Human Bio Exam 1

matter

Anything that occupies space and has mass.

atomic number

The number of protons in the nucleus of an atom, which determines the chemical properties of an element.

double bond

A covalent bond formed by sharing two pairs of electrons between two atoms.

energy

The capacity to do work or produce change.

atomic mass

The total mass of protons, neutrons, and electrons in a single atom (approximately equal to the number of protons plus neutrons).

polar covalent bond

A type of covalent bond where electrons are shared unequally between two atoms, creating partial charges.

elements

Substances that cannot be broken down into simpler substances by ordinary chemical means.

isotopes

Atoms of the same element that have the same number of protons but different numbers of neutrons.

polar molecule

A molecule with an uneven distribution of charge, resulting in slightly positive and slightly negative regions.

atom

The basic unit of a chemical element, consisting of a nucleus surrounded by electrons.

radioactivity

The process by which an unstable atomic nucleus loses energy by radiation.

electronegativity

A measure of an atom's ability to attract shared electrons in a chemical bond.

nucleus

The dense center of an atom composed of protons and neutrons.

ionic bond

A chemical bond formed through the electrostatic attraction between oppositely charged ions.

hydrogen bond

A weak attraction between a slightly positive hydrogen atom in one polar molecule and a slightly negative atom in another.

proton

A positively charged subatomic particle located in the nucleus of an atom.

ion

An atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

molecule

A group of two or more atoms bonded together.

neutron

A neutral subatomic particle with no electric charge located in the nucleus of an atom.

covalent bond

A chemical bond that involves the sharing of electron pairs between atoms.

electrolyte

A substance that dissolves in water to produce an electrically conducting solution containing free ions.

electron

A negatively charged subatomic particle that orbits the nucleus of an atom.

electron shell

An energy level surrounding an atom's nucleus where electrons are found.

single bond

A covalent bond in which two atoms share one pair of electrons.

What makes up matter?

Matter is composed of basic substances called elements, which are made of atoms.

How do elements differ from each other?

Elements differ in their atomic number, which is the number of protons present in the nucleus of their atoms.

Where do the proton, neutron, and electron reside within the atom?

Protons and neutrons reside in the central nucleus, while electrons orbit the nucleus in electron shells.

How are isotopes used?

Isotopes are used in medical imaging, radio-dating fossils/artifacts, cancer radiation therapy, and biological tracers.

How do isotopes differ from one another and from the element atoms on the periodic table?

Isotopes of an element differ in their number of neutrons and atomic mass, while having the same number of protons.

What is the difference between Carbon-12 and Carbon-14?

Carbon-12 has 6 neutrons and is stable, whereas Carbon-14 has 8 neutrons and is radioactive.

How are radioisotopes used?

Radioisotopes are used as diagnostic tracers in medicine, in radiation therapy to kill cancer cells, and for radiocarbon dating.

What is oxygen's role in water?

Oxygen draws shared electrons toward itself due to high electronegativity, creating partial negative charges in the water molecule.

What holds a single water molecule together?

Polar covalent bonds hold the oxygen and hydrogen atoms together within a single water molecule.

What attracts one water molecule to another water molecule?

Hydrogen bonds attract the partial positive hydrogen of one water molecule to the partial negative oxygen of another.

What are two important roles of calcium?

Calcium is critical for bone and teeth formation, muscle contraction, and blood clotting.

Sodium and potassium both have a role in what?

Sodium and potassium both play key roles in nerve impulse transmission and maintaining fluid/electrolyte balance.

Hydrogen acts as what sort of a carrier?

Hydrogen ions (protons) act as charge and energy carriers, such as in cellular ATP synthesis and pH balance.

Which element acts as the backbone of nucleic acids?

Phosphorus (along with carbon, nitrogen, and oxygen forming the sugar-phosphate backbone).

Which element is the backbone of organic molecules?

Carbon serves as the primary structural backbone for all organic molecules.

Nitrogen has an important role in the makeup of which two organic molecules?

Nitrogen is an essential component of proteins (amino acids) and nucleic acids (DNA and RNA).

Which elements make up CHNOPS, those that are predominant in all cells?

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur.

How are minerals critical for our well being?

Minerals regulate enzyme function, maintain fluid balance, build skeletal structures, and enable nerve/muscle activity.

We think of electrons in what two ways?

Electrons are thought of both as discrete particles and as waves forming a cloud (orbital) around the nucleus.

What happens when an electron is in an excited state?

When an electron absorbs energy, it jumps to a higher energy level (shell) farther from the nucleus.

What is an orbital?

An orbital is a three-dimensional region surrounding the nucleus where an electron is most likely to be found.

How many electrons does the first shell hold?

The first shell holds a maximum of 2 electrons.

Each shell after the first can hold a maximum of how many electrons?

The second and third shells typically hold a maximum of 8 electrons (following the octet rule).

In covalent bonding, the sharing of electrons, what is the valence?

Valence is the number of covalent bonds an atom can form, determined by the number of unpaired valence electrons.

How do ionic bonds form?

Ionic bonds form when one atom transfers electrons to another, creating oppositely charged ions that attract each other.

Which forms first, the ions or the ionic bond?

The ions form first (via electron transfer), and then the electrostatic attraction creates the ionic bond.

Are ionic bonds strong?

