BIO Lesson 4 - Cell Structure & Function
What is the difference between active transport and passive transport? - Passive transport involves the movement of substances directly through the lipid portion of a membrane. Active transport requires an input of energy, whereas passive transport does not. - Active transport requires energy and is unable to move substances against their concentration gradient. Passive transport does not require energy and can move substances against their concentration gradient. - Active transport requires energy and can move substances against their concentration gradient. Passive transport does not require energy and can move substances only down their concentration gradient.
Active transport requires energy and can move substances against their concentration gradient. Passive transport does not require energy and can move substances only down their concentration gradient.
Which of the following organelles is/are found in animal cells, but is/are absent in most plant cells? - mitochondria - chloroplasts - central vacuole - cell wall - cytoskeleton - centrioles
Centrioles produce microtubules of cilia and flagella, and those that form the spindle during animal cell division.
The membrane components that spontaneously form a bilayer are __________.
phospholipids.
The type of cell connection that makes the adjacent cells leakproof is a __________.
tight junction
A researcher has discovered an unusual organism deep in the crust of the Earth. She wants to know whether it is prokaryotic or eukaryotic. Imagine that she has rapid tests to determine whether the following molecules are present: DNA, RNA, phospholipids, and the proteins that form microtubules. Which test would you advise her to use and why? - Test for DNA, because only eukaryotes have a nucleus. - Test for RNA, because only eukaryotes have ribosomes. - Test for microtubule proteins, because only eukaryotes have microtubules. - Test for phospholipids, because only eukaryotes have phospholipids.
Test for microtubule proteins, because only eukaryotes have microtubules. A distinguishing feature of eukaryotic cells is the presence of a cytoskeleton, which is made of microtubule proteins (called tubulin) and other proteins.
Sorting and modification of proteins is an important function of _____. - mitochondria - chloroplasts - lysosomes - the Golgi apparatus - the plasma membrane
The Golgi apparatus receives protein cargo from the endoplasmic reticulum and then modifies it and sorts it into vesicles that are targeted to different destinations, including the plasma membrane and lysosomes.
Imagine that you are studying cell structure in various organisms in your biology lab. Your instructor gives you a microscope slide showing two types of cells that have been suspended in pure water. One type of cell swells up until it bursts. The other cell maintains its shape throughout the experiment. Suggest an explanation for these observations; assume that both cells were alive at the start of the experiment. Assume also that the concentration of water inside both types of cells is similar. - The cell that remained intact had plasmodesmata that allowed the excess water to leak out, thus balancing the tendency of water to enter the cell via osmosis. - The cell that burst lacked gap junctions, so water that entered the cell via osmosis could not leak back out through the junctions. - The cell that remained intact had a contractile vacuole for pumping out the excess water that entered the cell via osmosis. - The cell that burst lacked a plasma membrane for regulating osmosis.
The cell that remained intact had a contractile vacuole for pumping out the excess water that entered the cell via osmosis. Many freshwater protists can pump out excess water via contractile vacuoles. If you prevented the function of the contractile vacuole, what would happen to these cells?
Substances move from high to low concentration by a process called __________.
diffusion
Which of the following processes causes substances to move across membranes without the expenditure of cellular energy? - diffusion - pinocytosis - endocytosis - exocytosis - active transport
diffusion
The __________ consists of all of the internal contents of a cell, except the nucleus in eukaryotic cells.
cytoplasm
What do we call the fluid in which all cellular organelles are suspended? - cytoplasm - nucleus - endoplasmic reticulum - Golgi apparatus
cytoplasm The fluid inside the plasma membrane and outside the nucleus is considered cytoplasm.
Choose the substance that will diffuse most rapidly across the plasma membrane. - sodium ion - small polar molecule such as water - amino acid - oxygen
oxygen Oxygen is small and nonpolar and readily diffuses through the lipid bilayer.
In certain types of genetic engineering, DNA is injected into the nucleus of a recipient animal cell. What is the fewest number of membranes that must be pierced by the microscopic needle in order to inject the DNA? (Note that the needles used are not small enough to pass through a nuclear pore.) - one - two - three - four
three You must pass through the plasma membrane and both membranes of the nuclear envelope.
