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What causes different chemical properties in isomers?
The different arrangements of their molecules.
How is biological information coded in a DNA molecule?
The linear sequence of the base pairs.
How does the structure of ice benefit the organisms that live in the water below?
The water molecules in ice are farther apart than those in liquid water, so the ice floats, maintaining the warmer, denser lake at the bottom.
What properties must an amino acid have to be incorporated into a polypeptide?
The ability to form a covalent bond with both its NH2 group and its COOH group.
What is a common feature of the linking of monomers to form macromolecules?
Monomers are joined by a covalent bond, and a water molecule is produced.
If a mutation occurs in a polypeptide chain, how might the change affect the structure and function of the protein?
The R-group of the new amino acid has different chemical properties than the R-group of the original amino acid, causing the protein to misfold and not function properly.
In a phosphorus-limited environment, which macromolecule's production is affected the most?
Nucleic acids.
What is a key difference among the 20 amino acids used to make proteins?
Some amino acids are hydrophobic.
Depending on atom arrangement in a monosaccharide's ring structure, what trait may differ from its linear structure?
A different function.
How does the hydroxyl group affect the properties of a simple sugar?
They increase solubility of simple sugars (can also increase electronegativity, but not useful for sugar properties)
What happens when a glycosidic bond forms?
A monosaccharide unit is joined to another monosaccharide or to a chain of monosaccharides, and a water molecule is released.
What stabilizes the secondary structures of proteins?
Hydrogen bonds.
What is true of both proteins and carbohydrates?
Both are formed by dehydration synthesis reactions.
What is the major mechanism of change over time in biology?
Natural selection.
Many organisms depend on sugar as a source of energy for the cell. This observation suggests that the pathways that break down sugars:
Arose early in life’s history.
What type of bond is formed between a sodium ion and a chloride ion?
Ionic bond.
Proteins, nucleic acids, and carbohydrates are all:
Polymers made up of repeating subunits.
Which property of water allows it to travel upward from tree roots to leaves?
Cohesion.
What indicates that a substance is likely a carbohydrate?
It ends in -ose (e.g., sucrose, glucose).
What is the difference between saturated and unsaturated fats?
Saturated fats tend to be solid at room temperature; unsaturated fats are liquid at room temperature.
What determines the function of a protein?
The protein’s specific structure.
How can you distinguish between RNA and DNA nucleotides?
Whether it has a hydroxyl group or hydrogen atom on its 2’ carbon; its sugar identity; its nitrogen base identity (T vs. U)
What characterizes pyrimidines vs. purines?
Pyrimidines have a single-ring structure (thymine, cytosine, uracil), while purines have a double-ring structure (adenine, guanine).
What are the four main ideas from biology and an example of each?
Information storage and transmission (Central Dogma); systems interaction (different organisms interacting to create a variety of biomes and ecosystems with diversity of life); change over time/evolution (adaptation allows organisms to have the most beneficial traits to survive and reproduce); energetics (organelles of a cell function to help the cell live, thrive, and reproduce)
What forms the DNA backbone?
Bonds between sugars and phosphates of nucleotides.
What types of bonds are found inside DNA and why is that important?
Hydrogen bonds - they’re weak, making them easier to break for RNA formation.
How do the properties of water contribute to transpiration?
Cohesion and hydrogen bonding help remove heat energy and result in evaporation.
How do the properties of water contribute to thermoregulation?
Water’s polarity and strong hydrogen/covalent bonds need a lot of energy to be broken so specific heat capacity is high for water - water is increasingly resistant to outside changes in temperature so organisms are able to resist environmental temperature chances and regulate their body temperature
How do the properties of water contribute to the plasma membrane function?
Water’s polarity means that polar substances want to interact with water and nonpolar molecules will avoid interactions with water; hydrophilic parts of plasma membrane will be on exterior and hydrophobic parts on interior - plasma membrane effectively functions as a boundary between the outside/inside parts of the cell; hydrophobic inner structures prevent water from entering and hydrophilic parts can interact with water
What type of modification occurs to amino acids for functional proteins?
Post-translational modification; an R group is added to the amino acid, making it funcitonal.
The protein CFTR is made of 1480 amino acids linked together in a chain. Some humans produce a version of the protein in which phenylamine (an amino acid) has been deleted from position 508 of the amino acid chain. How will the amino acid deletion affect the CFTR protein structure?
It will affect the primary, secondary, and tertiary structures of the CFTR protein.
