Exam 2 Flashcards
What is the purpose of photsynthesis?
It produces energy from the sun by using Co2 and producing O2.
What is photooxidation?
Transfers electrons from chlorophyll to an electron acceptor
What is the net equation for photsynthesis?
CO2+ H2O+ light——> G3P, ATP, NADPH, O2
What are the characteristics of the photosynthetic electron transport system?
PS I, PS II, Cytochrome B6F, It is categorized as the light reactions, and depends on newly made carbohydrates as metabolic fuel for mitochondrial respiration
What are the characteristics of the calvin cycle?
Fixes carbon, contains rubsico enzyme, independent of light, most active in the light when ATP and NADPh are high, produces triose phosphates that are used to make hexose sugars
What is the greenhouse effect?
Increased levels of CO2 that affect climate change. Re-radiated heat from the Earth cannot escape due to the rising greenhouse gases. Increases Earth Temp.
What is the purpose of Photosynthetic Electron Transport?
Convert solar energy into chemical energy and carbohydrate sugar precursors.
What are the steps of Photosynthetic Electron Transport?
- 4 photons are absorbed into the chlorophyll molecule
2.Electron transport via carrier molecules
3.Photon absorbed by PS I - Chloroplast ATP synthase produces ATP
- ATP and NADPH are used in enzymes in the Calvin Cycle to drive carbon fixation
What is oxidized to provide 4 H+ to PS I?
Water
When is NADPH is generated?
When the photon is absorbed by PS I
What is used to synthesize G3P?
3 CO2
What are Chloroplasts?
They are the photosynthetic machinery in eukaryotic cells. They contain their own DNA, they carry out protein synthesis in the organelle
What are the three membranes of chloroplasts?
Outer, Inner, and thylakoid
What waves of light do chloroplasts absorb?
It absorbs the maximum amount of light at 400-700 nm
What are the structures of the chloroplasts and why they are important?
Contain light-absorbing pigments and alternating double bonds. They are associated with chromophore proteins that participate in energy transfer reactions.
What is the purpose of photons?
They excite electrons from a ground state to a higher orbital
What are the characteristics of PS II?
it is the P680 reaction center, meaning it absorbs light at this wavelength. It oxidizes water into H20.
What is an inhibitor of PS II?
DCMU
What are the characterstics of PS I?
It is the P700 reaction center, absorbing light at that wavelength. It generates NADPH for carbohydrate synthesis. It is a large protein complex embedded into the membrane. The Fe-S cluster is the final electron acceptor to ferroredoxin
What is Paraquat?
It is a potent herbicide. It accepts electrons from PSI and donates them to O2. It block NADPH production, and generates superoxide anion and hydrogen peroxide
What are the light harvesting complexes?
They act as solar panels to capture light energy for photooxidation in reaction center complexes. Proteins containing chromophores that participate in energy transfer reactions. They are the most abundant proteins in the thylakoid membrane.
What are the two types of light harvesting complexes?
LHCI and LHCII.
What is important about LHCII?
It outnumbers LHCI and is the major light-gathering antenna in photosynthetic membrane
What is the z scheme?
It is a series of photosystems, each requiring an input of energy from light absorption at PSI and PSII reaction center complexes. Photon absorption by PSII results in electron flow from water to plastocyanin. Photon is absorbed by PSI and provides energy to reduce NADP+ to NADPH. Plastocyanin transports 1 e- from cytochrome b6f to PSI reaction center
What must be available to replace the electron lost by photooxidation in each reaction center complex?
A reductant!
What is the PQ cycle?
analogous to the Q cycle, translocates 8 H+ into the thykaloid membrane
What are the two components of the chloroplast ATP synthase?
CF0 and CF1, it has the same binding mechanism as mitochondrial ATP synthase, a proton gradient is needed
What does the calvin cycle generate?
3-phosphoglycerate
glyceraldehyde-3-phosphate
dihydroxyacetone phosphate
What can the products of the calvin cycle generate?
fructose- 1,6- bisphosphate
fructose-6-phosphate
What are the three stages of the calvin cycle?
1.synthesis of a C6 molecule from rubisco which is cleaved to two molecules of 3-phosphoglycerate
2.3-phosphoglycerate is reduced to G3P
3. ribulose-5-phosphate is resynthesized
What is the net reaction for the calvin cycle?
3CO2+ 3RuBP+ 6NADPH+ 9ATP+ 6H20 —-> 1 G3P+ 3RuBP+ 6NADP++ 9ADP+ 9Pi
What is the C2 pathway?
It is the glycolate pathway, it converts-phosphoglycolate to glycolate in the stroma, it is the exported to plant cells to be oxidized into glycoxylate, the transamination in glycine then translocated into the mitochondria
What is the difference between C4 and CAM?
