Prokaryotes & Eukaryotes, Evolutionary origins of Mitochondria and Chloroplasts Flashcards
1
Q
Explain Prokaryotes ?
A
- Bacteria and Archaea
- Simple structure – no nucleus
- Derived from Greek word pro meaning “before”
2
Q
Explain Eukaryotes ?
A
- 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”
3
Q
Explain the basics of Prokaryotic cells ?
A
- Most diverse and numerous cells on earth
- Often small (5uM
4
Q
Explain the diverse chemistry of Prokaryotic cells ?
A
- 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)
5
Q
Explain the cell structure of Prokaryotic cells ?
A
- Tough cell wall surrounding plasma membrane
- Flagella for motility
- Single inner compartment containing cytoplasm, ribosomes and DNA (circular arrangement)
- No organised internal structure
6
Q
Explain Archaea ? give examples
A
- 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
7
Q
Explain the basics of Eukaryotic cells ?
A
- 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
8
Q
Explain the nucleus in eukaryotic cells ?
A
- 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
9
Q
Explain the mitochondria in eukaryotic cells ?
A
- 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
10
Q
Explain the origins of Mitochondria ?
A
- Believed to originate from bacteria engulfed by ancestral eukaryote
- Symbiotic relationship between host eukaryote and engulfed bacterium
11
Q
Evidence for endosymbiotic origins of mitochondria and chloroplasts ?
A
- 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)
12
Q
Explain the Plant cells contain chloroplasts for energy in Eukaryotic cells?
A
- 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
13
Q
Explain the origins of chloroplasts ?
A
- Similar origins to mitochondria – photosynthetic bacteria engulfed by ancestral eukaryote
- Symbiotic relationship between host eukaryote and engulfed bacterium
14
Q
Explain the contained membraned organelles in Eukaryotic cells ?
A
- Other membrane bound organelles
- Involved with import/export of raw materials
- Secretion of proteins and waste by products
15
Q
Explain the Endoplasmic reticulum in Eukaryotic cells?
A
- 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
16
Q
Explain the Golgi apparatus in Eukaryotic cells ?
A
- Stacks of flattened, membrane-enclosed sacs
- Packages materials made by ER for transport, export or secretion
- Site of post-translational modification of proteins(e.g. glycosylation)
17
Q
What are the other organelles in Eukaryotic cells and explain them ?
A
- Lysosomes:
- Intracellular digestion
- Release nutrients from
food particles
- Degrades unwanted cell
molecules for recycling or export - Peroxisome:
- Provides contained and safe environment for detoxification by hydrogen peroxide and other harmful enzymes - Vesicle:
- Ferry materials between organelles
18
Q
Explain the vesicle transport in Eukaryotic cells?
A
- Continual exchange of materials between organelles mediated by transport vesicles
- Vesicles pinch off from one membrane organelle and fuse with another.
- Import of material = Endocytosis
- Export of material = Exocytosis
19
Q
Cytosol is an aqueous gel. Further explain this cell in Eukaryotic cells ?
A
- Organelles are housed within aqueous gel environment
- Cytosol is usually largest compartment
- Dense with small and large molecules
- Roles in structure, motility, cell signalling, metabolism and manufacturing
20
Q
Explain the cytoskeleton in Eukaryotic cells ?
A
- Cytoskeleton directs cell movements
- Cytoplasm not structureless
- Contains internal framework of fine protein filaments called the cytoskeleton
- Different types detectable by different cellular stains
- Controls internal activities, strength, motility and shape
- Essential for all eukaryotic cells
21
Q
What are the 3 types of cytoskeleton and explain them ?
A
- Actin filaments
- Thinnest
- Abundant in muscle cells for strong contractile forces - Microtubules
- Thickest, hollow tubes
- Pull duplicated chromosomes apart during cell division - Intermediate filaments
- Intermediate thickness
- Strengthen cell mechanically
22
Q
What are the 8 things you need to remember about Eukaryotic cells ?
A
- Contain a nucleus
- Contain mitochondria for energy
- Plant cells contain chloroplasts for energy
- Internal membranes create distinct organelles with specific functions
- Cytosol is aqueous gel containing small/large molecules
- Cytoskeleton directs cell movement
- Cytoplasm is not static
- Eukaryotes probably originated as predators
23
Q
Explain how eukaryotic cells originated as predators?
A
- Large size, flexible membrane and cytoskeleton helped cell to move and eat
- Primitive eukaryotes engulfed bacteria (mitochondria, chloroplasts)
- This reflected in modern day protozoans which eat other cells
