Biology Test #1 Flashcards

Questions and Answers

Protein phosphorylation is commonly involved with all of the following EXCEPT _____.

Activation of G protein-coupled receptors (correct)

Regulation of enzyme activity

Cell signaling pathways

Gene expression

The toxin of Vibrio cholerae causes profuse diarrhea because it _____.

modifies a G protein involved in regulating salt and water secretion

Which of the following poses the best evidence that cell-signaling pathways evolved early in the history of life?

Signal transduction molecules found in the distantly related organisms are similar

Which of the following statements is true of signal molecules?

Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors Signup and view all the answers

Magnesium has an atomic number of 12. What is the most stable charge for a magnesium ion?

2+ Signup and view all the answers

What results from an unequal sharing of electrons between atoms?

polar covalent bond Signup and view all the answers

How many electrons are involved in a double covalent bond?

4 Signup and view all the answers

What is the maximum number of hydrogen atoms that can be covalently bonded in a molecule containing two carbon atoms?

6 Signup and view all the answers

What is the difference between covalent bonds and ionic bonds?

Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between charged atoms. Signup and view all the answers

Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers from 92-100. Therefore, which of the following can be true?

Molybdenum atoms can have between 50-58 neutrons Signup and view all the answers

In what way are elements in the same column of the periodic table the same? They have the same number of _____.

electrons in their valence shells when neutral Signup and view all the answers

What do you predict to be the charge on ammonium?

+1 Signup and view all the answers

If you change the number of neutrons in an atom, you create ____.

isotope Signup and view all the answers

Which of the following is a trace element that is required by humans and other vertebrates, but not by other organisms such as bacteria or plants?

Iodine Signup and view all the answers

How many electron pairs are shared between carbon atoms in a molecule that has the formula C2H4?

2 Signup and view all the answers

When are atoms most stable?

Atoms are most stable when they have satisfied the octet rule. Signup and view all the answers

What is true for the reaction 3H2 + N2 = 2NH3?

Ammonia is being formed and decomposed simultaneously. Signup and view all the answers

What correctly describes all chemical equilibrium?

Forward and reverse reactions continue with no net effect on the concentrations of the reactants and products. Signup and view all the answers

What is the atomic mass of an oxygen atom?

approximately 16 daltons Signup and view all the answers

Bonds between two atoms that are equally electronegative are _____.

nonpolar covalent bonds Signup and view all the answers

How many electrons are involved in a single covalent bond?

two Signup and view all the answers

Which bond or interaction would be difficult to disrupt when compounds are put into water?

covalent bonds between carbon atoms Signup and view all the answers

What describes a reaction that has reached chemical equilibrium?

The rate of the forward reaction is equal to the rate of the reverse reaction. Signup and view all the answers

Why are lipids and proteins free to move laterally in membranes?

There are only weak hydrophobic interactions in the interior of the membrane. Signup and view all the answers

The voltage across a membrane is called the _____

membrane potential Signup and view all the answers

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane. Signup and view all the answers

What determines whether a drug molecule selectively enters target cells?

similarity of the drug molecule to other molecules transported by the target cells Signup and view all the answers

Define diffusion.

is a passive process in which molecules move from a region of higher concentration. Signup and view all the answers

What happens to the membrane's permeability to glucose when increasing the proportion of unsaturated phospholipids?

Permeability to glucose will increase. Signup and view all the answers

Why do unsaturated fatty acids help keep a membrane more fluid at lower temperatures?

The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. Signup and view all the answers

According to the fluid mosaic model of cell membranes, phospholipids can _____.

move laterally along the plane of the membrane Signup and view all the answers

Why are cell membranes asymmetrical?

The two sides of a cell membrane face different environments and carry out different functions. Signup and view all the answers

Which proteins are NOT embedded in the hydrophobic portion of the lipid bilayer?

peripheral proteins Signup and view all the answers

How is lactose classified?

as a disaccharide Signup and view all the answers

Define a lipid.

A lipid consists of a glycerol molecule which is bonded to three long fatty acid chains. Signup and view all the answers

What are nucleic acids made of?

nucleotides Signup and view all the answers

How many molecules of water are used to completely hydrolyze a polymer that is 11 monomers long?

