Photosynthesis Notes PDF 2024

From last time… Energy Flow 1 From last time… Chloroplasts Chloroplasts – Double membrane – Contain chlorophyll (pigment needed for photosynthesis) – cells may have 40-50 Internal membra...

From last time… Energy Flow 1 From last time… Chloroplasts Chloroplasts – Double membrane – Contain chlorophyll (pigment needed for photosynthesis) – cells may have 40-50 Internal membranes (thylakoids) contain chlorophyll and other molecules important for photosynthesis. Watery stroma contains other enzymes for photosynthesis. 2 1  From last time… Chloroplast Figure 4.27 3 From last time… Mitochondria Mitochondria- “Powerhouse of the cell” – Folds of inner membrane (cristae) contain enzymes and other molecules important for energy metabolism. – Watery matrix contains other enzymes for energy metabolism. Believed to be descended from ancient bacteria engulfed by another cell. – Reproduce by binary fission like bacteria. – Ribosomes and small amounts of DNA similar to those in prokaryotes. 4 2  From last time… Mitochondrion 5 Electron Transport As electrons move down chain energy is lowered Chain Electron acceptors are proteins that accept an electron and then pass on an electron to the next acceptor Some energy given off as heat and some stored in bonds of ATP and NADPH 6 3  Photosynthesis In chloroplasts primarily in leaves – oxygen and carbon dioxide can enter and leave the leaf through the stomata, and water is brought in by the veins Thylakoid (chloroplast membranes) pigments absorb energy from light and store it in ATP molecules and the electron acceptor molecule NADPH. In stroma of chloroplasts, carbon units from carbon dioxide are hooked together to form carbohydrates. 7 8 4  Absorption of light Plants use visible light for photosynthesis – right amount of energy to excite electrons in organic molecules. – Chlorophyll a absorbs light in the red and blue- violet region and reflects green light – Accessory pigments (carotenoids and chlorophyll b) absorb light at different wavelengths and pass the energy on to chlorophyll a 9 Photosynthesis Overview 6 CO2 + 6 H2O → C6H12O6 + 6O2 Photosynthesis has two sets of reactions: Light reactions – Photosystems I and II capture solar energy – Use solar energy to split water and release electrons, protons and oxygen – Electrons and protons used to make ATP and NADPH (energy carriers) Calvin cycle (carbon hook up cycle) – Energy stored in ATP and NADPH during light reactions used to connect C’s from CO2 into simple sugars 10 5  Photosystem II: light absorbed by chlorophyll a Excited electron passed to an electron acceptor molecule Water molecule is split into protons and oxygen Electron from water replaces the chlorophyll electron that went to the electron acceptor. Electron is passed down an electron transport chain until it reaches photosystem I ATP is produced during electron transport. (Carbon hook up reactions) 11 Light excites the electron in photosystem I Electron accepted by electron acceptor Passes down another electron transport chain Produces NADPH ATP and NADPH are produced outside the thylakoid and are then used in the carbon hook up reactions. (Carbon hook up reactions) 12 6  Photophosphorylation: How ATP is synthesized Photosystems and electron transport molecules are in the thylakoid membrane As electrons pass down the electron transport chain, part of the energy is used to pump protons (H+) from stroma of chloroplast into the space inside the thylakoid membranes Buildup of positive charges and acidity inside the thylakoid: an electrochemical gradient the ATP synthase complex provides a channel for protons to flow back to the stroma and as they do, ATP molecules are made by adding phosphate to ADP. 13 Location diagram H+ flow to (Carbon hook up reactions) stroma Energy in excited electrons (e-) is used to through ATP split water (H2O) into e-, H+ and oxygen. synthase channel and make ATP H+ from H2O splitting and from pumping across Electron Transport Chain membrane Electron Transport Chain 14 7  Calvin cycle (“carbon hook up” reactions) Enzymes and reactions occur in the stroma of chloroplast Molecules of CO2 are attached and rearranged in multiple steps to make glucose Several reactions require ATP and NADPH (energy carriers) 6 turns of Calvin cycle needed to produce 1 glucose. 