Download AP Biology Study Guide Exam 2

AP Biology Study Guide Exam #2
1. Reactions
 Metabolism all of the chemical reactions in living organisms
 Catabolic/Anabolic- Cat= Breaking down of molecules, Ana= Building
 Molecules broken down by hydrolysis
 Molecules put together by dehydration
 Some reactions release energy, some store energy.
 Exergonic- release energy (Used in digestion, catabolism)
 Endergonic- input energy (Used for making energy molecules, anabolism)
 Sometimes reactions get coupled (exer and ender) this is to allow organisms to
get the energy they need to survive.
2. ATP
 Energy Molecule
 Structure= Adenosine molecule and three phosphate groups (Adenosine
Triphosphate)
 Energy stored in the bonds holding molecule together. Phosphates like charge
repel each other. Holding them together requires energy.
 Enzyme can pull a phosphate off the end releasing the energy that is stored in
the bonds of the molecule. Once phosphate is pulled, it becomes ADP.
 Short term storage molecule (Energy is found in greater amounts in carbs, lipids,
and proteins)
 Can be used and recreated (ATP/ADP Cycle)
3. Enzymes
 Lower Activation energy (amt of energy required for a reaction to happen)
 Are biological catalysts (made up of proteins usually end in -ase)
 Highly specific
 Enzyme and substrate (reactant) go together like a lock and key.
 Induced fit brings substrate in position for chemical reaction to happen
 Enzymes are reusable
 Enzyme concentration- more enzyme= faster reaction that levels off
 Substrate concentration- more substrate=faster reaction that levels up due to
saturation
 Temperature- optimum temp, then it gets too hot or cold denatures protein
 pH- disrupts reaction due to changing charges present.
 Salinity- disrupts shape of enzyme
 Activators- keep enzyme working
 Inhibitors- keep enzyme inactive
4. Cellular Respiration
 Way for organisms to make ATP
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Redox reactions (Reduction/Oxidation)
OXIDATION= GAINING OXYGEN, REMOVING HYDROGEN, LOSES ELECTRONS,
RELEASES ENERGY, AND IS EXERGONIC
 Reduction= removing oxygen, gaining hydrogen, gains electrons, stores energy,
and is endergonic
 Electrons are carried by carrier molecules NAD+ and FAD+2
 When reduced, NAD+= NADH, and FAD+2= FADH2
 Four stages to cellular respiration: glycolysis, pyruvate oxidation, Krebs Cycle,
and Electron Transport
5. Glycolysis
 Glycolysis= “breaking glucose”
 Anaerobic process that takes place in the cytosol
 Glycolysis was around in prehistoric times due to low amounts of free oxygen.
Organisms had to develop a way to create energy for themselves.
 It is a combo of endergonic and exergonic reactions.
 Energy is invested to get started (endergonic). 2 ATP
 4 ATP and 2 NADH+ 2H+ are created
 Results of glycolysis= 2 Pyruvate, 2 Net ATP, and 2 NADH+H+
6. Pyruvate Oxidation/ Krebs
 Once pyruvate is created, it has more energy to give off. This is done by taking
pyruvate and stripping carbons (3 to be exact). Oxidation
 If oxygen is present, oxidized pyruvate enters the Krebs Cycle.
 Pyruvate is combined with Acetyl CoA to create Citric Acid. The Citric Acid is
then taken and broken down by the Krebs Cycle
 The job of the Krebs cycle is to create energy/ electron carrying molecules.
 Net yield for Krebs cycle= 8NADH, 2 FADH2, and 2 ATP
7. Electron Transport Chain
 Series of molecules built into the inner membrane. (Protein Chains)
 Mitochondria= Double membrane, outer and inner. Inner membrane has: highly
folded cristae, and found in intermembrane spaces
 As electrons are being passed, energy is being dumped (bucket brigade)
 NADH and FADH2 drop off electrons and H+ ions. Electrons are used to provide
energy to the protein pumps (active transport).
 As H+ ions are pumped in to the inner membrane, it creates a concentration
gradient (Chemiosmosis). The hydrogen ions want to move out of the inner
membrane.
 The H+ ions then travel through a protein called ATP Synthase which makes ATP.
 ATP Synthase is like a turn style. It spins and creates ATP
 The H+ ions then are combined with O2 and those electrons that are floating
around to create H2O.
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If no O2 is present, then the ETC gets backed up, because there is no oxygen in
order to make H2O. The ETC will stop working until oxygen is present
 Net yield for ETC= between 30-34 ATP
 So Total ATP count for Cellular Respiration= 34-38 ATP.
8. Photosynthesis
 All autotrophs have to create their own food (Photosynthesis or
Chemosynthesis)
 Light energy is used to create chemical energy (Glucose)
 Divided into two phases Light Dependent and Light Independent
 Plant Structures involved with the process include: leaves=absorbing light (Sun),
stomates= gas exchange (CO2), Roots= H2O and nutrients.
 Chlorophyll a absorbs red and blue light the best. Green is reflect back at us
 Chloroplasts are double membraned. Stroma is the inside of the chloroplast they
surround stacks of disks called Grana (thylakoid is the name for a single disk)
 Chlorophyll and the ETC is found inside the thylakoid discs. H+ ions are then
pumped into the thylakoid sac to create a concentration gradient.
 Concentration gradient is combined with ATP Synthase to create ATP
(Photosystem II see below)
9. Light Dependent Reactions
 Happens inside the thylakoid membrane.
 There are two photosystems (collection of chlorophyll molecules). Photosystem I
and Photosystem II
 Photosystems act as light antennae. They are responsible for capturing light and
transferring it to electrons to get them excited (full of energy)
 Photosystem II is the beginning photosystem. Light is absorbed, and the excited
electron is passed down an Electron Transport Chain. The energy that is released
during this ETC is used to make ATP. The electron is then passed to Photosystem
I where it is reenergized and used to make NADPH (Carrier Molecule)
 Because Photosystem II lost an electron, it must be replaced. With the help of an
enzyme, Photosystem II splits water (Hydrolysis) and replaces the lost electrons.
 The O that is remaining is combined with another O (This reaction is happening
more than once) to form O2. This is why we say trees help us breathe.
 Results of Light Dependent Reactions= ATP and NADPH
10. Light Independent Reactions
 AKA the Calvin Cycle, it occurs in the stroma of the chloroplast
 Idea is to take CO2 and create glucose or C6H12O6
 Carbon fixation has to occur in order for glucose to be made. Carbon fixation is
when you take CO2 and combine it with a 5 carbon molecule called RuBP and
with the help of an enzyme called rubisco, it forms an unstable six carbon
molecule.
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Rubisco is the most abundant enzyme out there. It is responsible for making life
out of air.
Calvin Cycle Breakdown:
3 turns of Calvin cycle = 1 PGAL
3 CO2 1 PGAL (3C)
6 turns of Calvin cycle = 1 C6H12O6 (6C)
6 CO2 1 C6H12O6 (6C)
18 ATP + 12 NADPH  1 C6H12O6
6 ATP = left over from light reactions for cell to use elsewhere