The function of the mitochondria is __________. - to contain the genetic material - to synthesize proteins - to convert food to energy for the cell - to package materials for export from the cell
to convert food to energy for the cell
The following is a characteristic of a plasma membrane: - It separates the cell contents from its environment. - It is permeable to certain substances. - It is a lipid bilayer with embedded proteins. - It contains pumps for moving molecules against their concentration gradient. - all of the above
- It separates the cell contents from its environment. - It is permeable to certain substances. - It is a lipid bilayer with embedded proteins. - It contains pumps for moving molecules against their concentration gradient.
Which of the following processes does a cell use to take up molecules against their concentration gradient? - simple diffusion - facilitated diffusion - active transport - endocytosis - Both the c and d are correct.
- active transport - endocytosis
The point at which a substance is evenly dispersed within a fluid __________. - happens when net diffusion is zero - occurs when random movements of the substance cease - is referred to as a dynamic equilibrium - Both the first and third answers are correct.
Both the first and third answers are correct.
Why are living cells limited to remaining microscopic in size? - Cells produce a limited number of enzymes. - The energy needs of giant cells would outstrip available supply from the environment. - Exchanges of substances at the membrane surface would take too long to diffuse throughout the interior of the cell. - Cells have a limited amount of genetic material.
Exchanges of substances at the membrane surface would take too long to diffuse throughout the interior of the cell. The net diffusion rate of substances in the cytoplasm of a cell is so slow that the diffusion distances must be very small (on the order of a few micrometers); otherwise, cells would be unable to distribute nutrients within a cell, or remove wastes that are produced.
If the nucleus is the control center of the cell, how is information encoded and shipped to the cytoplasm? - It is encoded and shipped by RNA. - It is encoded and shipped by chromosomes. - It is encoded and shipped by nuclear pores. - It is encoded and shipped by the nucleolus.
It is encoded and shipped by RNA. Genetic directions from DNA are transcribed as RNA, which is moved through the nuclear pores to the cytoplasm, where it is used for the translation of proteins.
How do molecules such as proteins and RNA enter into or exit from the nucleus? - Molecules diffuse through the lipid bilayers of the nuclear envelope. - Molecules move through pores in the nuclear envelope. - Molecules move by osmosis through the lipid bilayers of the nuclear envelope. - Molecules break down the nuclear envelope.
Molecules move through pores in the nuclear envelope. Large pores made of proteins provide channels through which large molecules and even larger particles can enter into or exit from the nucleus.
How does a Paramecium survive in fresh water? - The contractile vacuole expels water from the cell. - The mitochondria will use the excess water during energy production. - The central vacuole stores the water. - The cell wall can withstand the increased turgor pressure.
The contractile vacuole expels water from the cell. The contractile vacuole is the organelle that collects and eliminates the excess influx of water.
Lysosomes contain very powerful digestive enzymes that can break down proteins, carbohydrates, and other molecules. Why don't these enzymes digest the cell itself? - The enzymes will digest only foreign material. - The enzymes are separated from the cytoplasm by the lysosomal membrane. - The enzymes are inactive until secreted from the cell. - The enzymes are only synthesized inside the lysosome when needed.
The enzymes are separated from the cytoplasm by the lysosomal membrane. The membrane segregates the enzymes so they do not harm the cell.
Imagine that you are late for an appointment and you reach the office door out of breath because you just ran the last three blocks from the bus stop. Which of the following descriptions of what oxygen is used for in your cells is correct? - The lysosomes in my muscle cells need this extra oxygen to digest sugars and provide me with energy for running. - The cellular enzymes in my leg muscles need this extra oxygen to repair the damage that occurs to my muscle cells as I run. - The mitochondria in my muscle cells need the extra oxygen to produce sugars that, in turn, provide the energy I need to run. - The mitochondria in my muscle cells need this extra oxygen to break down sugars and produce the energy I need to run.
The mitochondria in my muscle cells need this extra oxygen to break down sugars and produce the energy I need to run. Mitochondria capture chemical energy gained by breaking down sugars using oxygen and use that energy to produce ATP. The ATP can then provide energy for cellular processes such as muscle contraction.
Which of the following statements about mitochondria is true? - They are able to take energy from food molecules and store it in high-energy bonds of ATP. - All metabolic conversion of high-energy molecules (e.g., glucose) to ATP occurs within the mitochondria. - They are able to directly convert solar energy to high-energy sugar molecules. - They release oxygen during the process of aerobic metabolism.
They are able to take energy from food molecules and store it in high-energy bonds of ATP. This is done utilizing a series of enzymes within the intermembrane compartment.
