Biology: Properties of Life and Cell Structure

Levels of Life

Eleven hierarchical stages of biological organization.

Emergence of Life

Life begins at the cellular level.

Domains of Life

Three classifications: Archaea, Bacteria, Eukarya.

Inductive Reasoning

Generalizations based on specific observations.

Matter

Anything that has mass and occupies space.

Element

Pure substance consisting of one type of atom.

Atom

Smallest unit of an element retaining properties.

Four Major Elements

Oxygen, carbon, hydrogen, nitrogen; 96% of body.

Proton

Positively charged particle in atomic nucleus.

Neutron

Neutral particle in atomic nucleus.

Electron

Negatively charged particle orbiting atomic nucleus.

Atomic Number

Number of protons in an atom's nucleus.

Atomic Mass

Weighted average mass of an element's isotopes.

Properties of Life

Eight characteristics defining living organisms.

Scientific Method

Systematic steps for scientific investigation.

Hypothesis

Testable prediction based on observations.

Theory

Well-substantiated explanation of phenomena.

Types of Scientific Writing

Three forms: research articles, reviews, and reports.

Deductive Reasoning

Specific conclusions drawn from general principles.

Covalent Bond

Sharing of electron pairs between atoms.

Ionic Bond

Transfer of electrons between charged atoms.

Hydrogen Bond

Attraction between hydrogen and electronegative atom.

Properties of Water

Cohesion, adhesion, high specific heat, solvent.

pH Scale

Measures acidity/basicity; each unit changes H ions by 10.

Organic Macromolecules

Large molecules essential for life: carbohydrates, lipids, proteins, nucleic acids.

Phospholipid Bilayer

Double layer forming cell membranes; hydrophilic heads, hydrophobic tails.

Cell Theory

All living things are composed of cells.

Cell Organelles

Specialized structures within cells performing specific functions.

Passivetransport (diffusion)

A passive process of transport of low-molecular weight material down its concentration gradient.

Facilitated transport

A process by which material moves down a concentration gradient (from high to low concentration) using integral membrane proteins.

Diffusion

A passive process of transport of low-molecular weight material down its concentration gradient.

Osmosis

The transport of water through a semipermeable membrane from an area of high water concentration to an area of low water concentration across a membrane.

Passive transport

A method of transporting material that does not require energy.

Active transport

The method of transporting material that requires energy.

Endocytosis

A type of active transport that moves substances, including fluids and particles, into a cell.

Exocytosis

A process of passing material out of a cell.

Hypertonic

Describes a solution in which extracellular fluid has higher osmolarity than the fluid inside the cell.

Hypotonic

Describes a solution in which extracellular fluid has lower osmolarity than the fluid inside the cell.

Isotonic

Describes a solution in which the extracellular fluid has the same osmolarity as the fluid inside the cell.

Applied science

A form of science that solves real-world problems.

Basic science

Science that seeks to expand knowledge regardless of the short-term application of that knowledge.

Biology

The study of life.

Biosphere

A collection of all ecosystems on Earth.

Cell

The smallest fundamental unit of structure and function in living things.

Community

A set of populations inhabiting a particular area.

Control

A part of an experiment that does not change during the experiment.

Deductive reasoning

A form of logical thinking that uses a general statement to predict specific results.

Descriptive science

A form of science that aims to observe, explore, and find things out.

Ecosystem

All living things in a particular area together with the abiotic, nonliving parts of that environment.

Eukaryote

An organism with cells that have nuclei and membrane-bound organelles.

Evolution

The process of gradual change in a population that can also lead to new species arising from older species.

Falsifiable

Able to be disproven by experimental results.

Homeostasis

The ability of an organism to maintain constant internal conditions.

Hypothesis-based science

A form of science that begins with a specific explanation that is then tested.

Inductive reasoning

A form of logical thinking that uses related observations to arrive at a general conclusion.

Life science

A field of science, such as biology, that studies living things.

Macromolecule

A large molecule typically formed by the joining of smaller molecules.

Molecule

A chemical structure consisting of at least two atoms held together by a chemical bond.

Natural science

A field of science that studies the physical world, its phenomena, and processes.

