Chapter 1 - Review Flashcards
1
Q
Which elements are more essential to human live and health?
A
Elements that are most essential to human life include carbon, oxygen, hydrogen, nitrogen, calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, iodine, iron, manganese, molybdenum, nickel, selenium, zinc, copper, cobalt, and chromium.
2
Q
Which substance is composed of lipids?
- honey
- wood
- oil on feathers
- hair
A
oil on feathers
3
Q
Explain the relevance of the lattice structure of ice to a species of fish, such as carp, that lives in lakes.
A
The rigid lattice structure of ice means the water has a density as a solid that is lower than its density as a liquid. This means that ice floats on the water, and in the winters, forms an insulating layer preventing the lake from freezing all the way to the bottom so species, such as carp, can survive in deep lakes by living in the lower layers.
4
Q
What is the biological importance of phospholipids?
A
All biological membranes are made of phospholipids.
5
Q
Is the following statement true or false? If it is false, correct it.
A gram of fat carries the same energy as a gram of simple sugar.
A
False
A gram of fat carries more than twice the energy as a gram of simple sugar.
6
Q
What are the components of a nucleic acid?
A
Each nucleotide contains the nitrogen-containing base, a 5-carbon sugar (ribose or deoxyribose), and a phosphate group.
7
Q
Explain how the structure of a phospholipid contributes to its function.
A
Hydrophilic molecules are strongly attracted to water and readily mix with water. Hydrophobic molecules are not strongly attracted to water and will tend to separate from water. The water-soluble heads of the lipid bilayer line up toward the outside of the membrane. Watersoluble molecules do not freely pass through the hydrophobic inner membrane, however.
8
Q
Which component or action does a neutralization reaction involve?
- formation of water
- presence of an acid and a base
- exchange of electrons
- formation of water and presence of an acid and a base
A
formation of water and presence of an acid and a base
9
Q
Is it likely that an enzyme that would catalyze a sugar could also catalyze protein? Explain why or why not.
A
No, only a sugar molecule would fit into an active site of the enzyme. The enzyme-substrate complex is like a lock and key. A protein would not fit into this active site as it is configured differently.
10
Q
Humans produce cerumen, a waxy secretion, in their outer ears. Base on what you have learned about the characteristics of lipids, what purpose do you think this serves and why?
A
Cerumen can have a water-proofing effect that controls the amount of water that enters the ear canal. It is also “sticky,” trapping dirt and debris so that it does not enter the ear canal.
11
Q
Is the following statement true or false?
Unsaturated fats stay fluid at lower temperatures than saturated fats do.
A
True
12
Q
One of the unifying themes in biology is that structure facilitates function at all levels of organization. Explain how the structure of carbohydrates facilitates their function as sources of energy.
A
Disaccharides need to break only one bond to release a monosaccharide allowing them to provide a quick source of energy. Polysaccharides contain multiple bonds that need to be broken to release the monosaccharides. The polysaccharides are a longer-term source of energy.
13
Q
Approximately what percent of human body weight is water?
- 23%
- 35%
- 60%
- 97%
A
60%
14
Q
Which of the following displays specific heat capacity?
- temperature moderation
- capillary action
- ice floating on liquid water
- surface tension
A
temperature moderation
15
Q
Compare and contrast a glycosidic bond and a peptide bond.
A
Peptide bonds and glycosidic bonds are both covalent bonds. A glycosidic bond is a bond between a sugar and another molecule while a peptide bond is a bond between two amino acids.
16
Q
Compare and contrast a monomer and a polymer.
A
A monomer and a polymer are both molecules. A monomer is a small reactive molecule that can chemically bond to other monomers to form a polymer. A polymer is a larger molecule composed of many repeated units (monomers).
17
Q
Which of the following displays density?
- temperature moderation
- capillary action
- ice floating on liquid water
- surface tension
A
ice floating on liquid water
18
Q
Is the following statement true or false? If it is false, correct it.
An enzyme can bind with many different substrates.
A
False
An enzyme can bind with only one substrate.
19
Q
A dehydration synthesis reaction involves which of the following?
- the breakdown of molecules with the removal of water
- the formation of large molecules with the removal of water
- the breakdown of large molecules by the addition of water
- the joining of small molecules with the addition of water
A
the formation of large molecules with the removal of water
20
Q
Is the following statement true or false?
