The cell Flashcards
How many cells are in our body?
40 trillion
Why do cells need to be small?
Chemical reactions in cells require diffusion; diffusion can only happen efficiently over small distances because of a cells “random walk”
What is the exception to all cells being small?
Eggs!! eggs can be big because they store stuff
Why are Prokaryotes able to be so much smaller than Eukaryotes?
Prokaryotes can live in any environment, oxidize anything…
However they have no specialized functions nor do they contain any specialized organelles.
Eukaryotes have compartmentalization and a membrane bound nucleus.
What things make plant cells unique/ different from animal cells?
Plants have a cell wall, chloroplasts and a vacuole.
Because they have a cell wall, they do not require a sodium potassium pump
What is the interior of Vesicles, Golgi and ER?
It is called the lumen and is equivalent to extracellular space
Describe the nucleus
- It is surrounded by the nuclear envelope made up of two membranes
- Nucleus contains DNA
- DNA is replicated and transcribed in the nucleus
- Nucleus contains the nucleolus where ribosomes are made from rRNA and proteins.
Where are ribosomes made?
In nucleolus and out of rRNA and proteins
How do nuclear proteins get out of nucleolus
Through nuclear pores
What is the function of the rough ER?
- The rough ER is close to the nucleus
- Membrane proteins are made at the rough ER
- It is called rough ER because ribosomes are attached to the membrane.
- Ribosomes are the site of protein translation
What is the function of the smooth ER?
- Site of lipid creation
- Site of Detoxification (making a molecules more hydrophilic so it can be excreted)
- Amount of smooth ER varies with where in body the cell is
Would drug use affect amount of smooth ER in a person’s cell?
Drug users would have more smooth ER in their liver
What is function of Golgi apparatus?
- Vesicles coming from Er fuse on cis face of the golgi, while vesicles bud off trans side of golgi
- Sugars and lipids are modified in the golgi
An “organizer”, “transporter”- communicates to vesicles where to go
Where do cis and trans sides of ER face?
- Cis side faces ER
- Trans side faces plasma membrane
What is endocytosis?
Endocytosis is when macromolecules bind to receptors on outside of cell and form a lysosome inside cell
What is phagocytosis?
A phagosome is like endocytosis but only particles are realeased into cytosol- no macromolecules
It “consumes” an entire lysosome
What is autophagy?
When lysosome consumes damaged organelle
Function of mitchondrion
“power plants of a cell”
Where most ATP is produced
- has matrix- enzymes that catalyze the citric acid cycle and contains dna, rna and ribosomes
How many membranes does a mitochondrion have? Are they smooth?
A mitochondrion has an inner membrane and an outer membrane.
The inner membrane has invaginations called cristae
Function of chloroplast
Only is plants!
- They are photosynthesizers
- They have an outer and inner membrane
- membrane stacks called thylakoids
- the gap in middle is called the stroma- site of carbon fixation
What are the products of carbon fixation?
Carbon fixation yields sugar, amino acids, DNA, RNA and ribosomes
What do mitochondrion and chloroplasts have in common?
They are both endosymbiotic organelles- descendants of bacteria
What are 3 pieces of evidence of mitochondrion chloroplasts are endosymbiotic?
- double membrane due to endosymbiosis
- own genome (similar to bacteria)
- own ribosomes (similar to eubacteria)
What is a cytoskeleton? What would be the two most important?
Any structural element important to cell shape and movement.
Two most important structural proteins would be:
- Actin filaments
- Microtubules
Describe actin filaments
-Actin filaments are responsible for cell shape and cell shape changes
actin filaments are polar, they have a plus and minus end
-Polymerize and depolymerize from monomers through non-covalent protein interactions
Where are actin filaments found
- Found below the cell membrane
What pairing mediates muscle contractions? How does it work?
Muscle contractions are mediated by actin filaments and myosin.
Myosin heads walk towards the plus end of actin filaments
What is a microtubule?
MTs are larger than actin
They come from the nucleus- are polar with a plus and minus end.
They organize cells (move organelles and provide tracks for intracellular transport)
Also move chromosomes during cell div
What are the two motor proteins of Microtubules
- Kinesin
- Dynein
They walk in opposite directions
Describe cilia and flagella
- Formed by 9 doublet microtubules and 2 central MTs
- Flagella are found on sperm
- Cilia are found in cells lining the lung, and oviduct and single celled eukaryotes
What is an intermediate filament?
Intermediate filaments are intermediate in size between actin and microtubules- are fairly diverse.
- have no polarity, don’t polymerize or depolymerize
Serve mainly to provide additional mechanical strength to cells (hair)
What are transmembrane proteins?
Protein integrin that binds to extracellular matrix - attaching cells to their environment via focal adhesions
What are focal adhesions?
the adhesion sites of cytoskeleton and extracellular matrix
What are the 4 types of cell-cell junctions?
- gap (create channels)
- tight (seals cells together)
- desmosome
- adherens
Where is the glucose cotransporter and glucose carrier made?
Rough ER, then sorted in golgi to different vesicles
What is main junction involved in use of pacemaker?
Gap junction
