Keystone Exam 2025 Cells: Structure and Function

Vocabulary flashcards for review.

Cell

The smallest unit that can carry out all the functions of life.

Prokaryotic cells

Single-celled organisms with a cell wall, plasma membrane, cytoplasm, and DNA, such as bacteria.

Eukaryotic cells

Multicellular organisms with organelles, complex with specialized cells and a nucleus, including animals, plants, protists, and fungi.

Tissue

A group of similar cells that work together to perform a specific function.

Organ

A structure made up of several types of tissues that work together to perform a specific function.

Organ System

A group of organs that work together to perform a specific function.

Homeostasis

Keeping cells in a living multicellular organism in a stable balanced internal and external environment.

Thermoregulation

Processes that help an organism keep its body temperature in a safe range, like sweating or shivering.

Macromolecules

Large polymers made up of smaller repeating monomers; includes carbohydrates, proteins, lipids, and nucleic acids.

Carbohydrates

Organic compounds composed of C, H, and O in a 1:2:1 ratio, including sugars, starch, and glycogen; the primary source of energy.

Proteins

Composed of C, H, O, N, and S; made up of amino acids; function as enzymes, storage molecules, plasma membrane components, hormones, antibodies, and structural support.

Lipids

Fats composed of H, C, and O (few O atoms); do not dissolve in water; monomers are fatty acids and glycerol. Can be saturated or unsaturated.

Nucleic Acids

Large molecules that make up DNA and RNA; monomers are nucleotides.

Enzymes

Catalysts in biochemical reactions that provide a site where reactants (substrates) can come together to react. The enzyme's surface has a distinct shape that allows it to interact with specific substrates. This site is called the active site which works like a lock and key.

Polarity of Water

Water is uniquely polar from the hydrogen bonds between molecules and the negative end at the oxygen end and positive end at the hydrogen end of the molecule.

Cohesion

Water's property of sticking to itself due to hydrogen bonds.

Adhesion

The tendency of water to stick to other substances.

Capillary Action

The movement of liquid in contact with a solid due to adhesion and cohesion forces.

Specific Heat of Water

The amount of energy it takes to increase the temperature of water by one degree C; a relatively large amount of energy.

Solvent

Water is the universal solvent as it dissolves so many substances.

ATP (Adenosine Triphosphate)

The organic molecule used for energy in cells.

Photosynthesis

Uses energy from sunlight to convert carbon dioxide and water into glucose and oxygen gas. Occurs in chloroplasts.

Cellular Respiration

Breaks the chemical bonds of glucose to release energy, which is captured as ATP. It occurs through the reaction of Glucose (C6H12O6) + oxygen gas (O2) which produces Carbon dioxide (CO2) + water (H2O) + energy

Plasma Membrane

The regulator of the internal conditions of the cells that serves as a partial barrier between the intracellular and extracellular environment

Diffusion

The movement of particles from an area of higher concentration to an area of lower concentration.

Facilitated Diffusion

The movement of substances across a plasma membrane with the aid of protein molecules embedded in the membrane.

Osmosis

The movement of water molecules into a concentrated solution from a less concentrated solution, either into or out of a cell.

Hypertonic

The concentration of solute outside the cell is higher than the concentration in the cytoplasm.

Hypotonic

The concentration of solute in the cytoplasm is higher than that outside the cell.

Isotonic

Solutions with equal concentrations on both sides of a membrane.

Active Transport

When materials move against the concentration gradient, requiring energy.

Endocytosis

The process in which a cell surrounds and takes in material from its environment.

Exocytosis

The membrane of a vacuole fuses with the plasma membrane to remove unwanted materials.

Cell Cycle

The process by which a cell divides to form two or more new cells, called daughter cells, from a parent cell.

Mitosis

The process where the nucleus divides into two nuclei/ PMAT are its phases. Sister chromatids are connected at a centromere.

Meiosis

The process of two nuclear divisions that produce gametes.

Homologous Chromosomes

Paired chromosomes that are similar in size, shape, and genetic material.

Crossing Over

Segments of homologous chromosomes break off and are exchanged.

Alleles

The different forms of the gene for a specific trait.

Dominant Allele

The allele expressed in an organism if it is present.

Recessive Allele

Two matching recessive alleles are necessary to express this trait.

Genotype

All or part of an organism’s genetic makeup.

Phenotype

The physical outward appearance that the organism shows.

Homozygous

An organism with a genotype made up of two matching alleles, either dominant or recessive for that gene.

Heterozygous

An organism with two different alleles.

Punnett Square

A diagram that shows possible combinations of dominant and recessive alleles in offspring based on the genotypes of the parents.

