Exam 2 Flashcards
Lectures 7-12
1
Q
What are the 5 characteristics of life?
A
- Organization and complexity (uses energy to maintain both actively)
- Respond to the environment:
- Actively maintain internal conditions within idea ranges (homeostasis ex. body temp) - Growth and metabolism
- Reproduction/heredity
- Evolve
2
Q
What are the 2 types of cells?
A
- prokaryotes - bacteria & archaea
- dominant forms of life in terms of biomass (if you weighed all the prokaryotes on earth and all eukaryotes, prokaryotes would weigh way more) and diversity (more species) - eukaryotes - (everything else that’s not bacteria and archaea) animals, plants, fungi, and protists (protists are everything that isn’t animals, plants, and fungi)
3
Q
What is the major difference between eukaryotes and prokaryotes?
A
Eukaryotic cells can be up to 1000x larger than prokaryotic cells
4
Q
What are the economics of cell size?
A
- Cell volume represents DEMAND - lots of metabolism occurring to keep cell alive (greater volume of cell = greater demand)
- Cell surface area represents SUPPLY - everything that enters/exits the cell must go through its surface area
- To survive: SUPPLY ≥ DEMAND
- As cell size increases, cell volume (demand) increases faster than the cell’s surface area (supply), so at some point, demand exceeds supply
- So remaining small allows cells to maintain a workable surface area to volume ratio
5
Q
Prokaryotes’ differences with eukaryotes
A
- No nucleus, DNA is in the nucleoid
- No internal membrane system
- Have a cell wall (a protective outer barrier) composed of peptidoglycans
6
Q
Prokaryotes’ similarities with eukaryotes
A
- Both use DNA as their genetic material
- Both have an outer plasma membrane (phospholipid bilayer)
- Both have cytoplasm: a semi-solid substance that contains the cell’s internal components
- Both have ribosomes, the universal organelle, responsible for synthesizing proteins
7
Q
Prokaryotic cell structure (some vs all)
A
- structures all prokaryotes have: cell wall, phospholipid bilayer, cytoplasm, ribosome, DNA, nucleoid
- structures only some prokaryotes have: capsule, pili, flagellum
8
Q
What is a distinctive feature of eukaryotic cells?
A
internal compartmentalization
- Possible b/c of an internal membrane system
- Internal membrane-bound compartments are called organelles which means little organs
9
Q
What is the one organelle prokaryotes have?
A
ribosomes (exception to the rule that organelles needs membranes)
10
Q
What are the functions (3) of the nucleus?
A
- Stores genetic information (like a suitcase 🧳)
- Ribosomes are assembled here
- RNA is produced (transcription) here
11
Q
What is the structure of the nucleus?
A
- Nuclear envelope: a double lipid bilayer membrane that defines the nucleus (has an inner and outer lipid bilayer) (bilayer that surrounds cell is single)
- Outer lipid bilayer is connected to the smooth and rough ER
- Nuclear pores: passages through the nuclear envelope that regulate nuclear transport
- Nucleus contains chromatin: chromosomal DNA bound to DNA-binding proteins
- Nucleolus: an area inside the nucleus where ribosomes are assembled
(not an organelle
On tests, don’t read too fast and read it as nucleus)
12
Q
Function of ribosomes
A
synthesize proteins
13
Q
Structure of ribosomes
A
- Made of ribosomal proteins and ribosomal RNAs (rRNAs)
- Some rRNAs have enzymatic function: ribozymes
- Ribosomes are assembled at the nucleolus
14
Q
Endomembrane system definition and components (3)
definition and what it includes
A
a network of internal (lipid bilayer) membranes that include
* Endoplasmic reticulum (ER)
- Smooth (SER): no ribosomes
- Rough (RER): ribosomes on surface
* Golgi apparatus - like Amazon distributor system of the cell, go in and shipped out
* Vesicles (like a balloon but walls are made of lipid bilayer membrane)
- Amazon trucks - delivering content
15
Q
Endoplasmic Reticulum (ER) Structure
tubules, lumen definition
A
- Network of interconnect tubules (tiny tubes)
- Walls of tubules made of lipid bilayer
- Lumen: space inside tubes
- Smooth and rough ER are interconnected with each other and the outer lipid bilayer of the nuclear envelope
16
Q
SER Specialized Functions (4)
A
- Site of lipid synthesis (phospholipids made here)
- Site of fatty acid desaturation (fatty acid made saturated then can become unsaturated)
- Site of cholesterol synthesis
- Some carbohydrate synthesis occurs
17
Q
RER specialized functions
