Science Olympiad - CellBio Cheat Sheet (DRAFT) by Camputy

Energy  Sunlight contains energy – under the right conditions it can be converted into other forms of energy as chemical bond energy, electr­icity, kinetic energy, heat, etc.  Light has both wave-like and partic­le-like proper­ties. o Packets of energy are called photons o Wavele­ngths of light are measured in units called nanometers (very small units) o The shorter the wavelength of light, the more energy it contains photon  Plants contain the pigment chloro­phyll (a & b) in the thylakoids of the chloro­plast  When sunlight hits a leaf, the light is absorbed – some of the light is transm­itted through the leaf like a filter and the rest is reflected away  The green in the photos­ynt­hesis causes red and blue to be absorbed while green and yellow are reflected away Importance of ATP  Chemical storage battery for cells – major energy currency for the cell  Production of much ATP requires membranes to generate current to make ATP  ATP cell functions o Transport work – moving substances across the cell in active transport o Mechanical work – supplying energy for muscle contra­ction, chromo­somes, and flagella o On-off switch to control chemical reactions and send messages.  Plants carry out both photos­ynt­hesis and cellular respir­ation  Almost all of ATP produced in photos­ynt­hesis is used in photos­ynt­hesis to provide the energy to produce the bonds for the glucose molecules  Amount of ATP produced in cellular respir­ation varies from cell to cell; emphasize quanti­tative aspects; most of ATP is produced via electron transport chain.  Main reason that cells need oxygen: to allow them to make lots of ATP. Oxygen cannot be stored, so it must be constantly supplied.

Regulating the Cell Cycle  Normal cells divide and reproduce until they come in contact with other cells o In a multic­ellular organism, cell growth and cell division are carefully contro­lled. o Skin and bone cells grow and divide rapidly throughout life while nerve and muscle cells usually stop dividing once developed o For example, when an injury such as a cut in the skin occurs, cells at the edge of the cut divide rapidly o When the healing process is nearly complete, the rate of cell division slows and then returns to normal o The main components of cell cycle regulation are CDKs (cyclin dependant kinases) and cyclins o CKDs remain at a constant number throughout the cycle whereas cyclins fluxuate. o Cyclins – a group of proteins – regulate the timing of the cell cycle o Controls on cell growth can be turned on and off by the body  The two main checkp­oints are G1-S and G2-M.  If there is no DNA damage in G1, then there will be enough cyclins produced to bind to the CDKs which allows the cell to enter S phase (DNA replic­ation).  The G2-M checkpoint ensures there is no DNA damage, and also that the chromo­somes have succes­sfully replic­ated.  If everything is in order, then the M phase cyclins will be abundant enough to bind to the CDKs. This allows the cell to enter into mitosis.  There are also other mechan­isms, such as p53 and Rb that are activated when damage is detected. They will either hold the cell in G1 phase until the damage is repaired or induce apoptosis (cell suicide) if the damage is too overwh­elming.  The condition caused by irregular cell growth is cancer.

Fluid Mosaic Model  For 30 years, the fluid mosaic model of Singer and Nicolson has provided the foundation for our unders­tanding of the structure of cellular membranes.

Cell membrane with lipid rafts  Functions of the lipid rafts o Lipid rafts appear to exert both positive and negative control on signal transd­uction. o In their positive role, rafts containing different signaling proteins may cluster or fuse upon agonist stimul­ation, leading to the mixing of components and resulting in the activation of signaling pathways. o In their negative role, rafts may spatially segregate intera­cting components to block nonspe­cific pathway activa­tion, or may directly suppress the activity of signaling proteins present in rafts.

 Photos­ynt­hesis is a reduction process, where hydrogen is reduced by a coenzyme. This is in contrast to respir­ation where glucose is oxidized.  Two major parts of photos­ynt­hesis o Light reactions: (Photo­lysis) conversion of light energy into ATP and NADPH o Dark reactions: Calvin Cycle (the thermo­che­mical stage) use of energy (ATP & NADPH) to form carboh­ydrates  Purpose of photos­ynt­hesis  Main biosyn­thetic pathway by which carbon and energy enter the web of life  Where it occurs – in the Chloro­plast  Light reactions - granum (several thylak­oids) and thylakoid membranes  Dark reactions - stroma

Transport Proteins – that move chemicals into and out of the cell o Channel Proteins that form small openings for molecules (elect­rol­ytes) to diffuse through by means of passive transport o Carrier Proteins- binding site on protein surface "­gra­bs" certain molecules and pulls them into the cell (gated channels) – it involves active transport so energy is required 11  Receptor Proteins - molecular triggers that set off cell responses (such as release of hormones or opening of channel proteins)  Adhesion Proteins – attach cells to other cells or fibrous extrac­ellular material  Cell Recogn­ition Proteins - ID tags, to identify cells to the body's immune system  Enzymatic Proteins - carry out metabolic reactions  Structural Proteins – stabilize the cell

Enzymes -  Enzymes are specific in their activity; each enzyme catalyzes the reaction of a single type of molecule or a group of closely related molecules  Enzymes are saturated by high substrate concen­tra­tions  Enzymes are released unchanged after catalyzing the conversion of reactants to products because they do take part in the reaction.  Enzymes are proteins (usually, some RNA molecules can act as enzymes); proteins are sensitive to changes in temper­ature and pH. They will change shape and become inactive. some enzymes are larger inactive molecule; activation involves enzymatic removal of some amino acids  Many enzymes contain non-pr­otein groups called cofactors  Co-fac­tors, usually metal or vitamin; others activated by additi­on/­removal of phosphate o Inorganic cofactors = metal ions o Organic cofactors = coenzymes (ex: vitamins)  Compet­itive Inhibition has the molecule binding at active site; it resembles the substrate and is overcome by increase in substrate concen­tration while Non-co­mpe­titive Inhibition has binding at a site other than the active site; its molecule is different than the substrate and it is not reversed by increased substrate but it may be irreve­rsible if it covalently alters the enzyme. It binds only to enzyme substrate complex

Introd­uction - Types of chemical reactions  Endergonic: require energy  Exergoinc: give off energy  Catabolism: reactions breakdown large molecules and produce small molecules; Ex. Digestion of protein into amino acids  Anabolism: reactions requiring energy to make large molecules from small molecules; Ex: the synthesis of a protein from amino acids