15 Photosynthesis: Chloroplast H+ H+ + H+ H+ H+ H + H+ H Electron acceptor e - H+ H+ e- Electron acceptor e- e- H+ ATP Synthase H+ e- e- e- Electron acceptor H+ e- ATP Electron acceptor H2O H2O contains H+, e-, e- = Electron and Oxygen H+ = Proton 16 8  Respiration Respiration: break down glucose in the presence of oxygen to produce carbon dioxide and water and capture some of the energy released as ATP. 6 O2 + C6H12O6 → 6 H2O + 6 CO2 Respiration multiple “carbon break down” steps. – Kreb’s cycle-“Carbon break down” steps – Electron transport chain – (Chemiosmosis and) oxidative phosphorylation 17 Respiration Glucose (6C sugar) Energy Carriers: ATP & NADH, FADH2 18 9  From last time… Energy Flow 19 Electron From last time… Transport As electrons move down chain energy is lowered Chain Electron acceptors are proteins that accept an electron and then pass on an electron to the next acceptor Some energy given off as heat and some stored in bonds of ATP and NADPH 20 10  From last time… Photosynthesis Overview 6 CO2 + 6 H2O → C6H12O6 + 6O2 Photosynthesis has two sets of reactions: Light reactions – Photosystems I and II capture solar energy – Use solar energy to split water and release electrons, protons and oxygen – Electrons and protons used to make ATP and NADPH (energy carriers) Calvin cycle (carbon hook up cycle) – Energy stored in ATP and NADPH during light reactions used to connect C’s from CO2 into simple sugars 21 From last time… Location diagram H+ flow to (Carbon hook up reactions) stroma Energy in excited electrons (e-) is used to through ATP split water (H2O) into e-, H+ and oxygen. synthase channel and make ATP H+ from H2O splitting and from pumping across Electron Transport Chain membrane Electron Transport Chain 22 11  From last time… Photosynthesis: Chloroplast H+ H+ + H+ H+ H+ H H+ H+ Electron acceptor e - H+ H+ e- Electron acceptor e- e- H+ ATP Synthase H+ e- e- e- Electron acceptor H+ e- ATP Electron acceptor H2O H2O contains H+, e-, e- = Electron and Oxygen H+ = Proton 23 From last time… Respiration Glucose (6C sugar) Energy Carriers: ATP & NADH, FADH2 24 12  Energy carriers NADH and FADH from Carbon break down reactions in matrix furnish e-, H+. Electron Transport Chain 25 Respiration: Mitochondrion e- e- e- H+ H+ + Energy carriers H+ H+ H+ H + H+ (NADH and FADH) H Electron acceptor e - from Krebs/Carbon Break down in H+ Matrix H+ Electron acceptor e- H+ ATP Synthase H+ e- Electron acceptor H+ e- ATP O2 terminal electron acceptor ATP goes elsewhere in the O2 = terminal electron acceptor. cell to power stuff H2O contains H+, e-, e- = Electron Adds e- to H+ to make H2O and Oxygen H+ = Proton 26 13  Photosynthesis: Respiration: 6CO2 + 6H2O → C6H12O6 + 6O2 C6H12O6 + 6O2 → 6CO2 + 6H2O 1) Sun Light boosts electrons from 1) Kreb’s/Carbon Breakdown splitting water. Happens in chlorophyll Reactions (mitochondrion matrix) in chloroplast thylakoid membranes at break bonds holding 6C sugar glucose start of ETC. Oxygen is released. together. Store energy in energy 2) Electron Transport Chain (ETC) carriers NADH and FADH2 (energy in thylakoid membranes makes Proton stored in -H bonds) (H+) gradient and energy carrier 2) High energy electrons at the start molecule NADPH (energy stored in -H of ETC in mitochondrion cristae from bond). NADH and FADH2 in Kreb’s/Carbon 3) ATP synthase (spans thylakoid breakdown. membrane) uses proton gradient to 3) Electron Transport Chain (ETC) make ATP (energy stored in -P bonds) in mitochondrion cristae makes Proton 4) Calvin/Carbon link-up reactions (H+) gradient. Oxygen accepts the (in stroma of chloroplast) use energy electrons, makes water. stored in NADPH and ATP to make 4) ATP synthase (spans cristae bonds to link up 6 Cs (CO2) into 6C membranes) uses proton gradient to sugar (Glucose C6H12O6). make ATP (energy stored in -P bonds) 27 Adenine Guanine Thymine Cytosine 28 14  Nucleotide chain 29 30 15  From last time Adenine Guanine Thymine Cytosine 31 From last time Nucleotide chain 32 16  From last time 33 Sugar= deoxyribose O (oxygen) C5 C1 C4 C2 C3 C1 C4 C5 C5 T C sugar C1 Bases in C and T both have a single ring sugar 34 17  C3 P C5 35 DNA double helix: two complementary strands running in opposite directions 36 18 37 Replication (DNA DNA) DNA replication: hydrogen bonds between bases broken Each single strand has the information to make a new complementary strand; – T in the original strand, an A will be placed opposite it in the new strand Many enzymes and cofactors required. Replication starts at a specific sequence called an origin of replication, Helicase enzymes break the hydrogen bonds between bases DNA polymerases synthesize the new strand recognizing each base and attaching the correct complementary base 38 19 39 Repair Errors – Mistakes sometimes during replication – chemicals and UV light If the damage is not repaired – change in DNA (a mutation) may be passed on to other cells. Can be good or bad Several enzymes work to repair damage: – DNA polymerases can reverse themselves and go back to repair damage during replication; – DNA repair nucleases can cut out damaged pieces of DNA and then put in the correct bases; – DNA ligase connects the repaired section to the main strand. 40 20 41 Genetic code 4 bases in DNA (ACGT)  20 amino acids code is triplet: a sequence of 3 nucleotides codon) along the DNA strand calls for particular amino acid Gene: the linear sequence of nucleotides in DNA that designates all the amino acids in a protein or polypeptide chain 42 21 43 Transcription (DNA mRNA) In eukaryotes, mRNA must be processed before leaving the nucleus Introns (sequences that do not code for protein) are cut out Exons (code for protein) remain To prevent degradation by RNAses in the cytoplasm – Cap is added at one end – Tail of adenine bases is added at the other end 44 22  Translation (RNA protein) Genetic code: Triplet/codon: a sequence of 3 nucleotides along the DNA strand calls for particular amino acid Redundant: more than one codon for most amino acids one start codon: only codon designating the amino acid methionine 3 stop codons 45 From last time Nucleotide strand C3 P C5 46 23  From last time DNA double helix: two complementary nucleotide strands running in opposite directions 47 From last time 48 24  Translation (RNA protein) Genetic code: Triplet/codon: a sequence of 3 nucleotides along the DNA strand calls for particular amino acid Redundant: more than one codon for most amino acids one start codon: only codon designating the amino acid methionine 3 stop codons 49 Genetic Code 50 25  Translation (RNA protein) Ribosomes made of protein and RNA (rRNA) Two subunits: – a smaller one with a binding site for mRNA – larger one with 3 binding sites for tRNAs. tRNAs (adaptor) – Different tRNA for each codon – each is folded in a characteristic way with stems and loops – One of the free ends of the tRNA has an attachment site for an amino acid – Specific enzyme (aminoacyl-tRNA synthetase) recognizes the shape of the tRNA and attaches the correct amino acid – In the loop opposite the free ends, 3 bases anticodon: – complementary to the codon for the amino acid that is attached to the tRNA 51 tRNA 52 26 Aminoacyl-tRNA 53 Translation (RNA protein) P=Polypeptide chain 54 27  A=Aminoacyl-tRNA site E= Exit site 55 56 28  DNA DNA RNA Protein Replication Transcription Translation Helicase Polymerase Ribosomes Polymerase tRNAs 57 Genetic Engineering Stems from “Universal Genetic Code” Based on ability to move genes from one organism to another “Recombinant” DNA products 58 29  Uses of genetic engineering Drugs purified from large populations of bacteria – previously expensive – some were very scarce because they could only be obtained from cadavers. Genetically engineered bacteria (make “recombinant” products) – interferon (fight viral infections) – human insulin (treat diabetics) – human growth hormone – Some vaccines 59 PLOIDY is the number of sets of chromosomes in the nucleus of a cell. – Haploid- typically gametes such as egg or sperm – Diploid-zygote http://en.wikipedia.org/wiki/Ploidy 60 30  Cell cycle Interphase: long phase cell replicates chromosomes and synthesizes other cell constituents Interphase: G1, S and G2 61 62 