Unit 2-AP Bio, AP Biology Unit 2 Cell Structure
ATP
(adenosine triphosphate) main energy source that cells use for most of their work, used in active transport
internal membranes
- facilitate cellular processes - compartmentalizations intercellular metabolic processes and specific enzymatic reactions
Osmoregulation
- maintains water balance and allows organisms to control their internal solute composition/water potential
Grana
- where light dependent reactions of photosynthesis occur
Solute potential
-iCRT - i=ionization constant (-1) - c= molar concentration - r= pressure constant (.0831) - t= temperature in kelvin (C degrees + 273)
Region 1 is hydrophilic because it interacts with an aqueous environment, whereas region 2 is hydrophobic because it interacts with the interior of the membrane.
A cell membrane is a phospholipid bilayer that separates one aqueous environment from another. The interior of a phospholipid bilayer is a hydrophobic environment. Because region 1 interacts with the aqueous environment on one side of the phospholipid bilayer, it is most likely hydrophilic. Because region 2 interacts with the interior of the phospholipid bilayer, it is most likely hydrophobic.
Nucleoid
A dense region of DNA in a prokaryotic cell.
nucleoid
A dense region of DNA in a prokaryotic cell.
solvent
A liquid substance capable of dissolving other substances (usually water)
viscosity
A liquid's resistance to flowing
Solution
A mixture that forms when one substance dissolves another.
Cytoskeleton
A network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement
Nucleus
A part of the cell containing DNA and RNA and responsible for growth and reproduction
plasmolysis
A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.
Selective permeability
A property of a plasma membrane that allows some substances to cross more easily than others.
selective permeability
A property of a plasma membrane that allows some substances to cross more easily than others.
Cell Wall
A rigid layer of nonliving material that surrounds the cells of plants and some other organisms.
Plasma Membrane
A selectively-permeable phospholipid bilayer forming the boundary of the cells
plasma membrane
A selectively-permeable phospholipid bilayer forming the boundary of the cells
Capsule
A sticky layer that surrounds the cell walls of some bacteria, protecting the cell surface and sometimes helping to glue the cell to surfaces.
Centrosome
A structure in animal cells containing centrioles from which the spindle fibers develop.
Solute
A substance that is dissolved in a solvent.
Endosymbiosis theory
A theorized process in which early eukaryotic cells were formed from simpler prokaryotes.
ion channels
A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.
proton pump
An active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process.
electrogenic pump
An active transport protein that generates voltage across a membrane while pumping ions.
Smooth Endoplasmic Reticulum
An endomembrane system where lipids are synthesized, calcium levels are regulated, and toxic substances are broken down.
Centromere
Area where the chromatids of a chromosome are attached
Vacuole
Cell organelle that stores materials such as water, salts, proteins, and carbohydrates
osmosis
Diffusion of water through a selectively permeable membrane
active transport
Energy-requiring process that moves material across a cell membrane against a concentration gradient
Cytosol
Fluid portion of cytoplasm
Small nonpolar molecules ....
Freely pass across the membrane
Some viral infections can lead to the rupture of the lysosome membrane. Which prediction of the effect of this disruption of cellular compartmentalization is most likely correct?
Hydrolytic enzymes will be released, which will cause cell death. Reason: Hydrolytic enzymes will be released, resulting in cell death and preventing further viral reproduction.
Cell Envelope
In a prokaryotic cell, the portion composed of the plasma membrane, the cell wall, and the glycocalyx.
transmembrane proteins
Integral proteins that extend all the way through the membrane.
Euglenids are single-cell eukaryotes that live in aquatic environments. The chloroplasts found inside euglenids are enveloped by three membranes, as represented in Figure 1. The inner membrane of euglenid chloroplasts resembles the thylakoid membrane. Which of the following claims about the origin of the euglenid chloroplast is best supported by the three-membrane structure of the envelope?
It originated from the incorporation of a photosynthetic prokaryote into a eukaryotic cell by two endosymbiotic events. The three-membrane structure of the chloroplast envelope best supports the claim presented in this answer choice. The three-membrane structure most likely resulted from two endosymbiotic events, with the middle membrane originating from the first event and the outer membrane originating from the second event.
