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Which of the following statements about proteins is true?
A) The sequence of amino acids is the primary structure of the protein.
B) For each amino acid joined to a polypeptide chain, two water molecules areformed.
C) The covalent bond that joins amino acids together is called a phosphodiesterbond.
D) The peptide backbone consists of the repeating sequence sugar-nitrogen-sugar.
A is correct
because the sequence of amino acids is theprimary structure, the secondary structure is formed by interactionsbetween stretches of amino acids.
Which of the following is NOT TRUE of a denatured protein?
A) hydrogen bonds are disrupted
B) enzyme activity would be inhibited
C) secondary structure is disrupted
D) primary structure is disrupted
E) The three-dimensional shape of the protein is altered
D is correct
primary structure is not disrupted because adenatured protein still maintains is sequence of amino acids.
A cell with a basic pH (relative to the solution outside the cell)contains ________________.
A) Higher concentration of H+ ions inside the cell than outside the cell
B) Lower concentration of H+ ions inside the cell than outside the cell
C) No H+ ions
D) The same concentration of H+ ions inside the cell as outside the cell
B is correct
because a basic (higher) pH has a lower H+ concentration. An acidic (lower) pHhas a higher H+ concentration.
Ice floats because water...
A) is a good solvent for polar compounds
B) has high surface tension.
C) is denser as a liquid than a solid.
D) it is a good solvent for nonpolar compounds
Answer C is correct
because density of ice is less than that of water.
Given the following DNA sequence, 5'ATGCTTAAC3' choose the correct complementary strand:
A) 5'GCCAAGCAT3'
B) 5'CAATTCGTA3'
C) 5'TAGCGGCCA3'
D) 5'GTTAAGCAT3'
E) All of the above are correct.
D is correct
In order to do this the students must construct the complementary strand in5'3' direction. Remember the complementary strand is antiparallel meaning itruns the opposite direction. A-T and C-G.
During DNA replication ______________.
A) hydrogen bonds between complementary base pairs are broken.
B) only one strand is replicated.
C) RNA is used as the template strand.
D) four new strands are synthesized, two of which are destroyed.
E) the final replicated DNA contains two new or two old stands.
A is correct -
In order for semiconservative replication (replication where each new dsDNA molecule contains one old strand) to take place the original DNA helix must come apart to produce two templates for DNA synthesis.
According to the fluid-mosaic model of membrane structure, anintegral membrane protein will __________.
A) include cholesterol in its amino acid side chains.
B) be covalently bound to the lipid bilayer.
C) contain only polar amino acids
D) contain polar and non-polar regions
D is correct-
has both hydrophobic and hydrophilic regions. An integral membrane protein has a region inside the membrane and region(s) outside. The internal regions will be hydrophobic the external regions will be hydrophilic. Therefore, it will be polar and nonpolar.
In biological membranes, the phospholipids are arranged in a___________.
A) bilayer with the fatty acid tails pointing toward each other.
B) bilayer with the fatty acid tails facing outward.
C) single layer with the fatty acid tails facing the interior of the cell.
D) single layer with the phosphorus-containing region facing theinterior of the cell.
E) bilayer with the phosphorus groups facing the interior of themembrane.
A is correct -
The tails are hydrophobic and therefore avoidwater and face in.
_______ is a gateway that allows molecules to move into and outof the nucleus.
A) active transport
B) Channel
C) Nuclear Pore
D) Osmosis
C is correct
The nuclear pore is the opening between the nucleus and the rest of the cell.
_______ is the passive movement of water across a selectivelypermeable membrane, from a region of low solute (high water) concentration to a region of high solute (low water) concentration.
A) active transport
B) Channel
C) Nuclear Pore
D) Osmosis
D is correct
Osmosis is the diffusion of water across a semipermeable membrane, fromareas of lower solute (higher water) concentration to an area of higher solute(lower water) concentration.
When animal cells are in a hypotonic medium (relative to the cellinterior),
A) they shrink
B) turgor pressure increases
C) they will burst
D) their vacuole will shrink
E) they lose water to the environment
C is correct-
A hypotonic solution has fewer particles pervolume than the cell placed in it. Therefore a hypotonic solution willcause an influx of water molecules into the cell. This will cause it toexpand and burst.
You isolated an mRNA that encodes proteins A, B, and C in this order in E. coli. When youinsert it into a prokaryotic cell, you obtain protein(s) ________. If you add a 5'-cap and a polyAtail to the mRNA and inject this mRNA into a eukaryotic cell, you obtain protein(s) -________.This is because the mRNA is ___________.
