Prokaryotes & Eukaryotes, Evolutionary origins of Mitochondria and Chloroplasts Flashcards
Explain Prokaryotes ?
- Bacteria and Archaea
- Simple structure – no nucleus
- Derived from Greek word pro meaning “before”
Explain Eukaryotes ?
- Plants, animals, fungi, yeast
- Complex structure – nucleus and other organelles
- Derived from Greek words: eu meaning “well” or “truly,” and karyon a “kernel” or “nucleus”
Explain the basics of Prokaryotic cells ?
- Most diverse and numerous cells on earth
- Often small (5uM
Explain the diverse chemistry of Prokaryotic cells ?
- Most diverse in metabolism
- Inhabit extreme environments – volcanoes, hot springs, darkness, north/south poles
- Aerobic (require O2), anaerobic (do not require O2) or facultative anaerobes (can do both!)
- Make energy from both organic (e.g. wood, petroleum) and inorganic substances (e.g. sulphur, nitrogen)
- Some perform photosynthesis (energy from sunlight)
Explain the cell structure of Prokaryotic cells ?
- Tough cell wall surrounding plasma membrane
- Flagella for motility
- Single inner compartment containing cytoplasm, ribosomes and DNA (circular arrangement)
- No organised internal structure
Explain Archaea ? give examples
- Prokaryotes split into bacteria and archaea
- Large molecular differences
- Live in very hostile environments resembling primitive earth – earliest predecessors?
Halophiles - High salt environments
Methanogens - Hypoxic environments (cow stomach)
Thermophiles - High temperatures
Explain the basics of Eukaryotic cells ?
- Generally bigger than prokaryotes (>10μM)
- Live independently as single cells (yeast, amoeba)
- Form multicellular organisms (fungi, plants, animals)
- Contain a nucleus and other membrane enclosed organelles
Explain the nucleus in eukaryotic cells ?
- Most prominent organelle – enclosed within two concentric membranes
- Contains DNA (genetic information) – about 2m long per cell!
- Tightly wrapped around histone proteins to form chromosomes
- Chromosomes condense during cell division
Explain the mitochondria in eukaryotic cells ?
- Abundant and visible in cytoplasm
- Enclosed within double membrane
- Folded inner membrane (increases surface area)
- Generate chemical energy for cell
- Oxidation of food molecules (sugars) to produced adenosine triphosphate (ATP) to power cell activities
- Consumes oxygen, generates CO2 – cellular aerobic respiration
Explain the origins of Mitochondria ?
- Believed to originate from bacteria engulfed by ancestral eukaryote
- Symbiotic relationship between host eukaryote and engulfed bacterium
Evidence for endosymbiotic origins of mitochondria and chloroplasts ?
- Shape and size akin to bacteria
- Contain circular DNA
- Can divide (fission) and recombine (fusion)
- Possess double membrane
- Similar ribosomal structure to bacteria
- Generates own proteins
- Eukaryotes capable of phagocytosis
- Sensitive to antibiotics (Chloramphenicol)
Explain the Plant cells contain chloroplasts for energy in Eukaryotic cells?
- Found only in plants and algae
- Similar structure to mitochondria-more complex
- Two surrounding membranes with internal membrane stacks containing chlorophyll
- Carry out photosynthesis (produce energy rich sugars from sunlight)
- Mitochondria extract energy from sugars via oxidation to produce energy for the cell
Explain the origins of chloroplasts ?
- Similar origins to mitochondria – photosynthetic bacteria engulfed by ancestral eukaryote
- Symbiotic relationship between host eukaryote and engulfed bacterium
Explain the contained membraned organelles in Eukaryotic cells ?
- Other membrane bound organelles
- Involved with import/export of raw materials
- Secretion of proteins and waste by products
Explain the Endoplasmic reticulum in Eukaryotic cells?
- Irregular maze of interconnected spaces enclosed by a membrane
- Site of production for membrane components and export materials
- Enlarged in cells specialised for secretion of proteins