Amino groups are found in all carbohydrates.
A
False
21
Q
Explain the use of polymerization in your body.
A
Polymerization of biological molecules allows for efficient storage molecules, which can be broken down into useful smaller molecules when needed. Polymerization allows for building complex protein molecules for a variety of functions and structures, DNA as storage of genetic information, and RNA as interpreter of that genetic information.
22
Q
What is a cofactor?
A
A cofactor is a non-protein group or atom that is required for a protein (or enzyme) to function.
23
Q
Discuss the typical size of fatty acids.
A
Fatty acids in living things are at least 4 carbons long, and typically 14-22 carbons per chain.
24
Q
Distinguish between saturated fats and unsaturated fats.
A
Saturated fats have no double bonds between carbons in the fatty acid side chains. They tend to have higher melting points. Unsaturated fats have fewer than the maximum number of hydrogen atoms for the number of carbon atoms because they have one or more double bonds in their fatty acid chains. They have lower melting points.
25
Which characteristic of a molecule does a functional group affect in order to increase the solubility of the molecule?
* polarity
* molecular mass
* overall shape
* none of the above
polarity
26
Is the following statement true or false? If it is false, correct it.
A cofactor is a non-protein group that binds to a site on an enzyme.
True
27
Explain how the structure of carbon influences the variety of different structures it can form?
Each carbon atom has four valence electrons allowing it to form up to four single bonds with other atoms. Its structure also allows it to form straight chains, branched chains, and rings, resulting in a variety of different structures.
28
During a dehydration reaction between two glucose molecules, water is formed. Can this reaction take place on any of the carbon atoms?
A dehydration reaction can take place on any of the carbons with available OH groups. The carbon at the 5 position is hindered and will not form glycosidic linkages.
29
What role does electronegativity of an atom play in the type of bond that it forms?
When there is a large electronegativity difference between two atoms, they are likely to form an ionic bond. Two non-metals have a smaller electronegativity difference and form a covalent
30
Which component or action does a redox reaction always involve?
* presence of oxygen
* bonding of a metal to a non-metal
* formation of a solid
* transfer of electrons
transfer of electrons
31
Is the following statement true or false? If it is false, correct it.
In competitive inhibition, a molecule competes with the normal substrate for the active site of an enzyme.
True
32
What are the four elements that make up 96% of human body mass?
Carbon, hydrogen, oxyegen, and nitrogen.
33
What is the difference between a triglyceride and a trisaccharide?
A triglyceride is made of three fatty acid molecules joined to a glycerol molecule. A trisaccharide is three sugar monomers joined together to make one larger sugar polymer.
34
Which substance is not a common source of plant based simple sugars?
* cellulose
* sugar beets
* maple sap
* sugar cane
cellulose
35
Is the following statement true or false? If it is false, correct it.
The pH scale represents logarithmic values of the molar concentration of H+.
True
36
Compare and contrast the structure and function of DNA with the structure and function of RNA.
DNA has thymine; RNA has uracil. DNA is double-stranded and arranged as a helix; RNA is a single strand. Both structures have the nucleotides adenine, guanine, and cytosine. DNA primarily serves as the storage material for genetic information; RNA can function as a carrier of genetic information, catalyst of biochemical reactions, and acts as a structural molecule in cellular organelles.
37
What is the purpose of a buffer system?
A buffer system can compensate for changes in pH by donating hydroxide ions or hydrogen ions.
38
Distinguish between covalent bonds and intermolecular forces.
Covalent or molecular bonds join two atoms together into a molecule by sharing electrons. Intermolecular forces are forces of attraction between molecules (e.g., weak van der Waal forces, hydrogen bonding).
39
If the number of neutrons in an atom changes, which of the following is created?
* an element
* an anion
* a cation
* an isotope
an isotope
40
A large drop of water forms and hangs on the end of a leaky tap for a moment or two before it falls to the ground. Which of the following properties of water are involved in this process?
* cohesion and adhesion
* surface tension and cohesion
* adhesion and specific heat
* surface tension and specific heat
cohesion and adhesion
41
Based on what you have learned about the effect of temperature on enzymatic activity, why do you think that organs and tissues for transplantation are cooled?
