Exam II Powerpoint II

1. Exam II Powerpoint II

2. PHOTOSYNTHESIS CO2 + H2O sunlight energy>C6H12O6 + O2 + H2O

3. The Sun is the ultimate source of biological energy for living organisms. The light waves that come from the Sun include visible light that we see and shorter wavelengths (with more energy) and longer wavelengths that we cannot see.

4. Primary Producers Plants, some protists, and some prokaryotes capture sunlight energy with photosynthetic pigments

5. Plant Pigments Chlorophyll which is found in chloroplasts is the most common pigment. It appears green because it absorbs light of colors other than green and allows green light to be reflected and thus detected by other organisms. There are also accessory photosynthetic pigments that make plants appear yellow and orange

6. Leaves and Chloroplasts The primary photosynthetic organs of plants are leaves. Plants and photosynthetic know thylakoids, stroma, granuum, and inner and outer membranes)

7. Photosynthesis

8. Light dependent reactions the “photo part of photosynthesis” that occur in the thylakoids

9. Light absorption Photochemical reactions involve the trapping of light. Light energy excites pigment molecules and causes an electron to be freed which begins moving through an ETS (next step). There are two photosystems [Photosystem I (with chlorophyll a absorbing lightwaves of 700 most efficiently; P700) and Photosystem II (also with chlorophyll a but absorbing lightwaves of 680 most efficiently; P680)] that are involved in capturing the energy and the beginning of electron transfer

10. Electron transfer The electron that is excited in Photosystem I is sent along the ETS to NADP+ and as another electron is passed to NADP+, the latter is reduced to NADPH (a coenzyme and energy intermediate) which carries electrons. Now light energy absorbed by Photosystem II is transferred into an electron thus exciting it and causing it to be sent to P700 (of Photosystem I) which can now absorb more light energy because of the replaced electron (note that Photosystem II has electrons replaced from split water molecules which also results in the formation of O2).

11. Chemiosmotic synthesis of ATP This is the final phase of energy capture and involves the movement of the hydrogen ions through ATP synthase with the release of energy and finally the synthesis of ATP from ADP. In addition, NADP+ picks up the H+ producing NADPH.

12. Overall, the light dependent reactions provide energy (in the form of cpe in ATP and cpe in NADPH), and H ions to be used as building blocks for glucose (from the NADPHs). Oxygen is released as a byproduct.

13. Light Independent Reactions or Carbon fixation the “synthesis part of photosynthesis” that occurs in the stroma of the chloroplast

14. Carbon fixation occurs when a gas (CO2) is incorporated into a solid (e.g., a carbohydrate) During energy capture the energy and the hydrogen needed for carbon fixation are required. Carbon fixation involving atmospheric CO2 occurs during the reactions of the Calvin Cycle

15. Readings The battle against world hunger can use plants adapted to water scarcity pp. 140-142 Greenhouse Gases pp. 607-609

16. DNA and Genetic Information

17. Genes and Chromosomes Genes are portions of DNA molecules that contain genetic information which controls protein synthesis. Each chromosome is made up of DNA and associated proteins. The DNA of each chromosome contains many genes.

18. Gene Expression the process whereby genes direct protein synthesis The order of this process is DNA > RNA > protein DNA is transcribed into RNA RNA is translated into proteins

19. Human karyotypes

20. DNA structure DNA is composed of subunits called nucleotides which consist of a 5Carbon sugar (deoxyribose), phosphate group(s), and nitrogenous bases (A, T, C, and G) Nucleotides are linked by sugar-phosphate bond which basically form a backbone The 3-D structure of DNA (from Franklin; Watson and Crick) is a twisted spiral (or more commonly called a helix) consisting of two strand of DNA, thus it is called a double helix

21. DNA Replication In addition to serving as the code for proteins, DNA also undergoes replication Replication is the duplication of DNA within a cell prior to cell division (e.g., mitosis or meiosis I) The original strands of the double helix serve as a template for the new strands (replication is semi-conservative) Enzymes are involved in replication (e.g., helicase and DNA polymerase)

22. Mutations Mistakes may occur during replication or mutations may be induced by a variety of mutagens (substances or phenomena that cause changes in DNA). Mutagens include: UV radiation which causes thymine dimers, X-rays, nicotine, and many other drugs or man-made chemicals

23. Mutations can be: beneficial - antibiotic resistance in bacteria is good for the bacteria (but not for us of course), sickle-cell anemia (actually a person with one gene for hemoglobin S, a carrier, is at an advantage to people with two normal hemoglobin genes in areas of the world where malaria is endemic), and mutations are a source of variation which is necessary for evolution to occur. deleterious - many mutations are bad in that they result in serious conditions and possibly death, for example- UV light causes thymine dimers in bacteria which prevent replication and thus eventually the colony of bacteria will die. Neutral or silent - some mutations do not change the protein that is coded for by that gene. This is because each amino acid has more than one triplet code

24. End of Notes for Exam II