10 Signup and view all the answers

The polypeptide sequence of hemoglobin from a new organism has many differences. This suggests the new organism is more closely related to _____

frogs than to humans Signup and view all the answers

Which polysaccharide is an important component in the structure of many animals and fungi?

chitin Signup and view all the answers

Normal hemoglobin is a tetramer. In sickle-cell disease, hemoglobin exhibits what?

altered primary and quaternary structure; secondary and tertiary structure may or may not be altered. Signup and view all the answers

What is the major ingredient of margarine?

is solid at room temperature Signup and view all the answers

What is a protein molecule that assists in the proper folding of other proteins called?

chaperonin Signup and view all the answers

Why can humans digest starch but not cellulose?

Humans have enzymes that can hydrolyze the α-glycosidic linkages of starch but not the β-glycosidic linkages of cellulose. Signup and view all the answers

Which one of the following is NOT a component of each monomer used to make proteins?

a phosphorus atom, P Signup and view all the answers

Why does ice float in liquid water?

Ice floats in liquid water because of its lower density as a solid than as a liquid. Signup and view all the answers

What is the predicted outcome when NaCl crystals are added to pure water and pure methanol?

NaCl crystals will dissolve readily in water but not in methanol. Signup and view all the answers

What is the rarest property among compounds regarding water?

solid water is less dense than liquid water Signup and view all the answers

The partial negative charge in a molecule of water occurs because _____

the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus Signup and view all the answers

Why do Portland and Minneapolis have different climates despite their similar latitudes?

The ocean is so large that it has a highly moderating influence on temperature. Signup and view all the answers

Which of the following is true of carbon?

It can form polar and nonpolar bonds. Signup and view all the answers

Compared to a hydrocarbon chain where all the carbon atoms are linked by single bonds, what happens with chains that have double bonds?

will be more constrained in structure Signup and view all the answers

What kind of bond(s) is a carbon atom most likely to form with other atoms?

covalent Signup and view all the answers

Which two functional groups are always found in amino acids?

carboxyl and amino groups Signup and view all the answers

Stanley Miller's 1953 experiments supported which hypothesis?

Organic molecules can be synthesized abiotically under conditions that may have existed on early Earth. Signup and view all the answers

Which amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction?

serine and threonine Signup and view all the answers

What is characteristic of a steroid hormone action?

Internal receptor binding Signup and view all the answers

What would be inhibited by a drug that blocks the addition of phosphate groups to proteins?

receptor tyrosine kinase activity Signup and view all the answers

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions?

ligand-gated ion channel Signup and view all the answers

What do phosphatases do in signal transduction?

inactivate protein kinases and turn off the signal transduction Signup and view all the answers

What is true during a typical cAMP-type signal transduction event?

Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs. Signup and view all the answers

Why do molecules involved in hydrogen bonding almost always contain either oxygen or nitrogen or both?

Oxygen and nitrogen are elements with very high attractions for their electrons. Signup and view all the answers

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by _____

polar covalent bonds Signup and view all the answers

Rank, from low to high, the pH of blood, stomach acid, and urine.

stomach acid, urine, blood Signup and view all the answers

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?

cell-cell recognition Signup and view all the answers

What digests a bacterium engulfed by a white blood cell through phagocytosis?

lysosomes Signup and view all the answers

How do the membranes of winter wheat remain fluid in extremely cold temperatures?

increasing the percentage of unsaturated phospholipids in the membrane Signup and view all the answers

What is a characteristic feature of a carrier protein in a plasma membrane?

It exhibits a specificity for a particular type of molecule. Signup and view all the answers

What does the use of proton pumps imply about the common ancestor of all three domains of life?

Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life. Signup and view all the answers

What is the difference between pinocytosis and receptor-mediated endocytosis?

pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity. Signup and view all the answers

Which membrane activity requires energy from ATP?

movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid Signup and view all the answers

Where do receptor molecules end up after endocytosis?

on the inside surface of the vesicle Signup and view all the answers

Why is the sodium-potassium pump called an electrogenic pump?

contributes to the membrane potential Signup and view all the answers

What describes the movement of phospholipids in a membrane according to the fluid mosaic model?

can move laterally along the plane of the membrane Signup and view all the answers

How do starch and cellulose compare?

are polymers of glucose Signup and view all the answers

What best fits the class of molecules known as nucleotides?

a nitrogenous base, a phosphate group, and a sugar Signup and view all the answers

Why are steroids considered lipids?

are not soluble in water Signup and view all the answers

What happens when a single amino acid in a protein consisting of 325 amino acids is changed?

always alter the primary structure of the protein, sometimes alter the tertiary structure of the protein, and sometimes affect its biological activity Signup and view all the answers

Which polysaccharide is an important component in the structure of many animals and fungi?

chitin Signup and view all the answers

Which of the following contain amino acids?

cholesterol Signup and view all the answers

What best summarizes the relationship between dehydration reactions and hydrolysis?

Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers. Signup and view all the answers

What is the highest level of structure found in proteorhodopsin, a light-sensitive molecule?

tertiary Signup and view all the answers

What are saturated fatty acids characterized by?

Signup and view all the answers

Why is carbon so important in biology?

It can form a variety of carbon skeletons and host functional groups. Signup and view all the answers

What can organic molecules with only hydrogens and five carbon atoms not do?

form enantiomers Signup and view all the answers

Compared to a hydrocarbon chain with only single bonds, a hydrocarbon chain with double bonds will _____.

be more constrained in structure Signup and view all the answers

Why are hydrocarbons insoluble in water?

The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages. Signup and view all the answers

In the formation of biofilms, what function does cell signaling serve?

aggregation of bacteria that can cause cavities Signup and view all the answers

What is programmed cell death called?

apoptosis Signup and view all the answers

Describing apoptosis, what happens during this event?

During apoptosis, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components of a cell. Signup and view all the answers

Study Notes

Trace Elements

Iodine is a trace element required by humans and other vertebrates but not by bacteria or plants.

Chemical Bonds

In a molecule with the formula C2H4, carbon atoms share 2 electron pairs.
Atoms achieve stability by satisfying the octet rule, needing eight valence electrons for a full outer shell.
Nonpolar covalent bonds exist between two atoms of equal electronegativity.
A single covalent bond involves two electrons.

Reactions and Chemical Equilibrium

Ammonia (NH3) formation occurs simultaneously with decomposition in the reaction 3H2 + N2 ↔ 2NH3.
In chemical equilibrium, forward and reverse reactions occur without net change in reactant and product concentrations.

Atomic Structure and Mass

Oxygen has an atomic number of 8 and a mass number of approximately 16 daltons.

Membrane Dynamics

Lipids and proteins in membranes can move laterally due to weak hydrophobic interactions.
Membrane potential refers to the voltage across a cellular membrane.
The unique proteins in each eukaryotic membrane contribute to membrane variation.
Increased unsaturated phospholipids raise membrane permeability to glucose.

Fluid Mosaic Model

Phospholipids can laterally move within the membrane, making cell membranes fluid.
The asymmetrical nature of membranes facilitates differing functions on either side.

Biological Molecules

Lactose is classified as a disaccharide, composed of glucose and galactose.
Lipids are composed of glycerol and three fatty acid chains.
Nucleic acids consist of nucleotide monomers.

Hydrolysis and Dehydration Reactions

Hydrolyzing a polymer of 11 monomers requires 10 molecules of water.
Dehydration reactions build polymers, while hydrolysis reactions break them down.

Protein Structure

Hemoglobin is a tetramer that can have altered structures in sickle-cell disease.
Chaperonins assist in the proper folding of proteins.

Enzyme Activity

Humans have enzymes for digesting starch but not cellulose, due to differences in glycosidic linkages.

Carbon Chemistry

Carbon can form polar and nonpolar bonds, making it versatile in biological systems.
Hydrocarbons are generally insoluble in water due to their nonpolar covalent links.

Signal Transduction

Phosphorylation is essential in protein signaling pathways, affecting receptor functions.
Ligand-gated ion channels alter ion distributions across membranes upon signaling molecule binding.

Properties of Water

Ice floats on liquid water due to lower density as a solid, allowing for environmental sustainability.
Water molecules' partial negative charge arises from unequal electron sharing between oxygen and hydrogen.

Cellular Processes

Apoptosis is programmed cell death involving DNA and organelle fragmentation.
In receptor-mediated endocytosis, receptors end up on the vesicle's inside surface after internalization.

ATP and Cellular Energy

Active transport, like the sodium-potassium pump, requires ATP to move ions against their concentration gradient.

Atomic Number and Isotopes

Magnesium's stable ion charge is +2.
Molybdenum can have 50-58 neutrons due to its isotopes with varying mass numbers.

Summary of Compounds

Starch and cellulose are both glucose polymers.
Nucleotides consist of nitrogenous bases, phosphate groups, and sugars.

General Chemistry

Covalent bonds involve electron sharing, while ionic bonds arise from electrical attraction between charged atoms.
Elements in the same periodic table column share the same number of valence electrons, influencing reactivity and properties.

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Description

Test your knowledge of essential biology concepts with this set of flashcards. Covering trace elements, molecular structures, and atomic stability, this quiz is perfect for students seeking to reinforce their understanding of biological principles. Challenge yourself and improve your retention of key terms in biology.