Unit 2 Test Flashcards
What are thylakoids?
A membranous system in the form of flattened and interconnected sacs
What are the functions of the smooth ER?
- Synthesize lipids
- Metabolize hydrates
- Detoxify drugs/poisons
- Store calcium ions
What organelles are in animal cells but not plant cells?
- Lysosomes
- Centrosomes/Centrioles
- Flagella
What organelles are in plant cells but not animal cells?
- Chloroplasts
- Central vacuole
- Cell wall
- Plasmodesmata
What are cristae?
The foldings of the inner, convoluted membrane
What are the main functions of intermediate filaments?
- Maintenance of cell shape
- Anchorage of nucleus
- Formation of nuclear lamina
What are dyneins?
A motor protein that are attached along each outer microtubule doublet
What is an amphipathic molecule?
a molecule containing hydrophobic and hydrophilic regions
What is the fluid mosaic model?
A model that states and shows that the plasma membrane is a mosaic of proteins bobbing in a fluid bilayer of phospholipids
What happens to membranes when temperatures cool? What controls this reaction?
Membranes switch from a fluid to solid state. A membrane can remain fluid at a lower temperature if it is rich in phospholipids and hydrocarbon tails
What are integral proteins?
Proteins that penetrate the hydrophobic interior of a lipid bilayer
What are transmembrane proteins?
Integral proteins that span the the membrane
What are peripheral proteins?
Proteins that are loosely bound to the surface of a membrane
How is the plasma membrane built? What determines the distribution of proteins, lipids and carbs?
The membrane is built by the ER and golgi apparatus, the vesicle becomes the membrane. This is when the asymmetrical distribution of carbs, lipids and protein in the membrane is determined.
What are transport proteins?
Proteins that allow hydrophilic substances to cross the membrane
What are aquaporins?
Channel proteins that facilitate the passage of water across the membrane
Which molecules cross the cellular membrane easily and which ones dont?
Hydrophobic/nonpolar molecules can dissolve in the lipid bilayer and cross it easily. Polar molecules such as sugars do not cross easily
What is passive transport?
Diffusion of a substance across a membrane with no energy investment
What is osmosis?
The diffusion of water across a selectively permeable membrane
What is tonicity?
The ability of a surrounding solution to cause a cell to lose or gain water
What is an isotonic solution?
Solute concentration is the same as inside the cell, no net water movement
What is a hypertonic solution?
Solute concentration is greater than inside the cell, the cell loses water
What is a hypotonic solution?
Solution concentration is less than inside the cell, the cell gains water
What is osmoregulation?
The control of solute concentrations and water balance
How do plants use cell walls to maintain water balance?
A plant cell in a hypotonic solution swells until the wall opposes uptake, making the cell turgid(firm). The cell becomes flaccid(limp) in an isotonic solution. In a hypertonic environment, the membrane eventually pulls away from the wall, a usually lethal effect called plasmolysis
What is facilitated diffusion?
Passive transport where transport proteins speed the passive movement of molecules across the plasma membrane
What are ion channels?
Channel proteins that open or close like a gate in response to a stimulus
What is active transport?
Diffusion that uses energy to move solutes against their gradients. It allows cells to maintain concentration gradients that differ from their surroundings
What form of energy is used for active transport?
ATP
How does the sodium potassium pump work?
- Cytoplasmic Na+ binds to pump, affinity for Na+ is high
- Na+ binding stimulates phosphorylation by ATP
- Phosphorylation leads to a change in protein shape, reducing affinity for Na+ which is pinched off on the outside
- The new shape has a high affinity for K+, which binds on to the extracellular side of the pump where he Na+ was released
- Loss of phosphate to inside of the cell restores its original shape which has a low affinity for k+ and a high affinity for Na* again
What is the electrochemical gradient?
The combined chemical(ion’s concentration gradient) and electric force(effect of membrane potential on environment) that drives the diffusion of ions across a membrane
What is the membrane potential?
The voltage across a membrane, created in the distribution of positive and negative ions
What is an electrogenic pump?
A transport protein that generates voltage across a membrane. These pumps help store energy that can be used for cellular work(active transport)
What is cotransport?
When active transport of a molecule indirectly drives transport of other solutes(active and passive transport)
What is a proton pump?
The main electrogenic pump of plants, fungi and bacteria(active)
What type of transport is a sodium-potassium pump?
electrogenic pump
How does endocytosis occur?
The cell forms new vesicles on the plasma membrane to take in particles
What are the 3 types of endocytosis?
Phagocytosis: eating
Pinocytosis: drinking
Receptor mediated endocytosis: taken in by protein receptors
