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DAT Bootcamp- Cell Biology Practice
Terms in this set (59)
What is the original source of energy used to drive the light independent reactions of photosynthesis
Photons absorbed by chlorophyll-
The energy used to drive photosynthesis comes from light, or photons/ The light independent reactions (Dark reactions, also known as the Calvin-Benson Cycle) takes the energy produced in the light dependent reactions along with CO2 to produce glucose.
If 2n=8, how many chromosomes are present during anaphase
Before anaphase, the DNA in a cell has duplicated and condensed, given us 2 chromatids per chromosome. During anaphase, the chromatids split and begin to migrate towards opposite sides of the cell. Because of this, the number of chromosomes during anaphase doubles from the usual chromosome count. So 8 x 2 = 16 chromosomes.
An unknown biological sample is exposed to several enzymes and is found to react only with lipase. What is this sample composed of
Lipases are enzymes that digest fats. Adipose tissue is also known as body fat. Fats are made of triglycerides, which contain a glycerol backbone and fatty acid chains, which make up lipids.
Which of the following statements accurately describes cytokinesis in mammals
Microfilaments encircle the center of the cell and shorten-
Cytokinesis is the last stage of mitosis and actually begins occurring at the end of anaphase. It is the process of dividing the cytoplasm to form 2 cells. In mammals, a cleavage furrow develops from microfilaments encircling the cell and pulling the plasma membrane into the center.
Which one of the following is amphipathic, with both a hydrophilic and hydrophobic region
The cell membrane is composed of a phospholipid bilayer that has a hydrophilic head (where the polar phosphate is attached) and a hydrophobic tail (made up of hydrocarbon chains).
Which organelle modifies products from the endoplasmic reticulum and is responsible for protein packaging
The Golgi complex (or Golgi apparatus) is composed of stacks of membrane bound discs known as cisternae. It works with the endoplasmic reticulum to package and sort proteins and is specifically important in secreting proteins such as hormones.
Where does glycolysis occur in a cell
Glycolysis, the first step in cellular respiration, takes place in the cytosol of the cell. The cytosol consists of just the fluid of a cell, while cytoplasm consists of everything between the membrane and the nucleus, although cytoplasm is usually an acceptable answer too.
**The mitochondrial matrix and intermembrane space is where the rest of respiration occurs and the electron transport chain.
An animal cell was lysed, placed in a test tube, and centrifuged. Which organelle would pellet from the centrifuge first
The heavier a component is, the faster it will pellet out of the solution. The nucleus is the largest and most dense organelle in the cell and will pellet first.
Which of the following is NOT thought to be part of the Earth's primitive atmosphere
It is thought that if oxygen did exist in Earth's primitive atmosphere, organic molecules could not have formed because oxygen is very oxidizing. The original atmosphere of Earth was thought to be a reducing environment to support the creation of organic molecules. The original atmosphere of Earth consisted of CH4, NH3, CO, CO2, H2, N2, H2O, S, HCl, HCN, and little/no O2
What is the purpose of SDS (sodium dodecyl sulfate) in protein analysis
Denature non-covalent bonds in a protein -
Sodium dodecyl sulfate is a very strong anionic detergent that is used in gel electrophoresis to separate proteins based on their electrophoretic mobility (a function of the length of a protein and its charge). SDS is used to denature and linearize proteins and to impart a negative charge to the proteins. You could deduce it would impart a negative charge and not a positive one because sulfate is very negative and anionic. With this method, only the protein's size and charge will be compared. Generally, all gel electrophoresis will denature a protein to compare its size.
Catabolism can be described as a(n):
Catabolism is the breaking down of materials to smaller units, such as when glucose is broken down to release energy. If we're breaking down glucose, we're releasing energy, so this is an exergonic reaction
All of the following directly use an electrochemical gradient EXCEPT one. Which one is the EXCEPTION?
An electrochemical gradient is one where an electrochemical imbalance exists between a membrane.Aquaporins are protein structures in the membrane that help water passively flow into or out of the cell, a process known as facilitated diffusion.
In the alternation of generations, what do spores directly give rise to
haploid spores divide by mitosis to form the gametophyte stage. These gametes fuse together to form the diploid stage and develop into a sporophyte, which then divides by meiosis to get back to the haploid stage
All of the following statements are part of modern cell theory EXCEPT one. Which one is the EXCEPTION
All cells contain a nucleus for the storage of genetic material-
In eukaryotic cells the cell nucleus serves to protect the DNA of the organism. Prokaryotic cells do not have a centralized nucleus and do not have many of the other cell organelles that eukaryotic cells have with the exception of ribosomes. Prokaryotes have a nucleoid region.