A) ABC ; ABC ; monocistronic
B) ABC ; A ; polycistronic
C) A ; ABC ; monocistronic
D) A ; ABC ; polycistronic
B is correct-
a polycistronic message has multiple genes encoded in a single mRNA molecule. In bacteria, the message will have multiple Shine-Dalgarno sequences allowing ribosomes to bind in front of each gene, find the start codon, and translate the gene. In eukaryotes the ribosome binds the 5' cap and scans for the start codon, therefore they will only find the start codon of the first gene.
The anti-codon sequence of a tRNA is ACG. What amino acid will be attached to this tRNA?
A) Ala
B) Arg
C) Cys
D) Ser
E) Thr
B is correct-
the reverse compliment of ACG is CGU, which encodes Arg.
What is the difference between a hypothesis, theory, and prediction?
Hypothesis: A testable statement or educated guess based on observations.
Theory: A well-substantiated explanation of some aspect of the natural world, based on a body of evidence.
Prediction: A forecast of future events based on the hypothesis or theory.
What is the central dogma of molecular biology?
The process by which genetic information is transferred from DNA to RNA to protein:
DNA → RNA → Protein
What are the common features of living organisms, and why don't viruses qualify as living organisms?
Common features of living organisms:
Ability to reproduce
Growth and development
Metabolism
Response to stimuli
Adaptation through evolutionViruses don't qualify because they can't reproduce or carry out metabolic processes on their own and require a host cell.
What are common features of cells, and why are they considered the smallest unit of life?
Cells have:
A membrane
Genetic material (DNA/RNA)
Ribosomes for protein synthesis
Metabolic activityThey are considered the smallest unit of life because they are capable of performing all essential life processes.
What is the difference between prokaryotes and eukaryotes?
Prokaryotes: Simple cells without a nucleus or membrane-bound organelles (e.g., bacteria).
Eukaryotes: Complex cells with a nucleus and membrane-bound organelles (e.g., animal and plant cells).
Why is DNA considered the blueprint for life?
DNA contains the genetic instructions needed for the growth, development, functioning, and reproduction of organisms.
Given a scenario, how can you recognize or formulate an observation, hypothesis, prediction, or experiment?
Observation: Noticing something in the environment.
Hypothesis: A testable explanation for the observation.
Prediction: A specific outcome based on the hypothesis.
Experiment: A test to support or refute the hypothesis.
What is the difference between a control group and a test group?
Control group: The group that does not receive the experimental treatment and serves as a baseline.
Test group: The group that receives the experimental treatment.
What is transcription?
Transcription is the process by which an RNA copy is made from a DNA template.
What is translation?
Translation is the process by which RNA is used as a template to synthesize proteins.
What is metabolism?
Metabolism refers to all the chemical reactions that occur within a cell to maintain life, including breaking down substances to release energy and building up substances needed for growth and repair.
How is scientific inquiry used to answer questions about the natural world?
Scientific inquiry uses observation, hypothesis formation, experimentation, and analysis to gain knowledge and test explanations about the natural world.
How do you use the scientific method to form a hypothesis about observations?
Observe something in the natural world, ask a question, propose a possible explanation (hypothesis), and test it through experiments.
What are the common features of living organisms?
Common features include the ability to reproduce, grow and develop, maintain homeostasis, undergo metabolism, respond to stimuli, and adapt to the environment.
Why is a cell considered the smallest unit of life?
A cell can perform all the basic functions of life, including reproduction, metabolism, and response to stimuli, making it the smallest unit capable of independent life.
Compare and contrast prokaryotes and eukaryotes.
Prokaryotes: No nucleus, no membrane-bound organelles, smaller size (e.g., bacteria).
Eukaryotes: Have a nucleus, have membrane-bound organelles, larger size (e.g., animal, plant cells).
Draw and describe the central dogma of molecular biology.
The central dogma describes the flow of genetic information:
DNA (genetic code) → RNA (messenger molecule) → Protein (functional product).This process includes transcription and translation.
How does a scientist turn an observation into a hypothesis and investigate that hypothesis?
An observation is a phenomenon you notice in the world, prompting a question about it. A hypothesis is a tentative answer to that question, based on personal experience or previous research. From the hypothesis, you make a prediction, which can be tested through experiments or further observations. If the hypothesis is rejected, a new one is formed and tested. If the results support the hypothesis, it becomes more certain.
What are the differences among a guess, hypothesis, and theory?
A guess is an untested assumption, while a hypothesis is a testable explanation that predicts outcomes. A theory is a well-supported, broad explanation based on multiple tested hypotheses, like the theory of evolution, which has been validated over time.
Mice that live in sand dunes commonly have light tan fur. Develop a hypothesis to explain this coloration.
One hypothesis is that their tan fur protects the mice from predators by allowing them to blend in with their surroundings.
What are the differences between a test group and a control group, and why is it important for an experiment to have both types?
