chem unit 3

Lipids

Biomolecules that are hydrophobic or amphipathic, used for energy storage and membranes

Fatty acid

Long hydrocarbon chain with a carboxyl group at the end

Saturated fatty acid

Fatty acid with no double bonds; solid at room temperature

Unsaturated fatty acid

Fatty acid with one or more double bonds; liquid at room temperature

Cis double bond

Causes a bend in unsaturated fatty acids

Triglyceride

Lipid used for long-term energy storage; made of 3 fatty acids + glycerol

Phospholipid

Main component of cell membranes; forms bilayers

Amphipathic

Molecules with both hydrophobic and hydrophilic regions

Steroids

Lipids with four fused rings (ex: cholesterol)

Cholesterol

Helps maintain membrane fluidity in animal cells

Proteins

Polymers of amino acids that perform most cellular functions

Amino acid

Building blocks of proteins; contain amino and carboxyl groups

Peptide bond

Covalent bond linking amino acids in proteins

Polypeptide

Chain of amino acids before folding into a functional protein

Primary structure

Linear sequence of amino acids

Secondary structure

Folding into alpha helices or beta sheets via hydrogen bonds

Tertiary structure

Overall 3D structure of a single polypeptide chain

Quaternary structure

Association of multiple polypeptide chains

Denaturation

Protein loses structure and function due to heat or pH changes

Enzyme

Protein that speeds up chemical reactions

Active site

Location on an enzyme where substrate binds

Substrate

Reactant molecule an enzyme acts on

Nucleic acids

Polymers of nucleotides; store genetic information

Nucleotide

Monomer containing sugar, phosphate, and a nitrogenous base

DNA

Stores hereditary information; double-stranded helix

RNA

Single-stranded; involved in protein synthesis

Purines

Double-ring bases: adenine (A) and guanine (G)

Pyrimidines

Single-ring bases: cytosine (C), thymine (T), uracil (U)

Phosphodiester bond

Links nucleotides in nucleic acids

Complementary base pairing

A pairs with T (or U), C pairs with G via hydrogen bonds

Origin of life

Hypothesized chemical evolution leading to first cells

Protocell

Primitive cell-like structure capable of maintaining internal chemistry

RNA world hypothesis

Idea that RNA was the first genetic material and catalyst

Micelle

Circular structure of phospholipids with tails inward

Vesicle

Membrane-bound sphere used in protocell formation

Prokaryotic cell

Simple cell lacking a nucleus; bacteria and archaea

Eukaryotic cell

Cell with a nucleus and membrane-bound organelles

Nucleus

Organelle that contains DNA in eukaryotic cells

Ribosome

Structure that synthesizes proteins

Plasma membrane

Semi-permeable barrier that controls entry and exit of molecules

Cytoplasm

Fluid inside the cell where reactions occur

Nucleoid

Region where DNA is located in prokaryotes

Cell wall

Protective structure outside the membrane in many cells

Flagellum

Tail-like structure used for cell movement

Pilus

Hair-like structure used for attachment in bacteria

Plasmid

Small circular DNA in prokaryotes

Binary fission

Cell division method used by prokaryotes

Endosymbiosis theory

Mitochondria and chloroplasts originated from engulfed bacteria

Mitochondria

Organelle that produces ATP in eukaryotic cells

Chloroplast

Organelle for photosynthesis in plants and algae

ATP

Main energy currency of the cell