The breakdown of organs and tissues after death is catalyzed by enzymes. Cooling organs and tissues for transplant reduces this enzyme activity, slowing the natural decomposition process. Cooling also slows the normal metabolic processes and reduces the degradation of the structures.
42
Which molecule is always a reactant during a hydrolysis reactant?
* O2
* CO2
* H2
* H2O
H2O
43
Which of the following displays adhesion?
* temperature moderation
* capillary action
* ice floating on liquid water
* surface tension
capillary action
44
Explain the relationship between polarity and hydrogen bonds.
Polarity is the uneven sharing of electrons in a covalent bond. Hydrogen bonds are the result of the partial charges from polar covalent bonds.
45
Compare competitive inhibition and noncompetitive inhibition.
In competitive inhibition, an inhibitory molecule competes with the substrate for binding at the active site. In noncompetitive inhibition, an inhibiting molecule does not compete with the substrate for the active site but modulates the enzymes activity form an alternate site.
46
What do glycosidic bonds link together?
* monosaccharides to form disaccharides
* fatty acids and glycerol
* amino acids to form polypeptides
* phospholipids to form bilyers
monosaccharides to form disaccharides
47
Describe a glycosidic bond.
A glycosidic bond is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate.
48
Zymase is an enzyme complex that catalyzes the fermentation of sugar into ethanol and carbon dixode. As this conversion is taking placem the reaction gradually slows down. Explain why this happens.
As the sugar is catalyzed into different substances, the substrate concentration is gradually reduced. This reduction in the substrate concentration decreases the rate of reaction.
49
Which type of molecule is used to convey genetic information?
* nucleic acid
* protein
* lipid
* carbohydrate
nucleic acid
50
Is the following statement true or false? If it is false, correct it.
Radioactivity occurs when an ionic compound decays into ions.
False.
Radioactivity occurs when a **radioactive isotope** decayse into **an atom of another element**.
51
What is the function of RNA?
* to store genetic information in the nucleus
* to form a permanent bond with DNA
* to copy DNA for protein synthesis
* none of the above
to copy DNA for protein synthesis
52
How does allosteric regulation work?
Allosteric regulation controls enzyme function at a site other than the active site by changing the conformation of the enzyme to stabilize or destabilize the active form of the enzyme.
53
Compare and contrast the characteristics of radioisotopes and stable isotopes.
Atoms with the same number of protons but different number of neutrons are isotopes. Isotopes are unstable if they have too many or too few neutrons. Radioisotopes are unstable isotopes that will decay at a steady known rate into smaller particles. Stable isotopes have a stable number of neutrons. The chemical behaviour of stable isotopes is the same as radioisotopes except that they do not decay
54
List four characteristics of solutions that contain a relatively high concentration of hydronium ions.
They are acids, have a pH less than 7, are sour, and corrosive.
55
After enzymes participate in a reaction, what happens to them?
* They must be reactivated.
* They cannot be used again.
* They remain unchanged and can immediately be reused.
* They are consumed and become a new substance.
They remain unchanged and can immediately be reused.
56
Is the following statement true or false?
The enzymes in cells are not dependent on other molecules to function.
False
57
What is an orbital?
* a description of how atoms rotate
* a hard shell that encloses an atom
* a region where electrons are likely to be found
* another name for the nucleus
a region where electrons are likely to be found
58
Which of the descriptions below best describes an ionic bond?
* interactions between molecules that contain H and N or O
* bond between charged particles
* weakest intermolecular forces
* sharing of electrons
bond between charged particles
59
List the five bases that are found in a nucleic acid.
The five bases found in a nucleic acid are uracil, thymine, cytosine, adenine, and guanine.
60
An industrial company is preparing to use enzymes to carry out a reaction. If you were the scientist planning the reaction, what recommendation for substrate addition would you make to ensure a stable production rate?
The recommendation to run the reaction with a substrate concentration that allows saturation of the available enzymes would lead to a stable production rate.
61
In which part of the atom are valence electrons found?
* nucleus
* innermost orbital of the element
* outermost orbital of the element
* cannot be determine
outermost orbital of the element
62
How does competitive and noncompetitive inhibition relate to the feedback mechanisms of biological pathways.
