Final: Chapter 14 Flashcards
loss of testosterone
- Testosterone receptor missing
- Androgen insensitivity syndrome (AIS)
- XY, genetically male, develop female
oxidative phosphorylation
2 stages: one sets up an electrochemical proton gradient, the other uses that gradient to generate ATP
oxidative phosphorylation stage 1
- high-energy e- from the oxidation of food molecules from sunlight, or from other sources are transferred along a series of electron carriers—called an electron-transport chain—embedded in the membrane
- e-transfers release energy that is used to pump protons, derived from the water that is ubiquitous in cells, across the membrane and thus generate an electrochemical proton gradient
- ion gradient across a membrane is a form of stored energy that can be used to do useful work when the ions are allowed to flow back across the membrane down their electrochemical gradient
stage 2 of oxidative phosphorylation
- protons flow back down their electrochemical gradient through a protein complex called ATP synthase(catalyzes the energy-requiring synthesis of ATP from ADP and inorganic phosphate (Pi))
- This ubiquitous enzyme functions like a turbine, permitting the proton gradient to drive the production of ATP
chemiosmotic coupling
- When it was first proposed, this mechanism for generating energy was called the chemiosmotic hypothesis, because it linked the chemical bond-forming reactions that synthesize ATP (“chemi-”) with the membrane transport processes that pump protons(osmotic)
- chemiosmotic coupling lets cells harness energy of e- transfers in same way energy stored in battery lets u do work
mitochondria
- produce bulk of cell’s ATP(without mito, cells would rely on inefficient glycolyis for ATP)
- adaptable and can adjust their location, shape, and number to suit the needs of the cell
- some are fixed and supply ATP to direct site
- others, mito fuse to form elongated, dynamic tubular networks, which are throughout cytoplasm
- break apart by fission and fuse back together
structure of mitochondria
- outer and inner membrane plus internal space called matrix and narrower intermembrane space(each has unique proteins)
- outer membrane:
- lots of porin(forms wide channels in lipid bilayer)
- permeable
- intermembrane space is chemically equivalent to cytosol bc of small molecs and inorganic ions
- inner membrane:
- impermeable except with specific membrane transport proteins
- site of oxidative phosphorylation, contains e- transport chain proteins(proton pumps), and ATP synthase for ATP production
- contains transport proteins that allow entry of selected small molecs that will be oxidized into matrix
- forms infoldings(cristae) -inc SA
- mitochondrial matrix contains only molecules that are selectively transported into the matrix across the inner membrane(highly specialized)
citric acid cycle makes high energy e- used in ATP production
- burning food = ATP
- activated carriers from catabolism = high energy e-
- pyruvate can enter mitochondrial intermembrane space through porins, where they become acetyl CoA
- citric acid cycle
- some energy is saved in form of high energy e-, held by NADH and FADH2
- these donate e- to e- transport chain
electron transport chain: respiratory enzyme complexes
- 3 respiratoyry enzyme complexes(in order in which they receive e-)
- NADH dehydrogenase complex(catalyst)
- accepts e- from NADH
- cytochrome c reductase complex
- cytochrome c oxidase complex
- NADH dehydrogenase complex(catalyst)
- as e- move thru complexes,protons pump from mitochondrial matrix to intermembrane space
- energetically favorable
electron transport chain proton gradient
- pumping of protons makes H+ gradient(aka pH gradient)
- higher pH in matrix than intermembrane
- pumping protons generates voltage gradient(membrane potential) across inner membrane
- H+ flow outside makes intermembrane side more pos
ATP synthase
- drives synthesis of ATP from ADP and Pi
- Catalyzes the phosphorylation of ADP
- it is attached by a central stalk to a transmembrane H+ carrier
- The passage of protons through the carrier causes the carrier and its stalk to spin rapidly
- As the stalk rotates, it rubs against proteins in the stationary head, altering their conformation and prompting them to produce ATP
- ATP synthase produces more than 100 molecules of ATP per second—3 molecules of ATP per revolution
ATP synthase in reverse
- use ATP as energy to pump protons against gradient
electrochemically proton gradient in mitochondria
- drives formation of ATP AND transport selective metabolites across mitochondrial membrane
The Rapid Conversion of ADP to ATP in Mitochondria Maintains a High ATP/ADP Ratio in Cells
- ADP molecules—produced by hydrolysis of ATP in the cytosol—are rapidly drawn back into mitochondria for recharging, while the bulk of the ATP molecules produced in mitochondria are exported into the cytosol
- ATP can go out of mitochondria and back in as ADP in 1 min
Cellular respiration efficiency
- 1 NADH = 2 ATP
- The NADH molecules produced in the mitochondrial matrix during the citric acid cycle pass their highenergy electrons to the NADH dehydrogenase complex—the first complex in the chain. As the electrons pass from one enzyme complex to the next, they promote the pumping of protons across the inner mitochondrial membrane at each step along the way
- 1 FADH2 = 1.5 ATP(bc they enter further down chain
- almost 50% of energy that could be realeased by burning sugars is actually captured
chloroplasts + photosynthesis overview
- chloroplasts contains light-capturing pigments such as the green pigment chlorophyll
- most plants, leaves are the major sites of photosynthesis.
