Cell & Molecular Biology Flashcards
What is an eukaryotic cell?
Plant or animal cell
What is a prokaryotic cell?
Bacteria (single organism)
What is magnification?
Enlargement of an image
What is resolution?
Measure of clarity of an image
What is contrast?
Difference in brightness between light and dark areas of an image
What are the different types of microscope?
Light microscope (LM): Fluorence microscope
Electron microscope (EM): Scanning electron microscope (SEM) + Transmission electron microscope (TEM)
What is light microscopy used for?
Used to visualise whole cells and large subcellular organelles (nucleus, chromosomes)
Fluorescence to stain
What is electron microscopy used for?
EMs use electronmagnets to focus a beam of electrons through/inside the specimen (TEM) or onto its surface (SEM)
What is TEM used for?
To study internal cell structure: organelles, proteins and nucleic acids
Focus a beam of electrons through the specimen
What is SEM used for?
To study cell surface and generate 3D images
Focus a beam of electrons onto the surface of specimen
Remember this
Order of organelles in cell fractionation
Nuclei -> Mitochondria -> Ribosomes
What does prokaryotic cells have instead of a nucleus?
A nucleoid (DNA concentrated but not enclosed by membrane)
Does prokaryotic cells have organelles?
No. Little or no internal structure or organelles
Does prokaryotic cells have ribosomes?
Yes to synthesise proteins
What organelles do prokaryotic cells have?
- Plasma membrane (encloses cytoplasm)
- Fimbriae (attachment to other bacteria)
- Flagella (locomotion)
- Cell wall (rigid structure)
- Glycocalyx (outer coating consisting of a capsule or slime layer)
- Ribosomes
- Nucleoid
Do eukaryotic cells have a nucleus?
Yes, a membrane bound nucleus which contains most of the cell’s DNA
Do animal cells have a cell wall?
No
Do plant cells have a cell wall?
Yes
Do animal cells have a central vacuole?
No
Do plant cells have a central vacuole?
Yes
Do plant cells have chloroplasts?
Yes
Do animal cells have chloroplasts?
No
The nucleus and its envelope
Ribosomes can be…
Bound to ER or free in the cytosol
Relationship among organelles of the endomembrane system
ER -> cis Golgi -> trans Golgi -> plasma membrane
What happens at the golgi?
Golgi apparatus - shipping and receiving centre
- vesicles also transport certain proteins back to ER
- vesicles coalesce to form new cis Golgi cisternae
- cisternal maturation: golgi cisternae move in a cis to trans direction
- vesicles form and leave golgi, carrying specific proteins to other locations or to the plasma membrane for secretion
- vesicles transport specific proteins backward to newer golgi cisternae
- vesicles also transport certain proteins back to ER
What happens at phagocytosis in lysosomes?
Lysosomes digest food
- Lysosomes contain active hydrolytic enzymes
- Food vacuole fuses with lysosome
- Hydrolytic enzymes digest food particles
What happens at autophagy (lysosome breaking down damaged organelle) in lysosomes?
- Lysosome fuses with vesicles containing damaged organelle
- Hydrolytic enzymes digest organelle components
What does mitochondria do?
Convert chemical energy to a form the cell can use
Where are the respiratory enzymes in mitochondria located and what do they contain?
- Respiratory enzymes (Kreb’s cycle) located in the inner membrane and matrix
- Contain own DNA and ribosomes
What does the chloroplast do?
- Convert light energy to a chemical form the cell can use
- It is the site of photosynthesis
- Bound by an outer and inner membrane
- Carry own DNA and ribosomes
- Also contain thylaoids which are a 3rd internal membrane network which contains photosynthetic apparatus
Where are chloroplasts found?
In plants and algae
What does the cytoskeleton do?
- Maintains cell shape
- Facilliates cell movement (eg. psudopodia, cilia, flagella)
- Facilliates movement of components within the cell (eg. vesicles)
- Interconnecting protein structures within the cytoplasm
What are the three types of cytoskeletal filaments?
- Microtubules
- Microfilaments
- Intermediate filaments
What is the structure of microtubules?
Hollow tubes; wall consists of 13 columns of tubulin molecules
What are the protein subunits of microtubules?
Tubulin, a dimer consisting of alpha-tubulin and beta-tubulin
What are the main functions of microtubules?
Maintenance of cell shape, cell motility (as in cilia and flagella), chromosome movements in cell division, organelle movements
What is the structure of microfilaments?
Two intertwined strands of actin, each a polymer of actin subunits
What are the protein subunits of microfilaments?
Actin
What are the main functions of microfilaments?
Maintenance of cell shape (tension-bearing elements), changes in cell shape, muscle contraction, cytoplasmic streaming, cell motility (pseudopodia), cell division (cleavage furrow formation)
What is the structure of intermediate filaments?
Fibrous proteins supercoiled into thicker cables
What are the protein subunits of intermediate filaments?
One of the several different proteins (such as keratins), depending on cell type
What are the main functions of intermediate filaments?
Maintenance of cell shape (tension-bearing elements), anchorage of nucleus and certain other organelles, formation of nuclear lamina
