Bi 1a Bi 1h Modified from Kim Foglia

 (Bi 1a) Know that cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.  (Bi 1h) Know that most macromolecules ( polysaccharides, nucleic acids, proteins, lipids) in cells and organisms are synthesized from a small collection of simple precursors.

What are living creatures made of? Why do we have to eat?

 Major chemicals- >96% ( non-metal, covalent bonds) carbon (C) oxygen (O) hydrogen (H) nitrogen (N) Phosphorus (P) Sulfur (s)

 Put C, H, O, N,P,S together in different ways to build living organisms  What are bodies made of?  carbohydrates ▪ sugars & starches  proteins  fats (lipids)  nucleic acids ▪ DNA, RNA

 We eat to take in more of these chemicals  Food for building materials ▪ to make more of us (cells) ▪ for growth ▪ for repair  Food to make energy ▪ calories ▪ to make ATP ATP

 Water  65% of your body is H 2 O  water is inorganic ▪ doesn’t contain carbon  Rest of you is made of carbon (valence electrons? bonds?)  organic molecules ▪ carbohydrates ▪ proteins ▪ fats ▪ nucleic acids

We build them!

 Carbohydrates  Nucleic Acids  Proteins  Lipids

 Small molecules = building blocks/ monomers  Bond them together = polymers

sugar – sugar – sugar – sugar – sugar – sugar nucleotide – nucleotide – nucleotide – nucleotide Carbohydrates = built from sugars Proteins = built from amino acids Nucleic acids (DNA) = built from nucleotides amino acid amino acid – amino acid – amino acid – amino acid – amino acid –

 Building blocks of fat are not considered as monomers.  One common type is made up of: 3 fatty acid molecules + 1 glycerol molecule= 1 triglyceride

 Synthesis  building bigger molecules from smaller molecules  Monomer+monomer= POLYMER + ATP

amino acidsprotein amino acids = building block protein = polymer  Proteins are synthesized by bonding amino acids

 Digestion  taking big molecules apart  getting raw materials ▪ for synthesis & growth  making energy (ATP) ▪ for synthesis, growth & everyday functions + ATP

starchglucose ATP  Starch is digested to glucose

PROCESSORGANELLES CARBOHYDRATES cellular respiration, photosynthesis Mitochondria, chloroplast NUCLEIC ACIDS DNA transcription, translation Nucleus PROTEINS Protein synthesis, cell transport Ribosomes, ER, Golgi apparatus, cell membrane LIPIDS Cell transport Cell membrane

 Examples  Fats  oils  waxes  hormones ▪ testosterone (male) ▪ estrogen (female)

 Function:  energy storage ▪ very concentrated ▪ twice the energy as carbohydrates!  cell membrane  cushions organs  insulates body ▪ think whale blubber!

not a chain (polymer) = just a “big fat molecule”

 Cell membrane separates living cell from aqueous environment  thin barrier = 8nm thick  Controls traffic in & out of the cell  allows some substances to cross more easily than others ▪ hydrophobic (nonpolar) vs. hydrophilic (polar)

POLAR: unequal sharing of electrons NON-POLAR: equal sharing of electrons

Fatty acid Phosphate  Phosphate head  hydrophilic  Fatty acid tails  Hydrophobic Oil & water don’t mix!  Arranged as a bilayer Aaaah, one of those structure–function examples “repelled by water” “attracted to water”

polar hydrophilic heads nonpolar hydrophobic tails polar hydrophilic heads  Serves as a cellular barrier / border H2OH2O sugar lipids salt waste impermeable to polar molecules

 In 1972, S.J. Singer & G. Nicolson proposed that membrane proteins are inserted into the phospholipid bilayer It’s like a fluid… It’s like a mosaic… It’s the Fluid Mosaic Model!

 Membrane becomes semi-permeable via protein channels  specific channels allow specific material across cell membrane inside cell outside cell sugaraa H2OH2O salt NH 3

 Transmembrane proteins embedded in phospholipid bilayer ( fat) are like “gates”  create semi-permeable channels ( or tunnels ) lipid bilayer membrane protein channels in lipid bilayer membrane

 Building block = amino acid amino acid – amino acid – amino acid – amino acid – —N——N— H H H | —C— | C—OH || O variable group amino acids  20 different amino acids There’s 20 of us… like 20 different letters in an alphabet! Can make lots of different words

 Amino acid (monomer) chains in a peptide bond => polypeptide (polymer)  Each amino acid is different  some “like” water & dissolve in it  some “fear” water & separate from it amino acid

pepsin collagen  Proteins fold & twist into 3-D shape  that’s what happens in the cell!  Different shapes = different jobs hemoglobin growth hormone

 Proteins do their jobs, because of their shape  Unfolding a protein destroys its shape  wrong shape = can’t do its job  unfolding proteins = “denature” ▪ temperature ▪ pH (acidity) folded unfolded “denatured” In Biology, it’s the SHAPE that matters!

Why are proteins the perfect molecule to build structures in the cell membrane?

What do these amino acids have in common? nonpolar & hydrophobic

 Hydrophillic  “water loving” amino acids  try to stay in water in cell  the protein folds

What do these amino acids have in common? polar & hydrophilic I like the polar ones the best!

 Hydrophobic  “water fearing” amino acids  try to get away from water in cell  the protein folds

 Within membrane  nonpolar amino acids ▪ hydrophobic ▪ anchors protein into membrane  On outer surfaces of membrane in fluid  polar amino acids ▪ hydrophilic ▪ extend into extracellular fluid & into cytosol Polar areas of protein Nonpolar areas of protein

Outside Plasma membrane Inside Transporter Cell surface receptor Enzyme activity Cell surface identity marker Attachment to the cytoskeleton Cell adhesion “Antigen” “Channel”

 Proteins determine membrane’s specific functions  cell membrane & organelle membranes each have unique collections of proteins  Classes of membrane proteins:  peripheral proteins ▪ loosely bound to surface of membrane ▪ ex: cell surface identity marker (antigens)  integral proteins ▪ penetrate lipid bilayer, usually across whole membrane ▪ transmembrane protein ▪ ex: transport proteins ▪ channels, permeases (pumps)

 Play a key role in cell-cell recognition  ability of a cell to distinguish one cell from another ▪ antigens  important in organ & tissue development  basis for rejection of foreign cells by immune system

Extracellular fluid Cholesterol Cytoplasm Glycolipid Transmembrane proteins Filaments of cytoskeleton Peripheral protein Glycoprotein Phospholipids 1972, S.J. Singer & G. Nicolson proposed Fluid Mosaic Model