C4 occurs in tropical plants, one cell type takes up CO2 and another fixes it. The CAM pathway occurs in desert plants. They capture CO2 at night and fixes CO2 in the day.
What is the purpose of the glyoxylate cycle?
It is most active in seedlings, and provides and mechanism for fats stored in seeds to be converted to sucrose. Converts acetyl CoA into succinate.
What is the net equation for the glyoxylate cycle?
Acetyl- CoA+ NAD++ 2H2O—-> succinate + 2CoA+ NADH+ H+
What happens after the glyoxylate cycle?
Succinate is converted into fumarate via the citrate cycle. It is then hydrated to form malate. then it is converted to oxaloacetate. Then used to form glucose via gluconeogenesis
What does fatty acyl-CoA synthetase do?
It catalyzes the priming reaction in fatty acid metabolism. It converts free fatty acids in the cytosol into fatty acyl CoA
What does carnitine acyltransferase I do?
It catalyzes the rate limiting step in fatty acid oxidation
What does acetyl-CoA carboxylase do?
catalyzes the rate limiting step in fatty acid synthesis
What does fatty acid synthase do?
Catalyzes a series of reactions that adds C2 units to a growing fatty acid chain
Is the formation Fatty Acyl-CoA favorable?
Yes!
Does the specificity differ for fatty acyl-CoA synthetase?
It varies depending on the size of the fatty acid
What are the steps of the formation of fatty acyl-CoA?
- fatty acid adenylation occurs (ATP coupled)
- CoA-SH attacks adenylate intermediate and release AMP
What is the fate of fatty acyl-CoA if energy cell charge is low?
fatty acyl-CoA is imported into the mitochondrial matrix by the carnitine transport cycle. Fatty acids are degraded into acetyl-CoA, FADH2, NADH
What is the fate of fatty acyl-CoA if energy cell charge is high?
fatty acid synthesis is favored. Transport into the mitochondrial is inhibited by malonyl-CoA
What is the purpose of the Carnitine Cycle?
It regulates cellular metabolism by controlling the flux of fatty acids to either degrade them or synthesize them and membrane lipids. It is controlled by malonyl-CoA , which prevents import of fatty acyl-CoA into the mitochondria
What is fatty acid B-oxidation?
It occurs in the mitochondria. It degrades fatty acids by 2 C units at a time via thiolysis. Generates FADH2, NADH, and acetyl- CoA, consists of 4 repeatable reactions
What are the steps of beta oxidation?
- Acyl- CoA dehydrogenase ( oxidation)
- Enoyl-CoA hydratase (hydration)
- 3- hydroxyacyl-CoA dehydrogenase (oxidation)
- B-ketoacyl-CoA thiolase (tholysis)
What happens if the fatty acids are odd numbers or unsaturated?
Different enzymes are used and can produce propionyl-CoA
What is ketogenesis?
Process in which excess acetyl-CoA is converted to ketone bodies. It occurs during starvation while carbohydrate sources are limited. Ketone bodies are exported from the liver into the muscle tissues
What is the rate limiting step of fatty acid synthesis?
The generation of malonyl CoA by acetyl-CoA carboxylase
What are the 4 steps of fatty acid synthesis?
Condensation, recution, dehydration, and reduction.
What is acetyl-CoA carboxylase?
A multi functional enzyme used in fatty acid synthesis
What is the net equation for the synthesis of palmitate?
8 acetyl-CoA+ 7 ATP+ 14 NADPH+ 14H+——> palmitate+ 8CoA+ 7Pi+ 14NADP+ 6H20
What is the purpose of elongation enzymes?
They are used to increase carbon chain in palmitate to make longer fatty acids
What is the purpose of desaturating enzymes?
they are membrane-bound ER proteins that use O2 as an oxidant to produce unsaturated fatty acids
How are triacylglycerol synthesized?
They are formed from phosphatidac acid. Dephosphorylation occurs and fatty acids are added through esterification
Where does fatty acid synthesis occur?
In the cytoplasm
What is the citrate shuttle?
citrate from the TCA cycle is shuttled into the cytoplasm and then broken down into acetyl-CoA and oxaloacetate. The acetyl-CoA is used to make fatty acids and the oxaloacetate is used to make malate and pyruvate and imported back into the mitochondria
How is acetyl-CoA carboxylase (FA synthesis) controlled?
Allosteric mechanisms (citrate and palmitoyl-CoA) and covalent modifications (AMP-activated protein kinase)
Where does cholesterol synthesis primarily occur?
In the liver
What are the 4 stages of cholesterol synthesis?
- Formation of mevalonate from acetyl-CoA
2.formation of isopentenyl diphosphate - formation of squalene
- cyclization of squalelene
What is the importance of cholesterol?
