [Na+] and low [K+] outside.
Submerging a red blood cell in distilled water will result in
Lysis of the cell
What types of proteins are synthesized by the Rough ER?
Lysosomal proteins
Which organelle plays a role in intracellular digestion?
Lysosome (The prefix "lyso-" means decomposition.)
Eukaryotic only
Lysosome, mitochondria, nucleolus
A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in
Lysosomes
Hydrolytic enzymes must be segregated and packaged to prevent general destruction of cellular components. In animal cells, which of the following organelles contain these hydrolytic enzymes?
Lysosomes
Chloroplast
Makes sugar by converting light energy into chemical energy
A primary function of polysaccharides attached to glycoproteins and glycolipids of animal cell membranes is to
Mediate cell-to-cell recognition.
During muscle contraction, myosin motor proteins move across tracks of ______.
Microfilaments
The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of ______.
Microfilaments
Centrosomes are sites where protein dimers assemble into ______.
Microtubules
In eukaryotic flagella, the fibers that slide past one another due to the inactivity dynein proteins are ______.
Microtubules
Which of the following will be found in nearly all eukaryotic cells?
Mitochondria
What types of proteins are not synthesized in the rough ER?
Mitochondrial proteins
Which plant cell organelle contains its own DNA and ribosomes?
Mitochondrian
Golgi apparatus
Modifies and packages proteins
When molecules move down the concentration gradient, they move from where they are ______ to where they are ______
More concentrated; less concentrated
Which of the following membrane activities requires energy from ATP hydrolysis?
Movement of sodium ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid.
One of the key innovations in the evolution of eukaryotes from a prokaryotic ancestor is the endomembrane system. Which eukaryotic organelles or features might have evolved as a part of, or as an elaboration of, the endomembrane system?
Nuclear envelope
Prokaryotic only
Nucleoid
Where is a bacterial cell's DNA found?
Nucleoid region (Bacteria lack a nucleus; their DNA is found in the nucleoid region)
Both (plant and animal cells)
Nucleus, mitochondrion, plasma membrane, cytoskeleton, endoplasmic reticulum, golgi apparatus
In receptor-mediated endocytosis, receptor molecules are initially localized on the outer surface of the plasma membrane. Where do the receprots end up following endocytosis?
On the inside surface of a vesicle
The chemical reactions involved in respiration in prokaryotic and eukaryotic cells are virtually identical. In eukaryotic cells, ATP is synthesized primarily on the inner membranes of the mitochondria. In light of the endosymbiont theory for the evolutionary origin of mitochondria, where is most ATP synthesis likely to occur in prokaryotic cells?
On the plasma membrane
In an animal cell, DNA may be found
Only in the nucleus and mitochondria
What name is given to the process by which water crosses a selectively permeable membrane?
Osmosis (Osmosis is the passive transport of water)
Select the correct statement about osmosis.
Osmosis is the diffusion of water molecules across a selectively permeable membrane. (Osmosis and diffusion are fundamentally similar processes.)
Three lab groups carried out an experiment to identify the correct molarities for five solutions. Each unknown contained one of the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and 1.0 M. Each data entry represents the average of 3 sample replications of 1 cm3 sweet potato cubes expressed as percent change in mass after an overnight (24 hr) soak in the unknown solutions. From the data given, which statement most accurately describes what is occurring in response to a particular unknown solution.
Osmosis of water molecules from unknown solution A likely caused the increase in mass observed.
Which of the following particles could diffuse easily through a cell membrane?
Oxygen (O2) (Small nonpolar molecules such as oxygen can diffuse across cell membranes.)
Diffusion across a biological membrane is called ______.
Passive transport
Facilitated diffusion is a type of ______.
Passive transport (During facilitated diffusion, the cell is not expending energy to move the particles across the membrane; therefore, facilitated diffusion is a form of passive transport.)
A white blood cell engulfing a bacterium is an example of ______.
Phagocytosis
A phosphate has a "head" made up of a glycerol molecule attached to a single ______, which is attached to another small molecule.
Phosphate group
Which of the following are localized on the exterior of a phospholipid bilayer?