Which of the following lists the correct order in which newly synthesized proteins are delivered to the plasma membrane? - They are delivered from the endoplasmic reticulum to lysosomes to the Golgi apparatus to the plasma. membrane. - They are delivered from the endoplasmic reticulum to the Golgi apparatus to the plasma membrane. - They are delivered from the Golgi apparatus to the endoplasmic reticulum to the plasma membrane. - They are delivered from the endoplasmic reticulum to the plasma membrane. - They are delivered from the endoplasmic reticulum to the Golgi apparatus to lysosomes to the plasma membrane.
They are delivered from the endoplasmic reticulum to the Golgi apparatus to the plasma membrane. Molecules are manufactured in the ER, packaged in the Golgi, and distributed to the membrane, when that is their final destination.
Which of the following generalizations can you make about the cytoskeleton? - The cytoskeleton is a fixed structure like the bones of a vertebrate or the boards in the wall of a building. - Various cytoskeletal elements are needed in the performance of numerous essential cellular functions. - It provides a type of cellular armor on the outside of cells that serves a protective function. - It is made up of a matrix of complex carbohydrates.
Various cytoskeletal elements are needed in the performance of numerous essential cellular functions. The cyctoskeleton performs many functions for the cell.
The term tonicity describes the solute concentration of the extracellular fluid relative to the solute concentration of the aqueous solution known as cytoplasm. In which direction would water flow according to the principles of osmosis if a cell were placed in a hypertonic solution? - Water would flow into the cell, causing it to swell and perhaps even burst. - Water would flow out of the cell, leaving the cell shriveled and wrinkled. - The net flow of water would be zero because the solute concentrations inside and outside a cell are equal in a hypertonic medium.
Water would flow out of the cell, leaving the cell shriveled and wrinkled.
Facilitated diffusion requires __________. - energy - a membrane transport protein - a concentration gradient - a membrane transport protein and a concentration gradient
a membrane transport protein and a concentration gradient Facilitated diffusion requires a membrane transport protein and a concentration gradient.
A hormone circulating in the bloodstream would most likely bind to __________. - a channel protein - protein filaments in the cytoplasm - a receptor protein - a recognition protein
a receptor protein Receptor proteins trigger cellular responses when specific molecules, such as hormones, bind to them.
During __________, energy is used to move substances against their concentration gradient.
active transport
Many metabolic poisons work by inhibiting ATP production. Which type of transport would be most affected? - simple diffusion - active transport - osmosis - facilitated diffusion
active transport Active transport requires cellular energy in the form of ATP.
The concentration of sodium ions is lower in the cytoplasm of a heart muscle cell than it is in the extracellular fluid. By what mechanism does the cell maintain this difference? - facilitated diffusion - active transport - osmosis - endocytosis
active transport Sodium ions must be constantly pumped out of the cell in order to maintain the concentration gradient.
The cell theory states that __________. - cells are generally small to allow for diffusion - all cells contain cytoplasm - cells are either prokaryotes or eukaryotes - all living things are composed of cells - all cells arise from organic molecules such as DNA
all living things are composed of cells This is a true statement and a central tenet of the cell theory.
Diffusion is the movement of molecules from __________. - an area of higher concentration of that type of molecule to an area of lower concentration - an area of lower concentration of that type of molecule to an area of higher concentration - outside the cell to inside the cell
an area of higher concentration of that type of molecule to an area of lower concentration
The antifungal drug nystatin combines with sterols in the plasma membrane of the fungal cell to disrupt the membrane and kill the cell. What other cell types might also be affected by nystatin? - animal cells - all cell types - plant cells
animal cells
Certain microorganisms have a high percentage of unsaturated fatty acids in their membrane. Because of this, these organisms __________. - are more rapidly recognized and destroyed by cells of the immune system - are able to withstand high temperatures because their membranes are firmer - are able to carry out sodium ion transport more efficiently than most organsims - are able to withstand low temperatures because their membranes do not solidify as rapidly
are able to withstand low temperatures because their membranes do not solidify as rapidly The double bonds in unsaturated fatty acids increase the fluidity of the membrane.
The smallest type of cell is a mycoplasma, which has a diameter between 0.1 micrometer and 1.0 micrometer. Mycoplasmas most likely are _____. - fungi - viruses - plant cells - bacteria - animal cells
bacteria Correct. Mycoplasma are bacteria.
