biol110 rec quiz 3

exocytosis

process by which material is exported out of the cell

• Example: production & export of insulin

endocytosis

material is “taken into” a cell via this

endocytosis specifics

can be specific process using receptors or non-specific taking up water and nutrients

1. plasma membrane surrounds materials from outside the cell, trapping it in an endocytic vesicle

2. endocytic vesicle will then fuse with a digestive vesicle (lysosome)

lysosomes definition and what happens

membrane bound vesicles with a low internal pH (4.5-5.0) that contains digestive enzymes

1. lysosomes “bud off” from trans face of golgi

• new lysosomes: primary lysosomes

2. primary lysosome fuses w/ endocytic vesicle or cellular organelle, forming a secondary lysosome

lysosome function

to digest: material from inside/outside the cell

• (ex. worn out organelles is outside the cell)

tuberculosis bacterium process

• bacteria can prevent fusion of endocytic vesicle and primary lysosome, so TB avoids destruction and multiplies inside the cell

  • TB multiplies inside macrophage

  • kills macrophage

  • then infects and kills more cells

how many people does TB kill annually

2 million

mitochondria structure

double lipid bilayer membrane

• outer membrane covers entire organelle

• inner membrane extensively infolded

  • folds are called cristae

  • liquid center is called matrix

mitochondria function

energy metabolism (ATP production)

endosymbiotic theory

• mitochondria/chloroplasts only arise from pre-existing mitochondria/chloroplasts (reproduce themselves)

chloroplast structure

double lipid bilayer membrane

• smooth outer and inner LB membranes cover entire organelle

• internal membrane organized into multiple stacks of disks within DLB

stack/disk names within chloroplast DLB

• thylakoid: single membrane disk

• granum: stack of thylakoids

• stroma: liquid substance surrounding the grana

chloroplast function

• site of photosynthesis in plant cells

• light energy converted into chemical energy

cytoskeleton structure

network of multiple types of proteins inside of cells

cytoskeleton functions

1. cell structure support

2. cell transport

3. helps mobile cells move

extracellular matrix structure

network of multiple types of proteins outside of cells

extracellular matrix functions

• structural support outside of cells

• glues cells into higher order structures (organs)

• cell-cell communication

plasma membrane

barrier; defines the inside/outside of a cell

PMs are _ barriers and why

selective

• regulates transport in/out of cells

PM is _ and cells can adjust _ and _

dynamic

• chemistry of PM

• molecules associated with the PM

what was known and not known in 1920s about membranes and phospholipids

• known: membranes were composed of phospholipids

• not known: how phospholipids were arranged in a membrane

evert gorter

• 1924: carried out a key experiment using RBCs

• wanted to determine if phospholipid membranes were “ 1 or 2 phospholipids thick”

why did dr. gorter use RBCs

1. easy to obtain

2. easy to count

3. of uniform size

explain dr. gorter’s experimental method

1. obtain and count RBCs

2. calculated total SA of RBCS (SA of 1 cell * total # of cells)

3. destroyed cells and collected membrane phospholipids (chemical separation)

4. placed phospholipids into chamber of liquid buffer where they formed a floating monolayer

5. measured total SA of phospholipids in chamber and compared it to total SA of the RBCs

what were the 2 possible outcomes of the RBC experiment, and what was the result?

1. SA of monolayer = SA of cells (1:1 ratio)

2. SA of monolayer is 2x surface SA of cells (2:1 ratio) (result)

what was the conclusion of the RBC experiment and what would the ratio have been if plasma membranes were double phospholipid bilayers

• cell membranes are phospholipid bilayers

• 4:1 (enough phospholipids to cover SA of each cell 4x)

how are plasma membranes much more than just a phospholipid bilayer

• peripheral proteins

• transmembrane proteins

• polysaccharides

• cholesterol

• cytoplasm

• extracellular environment

fluid mosaic model of membranes

• how do phospholipid bilayer and its molecules relate? (analogy)

• plasma membranes are fluid structures

• phospholipid bilayer is like a lake and molecules float around in it

how do we know that membranes are fluid

cell fusion experiment (1970)

• mouse and human membrane proteins displayed increasingly intermixed membrane proteins over time in fused hybrid cells

• conclusion: proteins laterally diffusing around membrane, so membrane is fluid

does changing concentration of pigment substantially alter the position/wavelight of peaks

no

does changing concentration of pigment substantially alter the height/absorbance of peaks

yes (when sample is diluted, height decreases significantly)

relationship between concentration of pigment and height of peaks

direct proportional relationship: as concentration of pigment decreases (through dilution), height/absorbance of peaks decreases proportionally (beer-lambert law)

which is more useful in identifying a substance, position or height, and why?

position

• wavelength where pigment absorbs light is a chemical property specific to that molecule’s structure

• absorbance height varies directly with concentration or amount

what would the consequences to photosynthesis be if the chlorophyll molecule were transparent to light

• Plants cannot absorb visible light photons

• → cannot convert light energy into chemical energy (ATP and reducing power)

• → cannot photosynthesize

What would the absorption spectrum of a colorless, transparent substance look like?

near-zero absorbance across the entire visible light spectrum (400 nm to 700 nm)

Chlorophyll is green; how does this relate to its absorption spectrum?

Chlorophyll appears green because it reflects or transmits green light rather than absorbing it

Does chlorophyll absorb in the green region of the spectrum?

No (or very poorly), which is why green light is reflected or transmitted

How much photosynthesis would a plant carry out if it were illuminated by green light alone? What about blue light alone? What about red light alone?

• Very little to none, due to minimal light absorption in the green region

• High amounts, because chlorophyll strongly absorbs blue light (peak around 430−450 nm).

• High amounts, because chlorophyll also strongly absorbs red light (peak around 650−680 nm)

What major property of chlorophyll a, chlorophyll b and carotenoids did we take advantage of in order to separate them from one another?

Solubility / Polarity differences in non-mixable solvents

• between polar solvents (ex. ethanol/methanol) and non-polar solvents (ex. petroleum ether)

total photon energy equation

E_photon= (2 × 10^-16) / (λ)

• fraction of photon’s energy captured by chlorophyll: (energy content increase/decrease) / (E_photon)