In biological pathways, noncompetitive inhibition is used to regulate negative feedback mechanisms, in which the product of a metabolic pathway inhibits upstream enzyme activity by binding to an allosteric site. Competitive inhibition occurs when multiple metabolites compete for the same enzyme, when the concentration of the inhibiting molecule is high enough the rate of enzyme activity is decreased.
63
How does the size of a fatty acid influence its solubility?
As carbon chain length increases, fatty acids become less water-soluble.
64
Which type of biological molecule is each type of glucose found in?
α-glucose forms starch polymers, which are digestible, but β-glucose forms cellulose, an indigestible polymer.
65
Explain how bonding results in a more stable electron situation for most atoms.
When atoms bond they “fill” or empty their outer electron orbital (shells), which results in their most stable conformation. This can be achieved by sharing (molecular bonding) or transferring electrons (ionic bonding).
66
Is the following statement true or false? If it is false, correct it.
In noncompetitive inhibition, specific molecules can inhibit enzymes.
True
67
Is the following statement true or false? If it is false, correct it.
The orientation of the bond between carbon and hydrogen in methane, CH4, forms 120° angles.
False
The orientarion of the bond between carbon and hydrogen in methan, CH4, forms **109.5°** angles.
68
What distinguishes saturated fats from unsaturated fats?
* number of carbon atoms
* types of covalent bonds
* presence or absence of oxygen
* shape of the carbon chain
types of covalent bonds
69
Is the following statement true or false? If it is false, correct it.
Cutin is a steroid that prevents water evaporation from the leaves of plants.
False
Cutin is a **wax** that prevents water evaporation from the leaves of plants.
70
Explain the difference between a dehydration reaction and a hydrolysis reaction.
A dehydration reaction removes a water molecule to join two smaller molecules into one larger one (also called condensation). A hydrolysis reaction adds a water molecule to split a large molecule into two smaller molecules.
71
Describe the composition of a phospholipid.
Phospholipids are composed of a glycerol molecule to which two fatty acids and a phosphate group are linked by dehydration synthesis.
72
Why do the isotopes of an element display the same behaviour in a reactions?
Isotopes behave similarly in chemical reactions because they maintain a similar electronic environment. Neutrons carry no electrical charge and are not involved in chemical reactions.
73
Is the following statement true or false? If it is false, correct it.
Cutin is a steroid that waterproofs the skins of fruits and vegetables.
False
Cutin is a **wax** that waterproofs the skins of fruits and vegetables.
74
Water in its solid state is less dense than its liquid state. How could this property be significant during the winter for organisms that live in lakes and ponds?
Since water in its solid state is less dense than its liquid state, the water in ponds and lakes freeze from the top down. The water will not freeze all the way through because the solid water will float on the surface protecting the remaining water from the elements allowing it to remain warm enough to stay in its liquid state. All but the smallest ponds can remain partly liquid. Aquatic animals can survive in this water until the ice thaws in the spring.
75
RNA and DNA differ from each other in which way?
* RNA has cytosine but DNA does not.
* DNA has ribose but RNA does not.
* DNA has thymine but RNA does not.
* DNA contains nucleotides but RNA does not.
DNA has thymine but RNA does not.
76
Enzyme actifity is affected by substrate and enzyme concentrations, temperatures, and pH. Enzyme activity is also affected by water. Why do you think water is an important factor in enzymatic activity?
Enzymes depend on water to reach their substrates and bind to them. Many active sites use water to form hydrogen-bonding networks critical to the function of the enzyme.
77
Is the following statement true or false?
Water is more dense at -20°C than it is at 80°C.
False
78
Is the following statement true or false? If it is false, correct it.
Water dissociates into H+ and OH- ions.
True
79
Which of the descriptions below best describes a hydrogen bond?
* interactions between molecules that contain H and N or O
* bond between charged particles
* weakest intermolecular forces
* sharing of electrons
interaction between molecules that contain H and N or O
80
What is the functional advantage of a fat that has several fatty acid chains, compared with a fat that has only a single fatty acid chain?
The functional advantage of fats containing several fatty acid chains is an increased capacity for energy storage.
81
Which of the following displays cohesion?
* temperature moderation
* capillary action
* ice floating on liquid water
* surface tension
surface tension
82
Which characteristics of water leads to formation of hydrogen bonds?
* density
* crystal structure
* shape
* polarity
polarity
83
What is an allosteric site?