A
A site for synthesis of some proteins that are
1. bound for export out of the cell
or
2. for use in the endomembrane system
18
Q
Golgi apparatus structure
A
- Series of flattened tubes (sacs)
- Walls of tubes are a lipid bilayer
- Not connected to other structures
- Cis face: receives transport vesicles from ER
- Trans face: transport vesicles exit
19
Q
Golgi Appartus Function (amazon center)
A
- Proteins and other molecules may be modified
- Molecules are sorted by eventual destination
- Molecules are released in vesicles
20
Q
Exocytosis
A
process by which material is exported out of the cell
ex. production and export of insulin
21
Q
Endocytosis
A
material is taken into a cell
- Plasma membrane surrounded material from outside the cell, trapping it in an endocytic vesicle
- Can be a:
- specific process using receptors on cell
- non-specific taking up water and nutrients
- The endocytic vesicle then fuses w/ a digestive vesicle: a lysosome
22
Q
Lysosome definition
A
membrane-bound vesicles with a low internal pH (4.5-5.0 b/c proton pumps) that contain digestive enzymes
* like a floating stomach
* Bud off from the trans face of Golgi
23
Q
Lysosome function
A
to digest material from outside or inside the cell (worn-out organelles that need to be destroyed and recycled)
24
Q
Primary lysosome
A
not fused to anything yet
25
secondary lysosome
fuse with an endocytic vesicle or cellular organelle; after fused, it is a secondary lysosome where the material that is going to be digested meets the enzyme that is going to break the bacteria down
26
What does tuberculosis bacterium do
* Can prevent fusion of endocytic vesicle and primary lysosome so TB avoids destruction and lives in cell
* Multiplies inside macrophage cell
* Kills it
* Spreads to infect more cells
27
Mitochondria structure
* double lipid bilayer membrane
* Outer membrane: covered entire organelle
* Inner membrane: extensively infolded
- Folds are called cristae
* Liquid center called the matrix
28
Mitochondria function
energy metabolism (ATP production)
29
Mitochondria and endosymbiotic theory
one time mitochondria were free-living prokaryotes and developed an endosymbiotic relationship with current-day eukaryotic cells
## Footnote
only arise from pre-existing mitochondria (reproduce themselves)
30
Chloroplast structure
* double lipid bilayer (DLB) membrane
* Outer and inner LB membranes cover the entire organelle
* Within DLB is an internal membrane into multiple stacks of disks
* Thylakoid: single membrane disk
* Granum: a stack of thylakoids
* Stroma: liquid substance surrounding grana
31
Chloroplast function
Site of photosynthesis in plant cells
Light energy converted into usable chemical energy
32
Chloroplast and endosymbiotic theory
applies
33
Cytoskeleton structure
## Footnote
not an organelle
Network of multiple types of proteins **inside** cells
34
cytoskeleton functions (3)
* Provides structural support within cells (can make cells change shape for when cells need to get into tight spaces)
* Has a role in transport within cells (motor proteins attached to vesicles and CS motor proteins walk vesicles along and take them where they need to go)
* Help mobile cells move ex. flagellum
35
Extracellular Matrix structure
## Footnote
not an organelle
Network of multiple types of proteins **outside** of cells
36
Extracellular Matrix functions (3)
* Structural support outside cells
* Glues cells into higher-order structures, like organs
* Has a role in cell-cell communication (signaling molecules along ECM)
37
Plasma Membrane
* Defines the inside and outside of a cell; it’s a barrier
* Are ‘selective barriers’
- Regulates transport into/out of the cells
* PM is dynamic (always changing) and cells can adjust the…
- chemistry of the pH
- molecules associated with the PM
38
Method and results of discovering membrane structure
* Obtain and count red blood cells
* Calculated the total surface area of the RBCs (multiplied SA of 1 cell by total # of cells)
* Destroyed the cells and collected the membrane phospholipids (through chemical separation)
* Placed the phospholipids into a chamber of liquid buffer where they formed a floating monolayer (all tails pointed up)
* Measured the total SA of the phospholipids in the chamber and compared it to the total SA of the RBCs
Results: he found that the SA of the monolayer was double the SA of the cells (2:1 ratio)
39
Why did Garter use red blood cells?
