Biology Chapter 6 Quiz

Questions and Answers

Additional hydrogen atoms can be added to saturated fats, a process called hydrogenation.

False

When unsaturated fats are partially hydrogenated industrially, this can produce trans fats which have been linked to elevated levels of low-density lipoprotein (LDL) 'bad cholesterol' and lowered levels of high-density lipoprotein (HDL) 'good cholesterol'.

True

Why are fats excellent energy storage molecules?

They have a relatively high ratio of energy storing C-H bonds.

What are some characteristics of phospholipids?

They contain a glycerol backbone, the phosphate head group is polar, and the molecule is an important part of cell membranes. Signup and view all the answers

How do membranes form spontaneously?

The hydrophobic fatty acid tails on phospholipids are repelled by water. Signup and view all the answers

How does the protein Ras associate with membranes?

Through an anchor. Signup and view all the answers

What are some properties of the interior protein network?

Helps determine the overall shape of a cell. Signup and view all the answers

Where do lipids, a class of organic compounds, fit on the hierarchy of biological organization?

DNA Signup and view all the answers

What are characteristics of an ionic bond?

An electron is completely pulled from one atom to another. The electronegativity difference is always high between atoms of this bond type. Signup and view all the answers

What are characteristics of a covalent bond?

Atoms of this bond might have equal electronegativities. This bond may also be polar or nonpolar. Signup and view all the answers

What are the 4 most common elements in living organisms?

Carbon, Oxygen, Hydrogen, and Nitrogen Signup and view all the answers

What elements are present in trace amounts only?

Iodine and Zinc Signup and view all the answers

What elements are found in greater than trace amounts?

Sodium, Chloride, Calcium, Phosphorus, Potassium, Sulfur, Magnesium, and Iron Signup and view all the answers

The atomic number of carbon-13 is ____

6 Signup and view all the answers

The atomic mass of carbon-13 is ______

13 Signup and view all the answers

C-12, C-13, and C-14 have the same number of protons but different numbers of neutrons so they are ______.

Isotopes Signup and view all the answers

Atoms that have gained or lost electrons and are no longer electrically neutral are called _____.

Ions Signup and view all the answers

Describe a single covalent bond.

Holds a molecule of hydrogen together, involves 2 atoms sharing 2 electrons, and two chlorine atoms are held together by this bond. Signup and view all the answers

Describe an ionic bond.

Formed by an attraction between atoms with opposite charges, it involves a transfer of one or more electrons from one atom to another, leading to the formation of a crystal lattice rather than distinct molecules. Signup and view all the answers

Describe a double covalent bond.

Holds a molecule of oxygen together, involves 2 atoms sharing 4 electrons, and is the strongest type of bond shown. Signup and view all the answers

A water molecule is held together by 2 single polar covalent bonds.

True Signup and view all the answers

Because oxygen has a greater electronegativity than hydrogen, water molecules are polar with 2 partial negative charges near the oxygen atom and one partial positive charge near each hydrogen atom.

True Signup and view all the answers

Atoms differ in their affinity for neutrons, a property called electronegativity.

False Signup and view all the answers

In general, electronegativity increases from left to right across each row of the periodic table and also increases down each column.

False Signup and view all the answers

In a nonpolar covalent bond, there is an equal sharing of electrons between two atoms while polar covalent bonds involve an unequal sharing of electrons.

True Signup and view all the answers

A single molecule of oxygen is held together by 2 double nonpolar covalent bonds.

False Signup and view all the answers

A covalent bond is formed when 2 atoms share one or more pairs of electrons.

True Signup and view all the answers

Polar molecules are electrically neutral, but the distribution of charge within the molecule is not uniform.

True Signup and view all the answers

Although C and H differ slightly in electronegativity, this small difference is negligible, and C-H bonds are considered polar.

False Signup and view all the answers

Of the 4 most common elements found in living organisms, nitrogen has the highest electronegativity and therefore, the greatest affinity for electrons.

False Signup and view all the answers

A slightly positive hydrogen atom on one water molecule can attract the slightly negative oxygen atom on a different water molecule, leading to the formation of a hydrogen bond.

True Signup and view all the answers

What are properties of water?

A wide variety of substances can move freely and interact within cells, the temperature of living organisms is relatively stable, evaporation of water is used to cool body surface, lakes freeze from top down, allowing fish and other life to survive below the surface, and nonpolar molecules tend to aggregate or organize in ways that minimize their contact with water. Signup and view all the answers

As the pH scale increases, the concentration becomes____.

Greater Signup and view all the answers

PH's H+ concentration increases by __.