A controlled experiment includes test groups, where a single variable is introduced, and a control group, where no variable is changed. Keeping conditions similar, researchers compare results to determine if the variable has an effect.
How would you design a controlled experiment to test the hypothesis that cigarette smoke causes lung cancer?
This experiment tests the effect of cigarette smoke on cancer development in mice. The test group is exposed to smoke, while the control group is not. If the test group develops cancer at significantly higher rates, it suggests a link between smoke exposure and cancer.
What does it mean to say that a cell is life's functional unit?
A cell is the basic unit of life, capable of independent existence. While some organisms are multicellular, others exist as a single cell. All cells have a boundary separating them from the environment and can obtain materials and energy to sustain life.
How does the central dogma help us to understand how mutations in DNA can result in disease?
DNA directs protein formation, which enables cell function. Mutations can alter protein structure, potentially causing malfunction and disease or, in some cases, improving cell function.
In the early 1900s, Ernest Rutherford produced a beam of very small positive particles and directed it at a thin piece of gold foil just a few atoms thick.
Most of the particles passed through the foil without changing their path; very rarely, a particle was deflected. What conclusions can you draw from this experiment about the structure of an atom?
Atoms are mostly empty space, allowing most particles to pass through without deflection. The nucleus, containing densely packed protons, is small but highly concentrated with positive charge.
What are atoms made up of? Describe each component.
An atom consists of protons (positively charged), neutrons (neutral), and electrons (negatively charged). The nucleus, made of protons and neutrons, is dense, while electrons orbit the nucleus in areas called orbitals, where they are most likely to be found.
What is the logic behind how the periodic table of the elements is organized?
The periodic table is organized by increasing atomic number, which represents the number of protons in an atom's nucleus. Elements in the same column share similar chemical properties and have the same number of electrons in their outermost orbital. Elements in the same row have the same number of energy levels (shells) and orbitals.
What are the differences between covalent bonds and polar covalent, hydrogen, and ionic bonds?
A covalent bond occurs when two atoms share valence electrons, with each shared pair forming a bond. In a polar covalent bond, electrons are not shared equally, creating partial positive and negative charges. A hydrogen bond forms when a hydrogen atom, covalently bonded to an electronegative atom, interacts with another electronegative atom. An ionic bond forms when one atom loses an electron (positive charge) and another gains an electron (negative charge), causing the two oppositely charged molecules to attract.
Why do containers of water, milk, soda, and other liquids sometimes burst when frozen?
Ice is less dense than liquid water, causing it to expand when it freezes. This expansion can lead to the bursting of closed containers, like soda cans or water pipes. This is unusual because, for most substances, the solid phase is denser than the liquid phase.
What are three properties of water that make water conducive to life?
Water has several properties that support life. As a polar molecule, it attracts hydrophilic substances and repels hydrophobic ones, helping form lipid cell membranes. Its polar nature also makes it an excellent solvent for hydrophilic compounds. Water's neutral pH (around 7) is essential for cellular reactions, as many require a near-neutral environment. Extensive hydrogen bonding allows water to resist temperature changes, helping regulate cellular and global temperatures. Ice, formed through hydrogen bonds, is less dense than liquid water, allowing it to float and protect aquatic life. Lastly, water's cohesion and surface tension aid in water transport in plants.
What are the four most common elements in organic molecules?
The four most common elements in organic molecules, in order of decreasing abundance by dry mass, are carbon, oxygen, hydrogen, and nitrogen.
What features of carbon allow it to form diverse structures?
Carbon has several features that enable it to form diverse structures. It has four unpaired electrons, allowing it to bond covalently with up to four atoms. These bonds can rotate freely, contributing to structural variety. Carbon atoms can also bond with other carbon atoms, forming chains, branches, or rings. Additionally, carbon can form double bonds, which share two electrons. Unlike single bonds, double bonds do not rotate freely, limiting the molecule's flexibility and structural possibilities.
What are the essential functions of proteins, nucleic acids, carbohydrates, and lipids?
Proteins act as catalysts, speeding up chemical reactions and providing structural support to cells. Nucleic acids store and transmit genetic information. Carbohydrates offer an energy source and are a key component of cell walls in bacteria, plants, and algae. Lipids store energy, function as signaling molecules, and form the cell membranes.
How is diversity achieved in polymers? Use proteins as an example.
Diversity is achieved in polymers through numerous combinations of subunits. A protein, for example, is a polymer of amino acid subunits. As we discuss in Chapter 5, there are 20 different kinds of amino acids. Thus, any combination of subunits can be made, each resulting in a different protein. In this way, polymers are capable of displaying virtually limitless diversity.
What are the three main parts of an atom?
Protons, neutrons, and electrons.
Where are protons and neutrons located?
