Carbohydrates
Carbon atoms linked to a hydrogen or hydroxyl group.
Monosaccharides: Glucose, Fructose, Galactose, Ribose.
Disaccharides: Sucrose, Maltose, Lactose.
Polysaccharides: Starch, Glycogen, Cellulose.
Structural Isomers: Glucose and Galactose.
Stereoisomers: a- and b- glucose. D- and L- glucose, enantiomers with mirror image structure.
Hexoses: Glucose, Fructose.
Pentoses: Ribose, Deoxyribose
Polysaccharides: Monomers lined together to form long polymers. Energy Storage: starch in plants,
glycogen in animals. Structural: Cellulose (plants), Chitin (exoskeleton of insects and cell wall of fungi),
Glycosaminoglycans (hyaluronan).
Protein: Composed of carbon, hydrogen, oxygen, nitrogen, and small amounts of other elements, notable
sulfur.
Amino acids are building blocks of proteins. 20 different amino acids.
Types of proteins
Structural Proteins: provide support.
Storage Proteins: provide amino acids for growth.
Concractile Proteins: help movement.
Transport Proteins: help transport substances.
Enzymes: help chemical reactions.
Polypeptide formation:
Amino acids joined by dehydration reactions.
Carboxyl + Amino acids form peptide bond.
Polymers of amino acids known as polypeptides.
Polypeptides are broken down by hydrolysis.
Primary Structure: The linear sequence of amino acids is the primary structure.
Secondary Structure: Certain sequences of amino acids form hydrogen bonds that cause the region to
fold into a spiral (a helix) or sheet (b pleated sheet).
Tertiary Structure: Secondary structure and random coiled regions fold into a 3-dimensional shape.
Quaternary Structure: Two or more polypeptides may bind to each other to form a functional protein.
Five Factors that promote protein folding and stability.
Hydrogen bonds, Ionic bonds, hydrophobic effects, Van der waals forces, Disulfide bridges.
STAT: Signal transducer and activator of transcription protein. Each domain of this protein is involved in
a distinct biological function.
Nucleic Acids: Responsible for the storage, expression, and transmission of genetic information.
Two classes:
DNA: Deoxyribonucleic Acid. Stores genetic information encoded in the sequence of nucleotide
monomers.
RNA: Ribonucleic Acid: Decodes DNA into instructions for linking together a specific sequence of
amino acids to form polypeptide chain.
Monomer is a nucleotide
Made up of phosphate group, a five-carbon sugar (either ribose or deoxyribose), and a single or double
ring of carbon and nitrogen atoms known as a base.
Lipids
Composed predominantly of hydrogen and carbon atoms
Defining feature of lipids is that they are nonpolar and therefore very insoluble in water
Include fats, phospholipids, steroids, waxes.
Fats
Also known as triglycerides or triacylglycerols
Formed by bonding glycerol to 3 fatty acids
Joined by dehydration; broken apart by hydrolysis
Fatty acids
Saturated – all carbons linked by single bonds, tend to be solid at room temperature
Unsaturated – contain one or more double bonds, tend to be liquid at room temperature (known as oils).
Cis forms naturally; trans formed artificially. Trans fats are linked to disease.
Phospholipids:
Formed from glycerol, two fatty acids and a phosphate group. Phospholipids are amphipathic
molecules. Phosphate head – polar / hydrophilic. Fatty acid tail – nonpolar / hydrophobic.
Steroids:
Four interconnected rings of carbon atoms. Usually insoluble in water. ex: Cholesterol. Tiny
differences in structure can lead to profoundly different, specific biological properties. Ex: Estrogen vs.
testosterone.
Chapter: Cell Membrane
Cell Membrane is made up of mainly proteins and phospholipids. Cholesterol is only present in animal
cells.
The membrane resembles a fluid because lipids and proteins can move relative to each other within the
membrane. Membranes are semifluid. Flippase requires ATP to transport lipids between leaflets.
Lipid raft: High concentration of cholesterol. High content of sphingolipids as sphingomyelin.
Unique set of membrane proteins.
Factors affecting fluidity: Makes it more fluid: Length of fatty acyl tails. Presence of double bonds.
Presence of cholesterol: Effect varies on temperature.
Glycosylation: Process of covalently attaching a carbohydrate to a protein or lipid.
Diffusion: Molecules move from an area of high concentrations to an area of lower concentrations.
Concentration gradient: difference in concentration of like molecules in two regions.
Dialysis: separation of solutes in a solution based on their ability to pass through a membrane.
Passive transport: Requires no input of energy – down or with gradient.
Passive diffusion – Diffusion of a solute through a membrane without transport protein.
Facilitated diffusion – Diffusion of a solute through a membrane with the aid of a transport protein.
Active transport: Requires energy – up or against gradient.
Isotonic: Equal water and solute concentrations on either side of the membrane.
Hypertonic: Solute concentration is higher (and water concentration lower) on one side of the membrane.
Hypotonic: Solute concentration is lower (and water concentration higher) on one side of the membrane.
Osmosis: Water diffuses through a membrane from an area with more water to an area with less water.
Crenation – shrinkage of a cell in a hypertonic solution
Osmotic Lysis – swelling and bursting of a cell in a hypotonic solution
Turgor pressure – pushes plasma membrane against cell wall. Maintains shape and size
Plasmolysis – plants wilting because water leaves plant cells.
Transport Proteins: Two classes based on type of movement. Channels or porins. Transporters or
carriers
Channels or Porins: Form an open passageway for the direct diffusion of ions or molecules across the
membrane. Most are gated. Example: Aquaporins.
Transporters or carries: Conformational change transports solute across membrane. Principal pathway
for uptake of organic molecules, such as sugars, amino acids, and nucleotides.
Types of transporters: Uniporter: Single molecule or ion.
Symporter or cotransporter: Two or more ions or molecules transported in same direction.
Antiporter: Two or more ions or molecules transported in opposite directions.
Active Transport: Movement of a solute across a membrane against its gradient from a region of low
concentration to higher concentration.
Energetically unfavorable and requires the input of energy.
3 Na+ are exported for every 2 K+ imported into cell.
Exocytosis: Material inside the cell packaged into vesicles and excreted into the extracellular medium.
Endocytosis: Plasma membrane invaginates (folds inward) to form a vesicle that brings substances into
the cell.
Three types of endocytosis: Receptor-mediated endocytosis, Pinocytosis, Phagocytosis.
Used to transport large molecules such as proteins and polysaccharides.