If an animal cell is placed into a solution whose concentration of dissolved substances is higher than that inside the cell, - the cell will swell - the cell will shrivel - the cell will remain the same size - the solution is described as hypertonic - both (1) and (4) are correct
both (1) and (4) are correct
Which of the following originated by endosymbiosis? - chloroplasts - mitochondria - lysosomes - both chloroplasts and mitochondria - ribosomes
both chloroplasts and mitochondria Biologists believe that mitochondria and chloroplasts both evolved from prokaryotic bacteria that became part of ancestral eukaryotic cells.
Which of the following transport processes require(s) energy? - endocytosis - osmosis - facilitated diffusion and osmosis - facilitated diffusion - facilitated diffusion, osmosis, and endocytosis
endocytosis Endocytosis is an energy-requiring process.
Prokaryotic cells do not contain _____. - endoplasmic reticulum - ribosomes - cytoplasm - DNA
endoplasmic reticulum Prokaryotic cells do not contain internal membranes.
During endocytosis, the contents of the endocytic vesicle __________. - enter the cell - enter or exit the cell, always moving down a concentration gradient - exit the cell
enter the cell Cells can take up certain molecules by the process of endocytosis.
If a cell is placed in a __________ solution, there will be net water movement out of the cell.
hypertonic
When placed in a certain sucrose solution, the volume of a cell decreases; therefore, the sucrose solution is __________ to the cell contents. - isotonic - hypertonic - hypotonic - cannot determine from given information
hypertonic Cell shrinking is due to a net movement of water out of the cell from an area of high water concentration to low water concentration.
Plasmids are located __________. - in the nucleus - in the nucleolus - in the cytoplasm - continuous with the nuclear envelope
in the cytoplasm Plasmids are found in the cytoplasm of prokaryotic cells.
Membrane fluidity within a phospholipid bilayer is based upon __________. - the presence of water in the lipid bilayer - the presence of transport proteins in the lipid bilayer - hydrophilic interactions among polar phospholipid heads - interactions among nonpolar (hydrophobic) lipid tails
interactions among nonpolar (hydrophobic) lipid tails Phospholipid tails are hydrophobic and face the interior of the membrane. Individual phospholipid molecules are not bonded to one another.
Active transport through the plasma membrane occurs through the action of: - DNA - membrane proteins - osmosis - diffusion - water
membrane proteins
Where are proteins that are going to be exported from the cell synthesized? - on the Golgi apparatus - on the rough endoplasmic reticulum - in mitochondria - on the smooth endoplasmic reticulum
on the rough endoplasmic reticulum Proteins that are going to be exported are synthesized on the RER by the attached ribosomes.
Small, nonpolar hydrophobic molecules such as fatty acids - must enter the cell via endocytosis - pass readily through a membrane's lipid bilayer - require special channels to enter a cell - diffuse very slowly through the lipid bilayer - are actively transported across cell membranes
pass readily through a membrane's lipid bilayer
Recognition proteins function to __________. - bind hormones and alter the intracellular physiology of a cell - permit the cells of the immune system to distinguish between pathogens such as bacteria and cells of your own body - regulate the movement of ions across the cell membrane - all of the above
permit the cells of the immune system to distinguish between pathogens such as bacteria and cells of your own body
Two types of connections between cells called "gap junctions" and "plasmodesmata" are specialized to __________. - tightly hold one cell against another at focal points, almost like a spot weld of superglue - permit the passage of substances (e.g., ions) between cells through small passageways that directly link the cytoplasm of one cell to the cytoplasm of another cell - prevent the movement of molecules between cells that are tightly joined along ribbons of cell membrane - None of these are correct.
permit the passage of substances (e.g., ions) between cells through small passageways that directly link the cytoplasm of one cell to the cytoplasm of another cell Substances can pass from one cell directly to the other through these intercellular bridges of cytoplasm that are continuous between cells.
Which of the following contain ribosomes? - plant cells - animal cells - bacterial cells - mitochondria - chloroplasts - plant cells, animal cells, bacterial cells, mitochondria, and chloroplasts
plant cells, animal cells, bacterial cells, mitochondria, and chloroplasts
All cells are surrounded by a thin __________.
plasma membrane
Which of the following structures is/are found in all cells? - cell wall - plasma membrane - nucleus - ribosomes - cell wall and nucleus - plasma membrane and ribosomes
plasma membrane and ribosomes Plasma membranes and ribosomes are structures that are found in all cells.