An allosteric site is where a regulatory molecule can bond to an enzyme.
84
Which of the descriptions below best describes a covalent bond?
* interactions between molecules that contain H and N or O
* bond between charged particles
* weakest intermolecular forces
* sharing of electrons
sharing of electrons
85
Which statement about an acitve site on an enzyme is true?
* It is only active in acid.
* It is a pocket or groove for binding a substrate.
* It is only operational during rest.
* It is always accompanied by a companion inactive site.
It is a pocket or groove for binding a substrate.
86
Distinguish between alpha-glucose and beta-glucose.
The two forms of glucose are isomers and differ in the arrangement of an OH group. In alpha-glucose, the hydroxyl group on C-1 is located on the opposite side of ring as C-6. In beta-glucose, the hydroxyl group on C-1 is located on the same side of ring as C-6.
87
In which food sources are omega-3 fatty acids abundant?
* red meat, ocean fish, chicken eggs
* ocean fish, chicken eggs, lake fish
* chicken eggs, lake fish, red meat
* lake fish, red meat, ocean fish
ocean fish, chicken eggs, lake fish
88
Is the following statement true or false? If it is false, correct it.
Hydrogen bonding is partly responsible for the ability of water to dissolve ionic substances in the blood.
False
Hydrogen bonding is **completely** responsible for the ability of water to dissolve ionic substances in the blood.
89
List four characteristics of solutions that contain a relatively high concentration of hydroxide ions.
They are bases, have a pH greater than 7, are bitter, corrosive, and slippery.
90
What components must a buffer system contain?
A buffer system contains a weak acid or a weak base or a combination of the two.
91
In an amino acid, what is an R group, and what is its purpose?
An R group is a functional side chain associated with amino acids. They give amino acids structural and functional diversity.
92
Some people experience "heartburn" when eating fatty, greasy foods (similar to the effect that is felt when eating acidic foods). Why would this occur with fats?
As the fats get digested the fatty acids are released from the triglycerides. This in combination with the gastric acidic secretions used to solubilize the fat cause heartburn.
93
Which property is responsible for the surface tension of water?
* mass
* density
* hydrogen bonding
* weak van der Waals' forces
hydrogen bonding
94
Is the following statement true or false? If it is false, correct it.
A buffer is a strong acid or base that can be used effectively to regulate the pH of a solution.
False
A buffer is a **weak** acid or base that can be used effectively to regulate the pH of a solution.
95
What are some potential benefits and risks of exposure to radioisotopes.
The radiation from radioisotopes may be dangerous to humans, causing mutations to genetic material. Radiation can also be very useful, for example, in medical diagnosis with X-rays or in treatments such as chemotherapy.
96
When two DNA strands are paired, how are they oriented?
* at right angles to each other
* in opposite directions
* at a 45° angle
* in the same direction
in opposite directions
97
Is the following statement true or false? If it is false, correct it.
RNA carries the genetic blueprint for viruses.
False
RNA carries the genetic blueprint for **some** viruses.
98
Describe the basic characteristics of primary, secondary, tertiary, and quaternary protein structure.
The primary structure is the linear sequence of its amino acids in the protein chain.
The secondary structure is the folding and interactions between peptide groups due to hydrogen bonding.
The tertiary structure is the overall shape of a protein due to bonding between the R groups of the amino acids.
The quaternary structure describes the organization of multiple polypeptide chains in proteins that have more than one.
99
When an enzyme is exposed to extreme changes in pH, its shape and ability to work are affected. What is this process called?
* denaturation
* deformation
* deamination
* coagulation
denaturation
100
Describe a prosthetic group in a protein, and explain what it does. Give an example.
A prosthetic group is a non-amino acid component that a protein needs to function. An example of a prosthetic group would be a tightly-bound cofactor such as an iron atom in a heme group of the hemoglobin.
101
Explain how the shape of a water molecule relates to its polarity.
Water molecules are polar with the electrons spending the most time near the partially negative oxygen atom. This causes the bent shape of the molecule.
102
Is the following statement true or false?
All proteins are enzymes.
False
103
Amino acids are to polypeptides as monosaccharides are to which of the following?
* nucleic acids
* polysaccharides
* polynucleotides
* disaccharides
polysaccharides
104
Is the following statement true or false?