31  From last time DNA DNA RNA Protein Replication Transcription Translation Helicase Polymerase Ribosomes Polymerase tRNAs 63 From last time 64 32  Interphase: G1 & G2 (Gaps) In G1& G2 (Gap) Phases – Cell increases in size – synthesizes proteins/enzymes, ribosomes, membranes, microtubules and microfilaments – Mitochondria and chloroplasts replicate 65 Interphase: S phase S Phase – replication of DNA and histone proteins. – Sister chromatids- replicated chromosomes – 2 exact copies stay attached to each other at centromere – Centromere: region where sister chromatids are attached. – Appears as constriction 66 33  Chromosomes in this image have already gone through S phase. There are 8 chromosomes (4 from mom, 4 from dad), each made up of 2 chromatids. 67 Each human chromosome contains about 1,000- 2,000 genes encoding proteins. 68 34 69 Mitosis Mitosis: Produces 2 cells with identical genetic content as parent cell. 1Diploid (2N) cell makes 2 diploid (2N) cells. – Human: Most body cells – Plants: most plant cells 70 35  Interphase= G1, S, G2 4 phases of Mitosis Mitosis Cheer 71 Mitosis: Prophase DNA Chromosomes condense: threadlike strands visible chromosomes. Microtubules appear Nuclear membrane starts to break down Mitosis: Metaphase Chromosomes line up in the middle of the cell. (Microtubules pull chromatids to line up along the middle). Mitosis: Anaphase Sister chromatids separate at the centromere and move apart towards opposite poles Mitosis: Telophase/cytokinesis New nuclear envelope forms around the two new sets of chromosomes Microtubules disappear DNA decondenses Cells separate (cytokinesis) 72 36  Mitosis Cheer 73 Meiosis Mitosis: Produces 2 cells with identical genetic content as parent cell (2n2n or 1n1n) – Human: Most body cells – Plants: most plant cells Meiosis: Produces 4 cells with half the genetic content of parent cell (Reduction division), variation in which version of each chromosome (mom or dad) (2n1n) – Human gametes: Eggs, sperm – Plant gametes: Eggs, sperm, pollen, spores Zygote: Results from fusion of gametes Meiosis gives potential for new combinations – Variation is the raw material that natural selection works on (evolution) 74 37  Meiosis Similar to mitosis – DNA replication before mitosis (S phase) produces two chromatids joined by a centromere. – Prophase: Chromosomes condense, nuclear envelope disappears, spindle forms – Metaphase: Chromosomes line up along the mid-point of the spindle Different from mitosis: – Extra pairing step bringing together homologous chromosomes Chromosome encoding different versions of same genes, one from mom and one from dad Need two divisions (Meiosis I and Meiosis II) 75 76 38  Meiosis I Prophase I – DNA Chromosomes condense, Microtubules appear, nuclear envelope disappears – Homologous chromosomes pair (one from mom and one from dad) Crossing over: homologous chromosomes lined up together, can exchange genetic material from the same part of the chromosome Metaphase I – Homologous pairs of chromosomes line up at center of cell (Microtubules pull to center) Anaphase I – Homologous pairs separate to different cells duplicated chromatids go to the same cell at the end of meiosis I Telophase I – In most organisms: partial telophase Chromosomes start to uncoil, nuclear envelope starts to reform – In some organisms skip telophase I 77 Meiosis II (looks like Mitosis, but happens in two cells) Prophase II – DNA Chromosomes condense, microtubules form, nuclear envelope disappears Metaphase II – Chromosomes (pairs of sister chromatids) line up at center of cell (microtubules pull to center) Anaphase II – Sister chromatids separate at the centromere and move apart towards opposite poles Telophase II – Chromosomes decondense – Nuclear envelopes reform – The final result of meiosis is 4 haploid cells. 78 39  Mitosis Meiosis Daughters same ploidy as Daughters half ploidy as parent cell (Haploid-1N to parent cell (Diploid-2N to 1N or Diploid- 2N to 2N) Haploid-1N) One division Two divisions Homologous chromosomes Homologous do not pair Chromosomes pair Chromatids separate Crossing over Homologous Chromosomes separate (Meiosis I) Chromatids separate Meiosis II) 79 40