Midterm 1 pt. 2

Question 1

what is the quaternary structure?

Answer 1

Association of two or more polypeptides
It is the overall protein structure that results from the aggregation of polypeptide subunits.

Question 2

Peripheral proteins

Answer 2

sit on the membrane surface. Noncovalently bonded to the polar head groups of the lipid bilayer and/or to an integral membrane protein

Question 3

Tonicity?

Answer 3

Ability of a solution to create a net movement of water inside or outside of a cell. It is calculated as the concentration of non-penetrating solutes only

Question 4

Lipid anchored proteins

Answer 4

covalently bonded to a lipid group that resides within the membrane.
Integral can pass multiple times through the hydrophobic part of the plasma membrane.

Question 5

Hyper, hypo, isoosmotic?

Answer 5

hyperosmotic if it has a higher concentration of solutes than the cell
hypoosmotic if it has a lower concentration of solutes than the cell
isoosmotic if it has the same concentration of solutes as the cell

Question 6

How are amino acids grouped?

Answer 6

One end of the polypeptide chain has a free amino group and one end has a free carboxyl group. The amino acids are grouped according to the properties of their side chain (R).

Question 7

Endocytosis?

Answer 7

cellular uptake of molecules via the formation of vesicles from the plasma membrane.
A small area of the plasma membrane sinks inward to form a pocket. The pocket pinches in, forming a vesicle containing the substance being endocytosed

Question 8

Amino acids?

Answer 8

Proteins are made of amino acids
bound together by peptide bonds between the carboxyl group and an amino group of two amino acids

Question 9

What is a uniporter/ its activation?

Answer 9

Uniporter (transports a single molecule)
Activation: ligand , stress (physical deformation), change in the voltage or always “ON

Question 10

What does passive diffusion rate depend on?

Answer 10

Gradients
Mass of the molecules
Temperature
Solvent density
Solubility
Surface area
Distance traveled
Pressure
Transport proteins
Membrane fluidity

Question 11

Melting points of fatty acids

Answer 11

Higher level of unsaturation (double bonds) leads to lower melting temperatures, less viscous.

Question 12

Pinocytosis?

Answer 12

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.

Question 13

Phagocytosis?

Answer 13

when a cell engulfs a large particle or a small organism (e.g. a prey) by extending pseudopodia around it and packaging it within a membranous sac called a food vacuole.

Question 14

Diffusion of molecules?

Answer 14

If a molecule is not charged (or large), its diffusion across the membrane only depends on the chemical gradient
If a molecule is charged (and small), its diffusion across the membrane depends on both the chemical gradient and the electrical gradient (electrochemical)

Question 15

K, Na, Cl, Ca uses?

Answer 15

K+, Na+, and Cl- are used in the neuron signal transmission.
Ca2+ is used in signaling pathways, neurotransmitter exocytosis, muscle contraction.

Question 16

Integral proteins?

Answer 16

penetrate the hydrophobic core, and are embedded in the membrane. Typically contain one or more transmembrane helices (e.g. ion channels, transporters, receptors).

Question 17

What is a lipid?

Answer 17

Any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water

Question 18

N and C terminus?

Answer 18

the N-terminus = 1st position
the C-terminus = last position

Question 19

Equilibrium potential?

Answer 19

the difference in charges across the membrane due to the difference in its concentration

Question 20

3 kinds of endocytosis?

Answer 20

Phagocytosis (“cellular eating”)
Pinocytosis (“cellular drinking”)
Receptor-mediated endocytosis

Question 21

What does the primary structure determine?

Answer 21

the secondary structure and the tertiary structure, due to the chemical nature of the backbone and the side chains (R groups) of the amino acids

Question 22

Transport proteins?

Answer 22

transmembrane proteins that can modify temporarily the permeability
of the membrane by allowing only specific molecules to cross

Question 23

Excotyisis?

Answer 23

secretion of molecules outside the cell
A vesicle buds from the Golgi apparatus
moves towards the plasma membrane
The contents of the vesicle spills out of the cell the vesicle membrane becomes part of the plasma membrane.

Question 24

What is passive diffusion?

