Endosymbiotic Theory. p

Size: px

Start display at page:

Download "Endosymbiotic Theory. p"

Avice Dixon
6 years ago
Views:

1 Endosymbiotic Theory p

2 The Endosymbiotic Theory Review: What is a theory? What is the difference between prokaryotic and eukaryotic cells? The endosymbiotic theory is the idea that a long time ago, prokaryotic cells engulfed other prokaryotic cells by endocytosis. This resulted in the first eukaryotic cells. First proposed by Lynn Margulis Explains the origin of eukaryotic cells Explains the origin of certain membrane-bound organelles

3 What Exactly Happened? Chloroplast Heterotrophic bacteria Ancient Prokaryotes Nuclear envelope evolving Photosynthetic bacteria Mitochondrion Plants and plant-like protists Primitive Autotrophic (Photosynthetic) Eukaryote Ancient Heterotrophic Prokaryote Primitive Heterotrophic Eukaryote Animals, fungi, and animal-like protists

4 Membrane-Bound Organelles Mitochondria = membrane-bound organelle that produces energy for the cell Chloroplast = membrane-bound organelle that captures sunlight and uses it to make food for the cell

5 Evidence in support of the endosymbiotic theory: Both mitochondria and chloroplasts contain DNA, which is fairly different from that of the cell nucleus, and that is similar to that of bacteria (circular and smaller). They are surrounded by two or more membranes, and the innermost of these shows differences in composition compared to the other membranes in the cell. The composition is like that of a prokaryotic cell membrane. New mitochondria and chloroplasts are formed only through a process similar to binary fission (prokaryote cell division).

Evidence in support of the endosymbiotic theory: Much of

for instance the presence of thylakoids and particular

The size of both organelles is comparable to bacteria.

6 Evidence in support of the endosymbiotic theory: Much of the internal structure and biochemistry of chloroplasts, for instance the presence of thylakoids and particular chlorophylls, is very similar to that of cyanobacteria. The size of both organelles is comparable to bacteria. These organelle's ribosomes are like those found in bacteria (70s).

7 Cell Energy: Cells usable source of energy is called ATP ATP stands for adenosine triphosphate Adenine Ribose 3 Phosphate groups

8 ADP stands for adenosine diphosphate Adenine Ribose 2 Phosphate groups

9 All energy is stored in the bonds of compounds breaking the bond releases the energy When the cell has energy available it can store this energy by adding a phosphate group to ADP, producing ATP

10 ATP is converted into ADP by breaking the bond between the second and third phosphate groups and releasing energy for cellular processes.

30 PHOTOSYNTHESIS Part II

31 Two Parts of Photosynthesis Two reactions make up photosynthesis: 1.Light Reaction or Light Dependent Reaction - Produces energy from solar power (photons) in the form of ATP and NADPH. SUN 2

32 Two Parts of Photosynthesis 2. Calvin Cycle or Light Independent Reaction Also called Carbon Fixation or C 3 Fixation Uses energy (ATP( and NADPH) ) from light reaction to make sugar (glucose). 3

33 Light Reaction (Electron Flow) Occurs in the Thylakoid membranes During the light reaction,, there are two possible routes for electron flow: A.Cyclic Electron Flow B. Noncyclic Electron Flow 4

34 Cyclic Electron Flow Occurs in the thylakoid membrane. Uses Photosystem I only P700 reaction center- chlorophyll a Uses Electron Transport Chain (ETC) Generates ATP only,, more ATP required for P ADP + ATP 5

35 Adenosine Triphosphate ATP A. Because cells need a steady supply of energy to carry on cellular processes they store energy by bonding a third phosphate molecule to ADP (adenosine diphosphate) forming ATP (adenosine triphosphate) 6

36 What makes up ADP (adenosine diphosphate)? Adenine base, ribose sugar and 2 (di)phosphates ATP consists of an adenine base, a ribose sugar and 3 phosphate molecules Adenosine Triphosphate Adenosine Diphophate 7

