BIOL10002 Lecture Notes - Lecture 7: Smallest-Circle Problem, Cellular Respiration, Intermembrane Space
Lecture 7: Mitochondria, plastids & endosymbiosis
Mitochondria: power plant of cell, site of aerobic respiration in
eukaryotes
cells have several or single
double membrane: highly convoluted inner membrane: cristae (folds of
inner membrane, increase surface area, contain key molecules for ATP
generation); outer membrane
matrix: interior; contains enzymes (site of Krebs cycle) for cellular
respiration and ribosomes, DNA
intermembrane space: creates concentration gradient; H+ go from here
to matrix
divide by binary fission; FtsZ protein: helps with pinching in two
mitochondrial ribosomes (smaller than ribosomes in cytoplasm) are
sensitive to some antibiotics, they translate their own proteins from
their genome
ETC and turbin ATPase of inner membrane are same as plasma
membrane
Circular DNA chromosome (genome)
−purple: bacteria that mitochondria originated from
Bacteria have membrane folds like mitochondria (gram - bacteria); bacteria, plastids and mitochondria all have a circular DNA chromosome
(mitochondria has smallest circle)
Evidence for endosymbiosis in mitochondria:
● respiration machinery in gram - -proteobacterium is same as in mitochondrion; chemistry of it is identical
● symbionts: an organism living in symbiosis with another: mitochondrial endosymbiont is an aerobic -proteobacterium (efficient)
● host (cell without mitochondria): nucleated cell only capable of glycolysis (2 ATP from each molecule; creates waste product) (inefficient)
● benefits: gives pyruvate waste product to bacterial prey, allowing ATP production from bacteria & bacterium allowed to live and get
pyruvate from host cell
Chloroplasts: cells contain one or more
double membrane: outer, inner; inner form thylakoids (folded
membrane, internal membrane stacks, increases SA)
site of photosynthesis: conversion of light energy to chemical energy:
light energy captured to make ATP and reduce NADP, then used to fix
CO2 into sugars; light dependent and light-independent reactions
photosynthetic pigments located on thylakoids
green pigment: chlorophyll, harvests light energy
granum: stack of thylakoids
stroma: fluid surrounding grana in chloroplasts
cyanobacteria: origin of chloroplasts: 3.5 billion years ago; first
identifiable form of life on earth
Photosynthesis: like aerobic respiration except the electron is released
by light energy instead of glucose oxidation
Photosynthesis and respiration make the biosphere work; bacteria
involved in both processes
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Phagotrophic: feeding by engulfing a food cell or particle and ingesting it in a vacuole
Primary endosymbiosis: process by which a eukaryote engulfs another living prokaryote then uses it to their advantage
Stromatolites: have cyanobacteria photosynthesizing on surface; have layers as evidence of sediment (dead algae); there are fossil stromatolites
everywhere; looking inside you can see fossil cyanobacteria
Evidence for endosymbiotic origin of mitochondria and chloroplasts:
1. Organelles appear morphologically similar to bacteria
2. Outer membrane like cell membrane & inner membrane invaginates to form lamellae or cristae; derived from gram - bacteria
3. Both are semi-autonomous, retaining their own genome (DNA, RNA, genome)
4. Retain own machinery for synthesizing proteins
5. Metabolism like existing prokaryotes
6. Some chloroplasts still have the bacterial peptidoglycan wall between the inner and outer membranes
Tree of ribosomal genes shows organelle genes grouping with Bacteria and not with own nuclei in eukaryotes
Lecture 8: Cell division: mitosis & meiosis
Bacterial division: binary fission (prokaryotes)
● FtsZ protein (filament temperature sensitive) = pinchase
● homologue of eukaryotic cytoskeletal protein tubulin (flagella, mitosis)
● involved in division of chloroplasts and mitochondria (endosymbiotic
bacteria)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Etc and turbin atpase of inner membrane are same as plasma membrane. Circular dna chromosome (genome) (cid:2009) purple: bacteria that mitochondria originated from. Bacteria have membrane folds like mitochondria (gram - bacteria); bacteria, plastids and mitochondria all have a circular dna chromosome (mitochondria has smallest circle) Evidence for endosymbiosis in mitochondria: respiration machinery in gram - (cid:2009)-proteobacterium is same as in mitochondrion; chemistry of it is identical. Symbionts: an organism living in symbiosis with another: mitochondrial endosymbiont is an aerobic (cid:2009)-proteobacterium (efficient) Host (cell without mitochondria): nucleated cell only capable of glycolysis (2 atp from each molecule; creates waste product) (inefficient) Benefits: gives pyruvate waste product to bacterial prey, allowing atp production from bacteria & bacterium allowed to live and get pyruvate from host cell. Photosynthesis: like aerobic respiration except the electron is released by light energy instead of glucose oxidation. Photosynthesis and respiration make the biosphere work; bacteria involved in both processes.