Answer 24

Simple diffusion across the phospholipids double layer, does not require energy (no ATP hydrolysis)! (water, CO2, Ca2+)
Substances follow their own concentration gradient
Gas follow their own partial pressure gradient
Diffusion depends only one one species of molecules, all molecules diffuse separately

Question 25

Fick’s law of diffusion?

Answer 25

molecules goes from regions of high concentration to
regions of low concentration. The magnitude of this diffusion is proportional to the concentration gradient
This is because of the stochastic movement of each molecule in all directions

Question 26

What is permeability high for?

Answer 26

smaller molecules
less polar (charged) molecules
more hydrophobic molecules
highly lipid-soluble substances
gas

Question 27

What is the primary structure?

Answer 27

the linear sequence of amino acids of a protein.
The order of amino acids is determined by the DNA sequence of the gene that codes for this protein.

Question 28

Frye and edidin experiment?

Answer 28

Labeled the plasma membrane proteins of a mouse cell and a human cell with two different markers and fused the cells. observed the markers on the hybrid cell
Phospholipids and proteins can move sideways Higher temp caused more exchange in phospholipids
Increased fluidity (more double bonds)

Question 29

How does the cell modify the entry/exit of molecules through…

Answer 29

the expression of genes that code for transport proteins
the temporary opening and closing of some of these transport proteins

Question 30

Hyper. hypo, isotonic?

Answer 30

hypertonic if it has a higher concentration of non-penetrating solutes than the cell.
hypotonic if it has a lower concentration of non-penetrating solutes than the cell.
isotonic if it has the same concentration of non-penetrating solutes as the cell

Question 31

Example of equilibrium potential?

Answer 31

if the membrane is selectively permeable to K+ only, then K+ diffuses outside the cell until the electrical gradient exactly compensates the chemical gradient
This is the K+ equilibrium potential. It is specific to K+ ions.
At the potassium equilibrium potential locally the membrane potential reaches the equilibrium potential of potassium (EK) = -90mV

Question 32

Issues with osmosis?

Answer 32

Turgid, flaccid, and plasmolized (plant cells) and lysed, normal, and shriveled (animal cells)

Question 33

Fatty acid?

Answer 33

carboxylic acid with a long carbon chain.
Can vary in the number and location of double bonds.
Can bond to a glycerol molecule to form a fat molecule

Question 34

Roles of plasma membrane?

Answer 34

Compartmentalization
Site for biochemical activities
Providing a selectively permeable barrier
Transporting solutes
Responding to external stimuli
Intercellular interaction
Energy transduction

Question 35

Osmosis/ osmotic pressure?

Answer 35

a net movement of water towards the compartment with higher concentration of non-penetrating solute,
osmotic pressure of a cell is the minimum pressure required so there is no movement of water across a semi-permeable membrane

Question 36

what is secondary active transport?

Answer 36

use the potential energy stored in ionic concentration gradients
They are cotransporters.

Question 37

What is a carrier?

Answer 37

are not open on both sides at the same time they changeshape to let the molecule pass in one or the other direction

Question 38

Osmolarity?

Answer 38

concentration of all solutes in a solution both penetrating and non-penetrating

Question 39

what is primary active transport?

Answer 39

use ATP as a source of energy

Question 40

Water moves in which direction?

Answer 40

moves from a compartment that is hypotonic towards a compartment that is hypertonic

Question 41

What is a phospholipid?

Answer 41

lipid made up of glycerol joined to two fatty acids and a phosphate group.
nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head.
phospholipid is said to be amphipathic

Question 42

what is the secondary structure?

Answer 42

structure of the protein made of segments that are coiled or folded determines the protein’s shape
Two types: α helices, β pleated sheets
results from hydrogen bonds between the hydrogens and oxygen atoms of the amide groups found along the backbone (not the amino acid side chains R groups).

Question 43

What comes in and out of cell concentration gradient?

Answer 43

Na/Cl out, K in

Question 44

How is the cell charged?

Answer 44

The inside of the cell is negatively charged relative to the outside. … due to the presence of phosphate groups and proteins, both negatively charged (-)