Ribosomes
Makes proteins within a cell; those on ER create proteins to be shipped out of a cell, and those in the cytoplasm create proteins that remain within the cell; free / bound depends on the protein being made
Glycolipids
Membrane carbohydrates that are covalently bonded to lipids.
glycoproteins
Membrane carbohydrates that are covalently bonded to proteins; assist in the communication between cells, adhesion between them, and as receptors for certain molecules
Hydrophilic substances (such as large polar molecules)...
Move across the membrane through embedded channel and transport proteins
facilitated diffusion
Movement of specific molecules across cell membranes through protein channels
Polar uncharged molecules (including h2o)...
Pass through the membrane in small amounts
Calvin-Benson cycle
Reactions of photosynthesis occur in the stroma
Charged ions....
Require channel proteins to move through the membrane
dynamic equilibrium
Result of diffusion where there is continuous movement of particles but no overall change in concentration on either side of the membrane
integral proteins
Span the membrane; serve as transporters, channels, linkers, receptors, centers for energy buildup, and are responsible for cell adhesion
tonicity
The ability of a solution surrounding a cell to cause that cell to gain or lose water.
osmoregulation
The control of water balance.
cotransport
The coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient.
electrochemical gradient
The diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of the ion across a membrane and its tendency to move relative to the membrane potential.
stroma
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
receptor-mediated Endocytosis
The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.
As cells increase in volume....
The relative surface area decreases and the demand for internal resources increases
Which of the following transport mechanisms will be affected most directly by a temporary shortage of ATP molecules inside the cell?
The transport of glucose molecules against a concentration gradient Reason: The active transport of glucose molecules against a concentration gradient requires an input of energy. Biological processes that require an input of energy typically incorporate the hydrolysis of ATP, an energy-rich molecule.
membrane potential
The voltage across a cell's plasma membrane.
As organisms increase in size...
Their surface area-to-volume ratio decreases, affecting properties like rate of heat exchange with the environment
solute potential
This measurement has a maximum value of 0; it decreases as the concentration of a solute increases.
pressure potential
This measurement has a minimum value of 0 (when the solution is open to the environment); it increases as pressure increases.
Smaller cells....
Typically have a higher surface area-to-volume ratio - more efficient exchange of materials with the environment
Water and osmosis
Water moves from areas of high water potential/low osmolarity/ low solute concentration to areas of low water potential/ high osmolarity/ high solute concentration
Endosymbiosis
a mutually beneficial relationship in which one organism lives within another
exocytosis
a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.
carrier proteins
bind to molecules and change shape to shuttle them across the membrane
amphipathic
having both a hydrophilic region and a hydrophobic region
polar heads
hydrophilic, heads of the phospholipid membrane
non-polar tails
hydrophobic, tails of the phospholipid membrane
nuclear envelope
layer of two membranes that surrounds the nucleus of a cell
transport proteins
membrane proteins that help move substances across a cell membrane
endosymbiotic organelles
mitochondria and chloroplasts
The Kreb cycle
occurs in mitochondria - produce carbon dioxide and ATP
endocytosis
process by which a cell takes material into the cell by infolding of the cell membrane
Homeostasis
process by which organisms maintain a relatively stable internal environment - constant movement of molecules
nuclear membrane
surrounds the nucleus
passive transport
the movement of substances across a cell membrane without the use of energy by the cell
cell membrane
the semipermeable membrane surrounding the cytoplasm of a cell.
Hydrophobic
water hating
hydrophilic
water loving
free water
water that is available for movement between two areas, as it is not clustered around a solute
turgid
when a cell is swollen from an excess of water
flaccid
when a fell is shriveled from a lack of water
formula for water potential
ψ= ψp + ψs
cholesterol
A lipid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids.
Flagellum
A long, hairlike structure that grows out of a cell and enables the cell to move.
Food Vacuole
A membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell.
Central Vacuole
A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.
contractile vacuoles
A membranous sac that helps move excess water out of the cell.
Peroxisome
A microbody containing enzymes that transfer hydrogen from various substrates to oxygen, producing and then degrading hydrogen peroxide.
phospholipids
A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail.
thylakoids
A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
actin
A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.