10 Signup and view all the answers

When given electronegativity, subtracting the difference between the two molecules will provide you with what information?

If the atom is polar or nonpolar Signup and view all the answers

Monosaccharides create what polymer?

Carbohydrates Signup and view all the answers

Nucleotides create what polymer?

DNA Signup and view all the answers

Fatty acids, glycerol create what polymer?

Triglycerides Signup and view all the answers

Amino acids create what polymer?

Protein Signup and view all the answers

Describe Dehydration synthesis.

A molecule of glycogen is formed by linking glucose molecules through this process, this process removes water to link 2 or more amino acids. Signup and view all the answers

Describe Denaturation.

This process does not involve breaking of peptide bonds, but it does involve unfolding protein structure. Signup and view all the answers

Describe Hydrolysis.

Breaking DNA into nucleotides, adding water to break proteins into amino acids, and the separation of polymers into smaller units. Signup and view all the answers

Describe the primary structure.

Amino acid sequence and it determines all other levels of protein structure. Signup and view all the answers

Describe the secondary structure.

Localized 3D structures and coil/sheet arising from chemical attractions among amino acids. Signup and view all the answers

Describe Tertiary structure.

The overall shape of a chain of amino acids and it results when R groups move toward or away from water. Signup and view all the answers

Describe the quaternary structure.

Not all proteins have this level of organization and interactions between multiple chains of amino acids. Signup and view all the answers

What might cause a protein to become nonfunctional?

An increase in the pH of the surrounding solution, change in temperature near the protein, the surrounding solutions shift from water to oil, change in amino acid sequence, decrease in pH of the surrounding solution, decrease in salt concentration near protein, and increase in salt concentration near protein. Signup and view all the answers

What levels of protein would be affected if all hydrogen bonding interactions were prevented?

Secondary, tertiary, and quaternary Signup and view all the answers

What types of bonds link individual amino acids together?

Peptide bonds Signup and view all the answers

In the stable form of protein, what is generally oriented to the interior of the protein molecule?

Hydrophobic portions Signup and view all the answers

A protein that has many hydrophobic R-groups pointing to the outside of the protein would be found...

Embedded within a membrane Signup and view all the answers

When proteins are denatured, which type of bond is NOT disturbed?

Covalent bonds Signup and view all the answers

If a protein's environment is altered, the protein may change its shape or even unfold completely, a process called dissociation.

False Signup and view all the answers

Proteins can denature when the pH, temperature, or ionic concentration of the surrounding solution changes.

True Signup and view all the answers

Denatured proteins are usually biologically active.

False Signup and view all the answers

When normal environmental conditions are reestablished after protein denaturation, almost all proteins can spontaneously refold back into their natural shape.

False Signup and view all the answers

If the 3D structure of a protein depends only on its primary structure and the surrounding environmental conditions, then when the protein is denatured and subsequently returned to its native conditions it will spontaneously refold back into its native structure.

True Signup and view all the answers

Proteins have a narrow range of conditions in which they fold properly; outside this range, proteins tend to renature.

False Signup and view all the answers

Some proteins require other proteins called chaperones in order to correctly fold into their normal 3D shape.

True Signup and view all the answers

Cells use chaperones both to accomplish the original folding of some proteins and to restore the structure of incorrectly folded ones.

True Signup and view all the answers

Some diseases may occur because a protein with the correct amino acid sequence fails to correctly fold into its final functional form.

True Signup and view all the answers

During a process called dissociation, the polypeptides of a protein with quaternary structure separate and unfold, losing their individual tertiary structure.

False Signup and view all the answers

The final 3D shape of a protein is determined entirely by its primary structure.

False Signup and view all the answers

What qualities of a chemical reaction are affected by enzymes?

The speed of reaction and the energy required to start the reaction Signup and view all the answers

What might happen if a substance that is not a substrate molecule binds to an enzyme's active site?

Enzyme activity will slow down. Signup and view all the answers

An enzyme may catalyze a reaction by stressing or destabilizing the bonds of substrates. This point in the enzymatic reaction is known as the?

Transition state Signup and view all the answers

Sucrase uses _____ to cleave sucrose into 2 monosaccharides.

Water Signup and view all the answers

When it binds to sucrose, sucrase?

Goes through a conformational change Signup and view all the answers

What can you say about the change in free energy of the cleavage of sucrose into glucose and fructose?

It is negative and the reaction is exergonic Signup and view all the answers

A mutation occurred in the gene that encodes the enzyme sucrase, resulting in a single amino acid substitution in the active site, whereby a polar amino acid changed to a nonpolar amino acid. The most likely result of this is?