Prokaryotic cells __________. - are large cells, typically greater than 10 millimeter in diameter - include numerous membrane-enclosed structures known as organelles - possess a single molecule of circular DNA, but no definable membrane-enclosed nucleus - possess many separate stick-like chromosomes
possess a single molecule of circular DNA, but no definable membrane-enclosed nucleus Prokaryotic DNA is organized into a region known as a nucleoid.
Chromosomes consist of _____. - DNA - proteins - RNA - proteins and RNA - proteins and DNA
proteins and DNA Chromosomes consist of a single DNA double helix wound around proteins.
Of the following list of substances that can enter a cell, match the order with the correct mechanism by which they would enter cells: oxygen, water, sodium ions, potassium ions, bacterium. (Note that sodium ions are more concentrated outside cells than inside; potassium ions are more concentrated inside cells than outside.) - osmosis, simple diffusion, facilitated diffusion, active transport, endocytosis - simple diffusion, osmosis, facilitated diffusion, active transport, endocytosis - endocytosis, active transport, active transport, facilitated diffusion, exocytosis - simple diffusion, osmosis, facilitated diffusion, active transport, exocytosis - passive transport, osmosis, simple diffusion, facilitated diffusion, active transport
simple diffusion, osmosis, facilitated diffusion, active transport, endocytosis
Which of the following types of molecules must pass through membranes via the aqueous pores formed by membrane proteins? - small polar molecules such as water and ethanol - small charged ions such as Na+ and Ca++ - gases such as carbon dioxide and oxygen - large particles such as bacteria
small charged ions such as Na+ and Ca++
Substances are able to cross the lipid bilayer of a cell at different rates that are unique for each substance. Which of the following characteristics would favor the simple diffusion of a substance across a cell membrane? - low lipid solubility - small concentration gradients - the number of membrane transport proteins for the substance - small molecule size
small molecule size The smaller the molecule, the more likely it will be able to pass across the lipid bilayer via simple diffusion.
Which of the following would be least likely to diffuse through a lipid bilayer? - carbon dioxide - water - sodium ions - oxygen - the small, nonpolar molecule butane
sodium ions
The endoplasmic reticulum is needed for __________. - synthesis of certain proteins - hormone synthesis - detoxification - synthesis of lipids - synthesis of proteins, hormones, and lipids, along with detoxification
synthesis of proteins, hormones, and lipids, along with detoxification All of the answers are functions of the endoplasmic reticulum.
In osmosis, water diffuses from the side of the membrane with a higher concentration of water to the side with a lower concentration of water. What determines the concentration of water in a solution? - the size of the container - the amount of molecules other than water dissolved in the solution - the volume of the solution
the amount of molecules other than water dissolved in the solution Water is less concentrated in solutions in which many other molecules are dissolved than in solutions with few other dissolved molecules.
The basic unit of life is _____. - compounds of silicon - the cell - the virus - protein
the cell All life is made up of cells.
Which of the following correctly lists organelles that are part of the internal membrane system of eukaryotic cells? - the endoplasmic reticulum, Golgi apparatus, and lysosomes - the endoplasmic reticulum and mitochondria - the Golgi apparatus and nucleus - the endoplasmic reticulum, Golgi apparatus, and cell wall
the endoplasmic reticulum, Golgi apparatus, and lysosomes These organelles are part of the internal membrane system.
The fluid mosaic model describes membranes as fluid because ___________. - the membrane is composed mainly of water - the phospholipids and proteins move from place to place within the bilayer - the phospholipids move from place to place around the motionless membrane proteins - the phospholipid molecules are bonded to one another, making them more moveable - the phospholipids of membranes are constantly moving from one layer to the other layer
the phospholipids and proteins move from place to place within the bilayer
The difference between smooth ER (SER) and rough ER (RER) is __________. - the presence of the Golgi apparatus in RER - the presence of ribosomes on the RER - the presence of nuclear pores in RER - the presence of mitochondria on the RER
the presence of ribosomes on the RER
When a drop of food coloring is placed in a glass of water, the spreading out of the molecules of food dye is caused by __________. - the concentration of the molecules of dye - osmosis - the molecules trying to move to a lower concentration - the random movement of molecules
the random movement of molecules Molecules of dye are randomly moving; collisions between dye molecules are more frequent when the molecules are in high concentrations.
Which organelle would you expect to be in abundance in the liver of a drug addict? - the Golgi complex - the smooth endoplasmic reticulum - the rough endoplasmic reticulum - the nucleolus - the ribosome
the smooth endoplasmic reticulum Enzymes for detoxification of drugs and alcohol are housed in the smooth endoplasmic reticulum.