In the nucleus of the atom.
What information does the atomic number provide?
number of protons
How do electrons differ in energy depending on their location?
Electrons in higher energy levels (farther from the nucleus) have more energy.
What are the four main types of chemical bonds?
Covalent, ionic, hydrogen, and van der Waals bonds.
What is a covalent bond?
A bond formed when two atoms share electrons.
What is an ionic bond?
A bond formed when electrons are transferred from one atom to another, creating charged ions.
What is a hydrogen bond?
A weak attraction between a slightly positive hydrogen atom and a slightly negative atom (often oxygen or nitrogen).
What causes van der Waals interactions?
Weak attractions due to temporary charge fluctuations in molecules.
Why does water have unique properties like cohesion and surface tension?
Due to hydrogen bonding between water molecules.
What makes a molecule hydrophilic?
Being polar or charged, allowing it to dissolve in water.
What makes a molecule hydrophobic?
Being nonpolar, causing it to repel water.
Why is carbon so versatile in forming molecules?
It can form four covalent bonds, allowing for complex structures.
What are the monomers of proteins?
Amino acids.
What are the monomers of nucleic acids?
nucleotides
What are the monomers of carbohydrates?
monosaccharides (simple sugars)
What reaction forms polymers from monomers?
Dehydration synthesis (condensation reaction).
What reaction breaks down polymers?
hydrolysis
What are the main characteristics of lipids?
Hydrophobic, energy storage, and structural components of membranes.
What determines whether a triglyceride is solid or liquid at room temperature?
The presence of saturated (solid) or unsaturated (liquid) fatty acid tails.
How does DNA differ from RNA?
DNA has deoxyribose sugar and is double-stranded, while RNA has ribose sugar and is single-stranded.
What are the base pairing rules for DNA?
A pairs with T, and C pairs with G.
Prokaryotic cells
Prokaryotic cells lack a nucleus and membrane-bound organelles.
Eukaryotic cells
Eukaryotic cells have a nucleus and membrane-bound organelles.
Common features of all cells
Cell membrane, cytoplasm, ribosomes, and DNA.
Cell wall
A rigid layer found in plant cells that provides structural support and protection.
Chloroplasts
Organelles in plant cells that conduct photosynthesis, converting light energy into chemical energy.
Large central vacuole
A prominent organelle in plant cells that stores nutrients and waste products and helps maintain turgor pressure.
Lysosomes
Organelles in animal cells that contain digestive enzymes to break down waste materials and cellular debris.
Centrioles
Cylindrical structures in animal cells that play a key role in cell division.
Structure of a phospholipid
A hydrophilic (polar) head and two hydrophobic (nonpolar) fatty acid tails.
Arrangement of phospholipids in a membrane
They form a bilayer with hydrophobic tails facing inward and hydrophilic heads facing outward.
Factors affecting membrane fluidity
Temperature, fatty acid tail length, degree of saturation, and cholesterol content.
Cholesterol effect on membrane fluidity
At high temperatures, it stabilizes the membrane; at low temperatures, it prevents it from becoming too rigid.
Small, nonpolar molecules
Molecules like oxygen, carbon dioxide, and steroid hormones that can easily cross the membrane without assistance.
Large, polar molecules
Molecules like glucose and ions that require transport proteins to cross the membrane.
Simple diffusion
The passive movement of molecules from high to low concentration without assistance.
Facilitated diffusion
The passive movement of molecules through transport proteins down their concentration gradient.
Passive transport
Does not require energy.
Active transport
Requires ATP.
Primary active transport
Transport that directly uses ATP to move molecules against their gradient (e.g., Na+/K+ pump).
Secondary active transport
Transport that uses the energy from one molecule moving down its gradient to move another molecule against its gradient.
Osmosis
The diffusion of water across a semi-permeable membrane from low solute concentration to high solute concentration.
Aquaporins
Channel proteins that facilitate water movement across the membrane.
Turgor Pressure
Pressure exerted by water inside the central vacuole; it helps maintain plant cell rigidity.
Components of the endomembrane system
Nuclear envelope, rough and smooth ER, Golgi apparatus, lysosomes, vesicles, and plasma membrane.
Function of the rough ER
Protein synthesis and modification.
Function of the Golgi apparatus
Modifies, sorts, and packages proteins and lipids for transport.
Mitochondria
ATP production through cellular respiration.
Chloroplasts
Photosynthesis, converting light energy into chemical energy.
amphipathic
A molecule with both hydrophilic and hydrophobic regions (e.g., phospholipids).
integral membrane proteins
Integral proteins span the membrane, while peripheral proteins are attached to the membrane surface.
peripheral membrane proteins
Integral proteins span the membrane, while peripheral proteins are attached to the membrane surface.