Cytoplasm
A jellylike fluid inside the cell in which the organelles are suspended
Golgi Apparatus
A system of membranes that modifies and packages proteins for export by the cell
organelles
A tiny cell structure that carries out a specific function within the cell
transport vesicles
A tiny membranous sac in a cell's cytoplasm carrying molecules produced by the cell.
prokaryotic cell
A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles; found only in the domains Bacteria and Archaea.
eukaryotic cell
A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles. Examples of organisms with these cells are protists, plants, fungi, and animals.
phagocytosis
A type of endocytosis in which a cell engulfs large particles or whole cells
A study was conducted to understand the factors controlling the rate at which molecules or ions travel across cell membranes. An artificial membrane was created that was composed of a phospholipid bilayer only. The speed at which various substances crossed this membrane was measured. Some substances can pass through an actual cell membrane much faster than they passed through the artificial membrane in this study. Which of the following statements best explains this finding?
Actual cell membranes have a variety of proteins embedded in the membrane that are absent in the artificial membrane. Reason: Actual cell membranes have a variety of embedded proteins that increase the movement of substances across the membrane by both active and passive transport.
A magnesium sulfate solution taken orally can cause a net movement of water into the large intestine, which results from water molecules diffusing through aquaporins embedded in the cells of the intestinal lining. By which of the following mechanisms do the water molecules most likely move into the large intestine?
By passive transport from an area of low osmolarity to an area of high osmolarity Reason: Based on the information presented, the water molecules move through aquaporins by diffusing from an area of low osmolarity to an area of high osmolarity, which is an example of passive transport.
Aldosterone (a steroid hormone) is a small, nonpolar, hydrophobic molecule that enters a target cell by moving across the plasma membrane, down a concentration gradient. Based on the information presented, how does aldosterone most likely enter target cells?
By simple diffusion Reason: Small, nonpolar, hydrophobic molecules can enter a cell by moving across the plasma membrane and down a concentration gradient by simple diffusion.
The cell membrane is selectively permeable due to its structure. Thus, the internal environment of the cell is distinct from the external environment of the cell. One biologist hypothesizes that small nonpolar molecules readily pass through the membrane. Another biologist alternatively hypothesizes that these types of molecules require channel and transport proteins that are embedded in the membrane in order to move across the membrane. Which of the following data would best refute this alternative hypothesis?
CO2 and N2 movement in and out of cells is unaffected when membrane protein activity is blocked. Reason: Both CO2 and N2 are small nonpolar molecules. Their ability to enter and leave cells normally when membrane protein activity is blocked would refute the alternative hypothesis.
Mitochondrion
Cell organelle that converts the chemical energy stored in food into compounds that are more convenient for the cell to use
Researchers have proposed a model of chloroplast evolution. According to the model, chloroplasts evolved from a small prokaryotic organism that was engulfed by an ancestral eukaryote. The engulfed prokaryote then formed an endosymbiotic relationship with the eukaryotic host. Which of the following observations best supports the model?
Chloroplasts and some prokaryotes share similar photosynthetic reactions. Reason: Photosynthesis is a feature of only a limited number of organisms, including cyanobacteria, algae, and plants. The fact that this specialized process is similar in prokaryotes, such as cyanobacteria, and in eukaryotes, such as algae and plants, provides evidence in support of the model.
microfilaments
Fine, threadlike proteins found in the cell's cytoskeleton
Nucleolus
Found inside the nucleus and produces ribosomes
Cilia
Hairlike projections that extend from the plasma membrane and are used for locomotion
Researchers investigate the transport of a certain protein into cells by endocytosis. In an experiment, the researchers incubate the cells in the presence of the protein and measure the amount of the protein that is absorbed into the cells over a five-minute period. Based on their observations, what should the researchers do to further clarify how the availability of the protein outside the cells affects the rate of endocytosis of the protein?
Incubate the cells in the presence of several different concentrations of the protein. Reason: Changing the concentration of the protein will change the availability of the protein outside the cells.
In an experiment, researchers compared the growth of two different plants, plant X and plant Y. The researchers maintained the plants under nearly identical conditions and observed that plant X grew faster than plant Y. The researchers also observed that the inner mitochondrial membranes of plant X had more folds than did those of plant Y. Which of the following conclusions about increasing the number of folds in the inner mitochondrial membrane is best supported by the results of the experiment?
