Ch6 Part 2

Question 1

Organelle

Answer 1

small structure within a cell that carries out a specific function.

Typically wrapped in on lipid bilayer.

Question 2

Nucleus

Answer 2

Contained by the nuclear envelope.

Replication, transcription, and splicing occur in the nucleus.

Question 3

Genome

Answer 3

Large size of the genome seems to drive the production of chromosomes.

If nuclei are treated with DNase and detergent, an insoluble component known as the nuclear matrix of nuclear scarf remains. Appears to contribute to structure. It may also play a role in gene expression.

Question 4

Nucleolus

Answer 4

Ribosome factory consisting of: RNA polymerases (I), rRNA, and protein components of ribosome.

NOT separated by membrane from the rest of the nucleus.

Ribosomes are partially assembled in the nucleus, with proteins being transported into nucleus as ALL translation occurs outside the nucleus.

Question 5

The nuclear envelope

Answer 5

Two lipid bilayer membranes (Inner and Outer).

ER is at points continuous with the outer membrane of the nuclear envelope. This makes the lumen of the ER continuous with the inter-membrane space of the nuclear envelope.

Has nuclear pores that permit the passage of material less than 60 kilodaltons.

Larger molecules must have a NUCLEAR LOCALIZATION SEQUENCE. This allows them to be translated onto a ribosome and transported into the nucleus.

Although RNA could technically diffuse passively through nuclear pores. Likely has a specific transport mechanism.

Question 6

Mitochondria

Answer 6

Oxidative phosphorylation.

Bound by two membranes (inner and outer).

Inner membrane is where electron transport chain, ATP synthase, and proton gradient used to drive ATP synthesis is located.

Inner membrane is folded ie. cistae and is impenetrable to polar molecules.

Question 7

Mitochondria Part 2

Answer 7

Has unique genome. Genome encodes rRNA and tRNA, as well as some components of electron transport chain and ATP synthesis.

Different system of transcription and translation. Including unique genetic code, RNA Pol., DNA replication machinery, ribosomes, and aminoacyl-tRNA synthestase.

Exhibit maternal inheritance.

Question 8

Endosymbiotic theory

Answer 8

Mitochondria as separate organism brought into a larger cell.

Question 9

Endoplasmic Reticulum

Answer 9

Can account for over half the membrane of some cells.

Rough ER - covered and ribosomes and produce proteins for the SECRETORY PATHWAY. Also directs protein traffic in the nucleus. Some glycosylation (though most in Golgi) and disulfide bonds here.

Smooth ER - not involved in protein synthesis, but can perform steroid synthesis in the gonads or degrade toxins in the liver.

Lumen - synonymous with the extracellular space.

Question 10

Sites of Protein synthesis in the cell.

Answer 10

Cytoplasm or Rough ER

Question 11

Protein synthesized by cytoplasmic ribosomes goes…

Answer 11

Peroxisomes, mitochondria, nucleus, or cytoplasm

Question 12

Protein synthesized by the rough ER can go…

Answer 12

Secreted into environment

Become plasma membrane proteins

Travel to the membrane or interior of the ER, golgi apparatus, or lysosomes. Communication between these bodies via vessicles, so can be considered continuous.

Question 13

Signal Sequence

Answer 13

At N-terminus, and determines where a protein in synthesized. All start in the cytoplasm.

Removed by a signal peptidase in the ER Lumen before transport to Golgi, Plasma Membrane, and potentially out to the exterior.

Question 14

Signal Recognition particle

Answer 14

Recognizes the signal sequence and transports early polypeptide to Rough ER surface.

Question 15

Integral Membrane Proteins

Answer 15

Processed slightly different than those with a signal sequence. They have TRANSMEMBRANE DOMAINS that are like a signal sequence but not at the N-terminus. They are not removed after translation.

During translation, transmembrane doomains are threaded through the ER membrane. Protein ends facing ER lumen will face exterior of cell.

Question 16

Default target for proteins in the secretory pathway

Answer 16

Plasma membrane

Question 17

Targeting Sequences

Answer 17

Required for any other destination on the secretory pathway besides the plasma membrane. (ie. Golgi, Lysosome, and ER)

Proteins destined for organelles not in secretory pathway require a LOCALIZATION SIGNAL.

Table 2. pg 177 good review!

Question 18

Golgi Apparatus

Answer 18

Membranous sacks stacked together.

Functions to: Modify proteins from RER; Sort and send proteins to necessary destinations; makes some macromolecules like polysaccharides.

Question 19

Direction of traffic in the Golgi

Answer 19

Mostly unidirectional.

Although retrogade traffic can occur if a protein intended for the ER ends up in the golgi apparatus.

Cis-stack: region closest to ER
Medial-stack: mid-region
Trans-stack: furthest region

Transfer of proteins and modification occurs from the Cis –> trans faces.

Question 20

Constitutive Secretory Pathway

Answer 20

Proteins are sent from the golgi directly to the plasma membrane

Question 21

Regulated secretory pathway

Answer 21

Some cells store secretory proteins for quick release, so they are stored in SECRETORY VESSICLES.

Question 22

Lysosomes

Answer 22

Membrane bound.

Responsible for degradation of macromolecules via hydrolysis.

Produced in ER. Released from trans surface of the Golgi.

Question 23

Crinophagy

Answer 23

Lysosomal digestion of secretory particles that are not needed.