Phosphate groups
Identify Structure D
Phospholipid bilayer of membrane (Phospholipids can be recognized by the presence of a head and two tails.)
The difference between pinocytosis and receptor-mediated endocytosis is that
Pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis is highly selective.
Select the correct statement describing cellular structure or function
Plant and animal cells both carry out cellular respiration, producing ATP. (All plant and animal cells carry out cellular respiration in mitochondria, producing ATP)
The volume enclosed by the plasma membrane of plant cells is often much larger than the corresponding volume in animal cells. The most reasonable explanation for this observation is that
Plant cells contain a large vacuole that reduces the volume of the cytoplasm
The ______ is a bacterial structure that acts as a selective barrier, allowing nutrients to enter the cell and wastes to leave the cell.
Plasma membrane (The plasma membrane is selectively permeable)
Which of the following organelles is found exclusively in plant cells?
Plastids
A cell with an abundance of free ribosomes is most likely
Producing primarily cytoplasmic proteins
What is a function of a bacterium's capsule?
Protection (A bacterium's capsule has a protective role)
Which of the following statements correctly describes a function of the Golgi apparatus?
Protein modification and sorting
Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
Proteins
Which of the following statements correctly describes some aspect of protein secretion from prokaryotic cells?
Proteins that are secreted by prokaryotes are synthesized on ribosomes that are bound to the cytoplasmic surface of the plasma membrane.
Which one of the following statements about the endomembrane system is correct?
Proteins that will be secreted from the cell are likely to be found in closed spaces bounded by membranes of the endomembrane system. (Proteins that will be secreted are always enclosed by some membrane of the endomembrane system until they are secreted)
Central vacuole
Regulates cytoplasm composition, creates internal pressure, and stores cell compounds
Some key innovations in the evolution of eukaryotes from a prokaryotic ancestor are membrane-bound organelles. Which of the following organelles or features is likely to be a common component shared by both eukaryotic cells and their prokaryotic ancestors?
Ribosomes
In a bacterium, where are proteins synthesized
Ribosomes (Ribosomes are involved in the manufacture of polypeptides (proteins)
both (prokaryotes and eukaryotes)
Ribosomes, plasma membrane, flagella
Which structure is the site of the synthesis of proteins destined for export from the cell?
Rough ER
Which of the following correctly describes the pathway taken by a protein destined for secretion from an animal cell?
Rough ER --> transport vesicle --> Golgi --> transport vesicle --> plasma membrane
What kinds of molecules pass through a cell membrane most easily?
Small hydrophobic
The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and therefor abundant in liver cells?
Smooth ER
Which type of organelle or structure is primarily involved in the synthesis of oils, phospholipids, and steroids?
Smooth endoplasmic reticulum
Structure A is a ______.
Solute (A solute is crossing the plasma membrane.)
Which solution will decrease in volume?
Solution A: 1.4% (m/v) starch (The water molecules actually move in both directions, but they move to a greater extend toward Solution B because it has a higher solute concentration than Solution A. The net movement of water molecules causes Solution A to decrease in volume and Solution B to increase in volume.)
Which solution will increase in volume?
Solution D: 12.4% (m/v) NaCl (The water molecules actually move in both directions, but they move to a greater extent toward Solution D because it has a higher solute concentration than Solution C. This net movement of water molecules causes Solution D to increase and Solution C to decrease in volume.)
What is the function of Structure E?
Stabilization of the phospholipids (Cholesterol helps to stabilize the structure of the plasma membrane.)
Plant cell wall
Strong, protective structure made from cellulose fibrils
Submerging a plant cell in distilled water will result in
The cell becoming turgid
You can recognize the process of pinocytosis when _____.
The cell is engulfing extracellular fluid
Submerging a red blood cell in a hypertonic solution will result in
The cell shriveling
After the system depicted in the figure reaches equilibrium, what changes are observed with respect to the concentrations of sugars?
The concentrations of glucose and sucrose are equal in sides A and B.
Which statement is correct?
The contents of a red blood cell are hyperosmotic to distilled water. (The red blood cell has a greater solute concentration than distilled water, which means that its contents are hypertonic to distilled water.)
