UAHS Honors Biology Midterm Review

Matter

Anything that occupies space, has mass, and is made up of elements.

Element

A substance made up of only one type of atom that can't be broken down into a simpler chemical substance.

CHNOPS (Six Most Common Elements)

The six most common elements in living things: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur.

Trace Elements

Elements required by an organism in only very small amounts (e.g., iron, which carries oxygen, and iodine, which is essential for a thyroid hormone).

Atoms

The smallest building blocks of matter that retain the characteristics of that element. They cannot be divided into smaller substances by any natural processes.

Nucleus

Small central part of an atom that contains the protons and neutrons.

Proton

An atomic particle with a positive charge and a mass of 1, located in the nucleus.

Neutron

An atomic particle with a neutral charge and a mass of 1, located in the nucleus.

Electron

An atomic particle with a negative charge and nil mass, located orbiting the nucleus.

Atomic Number

The number of protons in an atom.

Mass Number

The sum of the number of protons and neutrons.

Isotopes

The same type of atom, but they have different numbers of neutrons. They have the same number of protons and behave identically in chemical reactions.

Radioactive Isotopes

Isotopes whose nucleus decays spontaneously, causing particles and energy to be given off.

Electrons (in bonding)

The only atomic particles directly involved in the chemical activity of an atom. The further they are from the nucleus, the greater their energy.

Electron Shells

Different energy levels around the nucleus where electrons can be located.

Valence Electrons

Electrons located in the outermost electron shell. They participate in chemical bonding.

Chemical Bond

Formed when atoms interact by sharing, gaining, or losing valence electrons to achieve a full (stable) outermost shell.

Covalent Bond

A strong chemical bond that forms when two atoms share electrons. It is the strongest type of bond.

Nonpolar Covalent Bond

A bond where the electrons are shared equally between the atoms (e.g., between two atoms of the same element, like O_2).

Polar Covalent Bond

A bond where the electrons are shared unequally because one atom is more electronegative (a stronger pull on electrons) than the other (e.g., in a water molecule, H_2O).

Ion

An atom or molecule with an electrical charge as a result of gaining or losing valence electrons.

Ionic Bond

Occurs when two ions of opposite charges attract one another. It forms when electrons are lost or gained, typically between a nonmetal and a metal, to create a stable outer shell. It is the next strongest bond after covalent bonds.

Hydrogen Bond

Tends to form between the negatively charged region of an atom (like Oxygen) and a hydrogen atom. It is the weakest type of bond and is crucial for the functioning of a cell and creating the unique 3D shape of molecules (like in DNA).

Chemical Reaction

The process of breaking and making chemical bonds, which changes the composition of matter by converting reactants (starting materials) into products (resulting materials). Matter is only rearranged, not destroyed.

Polarity (of Water)

The uneven distribution of electrons in a water molecule, where electrons are pulled toward the oxygen atom, giving it a partial negative charge and the hydrogen atoms a partial positive charge.

Hydrogen Bonding (in Water)

The attraction between the partial negative charge on the oxygen of one water molecule and the partial positive charge on the hydrogen of another water molecule, which links water's life-supporting properties.

Cohesion

A property of water where molecules of the same substance stick to one another (e.g., water sticking to water). It creates surface tension.

Adhesion

A property of water where molecules of different substances stick to one another.

Surface Tension

The force that allows objects (like a paper clip or certain insects) to rest on the surface of water without breaking the surface. It is related to cohesion.

Specific Heat

Water's ability to resist changes in temperature, meaning it can absorb a lot of heat before its temperature increases. This helps organisms maintain a stable internal temperature (homeostasis).

Density (of Ice)

The property that makes ice less dense than liquid water (ice floats). This is important because it allows aquatic life to survive below the frozen surface.

Aqueous Solution

A solution where the solute particles are evenly distributed throughout the solvent, with water being the solvent.

Solute

The substance that is being dissolved in a solution.

Solvent

The substance that is doing the dissolving in a solution.

Universal Solvent

The term used to describe water due to its ability to dissolve practically any molecule.

Acid

Any compound that forms H+ ions in solution. These solutions have pH values that fall below 7. Strong acids usually have a pH between 0 and 3.

Base

A compound that produces OH- ions in solution. These solutions have pH values that fall above 7. Strong bases usually have a pH between 11 and 14.

pH Scale

Used to describe how acidic or basic a solution is, based on the concentration of H+ and OH- ions.

Buffer

A substance that helps keep the pH of a solution constant by preventing sharp, sudden changes in pH. They are vital for maintaining homeostasis in living systems

Monomers

Smaller units that are the building blocks of larger molecules (polymers).

Polymers

Long chains of molecules formed by linking monomers together.

Dehydration Reaction

The process of building macromolecules (polymers) where a water molecule (H2O) is released.

Hydrolysis Reaction

The process of breaking down a macromolecule (polymer) where a water molecule (H2O) is added.

Hydrophobic

"Water fearing" in nature; molecules that are not soluble in water (nonpolar).

Hydrophilic

"Water loving" in nature; molecules that are easily soluble in water (polar).

Carbohydrates

Macromolecules made up of sugar molecules; main function is to serve as an energy source.

Monosaccharides (Glucose)

The monomers (simplest sugars) of carbohydrates and the main source of energy for organisms.

Starch

A polysaccharide made of glucose monomers; how plants store sugar for energy.

Glycogen

A polysaccharide made of glucose monomers; how sugars are stored in animal cells.

Cellulose

A polysaccharide that serves as building material in plants (found in cell walls).

Lipids

The group of macromolecules known as "fats"; main functions are energy storage and membrane components.