It plays a critical role in cell membrane function and production of cell signaling molecules
1. cell membranes
2. steroid hormones
3. bile acids
4. myelin sheaths
What is the only way to get rid of cholesterol in the body?
Through bile
What is the critical regulatory and rate limiting step of cholesterol synthesis?
step 1: acetyl-CoA—> mevalonate using HMG-CoA reductase
What step of cholesterol synthesis uses ATP?
Step 2
What drugs are used to decrease the risk of CVD from cholesterol build up?
Statins
What are lipoproteins and what are they made of?
They serve as signaling molecules. They are made up of a phospholipid monolayer one or more apolipoproteins
What are apolipoproteins?
Membrane-bound vesicles contain a hydrophobic core and one or more proteins on the surface
How do lipoproteins differ?
the protein: triglyceride ratio and densities
What are the different classes of lipoproteins?
Chylomicrons, VLDL, IDL, Chylomicron remnants, LDL
How are lipoproteins transported?
They start in the blood as chylomicrons and VLDL, then break down into different kinds and go to different locations like tissue (LDL and HDl precursors) or liver (LDL and HDL), then go through the intestine and lymphatic system
What do HDL particles do?
They remove cholesterol from peripheral tissues through apoA-I. The cholesterol is then taken back to the liver.
What are SREBP’s?
They are large proteins embedded in the ER membrane. If cholesterol levels are low, they bind to SRE sequences. This controls the mechanism for cholesterol biosynthesis
What are the roles of lipids?
Energy storage, cell membranes, endocrine signaling
What are fatty acids?
They are molecules that have a carboxylic acid and a hydrocarbon tail. they usually are unbranched and even-numbered.
What is important about fatty acids?
They can be covalently bonded to proteins to tether proteins to biological membranes.
What is hydrogenation?
The commercial process of using H2 to reduce double bonds. It raises the melting point of the lipids. Converts unsaturated and saturated
What does partial hydrogenation cause?
Produces trans fats which are associated with high rates of CVD. Increases LDL and decreases HDL
What are waxes?
Lipids that are long chain alcohols linked to long chain fatty acids. They have high melting points.
What are triacylglycerols?
They are energy storage lipids
Where are triacylglycerols synthesized and how do they travel?
They are synthesized in the liver and travel in VLDL vesicles.
What are lipid droplets?
They are storage vehicles for newly formed triacylglycerols from adipocytes. They are surrounded by a phospholipid monolayer containing perilipin.
How are triacylglycerols metabolized?
They are cleaved by lipases to generate free fatty acids and glycerol. Those fatty acids are then passed through into the epithelial cells of the intestine.
What are the three major types of membrane lipids?
Glycerophospholipids, sphingolipids, cholesterol
What are Glycerophospholipids?
They are the most abundant membrane lipids. they are an important source of fatty acid derived signaling molecules. They contain two fatty acids and a phosphate group attached to a glycerol
How are fatty acid-derived signaling molecule released?
Through phospholipase enzyme catalysis?
What are sphingolipids?
They are derived from sphingosine and a fatty acid
What is Tay-Sachs disease?
In healthy individuals, Hexosaminidase A acts on gangliosides GM2 to remove a terminal GaINAc and form ganglioside GM3. In people with this disorder, this is defective and GM2 builds up in the spleen and brain. Can cause developmental delays and death.
How much of the lipid membrane is cholesterol?
25-40%
What are lipid rafts?
Proteins that are in densely packed protein packages. They contain large transmembrane proteins and act as receptors for cellular signaling
Why is lipids being hydrophobic important?
It contributes to their function as high-affinity stereospecific ligands that bind to hydrophobic pockets on receptor proteins
What is cholesterol derived from?
mevalonate
What are steroid hormones?
They are ligands for NRs which alter the expression for specific genes. They have a critical role in cell development, reproductive biology, and organismal physiology
What are some categories of steroid hormones?
Glucocorticoids, mineralcorticoids, androgens,estrogens
What are synthetic hormones?
Agonists that mimic the biological response of the hormone.
What is vitamin D?
It is a vitamin that is derived from cholesterol via Uv light
What are Eicosanoids?
A group of signaling molecules derived from C20 polyunsaturated fatty acids. They are released from the membrane by phospholipases and modified by mitochondrial enzymes.nThey are produced by cells of their sites of action and half short half lives.
What are the major classes of Eicosanoids?
prostaglandins, prostacyclins, thromboxanes, leukotrienes
What do eicosanoids do?
They help in immune cell regulation and immflamatory response.
What are COX inhibitors?
They are a type of NSAID that help with pain and inflammation, they are nonspecific, so bind to COX 1and 2