The deregulation of apoptosis may lead to the development of various diseases. Which of these may develop from insufficient apoptosis
a lack of apoptosis would lead to cell proliferation, as the body would not be able to successfully eradicate damaged cells. This cell proliferation often manifests as cancer.
A scientist wants to detach a peripheral membrane protein from the exterior of a cell membrane. Which is the best method to do so
Change the salt concentrations-
Peripheral membrane proteins are held in place by electrostatic interactions and hydrogen bonding. They are generally hydrophilic. Changing the salt concentration (a "salt wash") or the pH would disrupt both of these types of bonds and release the peripheral membrane protein from the cell membrane.
Which of the following were NOT observed by Miller-Urey in their classic experiment to check the hypothesis of the "chemical origins of life"
The Miller-Urey experiment used ammonia, methane, water and hydrogen sealed in a sterile arrangement of tubes and flasks with connecting loops. One flask was half-filled with liquid water and the other with 2 electrodes (to simulate lighting in early earth). The flask with water was heated to simulate the temperature of early Earth, and sparks were fired from the electrodes to simulate lightning. After 2 weeks, they observed several organic compounds, amino acids (11 out of 20) and their base starting materials. However, no complete nucleic acids were observed
Channel proteins allow particles to cross the cell membrane during what non-energy consuming process
With facilitated diffusion, particles are able to cross the membrane but with the help of integral proteins that span the length of the cell membrane
Enzymes that are placed in temperatures above their ideal conditions will
If an enzyme is taken outside of these conditions, its ability to catalyze reactions will change, usually decreasing dramatically. At higher than ideal temperatures, enzymes, which are proteins, lose their quaternary structure and denature
A toxin is released into the body that promotes the degeneration of microfilaments. Which of these structures is most likely to be directly affected
Our muscles are made of long chains of cytoskeleton comprised of two filaments - actin and myosin. Of these, actin is a microfilament, while myosin is a motor protein. If actin degenerates, then our muscles would not contract
Which is the most correct definition of competitive inhibition
An inhibitor binds directly to the active site and prevents the reactant from binding-
Competitive inhibition occurs when the inhibitor competes directly with the reactant at the active site, and this substrate takes the place of the reactant and prevents the reaction from occurring
What is the name of the structure that allows bacteria to stick to a surface
Pili are small short "hairs" called fimbriae on the surface of bacteria that can be used in the exchange of genetic material between bacteria and in cell adhesion
Chromosomes align on a cell's equatorial plane during which stages of meiosis
Metaphase I and Metaphase II-
Various colors of light were shined on a unique green plant for 24 hours in a closed container and the amount of CO2 present in the container was recorded. The results are below:
Initial Amount of CO2 Final Amount of CO2
Blue Light: 10 ppm Blue Light: 2.3 ppm
Red Light: 10 ppm Red Light: 1.9 ppm
Green Light: 10 ppm Green Light: 9.2 ppm
Which of the following conclusions can be drawn from the data?
The rate of photosynthesis was highest with the red light-
As a plant performs photosynthesis, the amount of CO2 present should decrease over time as the plant consumes the carbon to make glucose.The highest rate of photosynthesis occurred with the red light as it had the largest change in the amount of CO2 present, signaling a large consumption of CO2, which would have resulted in a high rate of photosynthesis.
Glycolysis is best described as what type of process
Glycolysis requires the use of energy when the glucose molecule is broken into two pyruvates. The two steps in which ATP is used can be considered endergonic, however, overall glycolysis produces energy to be consumed by the cells. If energy is released, then the reaction is exergonic.
