Ch. 3 & 4 Flashcards Preview

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Flashcards in Ch. 3 & 4 Deck (35):

The entire human body is made up of cells and materials secreted by cells. Does your body include additional materials?

No, everything is secreted by cells.


What type of biological molecule are cytoskeletal elements made of? Describe at least three roles/functions of the cytoskeleton.

Made up of proteins (Actin, Intermediate filaments, microtubles).
1. maintains shape of cell 2. produces cellular movement 3. movement of organelles


Why do certain cell types have far more mitochondria than others?

Requires more energy to carry out a specific function.
Ex: muscle tissue requires more vs adipose/fat tissue requires less


Why do certain cell types have far more RER and free ribosomes than others?

Certain cells have a greater demand to synthesize proteins - pancreatic


In order for RNA transcript to travel from the nucleus to the cytosol, it must cross a cell membrane. which one?

must cross the nuclear envelope (double membrane) surrounds and separates it from cytoplasm.


Explain how a mutation in a particular gene may lead to the formation of a protein that has a sub optimal or non functional three dimensional shape.

Mutation that alters the binding site of an enzyme of the mutation is detrimental and forms an incorrect shape, a substrate will not be able to bind to the enzyme.


In the plasma membrane, which molecules are amphipathic?

phospholipids, cholesterol and integral (transmembrane proteins)


3 functions/roles/purposes of the plasma membrane

1. gatekeeper, regulates the passage of molecules - maintains the chemical composition
2. communication allows for cell to cell communication - bears receptors - listening devices
3. provides cell identity - self vs. non self - cell-cell interactions
4. forms structural junctions - adjacent cells and extracellular material - proteins


Identify at least 3 functions/roles/purposes of plasma membrane proteins

1. allows specific materials to enter/leave cell - ion channels, transporters, pumps
2. act as receptors to which cellular molecules bind
3. form structural connections to neighboring cells or extracellular material
4. function as enzymes that mediate metabolism


Some plasma membrane molecules are hybrid molecules. 2 different biological molecules, glycolipid? glycoprotein?

glycolipd - lipid w/carbohydrate attached to outer surface, interacts w/exxtracellular fluid. fatty acid. cell to cell recognition.
glycoprotein - protein w/carbohydrate. receptors for signaling proteins.


what does it mean to say that a cell exhibits a membrane potential?

Characteristic of a cell. On one side of the Plasma Membrane is negative charges and other side is positive charges. So membrane potential occurs when there is charge difference across the plasma membrane. Differ b/w cell types in our body. Separation of charges - form of potential energy.


compare and contrast tight junctions with gap junctions. how are they similar? how do they differ?

Similar - structural connections to neighboring cells or extracellular material - part of central cell plasma membrane. pairs of plasma membrane molecules
Differ - Tight - attach plasma membrane from neighboring cell, quilting together plasma membrane, leak proof seal - stomach acidic liquid - wont leak.
Gap - connected together by connexons - fluid filled tunnels directly link cytosol b/w neighboring cells. no diffusion required. tunnel for cytosol.


Identify at least three types of vesicles and their function/purpose

Membrane vesicle - proteins in membrane verge w/plasma membrane
transport vesicle
secretory vesicle - proteins exported from cell


what type of biological molecule is present in cell junctions?



Oxytocin is a peptide hormone (a small protein). by which transport mechanism does oxytocin leave the secreting cell? why?

leave the cell: exocytosis. it is enclosed in vesicles, fuses with plasma membrane.


which types of membrane proteins undergo conformational changes as part of their normal function?

Gated ion channels - ligand, voltage, mechanically
Transporters - glucose
Pumps - sodium potassium pump


compare and contrast two forms of secondary active transport: cotransport (through symporters) and countertransport (through antiporters). how are they similar? how do they differ?

contransport - both substances that are being transported will move in the same direction (either into or out of the cell). symporter.
counter transport - two substances will be transported in opposite directions (one into the cell and one out of the cell). antiporter.


describe the function of sodium-potassium pumps. what is their major role or purpose? how do they function? how many ions of each kind are moved, and in which direction, for each molecule of ATP "spent"?

