Basic Eukaryotic Cell Biology Flashcards
Why are cells small?
- Need a large surface area to exchange materials, live, respire and survive
Describe the role of the cytoplasm?
It’s the site for nutrient and waste exchange
Describe the surface area to volume ratio as cells increase in size
The bigger the cell/organism the smaller the SA:V ratio
Describe how cells can increase SA:V ratio?
Cells specialised in absorption have membrane modifications e.g. microvilli
What two taxonomic domains are prokaryotic cells placed in?
Bacteria
Archaea
Compare prokaryotic cells to eukaryotic cells?
- Structurally smaller and simpler than eukaryotic cells
- Lack a membrane-bound nucleus
Describe the cell envelope of bacterial cell.
- Plasma membrane - lipid bilayer with embedded and peripheral protein
- Form internal pouches (mesosomes)
- Cell wall - maintains the shape of the cell and is strengthened by peptidoglycan
- Glycocalyx - layer of polysaccharides on the outside of the cell wall.
Describe the cytoplasm of bacterial cells.
- Semifluid solution
- Bounded by plasma membrane
– Nucleoid contains the single, circular DNA molecule.
– Plasmids small accessory (extrachromosomal) rings of DNA
Describe the appendages of bacterial cells.
- Flagella provides motility
- Fimbriae - small, bristle-like fibres that sprout from the cell surface
- Sex pili - rigid tubular structures used to pass DNA from cell to cell
What do eukaryotic cells contain?
– Membrane-bound nucleus that houses DNA
– Specialised organelles
– Plasma membrane
– Much larger than prokaryotic cells
What is the hypothesised origin of eurkayoic cells?
- Cell gains a nucleus by the plasma membrane invaginating and surrounding the DNA with a double membrane
- Cell gains an endomembrane system by proliferation of membrane
- Cell gains mitochondria
State the role of the rough ER.
- Modifies proteins
- Intracellular transport
State the role of smooth ER.
- No ribosomes
- Makes lipids
- Intracellular synthesis pathways
State the role of ribosomes.
Translates mRNA into a polypeptide chain.
State the role of lysosomes.
- Intracellular digestion
- Releases nutrients
- Breakdown of waste
State the role of the nucleus.
- Contains most of the cell’s genetic material
State the role of the Golgi.
- Receives and modifies
- Directs new materials
Summarise the endomembrane system
- Proteins produced in rough ER and lipids from smooth ER carried in vesicles to the Golgi apparatus
- Golgi apparatus modifies and packages them into vesicles - go to cell destinations
- Secretory vesicles carry products to membrane - exocytosis produces secretions
- Lysosomes fuse with incoming vesicles and digest macromolecules
What are peroxisomes?
- Similar to lysosomes
- Membrane-bounded vesicles
- Enclose enzymes
- Enzymes synthesized by free ribosomes in cytoplasm (instead of ER)
State the role of peroxisomes.
- Active in lipid metabolism
- Catalyze reactions that produce hydrogen peroxide
- Toxic
- Broken down to water & oxygen by catalase
Describe the structure of mitochondria
- Contain ribosomes and their own DNA
- Surrounded by a double membrane
- Inner membrane surrounds the matrix and is convoluted (folds) to form cristae.
- Matrix – Inner semifluid containing respiratory enzymes
State the role of mitochondria.
- Break down carbohydrates
- Involved in cellular respiration
- Produce most of ATP utilized by the cell
- Contains mitochondrial (maternal) DNA
What is the role of the cytoskeleton?
- Maintain cell shape
- Assists in movement of cell and organelles
- Assemble and disassemble as needed
State the role of actin filaments
- Extremely thin which maintain cell shape.
- Intracellular traffic control and movement
- Cytoplasmic streaming
- Important component in muscle contraction
State the role of intermediate filaments.
- Between actin filaments and microtubules
- Rope-like assembly of fibrous polypeptides
- Vary in nature from tissue to tissue and time to time
- Support nuclear envelope
- Cell to cell junctions e.g. those holding skin cells tightly together
State the role of microtubules.
- Hollow cylinders made of two globular proteins called a and b tubulin
- Form centromeres and centrioles
- Interact with proteins kinesin and dynein to cause movement of organelles.
