HOSA ATC BIOLOGY chapter 3

organic molecule

Molecule primarily made of carbon and hydrogen

carbon backbone

Chain or ring of carbon atoms forming molecular framework

hydrocarbon

Molecule made only of carbon and hydrogen

structural model

Shows how atoms connect (bonds shown as lines)

ball-and-stick model

Shows 3D positions of atoms and bonds

space-filling model

Shows overlapping electron clouds; realistic volume

ribbon model

Shows protein folding patterns (coils, sheets)

heme

Carbon ring structure with iron; binds oxygen in hemoglobin

Hydroxyl (‑OH)

polar, sugar alcohol

Methyl (‑CH₃)

nonpolar, fatty acids, some amino acids

Carbonyl (‑C=O)

polar, reactive sugars, amino acids, nucleotides

Carboxyl (-COOH)

acidic, fatty acids, amino acids

Amine (‑NH₂)

basic, amino acids, nucleotide bases

Phosphate (‑PO₄)

high-energy polar, ATP, DNA, RNA, phospholipids

Sulfhydryl (‑SH)

forms disulfide bridges, cysteine

condensation

Two molecules bond; water forms

hydrolysis

Molecule splits; water is used

functional group transfer

Functional group moved between molecules

electron transfer

Electrons moved between molecules

rearrangement

Covalent bonds reorganized

carbohydrates

Organic compound with 1:2:1 ratio of C:H:O

monosaccharides

One sugar unit (e.g., glucose)

disaccharide

Two sugar units (e.g., lactose, sucrose)

oligosaccharide

Short chain of sugars; often attached to proteins/lipids

polysaccharide

Long chain of sugars (hundreds-thousands)

glucose

main energy source; 6-carbon sugar

sucrose

Glucose + fructose; table sugar

cellulose

Structural polysaccharide in plants; tough fibers

starch

Plant energy storage; coils; insoluble

glycogen

Animal energy storage; branched

chitin

Polysaccharide with nitrogen; exoskeletons, fungal walls

lipid

Hydrophobic organic molecule (fats, oils, waxes)

fatty acid

Carboxyl group + hydrocarbon tail

saturated fatty acid

No double bonds; straight; solid at room temp

unsaturated fatty acids

One or more double bonds; kinked; liquid

omega-3 fatty acid

First double bond at 3rd carbon from tail end

triglyceride

Glycerol + 3 fatty acids; major energy reservoir

adipose tissue

Fat‑storing tissue; insulation and cushioning

trans fat

Unsaturated fat with trans double bond; unhealthy

hydrogenation

Process that adds hydrogen to fats; creates trans fats

protein

Most diverse biological molecule; structure determines function

amino acid

Protein monomer; contains amine, carboxyl, R‑group

peptide bond

Covalent bond linking amino acids

polypeptide

Chain of amino acids

primary structure

Amino acid sequence

secondary structure

Coils and sheets (H‑bonding)

tertiary structure

3D folding of polypeptide

quaternary structure

Multiple polypeptides together

enzyme

Protein that speeds reactions

denaturation

Loss of protein shape → loss of function

nucleotide

Monomer of nucleic acids; sugar + phosphate + base

ATP

Energy‑carrying nucleotide

DNA

Stores genetic information

RNA

Helps build proteins; carries information

nucleic acid

Polymer of nucleotides (DNA, RNA)