Triglyceride

The basic structure of fats; formed by joining one glycerol and three fatty acid molecules.

Saturated Fats

Fatty acids where all carbon atoms are linked by single bonds and tend to be solid at room temperature.

Phospholipids

Lipids that contain only two fatty acids attached to a glycerol; a major component of cell membranes.

Proteins

Polymers of small building blocks called amino acids (monomers); involved in nearly every dynamic function of the body.

Amino Acids

The monomers of proteins; there are 20 total types.

Peptide Bond

A covalent bond that joins the carboxyl group of one amino acid to the amino group of the next.

Denaturation

The process where a protein unravels or loses its specific shape (and thus its function) due to changes in the environment (e.g., pH or temperature).

Primary Structure

The first level of protein structure: the unique sequence of amino acids in its polypeptide chain.

Elements in Carbohydrates

Composed of Carbon (C), Hydrogen (H), and Oxygen (O).

Carbohydrate Ratio

The elements C, H, and O are in a fixed 1:2:1 ratio (e.g., C1H2O1).

Glucose Formula (Carbohydrate Monomer)

C6H12O6

Elements in Lipids

Composed mainly of Carbon (C) and Hydrogen (H) with a small percentage of Oxygen (O).

Lipid Characteristic

Lipids have large nonpolar sections, which makes them hydrophobic ("water fearing").

Elements in Proteins

Composed of Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).

Amino Acid Functional Groups

All amino acid monomers contain an Amino Group (NH2) and a Carboxyl Group (COOH).

Elements in Nucleic Acids

Composed of Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), and Phosphorus (P).

Nucleotide Phosphorus

The element Phosphorus (P) is found in the Phosphate Group component of a nucleotide.

DNA (Deoxyribonucleic acid)

Main function is to store and transmit hereditary information (the blueprint for life).

RNA (Ribonucleic acid)

Main function is to assist with protein production (making proteins).

Nucleotides

The monomers of both DNA and RNA.

Base Pairing Rule

A pyrimidine always pairs with a purine. In DNA, Adenine pairs with Thymine (A-T) and Cytosine pairs with Guanine (C-G)

Light Microscope (LM)

Uses visible light to pass through a specimen; it is good for observing living cells. Maximum useful magnification is about 1,000 times.

Scanning Electron Microscope (SEM)

Uses an electron beam to create detailed three-dimensional (3D) images of the surface of a specimen (only for dead specimens).

Transmission Electron Microscope (TEM)

Uses an electron beam to create detailed two-dimensional (2D) images of the internal structure of a specimen (only for dead specimens).

Cell Theory

The fundamental concept in biology that states all living things are composed of cells, that cells are the basic units of structure and function in living things, and that new cells are produced from existing cells.

Cell Size Limit

Limited by the surface area-to-volume ratio.

Surface Area-to-Volume Ratio

As a cell grows, its volume increases much faster than its surface area, which limits how fast the cell can move materials in and out to survive.

Prokaryotic Cells

Simple cells that lack a nucleus and most other membrane-bound organelles (examples: Bacteria and Archaea).

Eukaryotic Cells

Complex cells that contain a nucleus and many membrane-bound organelles (examples: Protists, Fungi, Animals, and Plants).

Flagellum

A long, whiplike tail that is used to propel the cell through its liquid environment (for movement).

Pilus (Pili)

Short, hairlike projections used for attachment to surfaces and for the transfer of DNA during conjugation.

Capsule (Slime Layer)

A sticky layer around the cell wall that helps some bacteria to cause disease.

Plasmid

Small, circular pieces of DNA separate from the main chromosome, which can carry genes (like antibiotic-resistance genes).

Cell Wall (Prokaryotes)

A structure that surrounds the cell membrane, gives the cell its shape, and prevents water from entering and bursting the cell.

Plasma Membrane

A barrier surrounding the cell that regulates what enters and leaves the cell.

Nucleus

The cell's control center that contains the cell's genetic material (DNA) and controls all cell activities.

Nuclear Envelope

A double membrane that surrounds the nucleus and regulates what enters and leaves through nuclear pores.

Nucleolus

A small, dense region inside the nucleus that is the site where ribosomes are made.

Chromatin/Chromosomes

The form that DNA takes when it is coiled around proteins inside the nucleus.

Ribosome

The organelle responsible for protein synthesis (making proteins). It can be found floating freely in the cytoplasm or attached to the Rough ER.

Endoplasmic Reticulum (ER)

An extensive network of membranes (tubules and sacs) that acts as the cell's transport system (highway).

Rough Endoplasmic Reticulum (Rough ER)

ER that has ribosomes attached. Its function is to modify, package, and transport proteins destined for secretion or the cell membrane.

Smooth Endoplasmic Reticulum (Smooth ER)

ER that lacks ribosomes. Its functions include synthesizing lipids (fats/steroids), processing toxins, and storing calcium ions.

Golgi Apparatus

A stack of flattened membranous sacs that modifies, sorts, and packages proteins and lipids from the ER into vesicles for delivery throughout the cell or for secretion outside the cell.

Lysosome

The cell's "clean-up crew" or "recycling center." It contains powerful digestive enzymes used to break down food, old organelles, and foreign invaders.

Mitochondria

The "powerhouse of the cell." It is the site of cellular respiration, where chemical energy (glucose) is converted into usable energy (ATP).

Chloroplast

The site of photosynthesis in plant cells and algae, where light energy is converted into chemical energy (glucose).

Vacuole

A membrane-enclosed sac used for storage of food, water, and waste.

Central Vacuole

A very large vacuole in plant cells that maintains the cell's structural rigidity by keeping the turgor pressure high.