Which statements about the fluid-mosaic structure of a membrane are correct? Select the three correct statements.
The diverse proteins found in and attached to membranes perform many important functions; Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane; The framework of a membrane is a bilayers of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center. (Membranes consist of diverse proteins suspended in and attached to a phospholipid bilayer. Kinks in the unsaturated fatty acid tails of some phospholipids keep the membrane fluid, and a mosaic of proteins perform a variety of functions.)
Tay-Sachs disease is a human genetic abnormality that results in cells accumulating very large, complex, undigested lipids. Which cellular organelle must be defective in this condition?
The lysosome
Gaucher disease is the most common of lipid storage diseases in humans. It is caused by a deficiency of an enzyme necessary for lipid metabolism. This leads to a collection of fatty material in organs of the body including the spleen, liver, kidneys, lungs, brain, and bone marrow. Using your knowledge of the structure of eukaryotic cells, identify the statement below that best explains how internal membrane and the organelle of cells would be involved in Gaucher disease
The lysosomes lack sufficient amounts of enzymes necessary for the metabolism of lipids
Which statement correctly describes the nuclear envelope of a eukaryotic cell?
The nuclear envelope is continuous with the endoplasmic reticulum.
Identify the correct statement about differences between rough and smooth endoplasmic reticulum (ER).
The outer surface of smooth ER lacks ribosomes, whereas the outer surface of rough ER has ribosomes.
A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water equal to the volume of blood lost -- is transferred directly into one of his veins. What will be the most probable result of this transfusion?
The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells.
Which of the following statements about Osmosis is correct?
The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis (Aquaporins facilitate water movement across membranes and thus speed up the process of osmosis)
Which of the following would be a factor that determines whether the molecule selectively enters the target cells?
The similarity of the drug molecule to other molecules that are transported into the target ells (If the target cells have transport proteins that specifically bind to certain molecules, they may bind with and transport a drug that is similar in structure.)
After the system depicted in the figure reaches equilibrium, what changes are observed?
The water level is higher in side A than in side B.
Some of the following statements are true for chloroplasts; others are true for mitochondria.
They are the sites of reactions that convert solar energy into chemical energy, they contain the green pigment chlorophyll, they have membranous sacs called thylakoids the are surrounded by a fluid called stroma
Which of the following is true of integral membrane proteins?
They are usually transmembrane proteins
According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?
They can move laterally along the plane of the membrane
Beginning within the nucleus, the first step leading to the synthesis of a polypeptide is ______.
Transferring of information from DNA to messenger RNA (Transcription is the first of the two main types of protein synthesis)
Structure B is a ______.
Transport Protein (The transport protein facilitates the movement of solute across the plasma membrane.)
Structure A in the figure is a(n)
Transport protein (The protein is allowing molecules to enter the cell)
In facilitated diffusion, what is the role of the transport protein?
Transport proteins provide a hydrophobic route for the solute to cross the membrane (Transport proteins provide corridors that allow specific molecules or ions to cross the membrane.)
True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.
True (The hydrophophilic, or water-loving, portion of a phospholipid is the polar head, whereas the hydrophobic portion is the nonpolar tail)
True of False? Osmosis is a type of diffusion.
True (diffusion of water across selectively permeable membrane)
Which of the following best describes the structure of a biological membrane?
Two laters of phospholipids with proteins either crossing the layers or on the surface of the layers. (The membrane proteins can be found either embedded in or attached to the surface of the phospholipid bilayer.)
What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium?
Water molecules move between the two solutions, but there is no net movement of water across the membrane. (Water molecules are constantly in motion and will continually move across the membrane. However, because the solutions are in equilibrium, there is not net movement across the membrane.
Which of the following clues would tell you if a cell is prokaryotic and eukaryotic?
Whether or not the cell is partitioned by internal membranes (Prokaryotic cells lack any internal membranous compartmentalization)
Endocytosis moves materials ______ a cell via _____.
into ... membranous vesicles
Mitochondrion
produces chemical energy (ATP) that can power the cell