A plant cell is placed into a salt-water mixture (70% salt). What is likely to result if the plant cell's membrane is permeable to water
The cell will undergo plasmolysis-
For cells with a selectively permeable membrane, water will move from higher water concentrations to lower water concentrations. In this problem, the salt is too large to cross the membrane, so the salt concentration will remain the same. Since plant cells have more water than the salt-water mixture, the water in the cell would leave to make the two environments isotonic, or have the same osmolarity. If water leaves the cell, the cell will become plasmolyzed
Which of the following stores the most amount of energy, gram for gram
Fats store the most amount of energy in the body. They store roughly double the amount of energy carbohydrates (starch, glycogen, cellulose) store, gram for gram. The reason our body prefers to burn glucose is because it is easier to use in respiration and it is more readily available
A bacterial cell has its cell wall removed and is placed in distilled water. Which of the following will happen
The bacterial cell will lyse because it is hyperosmotic to the water-
lacing the cell in distilled water will cause water to rush in, ultimately lysing the cell. This is because the cell has a higher osmolarity than the surrounding water, making it hyperosmotic to the water. Water will diffuse from areas of high concentration to areas of low concentration. The higher the osmolarity, the lower the concentration of water.
All of the following are statements that support the endosymbiotic theory EXCEPT one. Which one is the EXCEPTION
Mitochondria and chloroplasts both produce energy-
The endosymbiotic theory states that eukaryotic cells originated from a mutualistic relationship between two prokaryotes. Some evidence that points towards this includes:
Mitochondria and chloroplasts both have their own DNA separate from the rest of the cell, and this DNA is circular and without any proteins, much like prokaryotes.
Mitochondria and chloroplasts have different ribosomes that are more similar to prokaryotes than eukaryotes.
Mitochondria and chloroplasts reproduce independently of the host cell by a process that is similar to binary fission, used by prokaryotes.
Mitochondria and chloroplasts have a double membrane, which could have resulted from one prokaryote engulfing the other prokaryote in an endocytosis fashion, forming a vesicle.
The thylakoid membranes of chloroplasts resemble the photosynthetic membranes of cyanobacteria, which are autotrophic bacteria.
If a human cell has 46 chromosomes at the beginning of meiosis, then at the end of meiosis I each cell would have
Meiosis will take a diploid cell and produce two haploid cells. This means that our chromosome number will decrease to 23 chromosomes for each daughter cell. However, each of these chromosomes have two chromatids, so they will also have 23 x 2 = 46 chromatids
What are the products of the light-dependent reactions in photosynthesis
O2, NADPH, and ATP-
The light-dependent reactions of photosynthesis occur in the thylakoid membranes of chloroplast. Here, cyclic photophosphorylation produces ATP through an electron transport chain, and noncylic photophosphorylation produces NADPH. Water is split during these reactions, releasing O2
The structure of plasma membranes is often described as having proteins float on top of a sea of phospholipids. Which of the following matches this description
Fluid mosaic model-
The hydrophobic integral components, such as lipids, move laterally throughout the membrane, giving it a "fluid-like" state. The different kinds of macromolecules, including integral proteins, peripheral proteins, glycoproteins, and cholesterol give the plasma membrane its mosaic state. Together these describe the fluid mosaic model of the plasma membrane
Pancreatic beta cells secrete insulin into the body. Which organelle would you expect to be heavily expressed in beta cells
The Golgi apparatus is a group of flattened sacs that coordinate with the endoplasmic reticulum. The Golgi specializes in modifying and packaging proteins for secretion. Cells that secrete hormones often have a high expression of Golgi complexes to aid in protein secretion
What type of cell junction is most common between digestive tract cells
Tight junctions prevent the passage of materials between digestive tract cells in animals. This way, the body must absorb the food through intracellular space.
A scientist discovers small particles inside a cell and wishes to know what they are. Radioactive aminoacyl-tRNAs are microinjected into the functioning cell. The measured amount of radioactive aminoacyl-tRNAs decreases over time, while the amount of radioactive polypeptides increases. What are the small particles
A polypeptide is a protein, and proteins are made of amino acids. Ribosomes read mRNA and synthesize polypeptides out of aminoacyl-tRNAs. Aminoacyl-tRNAs are how amino acids are carried to the ribosome for elongation in translation
If 2n=46, how many tetrads are present during metaphase I
In prophase I of meiosis, homologous chromosomes pair in a process called synapsis. These pairs of homologous chromosomes are referred to as tetrads, which are composed of four chromatids (two from each chromosome).
We know that there are 46 pairs of chromosomes (because the DNA duplicated in S phase), so if each one of them pairs with their homologous pair we will have 23 tetrads to line up on the metaphase plate
Why does yeast undergo anaerobic respiration in the absence of oxygen
To oxidize NADH to NAD+ -
Normally, NADH will donate its electrons to oxygen in aerobic conditions, producing NAD+ for use again in respiration.