Organ

A structure formed of tissues operating together to perform a common function.

Organ system

The higher level of organization that consists of functionally related organs.

Organelle

A membrane-bound compartment or sac within a cell.

Organism

An individual living entity.

Peer-reviewed article

A scientific report that is reviewed by a scientist's colleagues before publication.

Phylogenetic tree

A diagram showing the evolutionary relationships among biological species based on similarities and differences in genetic or physical traits or both.

Physical science

A field of science, such as astronomy, physics, and chemistry, that studies nonliving matter.

Population

All individuals within a species living within a specific area.

Prokaryote

A unicellular organism that lacks a nucleus or any other membrane-bound organelle.

Science

Knowledge that covers general truths or the operation of general laws, especially when acquired and tested by the scientific method.

Scientific law

A description, often in the form of a mathematical formula, for the behavior of some aspect of nature under certain specific conditions.

Scientific method

A method of research with defined steps that include experiments and careful observation.

Scientific theory

A thoroughly tested and confirmed explanation for observations or phenomena.

Tissue

A group of similar cells carrying out the same function.

Variable

A part of an experiment that can vary or change.

unified cell theory

the biological concept that states that all organisms are composed of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells

vacuole

a membrane-bound sac, somewhat larger than a vesicle, that functions in cellular storage and transport

vesicle

a small, membrane-bound sac that functions in cellular storage and transport; its membrane is capable of fusing with the plasma membrane and the membranes of the endoplasmic reticulum and Golgi apparatus

acetyl CoA

the combination of an acetyl group derived from pyruvic acid and coenzyme A which is made from pantothenic acid (a B-group vitamin)

activation energy

the amount of initial energy necessary for reactions to occur

active site

a specific region on the enzyme where the substrate binds

allosteric inhibition

the mechanism for inhibiting enzyme action in which a regulatory molecule binds to a second site (not the active site) and initiates a conformation change in the active site, preventing binding with the substrate

anabolic

describes the pathway that requires a net energy input to synthesize complex molecules from simpler ones

anaerobic cellular respiration

the use of an electron acceptor other than oxygen to complete metabolism using electron transport-based chemiosmosis

ATP

(also, adenosine triphosphate) the cell's energy currency

ATP synthase

a membrane-embedded protein complex that regenerates ATP from ADP with energy from protons diffusing through it

bioenergetics

the concept of energy flow through living systems

catabolic

describes the pathway in which complex molecules are broken down into simpler ones, yielding energy as an additional product of the reaction

chemiosmosis

the movement of hydrogen ions down their electrochemical gradient across a membrane through ATP synthase to generate ATP

citric acid cycle

a series of enzyme-catalyzed chemical reactions of central importance in all living cells that harvests the energy in carbon-carbon bonds of sugar molecules to generate ATP; the citric acid cycle is an aerobic metabolic pathway because it requires oxygen in later reactions to proceed

competitive inhibition

a general mechanism of enzyme activity regulation in which a molecule other than the enzyme's substrate is able to bind the active site and prevent the substrate itself from binding, thus inhibiting the overall rate of reaction for the enzyme

electron transport chain

a series of four large, multi-protein complexes embedded in the inner mitochondrial membrane that accepts electrons from donor compounds and harvests energy from a series of chemical reactions to generate a hydrogen ion gradient across the membrane

endergonic

describes a chemical reaction that results in products that store more chemical potential energy than the reactants

enzyme

a molecule that catalyzes a biochemical reaction

exergonic

describes a chemical reaction that results in products with less chemical potential energy than the reactants, plus the release of free energy

feedback inhibition

a mechanism of enzyme activity regulation in which the product of a reaction or the final product of a series of sequential reactions inhibits an enzyme for an earlier step in the reaction series

fermentation

the steps that follow the partial oxidation of glucose via glycolysis to regenerate NAD+; occurs in the absence of oxygen and uses an organic compound as the final electron acceptor

glycolysis

the process of breaking glucose into two three-carbon molecules with the production of ATP and NADH

heat energy

the energy transferred from one system to another that is not work

in vitro

taking place in a test tube, culture dish, or elsewhere outside a living organism

kinetic energy

the type of energy associated with objects in motion