Ionic bonds are strong in solid crystals, but easily break and dissociate in aqueous (water) environments.

How do covalent bonds form?

Covalent bonds form when two atoms share one or more pairs of valence electrons to achieve stable shell configurations.

How does a polar covalent bond form?

A polar covalent bond forms when atoms share electrons unequally due to a significant difference in electronegativity.

This polar covalent bond results in what?

It results in partial positive ($\delta+$) and partial negative ($\delta-$) charges on opposite ends of the bond.

What role does electronegativity play in the formation of molecules?

It determines whether electrons are shared equally (nonpolar covalent), shared unequally (polar covalent), or transferred (ionic).

Which molecules are hydrophobic and which are hydrophilic?

Nonpolar molecules are hydrophobic (water-fearing), while polar and charged molecules are hydrophilic (water-loving).

How do hydrogen bonds form?

They form when a hydrogen atom covalently bonded to an electronegative atom is attracted to another electronegative atom nearby.

What are molecules?

Molecules are chemical structures composed of two or more atoms held together by covalent chemical bonds.

Combination reactions occur how?

Combination (synthesis) reactions occur when two or more substances unite to form a single, more complex product.

Disassociation reactions occur how?

Dissociation (decomposition) reactions occur when a complex compound breaks down into smaller molecules, atoms, or ions.

Biological systems are based around which element?

Biological systems are based around Carbon due to its ability to form four stable covalent bonds.

polar covalent bond

A covalent bond where electrons are shared unequally between two atoms, creating partial positive and negative poles.

energy

The capacity to perform work or cause change in a system.

hydrolysis

A chemical reaction that breaks down polymers into monomers by adding a water molecule.

unsaturated lipids

Lipids containing one or more double bonds in their fatty acid chains, making them liquid at room temperature.

hydrogen bonds

Weak attractions between a partially positive hydrogen atom of one polar molecule and an electronegative atom of another.

kinetic energy

The energy an object possesses due to its motion.

cellulose

A structural polysaccharide made of glucose monomers that forms the rigid cell walls of plants.

protein

A biological macromolecule made of amino acid chains folded into specific functional shapes.

solvent

The dissolving agent of a solution, usually present in the greatest amount (such as water).

potential energy

Stored energy resulting from an object's position, structure, or chemical bonds.

monosaccharide

The simplest unit of carbohydrates, consisting of a single sugar molecule like glucose or fructose.

enzyme

A protein catalyst that speeds up specific chemical reactions by lowering the required activation energy.

solute

A substance that is dissolved in a solvent to form a solution.

monomer

A small molecular subunit that can chemically bind with other identical or similar subunits to form a polymer.

photosynthesis

The biological process by which autotrophs convert light energy into chemical energy stored in sugars.

peptide bond

The covalent bond formed between two amino acids during protein synthesis.

solution

A homogeneous liquid mixture composed of two or more substances evenly distributed.

macromolecule

A very large biological molecule formed by joining smaller organic molecules (monomers) together.

polysaccharide

A carbohydrate polymer composed of many monosaccharide units linked together.

primary structure

The unique linear sequence of amino acids linked together in a polypeptide chain.

lipid

A diverse group of hydrophobic organic molecules, including fats, oils, phospholipids, and steroids.

condensation (dehydration) synthesis

A chemical reaction that joins two monomers together by removing a water molecule.

secondary structure

Local spatial patterns in a polypeptide chain, such as alpha-helices or beta-pleated sheets, stabilized by hydrogen bonds.

acidic solution

A solution with a higher concentration of hydrogen ions ($H^+$) than hydroxide ions ($OH^-$), with a pH less than 7.

acid

A chemical substance that increases the hydrogen ion ($H^+$) concentration of a solution.

glycogen

A highly branched storage polysaccharide made of glucose, stored in animal liver and muscle tissues.

tertiary structure

The overall three-dimensional shape of a single polypeptide chain, determined by interactions among R-groups.

basic solution

A solution with a lower concentration of hydrogen ions ($H^+$) than hydroxide ions ($OH^-$), with a pH greater than 7.

base

A chemical substance that reduces the hydrogen ion ($H^+$) concentration of a solution or releases hydroxide ions ($OH^-$).

phospholipid

A lipid containing a hydrophilic head (phosphate group) and two hydrophobic fatty acid tails, forming cell membranes.

quaternary structure

The functional shape formed by the association of two or more individual polypeptide subunits.

pH

A logarithmic scale measuring the concentration of hydrogen ions ($H^+$) in a solution, ranging from 0 to 14.

isomer

Organic compounds with identical chemical formulas but different structural arrangements or spatial orientations.

saturated fat

A lipid whose fatty acid chains contain only single carbon-carbon bonds, making them solid at room temperature.

nucleic acid

A macromolecule composed of nucleotide monomers that stores and transmits genetic information (DNA and RNA).

RNA

Ribonucleic acid; a single-stranded nucleic acid involved in protein synthesis and gene regulation.

DNA

Deoxyribonucleic acid; a double-stranded helical nucleic acid containing genetic instructions for development and functioning.

mRNA

Messenger RNA; the RNA molecule that carries genetic code from DNA in the nucleus to ribosomes for protein synthesis.

tRNA

Transfer RNA; an RNA molecule that delivers specific amino acids to the ribosome during protein synthesis (translation).