It increases the surface area available for ATP production, which results in faster cell growth. The increased surface area of the folds will contain more ATP synthase, allowing for more efficient use of the chemiosmotic gradient and more efficient production of ATP. The observation that plant X grew faster than plant Y supports this conclusion.
peripheral proteins
The proteins of a membrane that are not embedded in the lipid bilayer; they are appendages loosely bound to the surface of the membrane. They direct and maintain both the intracellular cytoskeleton and components of the extracellular matrix
In an experiment, researchers provided a radiolabeled amino acid to living plant cells. After one hour, the researchers determined the amount of the radiolabeled amino acid that was in each of several subcellular compartments. The results of the experiment are represented in the table. RELATIVE AMOUNTS OF RADIOLABELED AMINO ACID Nucleus Mitochondria Endoplasmic Reticulum Cytosol 2.1 2.7 1.9 1 Which of the following conclusions about the radiolabeled amino acid is best supported by the results of the experiment?
It was mostly incorporated into proteins that regulate and manage metabolic reactions. Reason: Amino acids are the building block of proteins, and the data indicate that most of the radiolabeled amino acid was in the mitochondria. Therefore, the data best support the conclusion that most of the amino acid molecules were incorporated into proteins that regulate and manage the metabolic reactions that occur in mitochondria.
Which of the following observations best supports the claim that mitochondria evolved from once-free-living prokaryotic cells by the process of endocytosis?
Mitochondria are surrounded by a double membrane. Reason: The double membranes of mitochondria provide evidence that an ancestor of mitochondria, which was most likely a type of free-living aerobic bacterium, was ingested via endocystosis by a primitive eukaryotic cell
diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration.
Intravenous (IV) therapy is used for fluid replacement in instances of dehydration in humans and other animals. One type of IV fluid is essentially a saltwater solution. To determine the best concentration for therapy in people, a team of students is researching the effects of solutions of different salt concentrations on red blood cells. The following observations were made from three different red blood cell samples viewed under a microscope. The team wants to extend the research project. What should the team of students do next to obtain data that are more conclusive?
Repeat the process with other salt concentrations. Reason: The figures illustrate the extremes of hypotonic (swollen cells) and hypertonic (shriveled cells) environments, so an extension would be to investigate the small range of acceptable salt concentrations in IV fluid solutions.
chromatin
granular material visible within the nucleus; consists of DNA tightly coiled around proteins
fluid mosaic model
Structural model of the plasma membrane where molecules are free to move sideways within a lipid bilayer.
Rough Endoplasmic Reticulum
System of internal membranes within the cytoplasm. Membranes are rough due to the presence of ribosomes. Functions in transport of substances such as proteins within the cytoplasm, as well as the creation of proteins (ribosomes)
Some membrane proteins help maintain the concentrations of ions inside a cell by transporting the ions across the cell's plasma membrane. Other membrane proteins form pores in the plasma membrane through which the ions can diffuse. A model showing the influence of membrane proteins on the movement of sodium (Na+) and potassium (K+) ions across a plasma membrane is presented in Figure 1.
The Na+ concentration inside the cell will increase. reason: Without ATP, the Na+ ions will continue to leak into the cell but will not be pumped out of the cell, resulting in a concentration increase inside the cell.
A group of mutations, known as MT-ND1, have been identified in mitochondrial DNA. These mutations are associated with a number of debilitating diseases stemming from the production of nonfunctional proteins in the mitochondria. Which of the following cellular deficiencies would most likely be related to these MT-ND1 mutations?
The cell is unable to complete reactions related to electron transport and ATP production. Reason: The electron transport chain and ATP production are associated with proteins in the inner membrane of the mitochondrion. Nonfunctional proteins in the mitochondrion are likely to result in reduced ATP production.
The valinomycin treatment caused a decrease in the activity of the mitochondria
The data indicate that the valinomycin treatment caused a decrease in the relative rate of ATP production, which likely resulted from impaired mitochondrial function.
A student is using dialysis bags to model the effects of changing solute concentrations on cells. The student places one dialysis bag that contains 25 mL of distilled water into each of two beakers that are filled with 200 mL of distilled water. (Figure 1). The membrane of each dialysis bag membrane contains pores that allow small solutes such as monoatomic ions to pass through but are too small for anything larger to pass. After 30 minutes, 5 mL of a concentrated solution of albumin (a medium-sized, water-soluble protein) is added to one of the two beakers. Nothing is added to the other beaker. After two more hours at room temperature, the mass of each bag is determined. There is no change in the mass of the dialysis bag in the beaker to which no albumin was added. Which of the graphs below best represents the predicted change in mass over time of the dialysis bag in the beaker to which albumin was added?