What is likely to occur as a result of an animal cell receiving a signal to initiate apoptosis?
Lysosomes will release digestive enzymes into the cytosol.
How can a scientist observe the transport of a solute across an artificial membrane?
Use a small, nonpolar solute instead of a protein.
What happens to water transport across the cell membrane without aquaporin?
Water molecules will still be able to move across the cell membrane but at a slower rate.
What is unique about archaea and bacteria?
No nuclear membrane surrounding their genetic material.
How is mitochondrial structure different in muscle cells because of the high energy demands of mitochondria?
The inner membrane of the mitochondria in muscle cells should have more folds to increase surface area, allowing more ATP to be synthesized.
What supports the claim that certain organelles evolved from free-living prokaryotic cells?
Some organelles contain their own DNA that is more similar to prokaryotic DNA in structure and function than to the eukaryotic DNA found in the cell’s nucleus.
Which of the following claims is scientifically accurate and consistent with an observation that a decrease in lysosome production within a cell leads to a decline in mitochondrial activity?
Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration.
Where does the newly synthesized protein go directly after the endoplasmic reticulum?
The Golgi Complex.
A spherical bacterial cell has a radius of 3 um. The human egg cell has a radius of 100 um. Which statement correctly indicates the cell that is able to more efficiently exchange materials with the external environment and provides a correct explanation?
The bacterial cell, because it has the largest surface-to-volume ratio.
Which best explains the orientation of the phospholipid molecules in the cell membrane?
The hydrophilic phosphate groups of the phospholipid molecules are attracted to the aqueous internal and external environments.
Most bacteria are small organisms with small volumes. Because of their size, bacteria can sometimes obtain nutrients by diffusion alone. In addition, bacteria contain numerous active transporters that move nutrients into the bacteria. What explains the need for active transporters in bacteria?
Diffusion can bring nutrients into the bacteria across the membrane only if their concentration is higher outside the bacteria than inside.
What can help ascertain if a membrane protein is a channel protein?
Add more proteins to the plasma membrane and measure particle movement rate.
Characteristics of the active transport pump used to move sodium ions across the membranes of gill cells in a freshwater fish:
Requires energy; has specific binding sites for ATP and sodium ions; is a protein
An investigator wants to understand whether a newly found membrane protein is involved in membrane transport of a certain particle. What will help determine whether the new membrane protein is a channel protein involved in membrane transport?
Add more of the proteins to the plasma membrane and measure the rate of the particle movement
A scientist designed an experiment to test an artificial membrane that mimics the phospholipid bilayer of a cell. The scientist built a tube that was divided by an artificial membrane and filled with distilled water. The scientist put a known amount of a protein into the water on one side of the membrane. After some time, the scientist measured the concentration of the protein on either side of the membrane but found that there had been no change. What experimental change would allow the scientist to observe transport of a solute across the artificial membrane?
Use a small, nonpolar solute instead of a protein.
Researchers propose a model to explain variation in phytoplankton cell sizes in a marine environment. They base their model on the idea that smaller cells absorb nutrients more efficiently. The researchers predict that the mean diameter of phytoplankton cells will change by 50 micrometers for every 5-kilometer increase in distance from the shore because of a gradual decrease in nutrient availability. To test their model, the researchers determine that the phytoplankton cells found closest to shore have a mean diameter of 900 micrometers. Based on the model, what will be the mean diameter of the phytoplankton cells that are found 25 kilometers from shore?
650 micrometers
Plant cell walls are composed of cellulose, while fungal cell walls are composed of chitin. A group of scientists hypothesize that this difference means the cell wall has largely different functions in plant cells and fungal cells. Alternatively, another group of scientists hypothesize that despite their biochemical differences, plant and fungal walls serve similar functions. Which of the following observations would best support the alternative hypothesis described above?
In both plant and fungal cells, the cell wall surrounds the outside of the cell membrane
A team of biologists develop a new drug, and one team member hypothesizes that the drug is incapable of freely passing across the plasma membrane and requires the help of membrane proteins to enter cells. Alternatively, another biologist on the team hypothesizes that the drug can diffuse passively across the plasma membrane like oxygen and carbon dioxide can. Which of the following, if true about the drug, supports the alternative hypothesis that the new drug will exhibit simple diffusion across the plasma membrane?
The drug is a small nonpolar molecule
During a lab a student is given a saliva sample from an unidentified animal. The student isolates a few cells from the saliva and examines the cells under a microscope. In one of the cells, the student observes an organelle that is able to replicate itself independently of the other organelles and contains its own DNA. Identify which organelle the student observed.
