Lecture 1- What is a Cell? Flashcards
T/F: Viruses are cells.
False! Viruses are NOT cells
Why aren’t viruses considered cells?
- They require cells to replicate & assemble
- Made o/ capsid (proteins) surrounding nucleic acids
- May have a membrane (stolen from a cell)
- Can infect cells & cause cell death or mis-regulation (some cancers)
What does a cell need to do in order to perform?
- Obtain food + energy- find it, take it in, and convert it into something usable
- Adjust + adapt to the environment- keep bad things out and good things in; getting enough O2, respond to changes in pH, preventing from drying out
- Reproduce- requires a lot o/ energy, how to get the right content into a daughter cell
- Fulfill specialized functions- neurons send/receive signals, “knowing” what to do
- Communication- within the cells + other cells, coordination between cells
- Maintenance/repair- o/ various parts o/ the cell, if not used for maintenance/repair, it must remove the “trash”
What are the two types of cells?
Prokaryotic and Eukaryotic
Describe a PROKARYOTIC cells.
- Unicellular
- Kingdoms- Bacteria and Archae
- No nucleus
- NOT BOUND by membrane
- Very small, can be diff. shapes
- Reproduce by fission
- Some carry out photosynthesis, nitrogen fixation
- Similar structure to bacteria
Archae live in ________ environments.
extreme
What are the two types o/ Archae?
Thermophiles
Haplophiles- require high salt
Describe EUKARYOTIC cells.
- Contain a well-defined nucleus and membrane-bound organelles
- Kingdoms- Protists, Fungi, Plants, and Animals
- Can be unicellular or multicellular
- Much bigger than prokaryotes
- Wide variety o/ shapes
- Some undergo sexual reproduction
What similarities do prokaryotic cells and eukaryotic cells share?
- Plasma membrane
- Molecular structure o/ DNA
- Mechanism o/ transcription, translation, metabolism and energy pathways, & breaking down proteins
Cell membrane
- Forms the boundary o/ cell
- Holds things together and separates the inside o/ cell from outside
- Has 2 layers (phospholipid bilayer)
- Composed o/ lipids, proteins, & carbs
- Selectively allows molecules in and out o/ cells
What structures are part of the nucleus?
- Chromatin
- Nucleolus
- Nucleoplasm
- Nuclear matrix
- 2 membranes- inner and outer membrane
- Nuclear pore complexes
- Connected to endoplasmic reticulum
What is chromatin?
- Has genetic material (DNA) + associated proteins (histones)
What is the nucleolus?
- Site o/ ribosomal RNA synthesis and assembly o/ ribosome components
What is the the nucleoplasm?
Non-nucleolar regions o/ nucleus
What is the nuclear matrix?
Composed o/ intermediate filaments (lamin) + associated proteins (gives support)
How do nuclear pore complexes help eukaryotic cells?
Helps move materials in and out o/ nucleus
What does the endomembrane system consist of?
- Series o/ interconnected, closed, membrane-bound vesicles
- Nuclear envelope
- Endoplasmic reticulum
- Golgi apparatus
- Lysosome
- Vesicles
- Endosomes
- Plasma membrane
What does the endomembrane system do?
Modify, package, & transport lipids + proteins
What is the endoplasmic reticulum?
- A network o/ membranous tubules within the cytoplasm o/ a eukaryotic cell
- Continuous w/ nuclear membrane
- Acts as an intracellular transporting system or canal
- Important in protein folding and quality control
What are the two types o/ endoplasmic reticulum?
Rough endoplasmic reticulum- studded w/ membrane-bound RIBOSOMES
Smooth endoplasmic reticulum- lacks ribosomes, makes phospholipids + fatty acids
What holds the endoplasmic skeleton in place?
Cytoskeleton
T/F: The cell’s function determine the size and structure of the endoplasmic reticulum (ER). Explain.
True
- e.g. Sperm cells and red blood cells don’ have an ER
- However, pancreas and liver cells have large endoplasmic structure as they synthesize and release lots
o/ protein
What is the Golgi complex (aka Golgi apparatus or Golgi body)?
- Membrane-bound organelle
- Cisternae- series o/ flattened, stacked pouches
- Responsible for modifying, sorting, & packaging proteins + lipids into vesicles for delivery to targeted destinations
What are lysosomes?
- Membrane-bound vesicles found exclusively in animal cells
- Acid hydrolases- degrades polymers into their monomeric subunits
- pH level o/ lumen~ 5.0
- Lysosomal hydrolases work most efficiently @ acidic pH
How does acidic pH help lysosomes do their job?
Helps denature proteins, making them accessible to action o/ lysosomal hydrolases
What does the mitochondria consist of?
- Outer mitochondrial membrane- large pores allow molecules to move from the cytosol to intermembrane space
- Inner mitochondrial membrane- many cristae foldings into aqueous matrix compartment
- Increase membrane surface area
Why is mitochondria important?
Site o/ aerobic respiration & ATP production
- Enzymes in matrix & cristae convert CO2 –> H2O releasing ATP
What is cytosol?
- Site o/ cellular metabolism, has ribosomes (protein synthesis) + proteasomes (protein degradation)
- Contains a network o/ cytoskeletal proteins
Why are cytoskeletal proteins important?
For structural integrity o/ cells & act as highways to move component
Name the 3 types o/ cytoskeletal filaments.
- Microtubules (20 nm diameter)
- Tubulin subunits - Microfilaments (7 nm diameter)
- Actin - Intermediate filaments (11 nm diameter)
- 70 diff. proteins
- e.g., lamins- structural function in nucleus
What purpose does the cytoskeleton serve?
- Provides strength + rigidity to cells
- Maintain cell’s shape
- Cell motility
- Intracellular motility o/ organelles & chromosomes during mitosis
Cilia and flagella contain a bundle o/ __________.
Microtubules
Why do cilia and flagella contain microtubules?
Helps propel materials across epithelia surfaces, enable sperm to swim, push eggs throughs oviduct, etc.
T/F: There are less microbes in our body than there are other cells.
False, there are MORE microbes in our body than there are other others