37 . Energy stored in the bonds between phosphate molecules is released when a phosphate molecule breaks off. Since every activity an organism performs requires energy, this cycle is repeated again and again throughout the life of the cell. 8

38 Cyclic Electron Flow SUN Primary Electron Acceptor e - Photons e - P700 e - e - ATP produced by ETC Accessory Pigments Photosystem I Pigments absorb light energy & excite e-e of Chlorophyll a to produce ATP 9

39 Noncyclic Electron Flow Occurs in the thylakoid membrane Uses Photosystem II and Photosystem I P680 reaction center (PSII) - chlorophyll a P700 reaction center (PS I) - chlorophyll a Uses Electron Transport Chain (ETC) Generates O 2, ATP and NADPH 10

40 Noncyclic Electron Flow Primary Electron Acceptor Noncyclic Electron Flow 2e - 2e - ETC Primary Electron Acceptor 2e - Enzyme Reaction SUN 2e - 2e - P700 NADPH Photon ATP H 2 O P680 Photon Photosystem I ½ O 2 + 2H+ Photosystem II H 2 O is split in PSII & ATP is made, while the energy carrier NADPH is made in PSI 11

41 Noncyclic Electron Flow P ADP + ATP NADP + + H NADPH Oxygen comes from the splitting of H 2 O, not CO 2 (Photolysis) H 2 O ½ O 2 + 2H + 12

42 Chemiosmosis Powers ATP synthesis Located in the thylakoid membranes Uses ETC C and ATP synthase (enzyme) to make ATP Photophosphorylation: addition of phosphate to ADP to make ATP 13

43 Chemiosmosis Thylakoid SUN H + H + (Proton Pumping) E PS II T PS I C high H H + H + + concentration H + H + H+ H + H + ATP Synthase Thylakoid Space ADP + P H + ATP low H + concentration 14

44 Calvin Cycle Carbon Fixation (light independent reaction) C 3 plants (80% of plants on earth) Occurs in the stroma Uses ATP and NADPH from light reaction as energy Uses CO 2 To produce glucose: : it takes 6 turns and uses 18 ATP and 12 NADPH. 15

45 Chloroplast Outer Membrane Inner Membrane STROMA where Calvin Cycle occurs Thylakoid Granum 16

46 Calvin Cycle (C 3 fixation) 17

47 Calvin Cycle Remember: C 3 = Calvin Cycle C 3 Glucose 18

48 Photorespiration Occurs on hot, dry, bright days Stomates close Fixation of O 2 instead of CO 2 Produces 2-C C molecules instead of 3-C C sugar molecules Produces no sugar molecules or no ATP 19

49 Photorespiration Because of photorespiration, plants have special adaptations (alternative pathways) to limit the effect of photorespiration: 1.C 4 plants 2. CAM plants 20

50 C 4 Plants Hot, moist environments 15% of plants (grasses, corn, sugarcane) Photosynthesis occurs in 2 places Light reaction - mesophyll cells Calvin cycle - bundle sheath cells 21

51 C 4 Plants 22

52 CAM Plants Hot, dry environments 5% of plants (cactus and ice plants) Stomates closed during day Stomates open during the night Light reaction - occurs during the day Calvin Cycle - occurs when CO 2 is present 23

53 Stomata Open Stomata Closed 24

54 CAM Plants Night (Stomates Open) Day (Stomates Closed) Vacuole CO 2 C-C-C-C Malate C-C-C-C Malate C-C-C-C Malate CO 2 C3 C-C-C PEP ATP C-C-C Pyruvic acid glucose 25

55 26

56 Question: Why do CAM plants close their stomata during the day? 27

57 Cam plants close their stomata in the hottest part of the day to conserve water

58 Rates of Photosynthesis 1. Light Intensity 2. CO 2 3. Temperature 29

Photosynthesis 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2

Photosynthesis 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 PHOTOSYNTHESIS Photosynthesis An anabolic, endergonic, carbon dioxide (CO 2 ) requiring process that uses light energy (photons) and water (H 2 O) to produce organic macromolecules (glucose). photons SUN