In the absence of oxygen as a final electron acceptor, NADH builds up inside of the cell (because it has no where to give its electrons). So the yeast will activate anaerobic respiration, which converts pyruvate into acetaldehyde, which releases CO2. Acetaldehyde will then convert into ethanol, and this is where the magic happens. The energy in NADH is used to drive this reaction, which releases NAD+. Now the free NAD+ can undergo glycolysis and the cell can produce at least 2 more ATP through anaerobic respiration, rather than dying
Which of the following is the source of energy for the synthesis of small organic molecules that predated the earliest forms of life
Several nonorganic molecules (excluding oxygen) were enclosed in a flask and allowed to react with firing electrodes to replicate lightning. There was a significant amount of lightning on primitive Earth, which we believe helped give the "spark" of life
Why are chromosomes not visible during interphase
They uncoil to allow replication and transcription-
During mitosis, the chromosomes condense to separate both copies of the DNA to each daughter cell. However, the DNA is so tightly coiled that enzymes cannot transcribe the DNA. During interphase, the DNA uncoils to allow enzymes to transcribe and replicate the DNA
The second law of thermodynamics can explain which of the following statements
Some of the energy transferred in a cell is lost as heat-
In centrifugation, which factor determines if a cellular component ends up in the pellet or supernatant
size and weight-
A centrifuge separates a homogenized solution into a precipitate, or a pellet, which is a solid mass at the bottom of the tube, and the supernatant, which is a solution of everything else in the original solution. Centrifugation separates cellular components based on their size and weight. This is why the nucleus pellets from a lysate first - it is the largest and heaviest organelle. Next, mitochondria are pelleted, and then microsomes (vesicles of the ER), and finally ribosomes. Small soluble proteins remain in the supernatant after ribosomes are pelleted
During cell division, which of the following stages are most similar
Mitotic metaphase and meiosis metaphase II -
During mitotic metaphase, all of the chromosomes (each with two chromatids) line up on the metaphase plate in the cell. During metaphase II in meiosis, half of the chromosomes (each with two chromatids) also line up on the metaphase plate. Metaphase II is more similar to mitotic metaphase because metaphase II only consists of chromosomes with 2 chromatids each, while metaphase I consists of homologous chromosomes (or tetrads, with 4 chromatids)
During which step can nondisjunction occur in mitosis
Nondisjunction is the failure of one or more chromosome pairs to separate properly during mitotic anaphase, anaphase I, or anaphase II. It most often occurs in embryonic development. The result is two daughter cells with extra or missing chromosomes. If this occurs in meiosis, and the aneuploidic gamete is fertilized, a number of syndromes may result. This is commonly known as trisomy; examples of trisomies include Down's syndrome (trisomy 21) and Turner syndrome (absence of one X chromosome in females, monosomy X).
Which product(s) is/are common in both glycolysis and the electron transport chain
Process Reactants Products
Glycolysis (Cytosol) Glucose, ATP, NAD+, ADP ATP, NADH, pyruvate
Krebs Cycle (mitochondrial matrix) acetyl CoA, NAD+, FAD, ADP CO2, NADH, FADH2, ATP
Electron Transport Chain (mitochondrial cristae) O2, NADH, FADH2, ADP ATP, H2O, NAD+, FAD
Alcohol fermentation Pyruvate, NADH CO2, NAD+, ethanol
Lactic acid fermentation Pyruvate, NADH Lactate, NAD+
All of the following events occur during photosynthesis EXCEPT for one. Which one is the EXCEPTION
The inner membrane of the chloroplast absorbs light -
The thylakoid membrane contains the chlorophyll molecules that absorb light. The inner membrane does not have a large role in photosynthesis. Most of photosynthesis occurs in the stroma and thylakoid. Water undergoes photolysis inside of the thylakoid to provide electrons for the chlorophyll molecules to excite with photons of light. As the electrons fall through the electron transport chain of the thylakoid membrane, H+ ions flow into the thylakoid (OPPOSITE of mitochondria, where H+ ions flow OUT of the matrix). The flow of H+ ions into the thylakoid decreases the pH because it becomes more acidic. The electrons react with NADP+ to form NADPH. ATP is produced by ATP synthase in the thylakoid membrane. The light dependent reactions generally take place inside of the thylakoid or in the thylakoid membrane.
