home work for bio 120

Q1 Explain why the polarity of the water molecule enables it to hydrogen bond with other polar molecules.

Q2 Explain how phospholipids are involved in the structure and functioning of the plasma membrane.

Q3 How are structure and function related in proteins ?

Q4 Match the description to the corresponding structure.

  • A structure within the nucleus where ribosomal RNA is made?
  • The organelle of a eukaryotic cell that contains genetic material.
  • The portion of the endoplasmic reticulum that lacks ribosomes.
  • The organelle in eukaryotic cells where cellular respiration occurs?
  • The network of protein fibers in a eukaryotic cell that is responsible for movement and structure?
  • The portion of the endoplasmic reticulum that makes membrane proteins and secretory proteins?
  • The site of protein synthesis?
  • The complex of DNA and proteins that makes up eukaryotic chromosomes?
  • The thickest of the three main fibers in the cytoskeleton. A hollow tube made of proteins called tubulins.
  • The phospholipid bilayer at the boundary of every cell. It acts as a selective barrier to the passage of ions and molecules into and out of the cell?
  • The organelle that uses sunlight to drive the synthesis of glucose from carbon dioxide and water?

Q5 In the equation 2 H2 + O2 → 2 H2O, the H2 molecules are ________ and the H2O molecules are ________.

  • created; destroyed
  • products reactants
  • used; stored
  • reactants; products

Q6 A hydrogen atom has one electron. How many covalent bonds can hydrogen form?

  • four
  • two
  • one
  • none

Q7 ——————— are weak bonds that are not strong enough to hold atoms together to form molecules but are strong enough to form bonds within and around large molecules?

  • Hydrogen bonds
  • Polar covalent bonds
  • Covalent bonds
  • ionic bonds

Q8 Which of the following statements about water is false?

  • Ice is denser than liquid water
  • Water naturally exists in all three physical states on Earth.
  • Floating ice on a pond insulates the liquid water below, slowing its rate of freezing
  • If ice sank, the oceans would eventually freeze solid.

Q9 How are genes used by cells to build proteins?

  • The genes in RNA direct the synthesis of proteins directly.
  • DNA transcribed into an amino acid sequence
  • The genes in DNA direct the synthesis of an RNA molecule, which is used to build a protein.
  • The genes in RNA direct the synthesis of a DNA molecule, which is used to build a protein.

Q10 Which of the following statements is true for all types of passive transport?

  • The concentration gradient is the driving force.
  • Only small polar molecules are able to cross the plasma membrane.
  • Proteins are needed to transport molecules across the membrane.
  • ions never cross the plasma membrane by passive transport.

Q11 Which of the following statements regarding diffusion is false?

  • Diffusion occurs even after equilibrium is reached and no net change is apparent.
  • Diffusion occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated.
  • Diffusion is a result of the thermal energy of atoms and molecules.
  • Diffusion requires no input of energy into the system.

Q12 The primary structure of a protein is

٠

  • an alpha helix or a pleated sheet.
  • the amino acid sequence of the polypeptide chain.
  • composed of two or more polypeptide chains.
  • maintained by hydrogen bonds.

Q13 A plant cell in a hypotonic solution

  • shrivels because of an outflow of water.
  • becomes turgid because of an inflow of water.
  • wilts because of an outflow of water.
  • bursts because of an inflow of water.

Q14. Which of the following is a typical feature of an ATP -driven active transport mechanism?

  • The transport protein must cross to the correct side of the membrane before the solute can bind to it
  • The transport protein catalyzes the conversion of ADP to ATP
  • The transport protein catalyzes the conversion of ADP to ATP.
  • The transport protein is irreversibly phosphorylated as transport takes place.

Q 15 Which of the following lists contains only polysaccharides?

  • sucrose, starch, and cellulose
  • cellulose, starch, and glycogen
  • fructose, cellulose, and glucose
  • starch, amino acids, and glycogen

Q16 Aquaporins

  • allow water to cross the plasma membrane against its concentration gradient
  • are found in all cells.
  • allow water to cross the plasma membrane via facilitated diffusion.
  • allow for the active transport of water.

Q17 DNA differs from RNA because DNA

  • contains the sugar ribose rather than the sugar deoxyribose.
  • contains thymine in place of uracil.
  • contains phosphate groups not found in RNA

Q18 What is the atomic mass of an atom that has 6 protons, 6 neutrons, and 6 electrons ?

Q19 Which of the following statements regarding membrane protein function is false?