The mitochondrion.
Large numbers of ribosomes are present in cells that specialize in producing which molecules?
Proteins
Which organelles are extremely important to plant cells for the regulation of water and water pressure?
Vacuoles.
Which is true of lysosomes?
Small sacks with pores/contains digestive enzymes that get rid of waste, worn-out cell parts, and captured invaders.
Why are viruses not considered living organisms? Why are they able to achieve an extremely small size not found in any prokaryotes/eukaryotes?
They lack a nucleus or organelles and must infect a host to reproduce. Their volume is extremely small because their insides are quite empty because they don’t need organelles or a nucleus, so the entire virus is small.
The eukaryotic protozoan parasite P. falciparum is the causative agent of malaria. P. falciparum cells contain an organelle called the apicoplast. Apicoplasts synthesize precursors of biomolecules that are required for growth and reproduction of the parasite. Based on figure 1, describe two pieces of evidence a researcher could use to support the claim that apicoplasts evolved from free-living, prokaryotic organisms.
Has a double membrane (evolved from 2 distinct organisms that underwent endocytosis and became a singular apicoplast); has its own DNA that’s separate from the DNA of the entire cell (apicoplast has its own nucleus and likely came from distinct, free-living organisms)
Cystic fibrosis is a genetic condition that is associated with defects in the CFTR protein. The CFTR protein is a gated ion channel that requires ATP binding in order to allow chloride ions to diffuse across the membrane. In the provided model of a cell, draw arrows to describe the pathway for production of a normal CFTR protein from gene expression to final cellular location.
From the nucleus through the ER to the Golgi to the plasma membrane (NOT through the mitochondrion or lysosome).
What distinguishes primary from secondary active transport and how is one of the dependent on the other?
Primary directly uses cellular energy of ATP to move molecules against concentration gradient; secondary uses the concentration gradient created by primary active transport to move the molecule across the cell.
What model describes our understanding of the cell membrane?
The fluid mosaic model.
A researcher claims that the synthesis of ATP from ADP and inorganic phosphate is essential to cellular function. What best helps justify the researcher’s claim?
ATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy
In chloroplasts, ATP is synthesized from aDP plus inorganic phosphate in a reaction catalyzed by ATP synthase molecules that are embedded in the thylakoid membrane. What provides evidence to support the claim that no ATP will be synthesized in the absence of a proton gradient across the thylakoid membrane?
No ATP is synthesized when channel proteins that allow the free passage of protons are inserted into the thylakoid membrane.
A researcher claims that different metabolic pathways allow bacteria to use different molecules as sources of matter and energy. What best helps justify the researcher’s claim by providing a relevant example?
E. coli bacteria reproduce in liquid media containing either glucose or galactose
A scientist claims that Elysia chlorotica, a species of sea slug, is capable of photosynthesis. What provides the best evidence to support the claim?
Elysia chlorotica grows when exposed to light in the absence of other food sources
Which statement accurately describes a similarity between photosynthesis and cellular respiration?
Both increase the entropy of the cell
In a study to evaluate new agricultural products, researchers treated plants with an experimental synthetic chemical to see if it would kill the plants. The researcher observed that after the chemical treatment, the plants continued to consume water and produce oxygen, but they stopped producing ATP and NADPH. The plants subsequently died as a consequence of having insufficient ATP. Based on the data provided, which is the most likely description of the chemical activity?
The chemical probably inhibits the photosynthetic electron transport chain.
What characterizes anaerobic respiration?
Has mitochondria but substitutes another molecule for oxygen.
What does fermentation produce?
Intermediate and NADPH, and it doesn’t require mitochondria.
A researcher proposes a model of an enzyme-catalyzed reaction in which a reactant is converted to a product. The model is based on the idea that the reactant passes through a transition state within the enzyme-substrate complex before the reactant is converted to the product. What best helps explain how the enzyme speeds up the reaction?
The enzyme’s active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction.
What explains an enzyme's reaction specificity?
The shape and charge of the substrates are compatible with the active site of the enzyme
The enzyme hexokinase catalyzes the conversion of glucose to glucose-6-phosphate, which is an important step in glycolysis. The reaction involves the transfer of a phosphate group from ATP to glucose. Either a glucose molecule or a water molecule can fit in the active site of hexokinase. The presence of a water molecule in hexokinase’s active site would result in the hydrolysis of ATP to ADP instead of the conversion of glucose to glucose-6-phosphate. What best helps explain the reaction specificity of hexokinase?
Glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not.
A researcher designs an experiment to investigate the effect of environmental temperature on the function of an enzyme. For each trial included in the experiment, the researcher will add the enzyme and its substrate to an aqueous buffer solution and then measure the amount of product formed over 20 minutes. What must remain the same for all trials of this experiment?
The initial concentration of the substrate.
Alcohol dehydrogenase (ADH) is an enzyme that aids in the decomposition of ethyl alcohol into nontoxic substances. Methyl alcohol acts as a competitive inhibitor of ethyl alcohol by competing for the same active side on ADH. when attached to ADH, methyl alcohol is converted to formaldehyde, which is toxic in the body. What best predicts the effect of increasing the concentration of substrate (ethyl alcohol), while keeping the concentration of the inhibitor (methyl alcohol) constant?
Competitive inhibitors will decrease because the proportion of the active sites occupied by substrate will increase.
A researcher claims that only a portion of the light energy captured by green plants is available for growth and repair. What best helps justify the researcher’s claim?
As light energy is converted to chemical energy by metabolic processes, some of the energy is lost as heat.
In addition to the pigments commonly associated with photosynthesis, a certain photosynthetic species contains two additional pigment types. What best supports the claim that this species is better adapted to environmental changes than other photosynthetic species are?
The additional pigments allow the species containing them to harvest energy from wavelengths of light that the other photosynthetic species cannot use
Which statement is true regarding Earth’s earliest organisms?
These organisms likely carried out fermentation and may have had rudimentary proton pumps
Which stage in cellular respiration produces carbon dioxide?
The Krebs cycle.
Many chemical reactions that take place inside the cell require an input of energy. Which best describes how these reactions can occur?
The reactions utilize energy released from hydrolysis of ATP
What types of reactions have a net use of energy?
Anabolic and endergonic reactions.
What type of inhibitor occupies the active site?
Competitive.
How does ADP turn into ATP?
By adding a phosphate.
Folded inner membranes in mitochondria increase their
Surface area.
What is the ultimate source of energy?
Solar energy.
Which of the following observations provides the best evidence that acetyl-CoA negatively regulates pyruvate dehydrogenase activity?
The rate of the pyruvate dehydrogenase-catalyzed reaction is slower in the presence of a higher concentration of acetyl-CoA
Antidiuretic hormone (ADH) is important in maintaining homeostasis in mammals. ADH is released from the hypothalamus in response to high tissue osmolarity. In response to ADH, the collecting duct and distal tubule in the kidney become more permeable to water, which increases water reabsorption into the capillaries. The amount of hormone released is controlled by a negative feedback loop. Based on the model presented, what expresses the proper relationship between osmolarity, ADH release, and urine production?
As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine
Cancer can result from a variety of different mutational events. What is LEAST likely to result in the initiation of a cancer tumor?
A defect in a cell-cycle checkpoint prevents a cell from entering the S phase
Most cells that have become transformed into cancer cells have which of the following characteristics when compared to normal, healthy cells?
Shorter cell cycles
A human liver cell reaches the end of G1 but fails to move into S phase researchers treat the cell with chemicals that stain the DNA to make it visible. The stains indicate that the liver cell’s DNA is undamaged. What is a possible explanation for why the cell can’t enter the S phase?
The cyclin-CDK complex for G1 is unable to form
Receptor proteins in cell signaling and cyclin-dependent kinases (CDKs), in the regulation of the cell cycle function similarly in which way?
They both change shape and activate upon binding a ligand or cyclin
Cancers that spread by metastasis
Usually include many different mutations in the DNA
Eukaryotic cells that don’t divide
Remain in the G0 phase most of the time
Which of the following processes take roughly 90-95% of the time of cellular division?
Interphase
The genetic material of the daughter cells (after mitosis) are:
Identical to the parent cell’s genetic material
How is a hydrophobic signal molecule’s effect on the cell different from that of a hydrophilic signal molecule?
Hydrophobic easily passes through the membrane and phospholipid bilayer, binds to a receptor on intracellular domain and permanently changes the cell; hydrophilic is harder to pass through the membrane and bilayer, binds to a receptor on extracellular domain, has a short-lived effect and needs to be redone if needed again
Which feedback mechanism is associated with negative feedback loops and why?
Homeostasis: stimulus disrupts balance so cell acts to restore that balance, but the cell is sensitive to its own output and needs to downplay response so the balance remains
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