Ch 25 - Endosymbiosis Flashcards
Endosymbiotic theory
Explains how eukaryotes could have evolved from prokaryotes
A larger cell engulfed smaller cells that evolved into mitochondrion and chloroplasts
Examples of endosymbionts
Dinoflagellates, photosynthetic protists
Eukaryotic cells contain:
1) nucleus w chromosomes
2) intracellular membranes (RER, SER, Golgi apparatus)
3) mitochondria
4) chloroplasts (plants)
How do eukaryotic cells divide?
Mitosis
Lynn Margulis
Proposed endosymbiotic theory in 1967
Similarities between mitochondrion and bacteria
1) 1-4 um in length
2) surrounded by 2 membranes
3) use O2 to generate ATP
4) have their own DNA
5) grow and divide by binary fission
6) similar genes
7) similar ribosomes
8) similar enzymes
What was the reason for the rise of eukaryotes?
Environment change from anaerobic to aerobic
What was the reason for the increase in atmospheric O2?
Photosynthesis by cyanobacteria
Great oxygenation event
Increase in molecular oxygen 2.3 billion years ago that resulted in mass extinction
Main events in evolution of eukaryotic cells
Origin of: flexible cell surface, cytoskeleton, nuclear envelope, phagocytosis, digestive vesicles/vacuoles,
Endosymbiotic acquisition of mitochondria and chloroplasts
Flexible cell surface
Prokaryotic cell wall lost, allowing cell to grow larger
As cell size increased, the surface area-to-volume ratio decreased
Infolding can occur, creating internal membranes and more surface area
Allowed endocytosis to develop
Origin of the nucleus
Nuclear envelope likely to have arisen from plasma membrane
DNA of prokaryote is attached to plasma membrane
Inward folding of the plasma membrane created a double layer of phospholipids that surrounded the DNA
Conversion from extra cellular digestion to intracellular digestion
Phagocytosis - created digestive vesicles and vacuoles
a-proteobacterium evolved into….
Mitochondrion
Rickettsia
a-proteobacterium
Intracellular parasites in plants and animals
Ticks, fleas, lice
Cause typhus and Rocky Mountain spotted fever
Symptoms of Rocky Mountain spotted fever
High fever, severe muscle pain, rash on wrists and ankles
Proteobacterium likely fed on ______ and released _______.
Carbon compounds, H+
Primitive eukaryotic cells used the H+ to make _____.
ATP
What was the initial function of mitochondrion?
To detoxify the increased amounts of O2 in the atmosphere by reducing it to water
Cells with mitochondrion are able to carry out ____.
Cellular respiration
Respiration yields much more energy from the breakdown of __________, than ________ do.
Carbon compounds, anaerobic pathways
Later, a primitive eukaryotic cell incorporated a photosynthetic prokaryote related to modern day __________.
Cyanobacteria
Cyanobacteria evolved into ________.
Chloroplasts
Advantage of cells containing chloroplasts:
ability to harness energy from the sun to make carbon compounds