Sucrase will not be able to bind to sucrose in the active site Signup and view all the answers

L-arabinose is a naturally occurring, non-caloric sweetener that acts as a non-competitive inhibitor of the enzyme sucrase. If L-arabinose is consumed, what will happen to the hydrolysis of sucrose?

Sucrose hydrolysis will be greatly reduced, since L-arabinose binding to sucrase will inactivate the enzyme. Signup and view all the answers

Your friend is studying a specific exergonic reaction. Your friend hypothesizes that the addition of enzyme X will reduce the delta-G of this reaction, thus allowing it to proceed spontaneously. What do you think of this?

Enzymes do not change delta-G, so this hypothesis does not fit with what is known about this reaction. Signup and view all the answers

What is the structure and function of the Golgi apparatus?

Stacked, flat, single-membrane sacs. Creates vesicles to enclose materials to be secreted; produces lysosomes. Signup and view all the answers

What is the structure and function of a ribosome?

Two subunits of RNA and protein synthesized in the nucleolus of eukaryotic cells. Location of protein synthesis. Signup and view all the answers

What is the structure and function of the smooth ER?

A single-membrane network. Synthesizes lipids; detoxifies drugs and poisons. Signup and view all the answers

What is the structure and function of the rough ER?

A single-membrane network covered with ribosomes. Produces proteins destined for secretion from the cell. Signup and view all the answers

What type of cells are in Smooth ER?

Intestinal cells that create new plasma membranes quickly, brain cells rich in lipids, and testes that produce lipid storage. Signup and view all the answers

What type of cells are in Rough ER?

Pancreatic cells that secrete protein hormones and mucus-secreting cells in the airway. Signup and view all the answers

Tay-Sachs disease causes lysosomes to rupture. How would this affect the cell?

Phagocytic cells would not destroy bacteria, material taken up through endocytosis would not be digested, and biological polymers would not be broken down by lysosomes. Signup and view all the answers

The lysosome contains _____ enzyme.

hydrolytic Signup and view all the answers

You are doing a study on the effects of lysosomal enzymes and want to follow the whole process from the formation of the enzymes to their use in the lysosome. In what location of the cell would you begin this observation?

ER Signup and view all the answers

What functions do microtubules have?

Used to move vesicles within cells and made of dimers of alpha- and beta-tubulin. Signup and view all the answers

What functions do actin have?

Used to move cells and also called microfilaments. Signup and view all the answers

What functions do intermediate filaments have?

A strong structural protein within cells; no polymerization once formed and prevent excessive stretching of cells. Signup and view all the answers

What are the functions of the cytoskeleton?

To provide scaffolding for the enzymes in certain areas of the cell, organize cell activities, provide movement of molecules in the cell, and provide cell shape. Signup and view all the answers

What are characteristics of desmosomes?

Destruction of intermediate filaments by cancers of epithelial tissues, adds strength in epithelial tissue of the top layer of the skin, and allows flexibility when stretching. Signup and view all the answers

What characteristics of plasmodesmata?

Penetrates the cell walls to allow a pathway for movement and allows flow of ions between two plant cells. Signup and view all the answers

What characteristics of gap junctions?

Allows immediate communication between cells such as 2 neurons and allows types of smooth muscle and cardiac muscle to contract in unison. Signup and view all the answers

What characteristics of a tight junction?

Resists the movement of material into and out of capillaries in the brain, holds together endothelial cells and seals epithelial cells to each other right beneath their surface on the top layer of skin. Signup and view all the answers

Suppose a researcher successfully produced a membrane composed of saturated triglycerides rather than from phospholipids. What characteristics would you expect the saturated triglyceride membrane to have?

Hydrophobic molecules would be attracted to the membrane and the saturated triglycerides would not form a bilayer. Signup and view all the answers

What do animal and plant cells have in common?

Membrane is a bilayer of phospholipids, transport proteins embedded in membrane, and they help the cell to maintain homeostasis. Signup and view all the answers

A triacylglycerol is composed of 3 glycerol molecules going to a fatty acid.

False Signup and view all the answers

The fatty acids of a triglyceride need to be identical, and often they are very different from one another.

True Signup and view all the answers

Glycerol is a 3-C alcohol, in which each carbon bears a carboxyl group.

False Signup and view all the answers

A fatty acid consists of a hydrocarbon chain joined to a hydroxyl group.

False Signup and view all the answers

The hydrocarbon chains of fatty acids vary in length as well as in the number and location of double bonds between the carbon atoms.

True Signup and view all the answers

Fatty acids with one double bond in their hydrocarbon chain are called monounsaturated, while those with more than one double bond are called polyunsaturated.

