Chemicals of life Cell Membrane

1. Bi 1a Bi 1h Chemicals of lifeCell Membrane Modified from Kim Foglia

2. I will be able to: • (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.

3. What are living creatures made of?Why do we have to eat? The Chemistry of Life

4. Elements of Life • Major chemicals->96% ( non-metal, covalent bonds) • carbon (C) • oxygen (O) • hydrogen (H) • nitrogen (N) • Phosphorus (P) • Sulfur (s)

5. Macromolecules of Life • 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

6. Why do we eat? • 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

7. Don’t forget water • Water • 65% of your body is H2O • water is inorganic • doesn’t contain carbon • Rest of you is made of carbon (valence electrons? bonds?) • organic molecules • carbohydrates • proteins • fats • nucleic acids

8. We build them! How do we make these molecules?

9. What are these 4 macromolecules? • Carbohydrates • Nucleic Acids • Proteins • Lipids

10. Building large organic molecules • Small molecules = building blocks/ monomers • Bond them together =polymers

12. amino acid amino acid amino acid amino acid amino acid amino acid – – – – – Building important polymers Carbohydrates = built from sugars sugar – sugar – sugar – sugar – sugar – sugar Proteins = built from amino acids Nucleic acids (DNA) = built from nucleotides nucleotide – nucleotide – nucleotide – nucleotide

13. LIPID ( fat) is an exception • 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

14. How to build large molecules • Synthesis • building bigger molecules from smaller molecules • Monomer+monomer= POLYMER + ATP

15. Example of synthesis amino acids = building block protein = polymer amino acids protein • Proteins are synthesized by bonding amino acids

16. How to take large molecules apart • Digestion • taking big molecules apart • getting raw materials • for synthesis & growth • making energy (ATP) • for synthesis, growth & everyday functions + ATP

17. Example of digestion ATP • Starch is digested to glucose ATP ATP ATP ATP ATP starch glucose ATP

18. 4 Macromolecules

19. Lipids: Fats & Oils

20. Lipids • Examples • Fats • oils • waxes • hormones • testosterone (male) • estrogen (female)

21. Lipids • Function: • energy storage • very concentrated • twice the energy as carbohydrates! • cell membrane • cushions organs • insulates body • think whale blubber!

22. Structure of Fat3 fatty acid + 1 glycerol= triglyceride not a chain (polymer) = just a “big fat molecule”

23. The Cell Membrane

24. Cell membrane defines cell • 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)

25. Polar and non-polar POLAR: unequal sharing of electrons NON-POLAR: equal sharing of electrons

26. Phospholipids Phosphate “attracted to water” • Phosphate head • hydrophilic • Fatty acid tails • Hydrophobic Oil & water don’t mix! • Arranged as a bilayer Fatty acid “repelled by water” Aaaah, one of thosestructure–function examples

27. Arranged as a Phospholipidbilayer • Serves as a cellular barrier / border sugar H2O salt polar hydrophilic heads nonpolar hydrophobic tails impermeable to polar molecules polar hydrophilic heads lipids waste

28. Cell membrane must be more than lipids… • 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!

29. Permeability to polar molecules? • Membrane becomes semi-permeable via protein channels • specific channels allow specific material across cell membrane inside cell H2O aa sugar salt outside cell NH3

30. Proteins* in the cell membrane • Transmembrane proteins embedded in phospholipidbilayer ( fat) are like “gates” • create semi-permeable channels ( or tunnels ) protein channelsin lipid bilayermembrane lipid bilayer membrane

31. H | —C— | H amino acid amino acid amino acid amino acid amino acid – – – – C—OH —N— O || H Proteins amino acids • Building block = • 20 different amino acids There’s20 of us… like 20 differentletters in analphabet!Can make lots of differentwords variable group

32. amino acid amino acid amino acid amino acid amino acid POLYPEPTIDE • 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

33. collagen For proteins: SHAPE matters! • Proteins fold & twist into 3-D shape • that’s what happens in the cell! • Different shapes = different jobs growthhormone hemoglobin pepsin

34. It’s SHAPE that matters! • 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) unfolded“denatured” In Biology, it’s the SHAPEthat matters! folded

35. Why areproteins the perfect molecule to build structures in the cell membrane?

36. Classes of amino acids What do these amino acids have in common? nonpolar & hydrophobic

37. Water-loving amino acids • Hydrophillic • “water loving” amino acids • try to stay in water in cell • the protein folds

38. Classes of amino acids What do these amino acids have in common? I like thepolar onesthe best! polar & hydrophilic

39. Water-fearing amino acids • Hydrophobic • “water fearing” amino acids • try to get away from water in cell • the protein folds

40. Proteins have polar & non-polar areas!!! Polar areas of protein • 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 Nonpolar areas of protein

41. Many Functions of Membrane Proteins “Channel” Outside Plasma membrane Inside Transporter Enzymeactivity Cell surfacereceptor “Antigen” Cell adhesion Cell surface identity marker Attachment to thecytoskeleton

42. Membrane Proteins • 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)

43. Membrane carbohydrates* attached to proteins-> glycoprotein • 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

44. Glycoprotein Glycolipid Transmembrane proteins Peripheral protein Filaments ofcytoskeleton Membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer Extracellular fluid Phospholipids Cholesterol Cytoplasm 1972, S.J. Singer & G. Nicolson proposed Fluid Mosaic Model