Digested products are released into cytoplasm for resuse.

Question 24

Acid Hydrolase

Answer 24

Enzymes contained in Lysosomes and mediate digestion.

Only function in low pH. A safety mechanism so that a rupture of a lysosome does not result in autophagy of the entire cell. Note though that if enough ruptured, pH could change enough.

Question 25

Peroxisomes

Answer 25

Produce metabolic tasks.

Essential for lipid breakdown.

Have an enzyme that produced hydrogen peroxide as a byproduct. Another enzyme CATALASE; however, breaks it into H2O and O2.

Question 26

Structure of animal cell membrane support…

Answer 26

Cytoskeleton

Question 27

Three common lipids in lipid bilayer

Answer 27

Phospholipids, glycolipids, cholesterol

Phospholipid - Phophatidyl Choline (hydrophilic head with Choline, phosphate, and glycerol; two fatty acid tails)

Note: Sometimes however, there can be more proteins in a membrane than lipids. Ex. mitochondrial inner membrane.

Question 28

Repair of a cellular membrane

Answer 28

Lipid bilayer is the lowest energy state of phospholipids, so a membrane will self-repair to reach lowest energy.

Question 29

Integral Membrane Proteins

Answer 29

Have portion embedded in the membrane

Question 30

Peripheral membrane proteins

Answer 30

Stuck to membrane and integral proteins via hydrogen bonding and electrostatic forces

Question 31

Fluid Mosaic Model

Answer 31

Membrane is a mosaic of lipids free to move laterally. Proteins anchored to cytoskeleton are not free to move.

Cannot flip head over tail though. Membrane has “polarity”

Question 32

Where does glycosylation occur on the cell membrane

Answer 32

Only on the extracellular surface. Likely because it occurs only in the rough ER and Golgi.

Question 33

Molality (m)

Answer 33

moles of solute per mass (kg) of solvent:

Moles/Mass solvent

Note: Useful as molality does not change with temperature. And is roughly an approximation of molarity.

Question 34

Mole Fraction

Answer 34

Moles substance / total moes in solution

Note: useful when more than one solute is present.

Question 35

Ionizability factor

Answer 35

describes how many ions a molecule will produce in solution.

i = 1; no dissociation. this is true of most hormones, proteins, steroids etc.

Question 36

Colligative Properties

Answer 36

Depend on the number of solute particles in solution rather than the type of molecule.

Four types on MCAT:
Vapour-pressure depression; boiling point elevation, freezing point depression; osmotic pressure.

Look at more sources on this!

Question 37

Vapour Pressure Depression.

Answer 37

Vapour pressure refers to the pressure exerted by gaseous phase of liquid that evaporated from exposed liquid surface.

Substances that have high vapour pressure are volatile.

Vapour pressure depression occurs when a solute is added to a solution (ie. volatility is decreased). This substance will require more heat to reach vapour pressure.

Note that boiling will still occur at the same vapour pressure at sea level (760 torr) but more energy will be required to achieve this.

Question 38

Boiling Pt Elevation

Answer 38

More solute particles, higher boiling point.

dT = kim

k - is solvent boiling point elevation constant. 0.5oC/molar concentration, for water.

i - is van’t Hoff factor

m - molar concentration of solution

Question 39

Freezing point depression

Answer 39

Solute interferes with a liquids capacity to form a solid structure.

dT = -kim

-k - is solvent freezing point depression constant. 1.9oC/molar concentration, for water.

i - is van’t Hoff factor

m - molar concentration of solution

Question 40

Osmosis

Answer 40

Type of diffusion in which a solvent diffuses, not the solute.

Question 41

Tonicity

Answer 41

Describes osmosis gradients.

Isotonic - environment same as cell

Hypertonic/hyperosmotic

Hypotonic/hypoosmotic

Question 42

Osmotic Pressure

Answer 42

Pressure required to stop Osmosis from happening. Only impacted by number of particles, not type.

π = MiRT

π - osmotic pressure in atm

M - molarity of solution

T- in Kelvins

Question 43

Simple Diffusion

Answer 43

Diffusion through a membrane without assistance of a protein.

Ex. Steroid transit across the membrane

Contrast to FACILITATED DIFFUSION.

Differentiate two types of diffusion using kinetics. Facilitated diffusion exhibits saturation kinetics as relies on a finite number of membrane proteins.

Question 44

Facilitated Diffusion

Answer 44

Gives quality of selective permeability.

Channel proteins or carrier proteins.

Question 45

Carrier Proteins

Answer 45

Uniports - conformational change brings molecule across membrane

Symports - two molecules are brought across

Antiports - two molecules are brought across but in opposite directions.

Question 46

Channel Proteins

Answer 46

Selective, and considered facilitated diffusion

Question 47

Pores

Answer 47

non-selective tube through the membrane.

Formed from polypeptides known as porins.

Porins are large and so you do not find membranes with ion channels AND porins, as ion channels would be pointless.

Question 48

Active Transport

Answer 48

Movement through membrane AGAINST a gradient

Question 49

Primary Active Transport

Answer 49

Directly coupled to ATP hydrolysis.

Question 50

Secondary Active Transport

Answer 50

ATP activity in indirect in its role of moving a molecule against the gradient.

For example glucose is transported against gradient when coupled with Na moving down its gradient. However Na gradient was established using an ATPase pump.