True Signup and view all the answers

A saturated fatty acid has the maximum number of oxygen atoms bonded to its hydrocarbon chain.

False Signup and view all the answers

Fats containing unsaturated fatty acids have high melting points because their fatty acid chains bend at the double bonds, preventing them from packing closely together.

False Signup and view all the answers

Most plant fats contain saturated fatty acids and therefore liquid at room temperature.

False Signup and view all the answers

Study Notes

Biological Hierarchy and Elements

Lipids are a class of organic compounds integral to biological organization.
The four most common elements in living organisms are carbon, oxygen, hydrogen, and nitrogen.
Trace elements present in minimal amounts include iodine and zinc, while elements like sodium, chloride, calcium, phosphorus, potassium, sulfur, magnesium, and iron are found in greater quantities.

Atomic Structure

Carbon-13 has an atomic number of 6 and an atomic mass of 13; it is an isotope alongside C-12 and C-14, which share the same protons but differ in neutron count.
Ions are defined as atoms that have gained or lost electrons, altering their electrical neutrality.
Single covalent bonds involve the sharing of two electrons between atoms, while double covalent bonds involve the sharing of four electrons.

Bonding Types

Ionic bonds arise from strong attractions between atoms with significant electronegativity differences, leading to electron transfer and formation of crystal lattices.
Covalent bonds can be polar or nonpolar, depending on the electronegativity of the bonded atoms.
Water is held together by two single polar covalent bonds, contributing to its unique properties.

Water Properties

Water enables free movement and interaction of substances within cells.
It maintains stable temperature within living organisms and allows life to persist under frozen lake surfaces due to its unique freezing properties.

pH Scale and Acidity

As pH increases, the concentration of hydrogen ions decreases; pH changes occur logarithmically, meaning each unit represents a tenfold difference in H+ concentration.
Understanding electronegativity differences helps determine whether a bond is polar or nonpolar.

Biomolecules and Polymers

Monosaccharides give rise to carbohydrates, while nucleotides form DNA, and fatty acids combine with glycerol to create triglycerides. Amino acids link to form proteins.
Dehydration synthesis joins monomers by removing water, while hydrolysis involves adding water to break polymers into simpler molecules.

Protein Structure

Protein structures:
- Primary: Sequence of amino acids.
- Secondary: Localized 3D structures formed by attractions among amino acids.
- Tertiary: Overall shape influenced by R group interactions.
- Quaternary: Interactions between multiple polypeptide chains.
Denaturation unfolds proteins without breaking peptide bonds, while hydrolysis breaks them down into amino acids.

Enzyme Functionality

Enzymes increase reaction speed and lower activation energy without altering the overall free energy change (delta-G).
Enzyme activity can be inhibited by non-substrate molecules binding to active sites.

Cell Components

The Golgi apparatus consists of stacked, flat sacs that create vesicles and lysosomes for material secretion and digestion.
Ribosomes, made of RNA and protein, serve as the site for protein synthesis.
The endoplasmic reticulum (ER) includes rough ER (with ribosomes) for protein production and smooth ER for lipid synthesis and detoxification.

Cytoskeleton and Cell Structure

Microtubules aid in intracellular transport; actin filaments enable cell movement; intermediate filaments maintain structural integrity.
The cytoskeleton provides organization, movement, and shape to the cell.

Cell Junctions

Desmosomes strengthen tissue by connecting intermediate filaments, while plasmodesmata in plant cells facilitate ion flow.
Gap junctions allow rapid communication between cells, and tight junctions prevent material movement between cells.

Lipid Characteristics

Saturated triglycerides do not form bilayers, while phospholipids create membranes with polar heads and hydrophobic tails, critical to cell membrane structure.
Trans fats result from partial hydrogenation of unsaturated fats, potentially increasing "bad cholesterol".

Protein and Enzyme Interactions

Enzymatic function can be affected by changes in environmental factors such as pH, temperature, and ionic concentration.
Chaperone proteins assist in proper protein folding, and any failure in this process can lead to diseases.

General Cell Knowledge

Animal and plant cells share features, including a phospholipid bilayer and embedded transport proteins.
Triglycerides provide efficient energy storage due to high C-H bond ratios.

Miscellaneous True/False Statements

True/False statements cover various facts about proteins, fatty acids, enzymes, and cellular structures, emphasizing concepts such as denaturation, protein folding, and the roles of different biological macromolecules.

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Description

Test your understanding of biological organization and chemical bonds in this quiz based on Chapter 6 of your biology textbook. Topics include the role of lipids and the characteristics of ionic and covalent bonds. Perfect for reinforcing your knowledge in fundamental chemistry within biology.