Basic Chemistry, Water, and Human Body Systems: A Study Guide for Students

Four most abundant elements in living organisms

Carbon, Hydrogen, Oxygen, Nitrogen.

Smallest unit of elements

Atoms.

Subatomic particle that determines chemical behavior

Electrons.

Strength comparison of hydrogen bonds and covalent bonds

Hydrogen bonds are weak; covalent bonds are strong (covalent = strongest).

Why is water a polar molecule?

Oxygen pulls electrons more strongly (higher electronegativity), making it slightly negative while hydrogen is slightly positive.

Charge resulting from unequal electron pull in covalent bonds

Partial charges → polar covalent bond.

Bonds within a water molecule (O-H)

Polar covalent bonds.

Bonds between adjacent water molecules

Hydrogen bonds.

Cohesion and adhesion in relation to surface tension and capillary action

Cohesion = water sticks to water, Adhesion = water sticks to other surfaces → allow surface tension and movement of water in plants.

Why is water a good solvent?

It dissolves hydrophilic (polar) substances due to polarity, but not hydrophobic (nonpolar) ones.

How hydrogen bonds help water regulate temperature

They absorb/release heat slowly → stabilizes climates & body temperature.

Real-world examples of water regulating temperature

Coastal climate moderation, sweating/evaporation cooling.

Water's role in dehydration synthesis and hydrolysis

Dehydration removes water to build molecules; hydrolysis adds water to break molecules.

Organ system that filters blood and eliminates wastes

Urinary system.

Process that balances salt and water inside the body

Osmoregulation.

Organs that make urine and where it is stored

Kidneys make urine, stored in bladder, exits via urethra.

Meaning of 'selectively permeable'

The membrane allows some molecules to pass while blocking others.

Definition of concentration gradient

A difference in solute concentration across a membrane that drives diffusion.

Effect of polarity, charge, and size on transport

Small, nonpolar molecules pass easily; large/charged need proteins or energy.

Does passive transport require energy?

No.

How simple diffusion works

Molecules move down concentration gradient without help.

Molecules that diffuse freely

Small nonpolar molecules like O₂ and CO₂.

Definition of osmosis

Diffusion of water across a membrane.

Direction of water movement in osmosis

Toward higher solute concentration.

Definition of facilitated diffusion

Movement of molecules down concentration gradient using membrane proteins.

Molecules that need protein channels

Large, polar, or charged molecules (e.g. glucose, ions).

Difference between active and passive transport

Active transport requires energy (ATP) and moves substances against gradient.

Requirements for active transport

ATP energy + membrane protein (pump).

Example of active transport

Sodium-potassium pump.

Why maintaining molecular distribution costs energy

Because it moves molecules against their concentration gradient.

How endocytosis and exocytosis work

Endocytosis = membrane engulfs substances into vesicles; Exocytosis = vesicles fuse with membrane to release substances.

Definition of heterotrophs

Humans must consume other organisms for organic molecules/food.

Definition of 'organic' in biology

Molecules containing carbon and hydrogen.

Definition of a Calorie (capital C)

A kilocalorie (energy to raise 1 kg of water by 1°C).

Three FDA healthy eating recommendations

Limit added sugars, limit saturated/trans fats, reduce sodium.

Difference between simple and complex carbohydrates

Simple = quick energy (mono/di-saccharides), Complex = long-term energy (polysaccharides).

Example of monosaccharide and disaccharide

Glucose; Sucrose.

Starch

Plant storage polysaccharide.

Glycogen

Animal storage polysaccharide.

Cellulose

Plant structure polysaccharide.

Triglyceride

Glycerol + 3 fatty acids.

Saturated fats

Fats with no double bonds, solid at room temperature.

Unsaturated fats

Fats with double bonds, liquid at room temperature.

Trans fats

Artificially hydrogenated unsaturated fats.

Phospholipids

Molecules that form membrane structure.

Cholesterol

Molecule that contributes to membrane fluidity.

Steroid molecules

Hormones such as estrogen and testosterone.

Amino acids

Monomers of proteins (20 types).

Protein functions

Roles include enzymes, structure, transport, signaling, and defense.

Protein shape

Determines function (lock & key fit).

Denaturation factors

Heat, pH, and salt concentration can denature proteins.

Essential amino acids

Amino acids that the body cannot synthesize.

Vitamins

Organic molecules that act as coenzymes.

Minerals

Inorganic elements essential for various functions.

Digestive steps

Ingestion, Digestion, Absorption, Elimination.

Substrate

Molecule an enzyme acts on.

Product

Molecule formed after an enzyme reaction.

Enzyme

Biological catalyst that speeds up reactions by lowering activation energy.

Important digestive enzymes

Amylase (starch), Protease (proteins), Lipase (fats).

Peristalsis

Wave-like muscle contractions that move food along the digestive tract.

Bile

Emulsifies fats into smaller droplets; made in liver, stored in gallbladder.

Alveoli

Air sacs in lungs where gas exchange occurs.

Hemoglobin

Protein that carries oxygen in blood.

COPD

Chronic Obstructive Pulmonary Disease (chronic bronchitis + emphysema).

Composition of blood

Plasma (water + solutes) + cells (RBCs, WBCs, platelets).