* Easy to obtain and count
* Uniform in size across all animals and people
* Was perfect b/c eukaryotes have a nuclear membrane w/ phospholipids which would have messed up the results; **mature** red blood cells eject all other membranes except for the plasma membrane so it worked perfectly
40
Fluid mosaic model
* plasma membranes are fluid structures
* The phospholipid bilayer is like a lake
- Molecules are ‘floating’ around in it
41
Cell fusion experiment
* The membrane proteins of cells were stained with fluorescent dyes (human cell membrane proteins w/ red dye and mouse cell membrane proteins w/ green dye)
* The cells were fused together
* Conclusion: proteins diffuse around the membrane which means they’re fluid
* if it was static, it red and green would stay on their respective side
42
Photo-bleaching experiment
demonstrated fluidity of plasma membranes
* Labeling membrane associated proteins w/ fluorescent dye so it glows under fluorescent light
* Exposed specific area of cell to laser which destroys the fluorescent dye
* Proteins are still there
* Dye is not there
* If membranes are static, bleached out area will stay in same place
* Membranes are fluid so bleached out area got filled back up with fluorescence
43
What is the importance of maintaining fluidity level?
* If the membrane is too fluid, it will not serve as a barrier and will fall apart
* If the membrane is too solid, transmembrane proteins (in phospholipid bilayer) won’t be able to flex (change their shape) and carry out their functions
- Ex. transport and signaling proteins
44
How do membranes regulate fluidity?
* Cells regulate fluidity of their membranes by changing the fatty acid chains of phospholipids in 2 ways
1. Cell can generate phospholipids that have more or fewer unsaturations in the fatty acid chains
2. Cell can generate phospholipids that have longer or shorter fatty acid chains
## Footnote
* If it’s too liquid, phospholipids will become more unsaturated and shorter at the same time, not at different times
45
How does the plasma membrane respond to lower temperatures? ex. fridge
* plasma membrane becomes less fluid (too solid) → cell makes phospholipids with fatty acid chains that are
* Shorter
* More unsaturated
46
How does the plasma membrane respond to higher temperatures?
* plasma membrane becomes too liquidy → cells make phospholipids with fatty acid chains that are
* Longer
* More saturated
47
What is the major barrier for molecules crossing a plasma membrane?
the hydrophobic interior
48
hydrophobic interior permeability levels
* Permeable to nonpolar molecules (size doesn’t matter as long as they’re nonpolar)
* Less permeable to small polar molecules w/ no electric charge
- Ex. H2O
* Not permeable to large polar molecules and ions
- Ex. glucose
49
What are the types of membrane transport
1. passive transport (diffusion): movement of molecules across the membrane from **high** concentration to **low** concentration
Does NOT require cellular energy
2. active transport: movement of molecules across the membrane from **low** concentration to **high** concentration
DOES require cellular energy
50
What are the types of passive transport?
1. **simple diffusion:** IF the PM is permeable to a molecule
AND there is a difference in concentration of that molecule across the membrane
THEN the molecule will diffuse across the membrane by simple diffusion
* No energy input from cell required
* No transport proteins required
2. **facilitated diffusion:** diffusion of molecules that can’t cross the membrane on their own must be facilitated
* No energy required
* Requires transport proteins are selective
- Channel proteins
- Carrier proteins
51
How do cells regulate facilitated diffusion
1. Regulating the concentration of particular transport proteins in the membrane
- The cell can make more or less of a type of transport protein to increase/decrease a protein
2. Regulating the activity of transport proteins
- Some proteins are always on, so always transporting
- Some have an on-and-off switch
52
Channel proteins in FD
## Footnote
5 points
* Like tunnels
* Don’t bind to the molecules they transport
* Direction of moment depends on concentration
* Movement doesn’t require energy input from cell
* Channels can be
- Always open (molecules always going through them)
- Gated: opened or closed
53
Carrier proteins
## Footnote
3 points
* Must bind to molecules they transport
* Direction of movement depends on concentration (remember it’s in facilitated diffusion, not active transport)
* Movement doesn’t require energy input from cell
54
What are the 3 types of carrier proteins in FD?
1. **Uniporters:** carrier proteins that only transport 1 type of molecule
2. **Symporters:** carrier proteins that transport 2 types of molecules, in the same direction, at the same time
3. **Antiporters:** carrier proteins that transport 2 types of molecules, in opposite directions, at the same time
55
Kinetics of channel vs carrier proteins
* Channel proteins display **linear** kinetics (no speed limit)
* Carrier proteins display **saturation** kinetics (carrier proteins have binding sites, so at high concentrations, binding sites will eventually run out)
56
Active transport
* Used by cells to go against the concentration gradient of a molecule across a plasma membrane
- b/c concentration gradients are critical for some biological processes
* Moving molecules against a concentration gradient requires:
**Carrier** proteins
Energy input from cell
57
peripheral proteins
attached to surface of lipid layer
58
integral proteins
integrated into the lipid bilayer in whole or part