For every molecule of ATP spent 3 Na+ ions are transported out of the cell and 2 K+ ions are transported into the cell. both of these ions are moved against their concentration gradients. primary use ATP to perform their functions.


describe the process of primary active transport.

Uses ATP to move substances against their concentration gradient. Substances are "pumped" from an area of low concentration to an area of high concentration - uphill. pumps are proteins embedded in the phospholipid bilayer. they use the energy in ATP to drive the uphill movement of a substance. Energy changes shape of protein.


two 1L compartments, A and B, are separated by a membrane. the membrane is permeable to glucose but not to water. to compartment A, 20 mmol/L glucose solution is added. to compartment B, a 10 mmol/L glucose solution is added. diffusion occurs until the two compartments are in equilibrium. what is the final concentration of glucose in each compartment?

15 mmol/L


if a small amount of urea is added to a suspension of cells in an isosmotic solution, what would happen to the size/shape of the cells (assume the plasma membrane is impermeable to urea)?



the osmolarity of a urine specimen is 482 mOsm. relative blood plasma, is this urine specimen isomotic, hyperosmotic, or hypoosmotic?



what is the osmolarity of one liter of solution that contains 2 moles NaCl, 2 moles glucose and 1 mole urea?

4+2+1 = 7


if a cell is placed into a hypertonic solution, will it swell, crenate or remain the same? why? repeat the previous questions for a hypotonic solution and isotonic solution?

hypertonic - cell will shrink b/c water from the ICF will travel to ECF where solute concentration is higher.
hypotonic - cell will swell b/c water from ECF will travel to the ICF where solute concentration is higher
isotonic - no alteration in cell shape will occur b/c there is no net flux of water in/out of cell


how do water molecules traverse the relatively large hydrophobic region of the plasma membrane?

through aquaporins, proteins embedded in the plasma membrane that facilitate water transport via osmosis.
through momentary gaps in the phospholipid bilayer.


which transport mechanism are passive? which are active?

passive - high to low concentration. passive: simple diffusion - through phospholipid bilayer, faciliated diffusion, through a membrane protein and osmosis, the movement of water across the plasma membrane (through the bilayer or membrane protein). Active:


what role do concentration gradients play in determining if a substance will enter or leave the cell? which transport mechanisms rely on concentration gradient?

A concentration gradient exists when there is a higher concentration of a substance on one side of the plasma membrane than on the other. all passive transport mechanisms depend on the concentration gradient.


how do macromolecules like proteins or polysaccharides cross the plasma membrane?

Vesicles - move substances across the plasma membrane.
Endocytosis - brings material into the cell, when a vesicle pinches off from the plasma membrane.
Exocytosis - expels material from the cell. contents are expelled from the cell when the vesicle fuses w/the plasma membrane.


what types of materials cannot cross the lipid bilayer, but require a membrane protein in order to pass into or out of a cell?

Proteins, glucose, water, ions.
Charged, larger, water soluble molecules.


can a potassium pass through a sodium ion channel? why or why not?

K+ cannot pass through Na+ channel because ion channels are for a specific ion


compare and contrast ion channels with transporters. how are they similar? how do they differ?

Both involve transmembrane proteins and both have specificity to an ion.
diff - ion channels do not go through a conformational change to transport a molecule. Ion channels are always passive transport. ion channels will be to transport more molecules quicker - no conformational change.

Transporters - involved in active transport.


describe the process of protein synthesis.



What is passive transport? What is active?

Passive - does not require ATP. relies on existing potential/kinetic energy.
Active - require ATP. contribute additional energy to move something into or out of the cell.


if a cell cannot produce enough ATP, secondary active transport will cease (among other things). explain why adequate ATP is required to support secondary active transport

adequate ATP is needed for secondary active transport because one of the substances will be transported against its concentration gradient which requires the input of ATP.


what types of materials may cross the plasma membrane by simple diffusion?

Oxygen O2, C02, small fatty acids, steroid hormones and ethanol