  • Membrane proteins form junctions between cells .
  • Membrane proteins serve as enzymes .
  • Membrane proteins produce phospholipids .
  • Membrane proteins act as receptors to molecules like hormones .

Q20 Plasma membranes are selectively permeable. This means that

  • anything can pass into or out of cell as long as the membrane is intact, and the cell is healthy.
  • plasma membranes must be very thick.
  • Glucose cannot enter the cell.
  • the plasma membrane allows some substances to enter or leave a cell more easily than others.

Q21 Which of the following substances is made of lipids?

  • steroids
  • cellulose
  • enzymes
  • DNA

Q22 Water molecules stick to other water molecules because?

  • the oxygen atoms of adjacent water molecules are attracted to one another
  • covalent bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of other water molecules.
  • hydrogen bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of other water molecules.
  • water molecules are neutral, and neutral molecules are attracted to each other.

Q23 Most of the functions of a cell membrane, including transport and enzymatic function are performed by

  • cholesterol.
  • phospholipids.
  • proteins
  • glycolipids.

Q24 In a water molecule, hydrogen and oxygen are held together by a ————— bond.

  • double covalent
  • polar covalent
  • nonpolar covalent
  • hydrogen

Q25 Organic compounds

  • are synthesized only by animal cells
  • always contain nitrogen.
  • always contain carbon.
  • always contain oxygen.

Q26 When two aqueous solutions that differ in solute concentration are placed on either side of a semipermeable membrane and osmosis is allowed to take place, the water will

  • exhibit a net movement to the side with higher free water concentration.
  • exhibit a net movement to the side with lower solute concentration.
  • exhibit an equal movement in both directions across the membrane.
  • exhibit a net movement to the side with lower free water concentration.

Q27 What feature of fats makes them hydrophobic?

Q28 Which of the following statements regarding carbon is false?

  • Carbon has the capacity to form single and double bonds.
  • Carbon has the ability to bond with up to six other atoms.
  • Carbon has a tendency to form covalent bonds.
  • Carbon has the ability to bond together to form extensive branched or unbranched “carbon skeletons.”

Q29 Facilitated diffusion across a biological membrane requires————— and moves a substance ———— its concentration gradient .

  • transport proteins; against
  • transport proteins; down
  • energy and transport proteins; down
  • energy and transport proteins against

Q30 Fatty acids with double bonds between some of their carbons are said to be

  • saturated
  • completely hydrogenated.
  • unsaturated
  • monoglycerides.

Q31 The temperature of evaporation is much higher for water than for alcohol Without knowing more about the chemistry of alcohol, which of the following is the most logical chemical explanation for this phenomenon?

  • Alcohol has a higher surface tension than water. This means that alcohol molecules can easily break away from other alcohol molecules and evaporate at a lower temperature.
  • Ionic bonds form between alcohol molecules. These are the weakest type of bond and are easier to break than the hydrogen bonds between water molecules.
  • Alcohol molecules are more cohesive than water molecules. This means that as alcohol molecules evaporate, they pull other alcohol molecules into the air along with them.
  • Fewer hydrogen bonds form between alcohol molecules. As a result, less heat is needed for alcohol molecules to break away from solution and enter the air.

Q32 The hydrogen atoms of a water molecule are bonded to the oxygen atom by ________ bonds, whereas neighboring water molecules are held together by ________ bonds.

A) hydrogen; polar covalent

B) polar covalent; hydrogen

C) ionic; covalent

D) polar covalent; ionic

Q33 The tendency of water molecules to stick together is referred to as

  • transpiration
  • adhesion
  • cohesion
  • polarity.

Q34 Which of the following statements regarding membrane function is false?

  • The plasma membrane plays a role in transferring signals to the cell’s interior.
  • The plasma membrane is the control center of the cell.
  • The plasma membrane has receptors for chemical messages.
  • The plasma membrane forms a selective barrier around the cell.

Q35 Which of the following statements best describes a compound?

  • A compound is a solution.
  • A compound is exemplified by sodium.
  • A compound is a pure element.
  • A compound contains two or more different elements in a fixed ratio.

Q36 Which of the following statements regarding active transport is false?

  • Active transport is driven by the concentration gradient.
  • Active transport can move a solute against its concentration gradient.
  • Active transport requires the cell to expend energy.
  • Active transport uses ATP as an energy source.

Q37 Amino acids can be distinguishing from one another by

  • the number of R Groups found on the amino acid molecules.
  • the chemical properties of their amino and carboxyl groups.
  • the chemical properties of their R groups.
  • the type of bond between the R group and the rest of the amino acid molecule.
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