Unit 4: Cell Processes

all of the enzyme-catalysed reactions in a cell

anabolic: putting molecules together, forming bonds, condensation reaction, requires energy (i.e. photosynthesis) catabolic: big molecules to smaller molecules, breaking bonds, hydrolysis, release energy (i.e cell respiration)

globular protein, soluble, folded into specific shapes, determined by amino acid sequence, has an active site for catalysis

active site will change shape to fit substrate, affecting bonding in the substrate –> releases products, active site returns to original shape

inc. temp and conc. inc. collision rate molecules must be correct orientation when they collide with the active site of an enzyme

denaturation: permanent change to the 3d structure of the enzyme

change/time

intracellular = glycolysis and Krebs cycle extracellular = chemical digestion

energy transformation is not 100% efficient, so some energy is lost as heat heat generation can be by: shivering, fat burning

cyclical: Krebs cycle & Calvin cycle linear: glycolysis

non competitive inhibition = substance (allosteric inhibitor) binds to the allosteric site, changing the shape of the active site and making it impossible for the substrate to bind

competitve inhibition = a competitor with a similar shape binds to the active site, preventing substance from binding i.e. statins adding competitive inhibitor = reduce rate, but reaches maximum non competitive inhibitor, increases conc. of substrate will not increase reaction rate

the final product becomes a non-competitive inhibitor of the first enzyme in the chain, preventing unnecessary build up of the final product i.e. threonine to isoleucine (“3,9 to iso lucy ne”)

binds irreversibly to an amino acid somewhere in the chain, causing permanent change to the active site and rendering the enzyme permanently useless i.e. penicillin inhibits an enzyme in bacteria = antibacterial stops transpeptidase

molecule that distributes energy within cells is a nucleotide adenosine triphosphate characteristics = - bond between second and third phosphate group can be broken to release energy - can be regenerated - soluble and stable in water - cannot cross membranes

active transport, synthesis of macromolecules and movement of cell components (mitosis) or locomotion

energy released when 3rd phosphate group broken off, forms A-P-P (adenosine diphosphate) or ADP energy is required to regenerate ATP

Cell respiration is a system for producing ATP within the cell using energy released from carbon compounds Gas exchange: the process of O2 and CO2 diffusing into and out of cells Ventilation: mechanical movements that supply fresh air NOT THE SAME THING

aerobic: with oxygen 1. Humans: CO2 and H2O can start from carbohydrates, lipids or amino acids cytoplasm, then mitochondria 30 ATP produced anaerobic: with no oxygen 1. yeast: CO2 and ethanol 2. Humans: lactate start with ONLY carbohydrates only in mitochondria 2 ATP produced

when we need ATP but cannot supply fast enough –> lactic acid builds up, limiting physical ability to keep going –> oxygen debt = the amount of oxygen that must be absorbed following anaerobic respiration in order to break down the lactate

• decline in O2 conc. • decline in glucose conc. • increase in CO2 conc. can measure oxygen consumption using an respirometer controlled variable = temp and pressure what can you investigate using a respirometer? –> different organisms –> different temperatures –> different respiratory substances

chemical energy can be in the form of carbs, lipids, proteins, nucleic acids. this energy transfer is vital for most ecosystems

photolysis = using light energy to split water using hydrogen obtained by splitting water

O2 and glucose O2 changed the composition of the Earth’s atmosphere