Biology Key Concepts: Cells, Macromolecules, and Chemical Bonds

What are the common characteristics of living things?

Made up of a common set of chemicals, cells enclosed by plasma membranes, utilize molecules and energy from the environment, have a universal genetic code, replicate genes, evolve as populations, and self-regulate internal environments (homeostasis).

What is the major unifying principle of biology?

Evolution, suggesting all living things could be descendants of a common ancestor.

How do you assign electrons to their electron shells?

Electron shells are energy levels around the nucleus; the first shell holds a maximum of 2 electrons, while subsequent shells can hold up to 8 electrons.

What are isotopes?

Forms of an element with different numbers of neutrons and thus different mass numbers.

What is the octet rule?

Atoms tend to form stable molecules by having 8 electrons in their outermost shell.

What is the difference between polar and nonpolar covalent bonds?

Polar covalent bonds involve unequal sharing of electrons, while nonpolar covalent bonds involve equal sharing of electrons.

What is an ion?

An atom or molecule with a net electrical charge, formed when an atom gains or loses electrons.

What is the difference between cations and anions?

Cations are positively charged ions (more protons than electrons), while anions are negatively charged ions (more electrons than protons).

How are ionic bonds formed?

Ionic bonds form through the electrical attraction between oppositely charged ions after one atom steals an electron from another.

Why does salt dissolve in water?

Ionic bonds between Na and Cl are broken when water molecules attract the ions, separating them.

What are hydrogen bonds?

Attractions between the negative end of one molecule and the positive hydrogen end of another molecule.

Rank the strengths of covalent bonds, ionic bonds, hydrogen bonds, and van der Waals forces.

Covalent bonds (strongest), ionic bonds, hydrogen bonds, van der Waals forces (weakest).

What is the difference between hydrophilic and hydrophobic molecules?

Hydrophilic molecules have polar covalent bonds and interact with water, while hydrophobic molecules have nonpolar covalent bonds and do not interact well with water.

What properties of water are due to hydrogen bonds?

High heat of vaporization, surface tension, and cohesion.

Why does ice float?

Ice is less dense than liquid water due to hydrogen bonds holding its molecules further apart.

What does the pH scale measure?

The acidity or basicity of a solution, ranging from 0 to 14, with 7 being neutral.

What are the four types of macromolecules found in cells?

Proteins (from amino acids), carbohydrates (from monosaccharides), nucleic acids (from nucleotides), and lipids (from fatty acids and glycerol).

What are functional groups?

Groups of atoms that give biological molecules their chemical properties, influencing their interactions with water.

What are condensation (dehydration) reactions?

Reactions that form covalent bonds between monomers by releasing water.

What happens during hydrolysis reactions?

Polymers are broken down into monomers by the addition of water.

What are the important functions of proteins?

Catalyzing biochemical reactions, providing structural support, transporting molecules, and regulating gene expression.

How can you identify an amino acid?

It has an amino group, a carboxyl group, a side chain (R-group), and an alpha carbon.

What is a peptide bond?

A covalent bond formed between amino acids during a condensation reaction.

Why is a protein's shape crucial to its function?

The specific shape of a protein determines its ability to interact with other molecules and perform its biological functions.

What determines how a protein folds and interacts with other molecules?

The primary, secondary, tertiary, and quaternary structures of the protein.

What is the primary structure of a protein?

The sequence of amino acids in a polypeptide chain.

What are the two common secondary structures of proteins?

Alpha helix (ribbon) and beta pleated sheet (folded).

What interactions determine the tertiary structure of a protein?

Interactions of R-groups including hydrophobic aggregation, disulfide bridges, hydrogen bonds, van der Waals forces, and ionic bonds.

What is the quaternary structure of a protein?

The structure formed by interactions between multiple polypeptide subunits.

Which amino acid forms disulfide bridges in proteins?

Cysteine.

What environmental factors can affect protein structure?

Temperature, pH, and high concentrations of polar or nonpolar substances.

What is the typical chemical formula for carbohydrates?

Cm(H2O)n.

What distinguishes a monosaccharide from a disaccharide?

Monosaccharides contain one sugar unit, while disaccharides contain two sugar units.

What is the difference between α-glycosidic bonds and β-glycosidic bonds?

α-glycosidic bonds are on the opposite side of the --CH2OH group, while β-glycosidic bonds are on the same side.

What are oligosaccharides and their functions?

Oligosaccharides contain 3-20 monosaccharides and often serve as recognition symbols on cell-surface proteins or lipids.

What are polysaccharides and provide examples?

Complex compounds made of multiple sugar residues; examples include starch, glycogen, cellulose, and chitin.

What makes lipids hydrophobic?

Their nonpolar hydrocarbon structure, which is insoluble in water.

How are triglycerides formed?

From glycerol and fatty acids through three condensation reactions that form ester linkages.

What distinguishes saturated fatty acids from unsaturated fatty acids?

Saturated fatty acids have no double bonds, while unsaturated fatty acids contain one or more double bonds.

What is the structure of phospholipids?

Phospholipids have a polar head and two nonpolar fatty acid tails, making them amphipathic.

What are the three components of a nucleotide?

A base, a sugar (ribose or deoxyribose), and a phosphate group.

What is the difference between ribose and deoxyribose?

Ribose has a hydroxyl group at the second carbon, while deoxyribose has a hydrogen atom at that position.

What are pyrimidines and purines?

Pyrimidines (cytosine, uracil, thymine) have one ring, while purines (adenine, guanine) have two rings.

How are nucleotides linked together?

By phosphodiester bonds between the phosphate group of one nucleotide and the sugar of another.

What is cell theory?

The theory that states cells are the fundamental units of life, all living organisms are composed of cells, and all cells come from preexisting cells.

Why is the surface area-to-volume ratio important in cells?

It affects the amount of resources that can enter and waste that can exit the cell, impacting chemical activity.

What are key characteristics of prokaryotic cells?

Prokaryotic cells have a complex cell wall, nucleoid, and may have pili and flagella.

What structures are common to all cells?

DNA, plasma membrane, ribosomes, and cytoplasm/cytosol.