Phosphate groups are acidic and become negatively charged when they lose H+.
True
105
Which three elements do all four classes of biological molecules contain?
Carbon, hydrogen, and oxygen.
106
List the four main classes of biological molecules.
The four main classes of biological molecules are carbohydrates, lipids, proteins, and nucleic acids.
107
Which of the following is a function of enzymes?
* facilitate digestion
* facilitate light energy reactions in chloroplasts
* allow the reactions in the body to run at a coller temperature than would otherwise be possible
* all of the above
all of the above
108
How many bonds does a single nitrogen atom usually form?
* none
* one
* two
* three
three
109
Which statement about hydrogen bonds is true?
* They are stronger than ionic bonds.
* They are stronger than covalent bonds.
* They are weaker than both ionic bonds and covalent bonds.
* They are stronger than both ionic bonds and covalent bonds.
They are weaker than both ionic bonds and covalent bonds.
110
Explain how the valence electrons in a carbon atom are arranged.
Carbon has four valence electrons that are unpaired, and hence it is able to form four bonds. It can form two double bonds, one single and one triple, or four single bonds.
111
How would you explain to a parent or guardian the importance of consuming adquate amounts of omega-3 fatty acids?
Omega-3 fatty acids are suspected to counteract the effects of triglycerides and to have a good effect on heart, brain, joint, and digestive health.
112
Which of the bonds below is associated with disaccharides?
* phosphodiester bond
* glycosidic link
* peptide bond
glycosidic link
113
Is the following statement true or false? If it is false, correct it.
A bond is more polar when the electronegativity values of the atoms are closer together.
False
A bond is **less** polar when the electronegativity values of the atoms are closer together.
114
Is the following statement true or false?
A covalent bond is a shared pair of electrons.
True
115
How does the arrangement of carbon's valence electrons facilitate the bonding ability of a carbon atom.
Since the four valence electrons in carbon’s outer shell are unpaired, each one can take part in a covalent bond with another atom. In a covalent bond, one or more electrons in carbon’s outer and one or more electrons in another atom’s outer shell would be shared between both atoms.
116
Which type of molecule is used to convey genetic information?
* nucleic acid
* protein
* lipid
* carbohydrate
nucleic acid
117
Is the following statement true or false?
Hydrogen bonding is responsible for adhesion, which allows a substance to move against gravity in a plant.
True
118
Is the following statement true or false? If it is false, correct it.
Nucleic acids are the most diverse group of biological molecules in human cells.
False
**Proteins** are the most diverse group of molecules in human cells.
119
Which functional group causes ethanol to be polar and also allows it to dissolve in water?
* carboxyl
* alcohol
* amino
* phosphate
alcohol
120
Identify the six function groups.
Hydroxyl, carbonyl, carboxyl, amino, phosphate, and sulfhydrl.
121
List three characteristics of carbon that make it the backbone of biologically important molecules.
Carbon can covalently bond with four other atoms. Carbon can form straight chains, branching chains, and rings, which allow for a great variety of shapes and sizes in molecules. Carbon can form single, double, or triple bonds, forming structures of various strengths.
122
A marathon runner is preparing for a race and needs energy over a sustained period of time. What types of macromolecules should this athlete concentrate on consuming the day or two before the race begins? Explain your reasoning.
The marathon runner should consume foods containing complex carbohydrates like pasta and grains as they can be stored in the muscles and will break down more slowly than simple carbohydrates.
123
Is the following statement true or false? If it is false, correct it.
Kinks in fat molecules help them stay fluid.
True
124
Which of the bonds below is associated with DNA?
* phosphodiester bond
* glycosidic link
* peptide bond
phosphodiester bond
125
Which sugar is a disaccharide?
* sucrose
* glucose
* pentose
* hexose
sucrose
126
Which of the descriptions below best describes van der Waals' forces that are not hydrogen bonds?
* interactions between molecules that contain H and N or O
* bond between charged particles
* weakest intermolecular forces
* sharing of electrons
weakest intermolecular forces
127
Which atoms in an amino acid are removed when the amino acid forms a peptide bond?
The OH and a H are removed from an amino acid in a dehydration reaction to form peptide bonds.
128
Which of the bonds below is associated with proteins?
* phosphodiester bond
* glycosidic link
* peptide bond
peptide bond