Law of Segregation

The law states that alleles separate when gametes are formed, so each gamete contains only one allele of each gene.

Mutation

Any change to an organism’s genetic material.

Gene Mutation

A change in the sequence of DNA that makes up a single gene.

Point Mutation

A change in a single base pair in a gene.

Silent Mutation

A point mutation that results in the same amino acid being placed and does not affect the organism's phenotype.

Missense mutation

A change in a base that turns a codon for one amino acid into a codon for a functionally different amino acid. This can seriously harm the organism.

Nonsense mutation

This mutation changes a codon for an amino acid into a ‘stop’ codon. This results in a shortened protein which will not function properly.

Frameshift mutations

These mutations change the whole reading frame of the DNA and result in an amino acid sequence that is completely different from what it should be.

Selective Breeding

The intentional mating of organisms to produce offspring with specific traits.

Genetic Engineering

The direct manipulation of a cell’s genetic material to produce organisms with useful traits.

Genetically Modified Organism (GMO)

An organism whose genes have been altered, often involving the transfer of genes from one species to another.

Recombinant DNA

When DNA from one organism is inserted into the DNA of another organism; also known as gene splicing.

Gene Therapy

The alteration, insertion, or deletion of a gene in an individual’s cells to treat a disease.

Cloning

The artificial production of a DNA fragment, cell, or organism that is genetically identical to the original organism.

DNA Fingerprinting

A technique to compare images of DNA fragments to determine relationships among individuals, based on the fact that no two people have the same DNA (except identical twins).

Evolution

The change in species over time, from the earliest forms of life to the wide range of organisms that exist today.

Adaptation

Traits that increase an organism’s chance of survival tend to become more common in a population; can be structural, functional, or behavioral.

Gene Pool

This includes all the alleles carried by members of the population, whether the alleles are expressed

Allele Frequency

This is the ratio of a particular allele for a gene to all alleles for that gene in a population

Speciation

The formation of one or more new species from an existing species.

Genetic Drift

A change in a population's allele frequencies due to chance events.

Founder Effect

This is the loss of genetic variation that occurs when a small number of individuals leave a large population and start a new one.

Homologous Structures

Similar physical structures in different organisms that share a common ancestor.

Analogous Structures

Physical structures that have similar functions in different organisms but do not share ancestry.

Vestigial Structures

A physical structure that does not seem to play a key role in an organism’s life functions but was more important in the organism’s ancestors.

Ecology

The study of interactions among organisms and between organisms and their environments.

Community

All the populations that inhabit the same area at the same time.

Ecosystem

All the communities in an area and the nonliving parts of their environment.

Biome

A large group of ecosystems that have similar climates and types of organisms.

Biotic Factor

A living thing in an ecosystem (e.g., microorganisms, plants, animals).

Abiotic Factor

A nonliving part of an ecosystem (e.g., light, temperature, precipitation, soil pH, available oxygen).

Producers

Organisms that capture energy from the sun and convert it to chemical energy to make their own food.

Consumers

Organisms that obtain their energy by eating other organisms.

Decomposers

Organisms that obtain energy from organic wastes like fallen leaves or dead organisms.

Food Chain

The path of food and energy from producer to consumer to decomposer.

Trophic Level

Levels in an ecosystem, comprising organisms that share the same function in the food chain and the same nutritional relationship to the primary sources of energy.

Herbivore

Consumers that eat only plants or plant products.

Carnivore

Consumers that eat only other consumers.

Omnivore

Consumers that eat both plants and animals.

Biomass

The amount of living matter in an ecosystem.

10% Rule

Only 10% of the energy at any trophic level is passed to the next level.

Evaporation

The change of a liquid to a gas at the surface of a liquid.

Condensation

Gas changes to a liquid when it loses energy.

Precipitation

Water that falls from the atmosphere to Earth as rain, snow, sleet, or hail.

Predation

An interaction between organisms in which one organism kills and eats another.

Symbiosis

A close interdependent relationship between organisms of different species.

Mutualism

A symbiotic relationship in which both organisms benefit.

Parasitism

A symbiotic relationship in which one organism benefits (parasite) and the other is harmed.

Commensalism

A symbiotic relationship in which one organism benefits and the other is neither harmed nor benefits.

Succession

A series of predictable changes in an ecosystem over time, where one community of organisms gradually replaces another.

Primary Succession

The gradual development of a new community from nothing, occurring on bare terrain without soil or preexisting life.

Secondary Succession

Succession that occurs when a disturbance changes or partially destroys an ecosystem without destroying the soil.

Pioneer Species

The first species to move into a devastated area of land, such as lichens.

Climax Community

A stable community that marks the end of succession in an area.