NLN NEX Science cheat sheet

Cell theory states that all living organisms are made of one or more cells, cells are the basic unit of life, and new cells arise from existing cells.

DNA is a double helix with adenine pairing with thymine and guanine pairing with cytosine; RNA uses uracil instead of thymine.

Photosynthesis equation: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2.

Newton's first law: an object at rest stays at rest and an object in motion stays in motion at constant velocity unless acted on by a net external force.

Ohm's law: V = IR, where V is voltage, I is current, and R is resistance.

Kinetic energy formula: KE = ½mv², where m is mass and v is velocity.

The pH scale runs from 0 to 14; pH below 7 is acidic, pH 7 is neutral, and pH above 7 is basic.

Mitosis produces two genetically identical diploid daughter cells, while meiosis produces four genetically distinct haploid gametes.

The left ventricle pumps oxygenated blood into the aorta and has a thicker muscular wall than the right ventricle.

Pulmonary circulation carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium.

Alveoli are tiny air sacs where oxygen diffuses into pulmonary capillaries and carbon dioxide diffuses out.

The nephron is the functional unit of the kidney; it filters blood, reabsorbs useful substances, and secretes wastes into urine.

Hemoglobin in red blood cells binds oxygen in the lungs and releases it in tissues where oxygen partial pressure is lower.

Insulin is secreted by pancreatic beta cells and lowers blood glucose by promoting cellular uptake and glycogen storage.

An action potential is a rapid electrical change in a neuron caused by ion movement across the cell membrane.

Skeletal muscle is voluntarily controlled and striated; smooth muscle is involuntary and nonstriated; cardiac muscle is involuntary and striated.

Gram-positive bacteria retain crystal violet stain and appear purple; gram-negative bacteria lose the stain and appear pink or red.

Antibiotics target bacterial structures or processes such as cell wall synthesis, protein synthesis, or DNA replication; they do not treat viral infections.

Viruses are obligate intracellular parasites that require a host cell to replicate and lack independent metabolism.

Antibodies are Y-shaped proteins produced by plasma cells that bind specific antigens and help neutralize or mark pathogens.

Vaccines expose the immune system to a harmless antigen or instruction, producing memory cells and faster response on later exposure.

A nosocomial infection is an infection acquired in a healthcare setting, often associated with invasive devices or poor hand hygiene.

Sterilization destroys all microbial life including spores; disinfection reduces or kills many pathogens on surfaces but may not eliminate spores.

Normal microbiota are microorganisms that live harmlessly on or in the body and can compete with pathogens for nutrients and space.

The independent variable is the factor deliberately changed by the researcher; the dependent variable is the measured outcome.

A control group receives no treatment or a standard treatment and provides a baseline for comparison.

Correlation describes a relationship between two variables but does not by itself establish causation.

The mean is the arithmetic average; the median is the middle value when data are ordered from least to greatest.

Standard deviation measures the spread of data around the mean; a larger value indicates greater variability.

A hypothesis is a testable, falsifiable prediction about the relationship between variables.

Bar graphs compare discrete categories, line graphs show trends over continuous variables, and scatterplots show relationships between two variables.

Significant figures communicate measurement precision; trailing zeros after a decimal point are significant.