a. Energy flows into an ecosystem as __and exits as __; in contrast, the chemical elements essential to life are __
a. __ generates oxygen and organic molecules used by the __of eukaryotes as fuel for __
- cellular respiration
i. __breaks down the fuel, generating __
1. The waste products are __ and __, which are the raw materials for photosynthesis
- carbon dioxide
Organic compounds possess potential energy as a result of what?
What is fermentation?
the arrangement of electrons in the bonds between their atoms
a. catabolic process that is a partial degradation of sugars or other organic fuel that occurs without the use of oxygen
What is aerobic respiration?
a. the most prevalent and efficient catabolic pathway in which oxygen is consumed as a reactant along with the organic fuel
In respiration, __ is not always used.
i. Some prokaryotes undergo __, respiration that lacks oxygen
- anaerobic respiration
a. __is the fuel that cells most often use
a. Its breakdown is __with a free energy change of __ kcal per mole of glucose
a. __is linked to work by __
a. Catabolic pathways that decompose glucose and other organic fuels yield energy through what?
- the transfer of electrons in organic molecules
i. Redox reactions (LEO goes GER)
1. Not all redox reactions involve the__; some change the __
2. Energy must be __to pull an electron away from an atom
a. The more __the atom, the__
i. An electron loses __ when it shifts from a less electronegative atom toward a more electronegative one
- complete transfer of electrons from one substance to another
- degree of electron sharing in covalent bonds
- more energy is required to take an electron away from it
- potential energy
Explain redox reactions in respiration.
- a. In respiration, the fuel (glucose) is oxidized and oxygen is reduced. The electrons lose potential energy and energy is released.
- a. The oxidation of glucose transfers electrons to a lower energy state, freeing energy for ATP synthesis
Why are organic molecules with an abundance of hydrogen excellent fuels?
Main energy yielding foods:m __
a. Reservoirs of electrons associated with hydrogen
i. Only the __ holds back the flood of electrons to a lower energy state
a. because their bonds are a source of “hilltop” electrons, whose energy may be released as these electrons “fall” down an energy gradient when transferred to oxygen.
- carbs and fats
- barrier of activation energy
a. Energy is not released all at once; its__
a. At key steps, electrons are __
i. Each electron travels with a __
1. The H+ atoms are not transferred directly to oxygen, but are passed to an __ , which can cycle easily between oxidized NAD+ and reduced NADH. It is an __.
- broken down into steps, each with an enzyme
- stripped from glucose
- proton (H+ atom)
- electron carrier, a coenzyme called NAD+
- oxidizing agent
a. What do dehydrogenases do? i. What happens to the electrons and protons?1. By receiving two electrons and one proton, NAD+ is __
a. NAD+= most versatile electron acceptor in cellular respiration and functions in several redox steps
- remove a pair of hydrogen atoms (2 electrons/ 2 protons) from the substrate (glucose), thereby oxidizing it
- The enzyme delivers the 2 eletrons and one proton to NAD+ , while the other proton is released into the surrounding solution
- neutralized in chargeà NADH
a. Electrons lose a little potential energy when transferred from__
i. Each NADH molecule formed represents __
- glucose to NAD+
- stored energy that can be used to make ATP when electrons complete their fall down an energy gradient from NADH to oxygen
a. Two important differences for bringing H and O together in non-explosive manner
- i. In cellular respiration, the hydrogen that reacts with oxygen is derived from organic molecules, not H2
- ii. Instead of occurring in one explosive reaction, respiration uses an ETC to break the fall of electrons to oxygen into several energy-releasing steps
1. ETC: consists of __
a. electrons from glucose are shuttled by __to the top, higher-energy end of the chain
i. At the bottom, lower energy end, __ captures these electrons along with hydrogen nuclei, forming __
- numerous molecules, ostly proteins, built into the inner membrane of the mitochondria of eukaryotic cells and the plasma membrane of aerobic prokaryotes
a. Electron transfer from NADH to oxygen is __with a free energy change of__ kcal
a. wHAT DO THE STEPS ALLOW? small amount of energy to be released until reaching oxygen, the terminal electron acceptor, which has a strong affinity for electrons
i. Each downhill carrier is more __than its uphill neighbor= able to __
- small amount of energy to be released until reaching oxygen, the terminal electron acceptor, which has a strong affinity for electrons
1. Electrons removed from glucose by NAD+ fall __ IN the ETC to a more stable location in oxygen, which pulls electrons down the chain
- down an energy gradient
Stages of Cell Resp
- i. Location: cytosol
- ii. Function: begins degradation process by breaking glucose into two molecules of pyruvate.
Stages of Cell Resp
- i. Location: Mitochondria
- ii. Function: pyruvate enters the mitochondrion and is oxidized to a compound called acetyl CoA, which enters the CAC. There the breakdown of glucose to CO2 is completed
Stages of Cell Resp
OXidative Phosphorylation: Electron transport and Chemiosmosis
- i. Location: inner membrane of the mitochondrion
- ii. Function: the ETC accepts electrons from the breakdown products of the first two stages and passes these electrons from one molecule to another where, at the end of the chain, the electrons are combined with molecular oxygen and hydrogen ions, forming water
- 1. The energy released at each step is stored in a form that can be used to make ATP from DP
- a. This mode of ATP synthesis is oxidative phosphorylation because it is powered by the redox reactions of the ETC
a. Some steps of glycolysis and the CAC are __reactions in which __transfer electrons from substrates to __, forming __
a. ___ accounts for almost 90% of generated ATP
a. A smaller amount is formed during glycolysis and the CAC by__
- Oxidative phosphorylation
- substrate-level phosphorylation
When does substrate-level phosphorylation occur?
Occurs when an enzyme transfers a phosphate group from a substrate molecule to ADP, rather than adding an inorganic phosphate to ADP as in oxidative.
a. For each molecule of glucose degraded to carbon dioxide and water by respiration, the cell makes up to about __molecules of ATP, each with__kcal/ mol of free energy