The graph indicates no change in the mass of the dialysis bag for the first 30 minutes in an isotonic environment, but then it incorrectly shows an increase in mass when the environment became hypertonic with the addition of albumin.
A certain type of specialized cell contains an unusually large amount of rough endoplasmic reticulum (ER). Which of the following functions is this cell type most likely specialized to perform?
The production and secretion of proteins Reason: The cytosolic surface of the rough ER is covered by ribosomes that synthesize proteins that are then transported into the rough ER, then to the Golgi complex, and finally out of the cell.
Lysosomes digest food particles brought into a cell by endocytosis. After a vesicle containing food particles fuses with a lysosome, H+ ions are transported into the lysosome from the cytosol. This significantly lowers the pH of the lysosome relative to the cytosol and activates the enzymes that digest the particles. Which of the following best predicts what will happen to the lysosomal enzymes if the proteins that transport H+ ions from the cytosol into the lysosome are damaged?
The lysosomal enzymes will not become active, since there will be no active transport of H+ ions. Reason: Since the pH of the lysosome has to become lower than that of the cytosol, active transport is needed to move H+ ions into the lysosome, against the H+ ion concentration gradient, to activate the enzymes.
cell theory
idea that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells
Two competing hypotheses exist regarding the cell membrane structure. One hypothesis states that membrane structure is static and membrane components throughout the bilayer are rigidly bound. Alternatively, the other hypothesin? states that cell membranes are a fluid mosaic in which membrane components may drift within the bilayer around the surface of the cell. An experiment is set up in which membrane proteins of two different cells are fluorescently labeled with two different colors and then fused Which of the following results, one hour after membrane fusion, best supports the alternative hypothesis that the cell membrane is a fluid mosaic?
The membrane proteins from each cell have mixed and drifted within the bilayer, which supports the fluid mosaic model of cell membranes. Cell membranes consist of a structural framework of phospholipid molecules that is embedded with proteins and steroids that may flow around the surface of the cell within the bilayer.
Cholesterol is a naturally occurring substance that helps regulate the fluidity of a cell's plasma membrane. A cholesterol molecule can be represented as having a polar head and a nonpolar region, as shown in the figure. Which of the following models shows how cholesterol molecules most likely interact with the phospholipid bilayer of a cell's plasma membrane?
The model correctly shows the polar heads of the cholesterol molecules interacting with the polar heads of the phospholipids. Also, the model correctly shows the nonpolar regions of the cholesterol molecules interacting with the hydrophobic interior of the phospholipid bilayer.
Stomata are pores on the surfaces of the leaves and stems of plants that regulate gas exchange between the plants and the atmosphere. Researchers found that the stomata density on the leaves of a species of plant change as the concentration of CO2 in the atmosphere changes. When grown at 350 ppm CO2 the plant has an average density of 300 stomata per mm2, but when grown at 400 ppm CO2 the plant has an average density of 250 stomata per mm2. Which of the following best describes how the ratio of the density of stomata (stomata per mm2) per CO2 concentration (ppm CO2) changes as the CO2 concentration increases?
The ratio decreases from 0.86 to 0.63 , because fewer stomata are needed at higher CO2 concentrations. Reason: he ratio of 300 stomata per mm2 to 350 ppm CO2 is 0.86, and the ratio of 250 stomata per mm2 to 400 ppm CO2 is 0.63. This reflects that fewer stomata are needed as the concentration of CO2 increases.
Hereditary spherocytosis (HS) is a disorder of red blood cells that causes the cells to be smaller and spherical instead of having the usual flattened, biconcave shape. The average diameter of normal red blood cells is 7.2μm, and the average diameter of red blood cells in a person with HS was found to be 6.7μm. The normal red blood cell has an average surface area of 136μm2 and an average volume of 91μm3. Which of the following provides an accurate calculation of the surface area to volume ratio of an HS red blood cell, as well as a prediction of its effect on the efficient transferring of oxygen compared to a normal red blood cell?
The ratio is 0.89 , and the cells are less efficient at transferring oxygen. Reason: The correct calculation of the surface area to volume ratio of the HS cell is 0.89. This ratio is less than the ratio found in a normal red blood cell, 1.49, so the cell would be less efficient at transferring oxygen.