- Photosynthesis occurs only during the daylight hours, producing ATP and NADPH.
- ATP and NADPH can then be used, at any time of day, to convert CO2 into sugar inside the chloroplast—a process called carbon fixation
chloroplast structure
- resemble mitochondira
- has highly permeable outer membrane and less perm inner membrane(holds proteins)
- inner membrane surrounds large space called stroma(equiv of mitochondrial matrix) which contains metabolic enzymes
- light-capturing systems, electron-transport chain, and ATP synthase that produce ATP during photosynthesis are all contained in the thylakoid membrane
- forms a set of flattened disclike sacs(thylakoids)
- stack = grana
- thlyakoid space: space inside each thylakoid is thought to be connected with that of other thylakoids, creating a third internal compartment
photosynthesis stage 1
- equiv to ox phosphorylation
- 1) e- transport chain in thylakoid membrane harnesses energy to pump protons to thylakoid space
- results in proton gradient that that drives synthesis of ATP by ATP synthase
- diff from ox phos bc e- coming in come from 1 molec of chlorophyll from sunlight
- these are called light rxns
- diff bc the high E e- end up with NADP+ to produce NADPH (in ox phos it goes to O2)
photosynthesis stage 2
- ATP and NADPH from stage 1 drive manufacture of sugars from CO2
- these are carbon fixation rxns called fark rxns
- begin in chloroplast stroma where they generate a three-carbon sugar called glyceraldehyde 3-phosphate
- this sugar is moved to cytosol where it produces sucrose and other organic molecs
how does chlorophyll absorb energy of sunlight
- e- in chlorophyll are distributed in a decentralized cloud around molecs light absorbing porphyrin ring
- when light of right wavelngth(blue/red bc they absorb green poorly) hits chlorophyll, it excites these e- into an unstable state, so chloropyll wants to remove excess energy to become stable again
- instead of releasing energy, chlorophyll converts light E into E usable for cell bc they associate with photosynthetic proteins in thylakoid membrane
how does excited chlorophyll funnel E into rxn center
- photosystems: large multiprotein complexes that hold chlorophyll
- each photosystem contains antenna complexes that capture light energy
- each has hundreds of cholorophyll molecs
- one captures light and passes it to next along chain
- eventually it encounters a chlorophyll dimer called the special pair which holds its e- at lower R so it can trap the light energy
- each has hundreds of cholorophyll molecs
- and a rxn center that converts ligh E into chemical E
- the special pair is actually part of the rxn center
- evolved >3 bil years ago
- special pair is right next to a set of e- carriers that will accept a high E e- from light
- as soon as high E e- is handed off, special pair becomes + charged and e- carrier becomes -
- each photosystem contains antenna complexes that capture light energy
- overall, creates a charge separation that sets in motion of e- flow from rxn center to an e- transport chain
a pair of photosystems allow generation of ATP and NADPH
- first photosystem is called photosystem 2
- absorbs light E, rxn center passes e- to mobile e- carrier(plastoquinone)
- pastoquinone transfers high E e- to proton pump which uses movement of e- to generate proton gradient
- gradient drives ATP production by ATP synthase in thlakoid membrane
- photosystem 1(step 2)
- captures E from sun, passes high E ei to a diff e- carrier, which brings them to enzyme that uses them to reduce NADP+ to NADPH
- OVERALL: prodyces ATP and NADPH to use in photosynthesis stage 2