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All organisms consist of four basic classes of molecules (macromolecules):
1) Carbs
2) Proteins
3) Lipids
4) Nucleic acids
Dehydration Synthesis
● Connects molecules to make macromolecules
● Condensation reaction that releases water as waste
● Requires enzymes
Hydrolysis
● Uses water to break down macromolecules
● Basically reverse of dehydration synthesis
● Macromolecules from other forms of life our broken down so we can use the molecules
for energy
● Requires enzymes
Carbs
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Sugars and sugar polymers
Monosaccharides- single sugar molecules
Useable energy for cells
Polysaccharides are used to store energy or structure

Polysaccharide Synthesis
● Happens through dehydration synthesis
● Links between sugar molecules are called glycosidic linkages
Storage Polysaccharides
● Plants & animals store glucose-based polysaccharides for energy
● In plants called starch
○ Starch is mostly unbranched (amylose) but some branches do occur
(amylopectin)
○ Stored in plastids in many plant tissues
● In animals called glycogen
○ Often branched
○ Stored in muscle and liver cells
Structural Polysaccharides
● Cellulose is a plant polysaccharide made of glucose
● Cellulose molecules form rope-like microfibrils
● Provides structure for plants & plant cells
● Chitin is a polymer made of a different type of sugar (not glucose)

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Makes a strong cells that protects insects
Can be used in stitching thread in medicine

Lipids
● Characterized by the fact that they are hydrophobic
● Assemble into fat droplets or bilayer membranes
● Triglycerides are common forms of fat
○ Made by dehydration reactions between glycerol and three fatty acid groups
● In phospholipids glycerol is linked to 2 fatty acids
○ Also linked to a hydrophilic chemical and a phosphate
○ Amphipathic- both hydrophobic and hydrophilic
○ Phospholipids in water self-assemble into bilayer
○ Basic component of all biological membranes
● Cholesterol is synthesized in liver
○ Component of many membranes
○ Decreases membrane fluidity
○ Provides structure to membrane
Proteins
● All amino acids have a conserved structure- an amino group and carboxylic acid group
attached to a central carbon atom
○ This is linked to a hydrogen atom and a side chain (referred to with variable R)
○ Side chains can be nonpolar or polar, basic or acidic
● The precise arrangement of amino acids in a protein gives that protein its function and
properties
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Synthesis
○ Amino acids bonds are called “peptide bonds” and are formed by dehydration
■ Peptide bonds have an amino end (“N-terminus”) and a carboxyl end
(“C-terminus”)
■ During synthesis amino acids are connected to the carboxyl end
○ Catalysed by ribosomes

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Four Levels of Protein Structure
○ 1) Primary- the order of amino acids
○ 2) Secondary- folding of regions of a protein into local structure
■ ex) helix or sheet
○ 3) tertiary- arrangements of secondary structures into a stable protein
○ 4) quaternary- arrangement of multiple polypeptides to make a functional protein

Nucleic Acids
● Made of nucleotides
● All cells have a genome made of DNA

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Cells
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○ Specifies the proteins of the cell
○ Antiparallel double helix stabilized by hydrogen bonds between bases
○ Adenine always bonds with thymine
○ Guanine always bonds with cytosine
DNA (double-stranded) is converted to RNA (single-stranded) in the nucleus
○ RNA has a more varied and flexible structure than DNA
mRNA is converted into protein in the cytoplasm

All cells are surrounded by a plasma membrane
○ Within membrane is viscous semi-fluid cytosol
■ Within cytosol is chromosomes (genetic material) and organelles
The cytosol plus all of the organelles within it is called the cytoplasm
Prokaryotic cells contain no membrane-bound organelles

Structure of Prokaryotic cells
● Some have pili for adhesion to surfaces
● The nucleoid is general region with DNA but not membrane-bound
● Has ribosomes for protein synthesis
● Many have cell wall and capsule surrounding the PM
● Some have flagella, which allow movement
● Usually smaller than eukaryotic cells
Cell-environment interactions
● Cells require useful solutes (anything dissolved in water), oxygen, and other molecules
● Must dispose of metabolic waste
● Materials pass through membrane at a limited rate
● As cell volume increases so must membrane surface area to maintain sufficient nutrient
● Cell size is limited by favorable volume/area ratio
● Microvili- long, thin projections that protrude from cell to increase surface area w/o
increases volume



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