The light independent reactions generally take place in the stroma. CO2 concentrates in the stroma to be fixed into glucose by the Calvin-Benson cycle.
Which organelle is the nucleus attached to
Endoplasmic Reticulum (Rough) -
All of the following are methods plants use to reduce water loss EXCEPT for one. Which one is the EXCEPTION
reflection of green light -
growing little "hairs" on their leaves to retain more moisture and a thin needle-like leaf structure. Christmas trees and other conifers have needle leaves as an adaptation to growing in a dry environment. Desert plants have thick waxy cuticles as a way to minimize the amount of moisture the plant transpires, and guard cells in the stomata close off the holes in the leaves when activated. The reflection of green light is irrelevant to reducing water loss
Which of the following has a similar function to the cristae of mitochondria
Thylakoid membrane in chloroplast -
The crista of mitochondria houses the electron transport chain (ETC) to create a proton force for ATP synthesis. The thylakoid membrane is the equivalent to this in photosynthesis; this is where the electron transport chain occurs to produce ATP and NADPH in photosynthetic organisms in the light-dependent reactions
Which of the following is the earliest event in the development of the first living cell
Development of RNA with enzymatic functions-
RNA is thought to be the original molecule for the origin of life. The reasons surrounding this are that RNA can store genetic information and also has enzymatic properties.
All of the following are secondary messengers used in signal transduction EXCEPT one. Which one is the EXCEPTION
One epinephrine molecule can cascade into the activation of 10,000 new molecules through the secondary messenger system. cAMP, cGMP, DAG, IP3, and Ca2+ are all common secondary messengers. Hormones, like epinephrine, are often just activators of the secondary messenger system
If 2n=46, how many chromatids would you expect to find in anaphase
During mitosis, 46 chromosomes will line up on the metaphase plate. Each chromosome will have two duplicate chromatids, for a total of 92 chromatids. When these chromosomes split during anaphase, we will still have 92 chromatids, but we will also have 92 chromosomes, since each chromatid is now separate. Once the two daughter cells separate each will have 46 chromosomes (and 46 chromatids)
Which of the following factors supports the structure of beta-pleated sheets in proteins
A protein has four levels of structure. The secondary structure results in a three dimensional protein with either alpha helices or beta-pleated sheets, depending on the types of amino acids present. These structures occur due to hydrogen bonding between the amino and carboxyl groups of adjacent amino acids
Which organelle can be referred to as the "stomach of the cell"
Lysosomes are essentially the stomach of the cell. They contain hydrolase enzymes that are only functional in a low pH environment, similar to pepsin in the stomach. Their job is to break down macromolecules and to digest excess or worn-out organelles of the cell
All of the following are proteins EXCEPT for one. Which one is the EXCEPTION
Chitin is a type of cell wall found in fungi. Chitin is a polysaccharide similar to cellulose but with a nitrogen-containing group called glucosamine.
Which cell would have the highest concentration of lysosomes
White blood cells-
Lysosomes are digestive organelles and are involved in phagocytosis. They are sometimes referred to as the "stomach of the cell". The cells that undergo the most amount of phagocytosis are the white blood cells. This is because they must engulf all foreign material in the body via phagocytosis. It is useful to have a high concentration of lysosomes to properly digest and destroy the foreign material
Which technique would a researcher use to observe the migration of chromosomes during mitosis
Fluorescence microscopy attaches fluorescent molecules to the desired specimen and illuminates it with ultraviolet light.
Where is the CO2 mammals exhale produced
Citric acid cycle in the mitochondrial matrix-
The citric acid cycle, or the Krebs cycle, occurs in the mitochondrial matrix. This is the process in respiration that produces the CO2 we exhale
In alcohol fermentation, which molecule is the final electron acceptor
If oxygen is not present to accept electrons the cell will undergo fermentation. The downside to fermentation is that a weaker electron acceptor will be used and less energy will be produced. In alcohol fermentation, acetaldehyde is the final electron acceptor used in place of oxygen
During oxidative phosphorylation, the pH of the mitochondrial matrix
increases as the electron transport chain proceeds-
During oxidative respiration, electrons flow through the electron transport chain (ETC) until they react with oxygen to form water. During this time, protons are pulled into the intermembrane space, or OUT of the matrix. If protons are being removed from the matrix, then the pH must INCREASE (remember, a higher pH indicates more base, and a lower pH indicates more acid).
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