A scientist is studying the various prokaryotic and eukaryotic species found floating in a sample of water taken from a marine ecosystem. Which cellular component will be found in the widest range of organisms in the sample?
The ribosome, since all organisms need to synthesize proteins. Reason: Correct. Ribosomes are found in all forms of life, allowing for comparison of the widest possible range of plankton species.
Extracellular Matrix
The substance in which animal tissue cells are embedded, consisting of protein and polysaccharides.
Some cells, such as intestinal cells, exchange a lot of material with their surroundings. The surface-to-volume ratio of these cells affects the efficiency of material exchange. Based on the data, which cell is likely to be most effective in the exchange of materials?
The surface area to volume calculation is 6010=6. Of the four cells, this one has the highest ratio of surface area to volume and is likely to be most effective in the exchange of materials.
endosymbiont theory
The theory that mitochondria and plastids, including chloroplasts, originated as prokaryotic cells engulfed by an ancestral eukaryotic cell. The engulfed cell and its host cell then evolved into a single organism.
What additional procedure would best help determine whether movements are due to active transport or to passive transport?
Use two additional treatments, one containing only ethyl alcohol and one containing only acetate. Include a substance known to block ATP use by the plasma membrane. Compare the graphs of these two treatments to the original graph. Active transport requires the availability of ATP. If the nutrients are actively transported, blocking ATP use should reduce the rate of transport along the whole concentration range. If these two graphs are the same as the original graph, the transport is passive. Separation of the nutrients eliminates the possibility that the two transport processes could interfere with each other.
cellular membrane
most important part of cell - gives protection, communication, and passage of substance in/out of cell
Beetroot cells contain a family of dark red pigments called betalains. The selectively permeable nature of the beetroot cells keeps the internal environment of the cell separate from the external environment of the cell. Researchers are interested in determining whether the selective permeability of beetroot cells is due to the cell membrane or if it is due to the cell wall. Exposure to cellulase is known to damage the structure of the cell wall. An experiment is set up in which beetroot cells are placed in an aqueous solution with cellulase and in one without cellulase. Which of the following results best refutes the alternative hypothesis that selective permeability is a consequence of the cell wall?
When beetroot cells are placed in a solution with cellulase, the solution remains clear. Cellulase digests cellulose and damages the structure of the cell wall, not the cell membrane. The lack of color change in the solution indicates that the betalain is not leaking out of the beetroot cells even though the cell wall has been damaged. This refutes the alternative hypothesis.
phospholipids
a lipid consisting of a glycerol bound to two fatty acids and a phosphate group; makes up cell membrane
nuclear pore
a protein-lined channel in the nuclear envelope that regulates the transportation of molecules between the nucleus and the cytoplasm
chromosomes
a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
Centriole
one of two tiny structures located in the cytoplasm of animal cells near the nuclear envelope
Chloroplast
organelle found in cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy
Testosterone is a small steroid hormone that is important in cell signaling. Which of the following indicates where testosterone enters a cell and why it is able to cross at that point?
because testosterone is nonpolar and can diffuse through the membrane. Reason: Steroids such as testosterone are hydrophobic lipids. Therefore, testosterone can cross the hydrophobic inner region of the phospholipid bilayer.
Lysosome
cell organelle filled with enzymes needed to break down certain materials in the cell (wastes, inactive organelles)
concentration gradient
difference in the concentration of a substance from one location to another
endomembrane system
ribosome --> Rough ER --> Golgi apparatus / vesicles --> plasma membrane includes Ribosomes, ER
granum
stack of thylakoids
Gaucher disease is an inherited disorder in which cells of the body are unable to break down a particular type of lipid, resulting in a buildup of the lipid in some tissues and organs. Based on the information provided, Gaucher disease results most directly from a defect in the function of which of the following organelles?
the lysosome Reason: The lysosome contains specific enzymes used to break down a variety of molecules and cellular waste products. A defect in the function of the lysosomal enzymes that are needed to break down lipids is the most direct cause of Gaucher disease.
water potential
the physical property that predicts the direction in which water will flow
permeability
the state or quality of a material or membrane that causes it to allow liquids or gases to pass through it.
hypertonic
when comparing two solutions, the solution with the greater concentration of solutes
hypotonic
when comparing two solutions, the solution with the lesser concentration of solutes
isotonic
when the concentration of two solutions is the same
