Bio tutorial questions

The mass number of an atom is 15, and its atomic number is 7. The atom probably has

8 neutrons in the nucleus. The atomic number (7) gives the number of protons, and the mass number is the number of protons plus neutrons

Which statement is true of atoms?

Electrons determine the atom’s size. With electrons on the surface, atoms repel one another when they come too close. Thus, electrons determine the space that an atom occupies.

Dr. Jones says an atom has 3 electrons in the first shell and four electrons in the second shell. Someone should tell Dr. Jones that

the first shell shouldn’t have 3 electrons.The first shell can only have 0, 1, or 2 electrons

Which statement is true of the energy levels of electrons in shells

The valence shell has higher energy than other occupied shells. The outer occupied shell is the valence shell, and outer shells hold electrons at higher energy than inner shells

An orbital is dumbbell-shaped. Which statement is most likely true

Only the second and higher shells have dumbbell-shaped orbitals. Each orbital can hold just two electrons, and the electrons move in unknown paths such that both electrons can be in one lobe at one moment, and in opposite lobes at the next moment

Two atoms always represent the same element if they have

the same number of protons. The number of protons defines a chemical element

An atom has 6 electrons, 6 protons, and 6 neutrons. You can tell that this atom belongs to the element _____ because _____________________

C; it has 6 protons.

An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have

10 neutrons. Isotopes have the same number of protons; different numbers of neutrons

Radioactive decay is likely to occur when

an atom has too many neutrons. The atomic nucleus becomes unstable if the ratio of protons to neutrons is too far from unity

Which model most accurately represents the current view of the structure of the atom

probability model

Elements are defined by the number of

Protons

Covalent bonds hold atoms together because they

fill shells without giving atoms much charge, bring electrons closer to protons

In molecules, C, H, O, and N atoms usually make __, __, __, and __ bonds respectively

4, 1, 2, 3

An atom’s atomic number is 7. Its valence is most likely

3. The neutral atom has 7 electrons. Two electrons fill the first shell, and 5 go into the second (valence) shell. The atom needs 3 more electrons to fill the valence shell.

By making two covalent bonds, an O atom (with 8 protons) fills its valence shell. Why does the atom’s charge stay close to zero

Shared electrons aren’t always near oxygen

In a double covalent bond, a carbon atom shares

electrons in 2 orbitals

Two C atoms form a double bond. Each C is bound to two H atoms. Which statement is true

All the atoms lie in a plane

Partial charges occur when

atoms share electrons unequally

To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add

2 electrons

Which answer helps to explain why carbon atoms tend to make 4 covalent bonds?

The valence shell needs 8 electrons.

An electrically neutral molecule has the formula C3H4O2N. If the carbon atoms form the usual number of bonds, how many covalent bonds will each hydrogen atom have with other atoms in the molecule?

1

Which answer correctly ranks the atoms in terms of decreasing electronegativity (the highest electronegativity first)

O,N,C,H

Dr. Haxton says the O-O bond is polar and the C-C bond is nonpolar. A good student would say

Wrong again, Ralph. Both bonds are nonpolar

the most polar bond is

O-H

If you want a molecule that is highly polar, look for one that contains

H-N

Which item is based on differences in electronegativity between atoms

the organization of phospholipids into bilayers, The pairing of bases in DNA, The tertiary folding of proteins

Compared to covalent bonds, ionic bonds

rely much less on electron-sharing

A cation with two units of charge has 10 neutrons and 8 protons. The ion also has

6 electrons. The part with the two units of + charge is a cation; the part with the unit of – charge is an anion

True or false: Ions may form by transferring an atomic nucleus (with or without electrons) to another molecule

True

A phrase that applies to covalent bonding and not other kinds of bonds is

electron-sharing

When chemists and biologists want to show how atoms are bonded in a molecule, they usually use a

structural formula

Polar attractions are

forces between atoms with partial charges, weaker than covalent bonds, important because they are numerous.

Hydrogen bonds

can form between H and N

Dr. Haxton told his class that a water molecule can make 4 hydrogen bonds, all of them in the same plane as the three atoms. What would a good student reply

Wrong! Two hydrogen bonds are not in the plane of the atoms

Which statement is part of the explanation for water’s high cohesion

Oxygen has four valence orbitals, Oxygen is much more electronegative than hydrogen.

Despite its cohesion, water can flow because

hydrogen bonds break and re-form rapidly

Which answer helps to explain how many hydrogen bonds a water molecule can form

Oxygen’s valence shell has four orbitals

Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface

Polar groups attract one another

Dissolving is best described as

a mingling of molecules and/or ions.

Water is a source of ______________ for chemical reactions in cells

hydrogen and oxygen atoms

Which statement is true of water’s tensile strength?

It results from hydrogen bonding, It helps to pull water through plants, It involves both cohesion and adhesion

Water has surface tension because …

hydrogen bonds between surface water molecules resist being stretched.

Which of the following helps most to explain why water has a high specific heat?

A water molecule can make 4 hydrogen bonds.

Primary Protein Structure

sequence of amino acids in a protein

Secondary Structure

describes the alpha-helices and beta sheets that are formed by hydrogen bonding between backbone atoms located near eachother in the poly peptide chain

Tertiary Structure

a protein folds into a compact 3D shape stabilized by interactions between side chain R-groups of amino acids

Quaternary

result of 2 or more protein subunits assembling to form a larger biologically active protein complex

Which polymers are composed of Amino acids

proteins

Which of the following is not attached to the central carbon atom in an amino acid?

an oxygen

what part of an amino acid is always acidic

Carboxyl Functional group

Which monomers make up RNA

Nucleotides

True or false? Enzymes in the digestive tract catalyze hydrolysis reactions

True

Proteins are polymers of

amino acids

amino acids of a protein are linked by

peptide bonds

The secondary structure of a protein results from

hydrogen bonds

Tertiary structure is not dependent on

peptide bonds

When is an enzyme denatured

when it loses it’s native conformation, and it’s biological activity

An enzyme is considered a catalyst because

speeds up chemical reactions without being used up

an enzyme is considred specific because

it’s ability to recognize the shape of a particular molecule

A cofactor

binds to an enzyme and plays a role in catalysis

Complex

When properly aligned, and enzyme and a substrate form an enzyme-substrate

A substrate binds to the enzyme at the

active site, where the reaction occurs.

In a catalyzed reaction, a reactant is also called a

substrate

Competitive inhibitor

has a structure that is so similar to a substrate that it can bond to the enzyme just like a substrate

Non competitive inhibitor

binds to a site on the enzyme that is not the active site

Irreversible inhibitor

forms a covalent bond with an amino acid side group within the active site, which prevents that substrate from entering the active site, or prevents catalytic activity

A competitive inhibitor competes with the substrate for the

active site

when the non competitive inhibitor is bonded to the enzyme

the shape of the enzyme is distorted

enzyme inhibitors disrupt normal interactions between an enzyme and its

substrate