Cellular Components
Where is the nucleolus and what does it do?
inside the nucleus a region that contains special DNA coding for ribosomal RNA (rRNA)
What is simple diffusion?
Molecules diffuse from high concentration to low concentration.
What is the extracellular matrix?
A system of proteins outside of the cell membrane that helps provide structure and is useful in cell communication.
What are the two types of phospholipids and what are the differences between the two?
Phosphoglycerides: main type of phospholipids in animal cell membranes and consist of a 3-carbon glycerol molecule with two fatty acid tails and a head.
Sphingolipids: similar to phosphoglycerides, except that they contain a sphingosinemolecule instead of a glycerol. These lipids are primarily found in nervous tissue.
What are the three steps of cellular communication?
Signal Reception, Signal Transduction, and Cellular Response
what is common to all cells? (3 things)
plasma membrane, cytosol, and ribosomes
Explain the effects of osmosis on cells in hypotonic, isotonic, and hypertonic solutions.
hypotonic: swelling and bursting
isotonic: no change to the cell; net movement of h2o is 0
hypertonic: shriveling
USABO Open 2018 Example 5.1 (On PDF)
1) A
2) B
What is cholesterol in the cell membrane responsible for? What type of cell is it not found in, and how does that cell perform the same function?
Maintains cell fluidity
Not found in bacteria, which alter their lipid fatty acid composition instead to maintain cell fluidity
What is added onto the tyrosines of RTK to activate it?
Phosphate
what is the gooey space connecting the primary walls of adjacent plant cells called?
middle lamella
What are the four types of transport? (NOT TYPES OF ENDOCYTOSIS)
Simple diffusion, Facilitated diffusion, Primary active transport, Secondary Active Transport
What is the role of kinesin and dynein in microtubule function.
Kinesin is responsible for moving cells to the plus end (towards plasma membrane) of the microtubule, while dynein is responsible for retrograde transport to the minus end (towards nucleus).
What transmembrane proteins maintain membrane asymmetry? What do they do?
Flippases (translocate amino phospholipids to the cytosolic side to prevent signals of apoptosis), floppases (move cytosolic phospholipids to extracellular side and use ATP), and scramblases (move phospholipids down their concentration gradient; activity increases with cytosolic Ca)
How is a GCPR deactivated?
GTPase hydrolyzes the GTP on the G protein
What are the three types of transport vesicles and what do they do?
COPI, COPII, and Clathrin
The cell contains three main transport vesicles, each with their own specific function. COPI transport vesicles are responsible for moving molecules retrograde (backwards) from the Golgi Apparatus back to the ER. COPII vesicles do the opposite, moving molecules from the ER to the Golgi. Clathrin vesicles move molecules from the Golgi to the Plasma Membrane. These clathrin-coated vesicles are surrounded by a protein shell that is called a triskelion skeleton.
How is receptor mediated endocytosis different from pinocytosis and phagocytosis?
Requires a ligand to attach to a receptor to start the vesicle folding process.
Explain the 5 cell to cell junctions.
Plasmodesmata are junctions found only in plant cells. Since plant cells have cell walls, they can not connect to each other by plasma membranes. Instead, plasmodesmata are small holes in cell walls that allow direct cytoplasmic exchange between plant cells.
Gap Junctions are like the plasmodesmata of animal cells. They function as holes directly connecting the cytoplasm of two animal cells. Connexins are the main protein that make up gap junctions.
Tight Junctions create a watertight seal between two cells, preventing liquids from passing in between the gaps of two cells. These junctions are especially important for epithelial cells in the bladder to prevent leakage of urine.
Desmosomes connect two cells together using intermediate filaments. They function to create structure between cells to prevent them from separating from each other.
Adherens Junctions connect two cells together using actin microfilaments. Cadherins are the main protein that make up adherens junctions.
What stabilizes transmembrane proteins in a membrane?
Hydrogen bonding from the nonpolar region of the cellular membrane. Alpha helices and beta barrels serve to form these bonds
What is an intracellular receptor?
A ligand that bypasses the cellular membrane and activates a cellular responses themselves from directly inside the cell.
Explain the 2 different transportation models in the Golgi and how they work. Draw a diagram.
Cisternal Maturation Model -
Cisternae are dynamic structures that move along with incoming vesicles. Vesicles are though to fuse with newly produced cis cisternae and mature, which signals the vesicles to bud off and move to the next cisternae.
Vesicular transport model - cisternae are more stable, not newly made as often, and stay in place. Each cisternae is distinct from one another and they rarely fuse their contents with each other. Nevertheless, when vesicles finally reach the trans end of the Golgi, they can travel to the plasma membrane to be secreted, to a lysosome, or directed to a vacuole.
Explain energy coupling (250 pts) and its role in Secondary Active Transport (250 pts).
Energy coupling - uses energy from an exergonic process to fuel an endergonic process to make the net reaction / transfer of energy exergonic
Uses the concentration gradient generated by primary active transport to provide the energy to move another molecule down its own concentration gradient.
What is the microtubule arrangement of a cilia and flagella basal body? (250). Explain how microtubule arrangement works (250).
9+0 doublet microtubule arrangement
9 = # of tubules or tubule groups
0 = # of center microtubules
doublet/triplet = # of tubules per group
1) 100 pts - What do porin channels and aquaporin channels do?
2) 100 pts - What kind of cellular AND/OR organelle membranes are porin channels commonly found in? (there are three) (hint: endosymbiotic theory)
3) 100 pts - What are aquaporins and porin channels made out of? (hint: secondary structure of proteins)
4) 200 pts - What are the two asparagine-proline-alanine (NPAs) responsible for in an aquaporin
1) Porin channels allow small hydrophilic molecules to cross the membrane. Aquaporin channels allow water to cross the cell membrane while preventing ions from passing through.
2) Bacterial, mitochondrial, chloroplast
3) Aquaporins are made of 6 alpha helices. Porin channels are made out of beta barrels, which are constructed from beta pleated sheets.
4) Creating a positive charge to prevent ions from entering the aquaporin channel
What are the two ways in which a signal can be amplified. Explain each.
Phosphorylation cascades and Secondary messengers.
Phosphorylation cascade: A receptor is activated through the binding of a ligand, causing a conformational change, activating a rely molecule that phosphorylates the first kinase in the chain, which then phosphorylates other kinases downstream, leading to a chain amplified reaction and cellular response.
Secondary messengers: A single receptor activation can lead to the production of many secondary receptors such as cAMP, which serve to activate the cellular response throughout the cell.