Exam 2 Flashcards
Lectures 7-12
What are the 5 characteristics of life?
- 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
What are the 2 types of cells?
- 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)
What is the major difference between eukaryotes and prokaryotes?
Eukaryotic cells can be up to 1000x larger than prokaryotic cells
What are the economics of cell size?
- 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
Prokaryotes’ differences with eukaryotes
- No nucleus, DNA is in the nucleoid
- No internal membrane system
- Have a cell wall (a protective outer barrier) composed of peptidoglycans
Prokaryotes’ similarities with eukaryotes
- 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
Prokaryotic cell structure (some vs all)
- structures all prokaryotes have: cell wall, phospholipid bilayer, cytoplasm, ribosome, DNA, nucleoid
- structures only some prokaryotes have: capsule, pili, flagellum
What is a distinctive feature of eukaryotic cells?
internal compartmentalization
- Possible b/c of an internal membrane system
- Internal membrane-bound compartments are called organelles which means little organs
What is the one organelle prokaryotes have?
ribosomes (exception to the rule that organelles needs membranes)
What are the functions (3) of the nucleus?
- Stores genetic information (like a suitcase 🧳)
- Ribosomes are assembled here
- RNA is produced (transcription) here
What is the structure of the nucleus?
- 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)
Function of ribosomes
synthesize proteins
Structure of ribosomes
- Made of ribosomal proteins and ribosomal RNAs (rRNAs)
- Some rRNAs have enzymatic function: ribozymes
- Ribosomes are assembled at the nucleolus
Endomembrane system definition and components (3)
definition and what it includes
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
Endoplasmic Reticulum (ER) Structure
tubules, lumen definition
- 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
SER Specialized Functions (4)
- 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
RER specialized functions
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
Golgi apparatus structure
- 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
Golgi Appartus Function (amazon center)
- Proteins and other molecules may be modified
- Molecules are sorted by eventual destination
- Molecules are released in vesicles
Exocytosis
process by which material is exported out of the cell
ex. production and export of insulin
Endocytosis
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
Lysosome definition
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
Lysosome function
to digest material from outside or inside the cell (worn-out organelles that need to be destroyed and recycled)
Primary lysosome
not fused to anything yet
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
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
Mitochondria structure
- double lipid bilayer membrane
- Outer membrane: covered entire organelle
- Inner membrane: extensively infolded
- Folds are called cristae
- Liquid center called the matrix
Mitochondria function
energy metabolism (ATP production)
Mitochondria and endosymbiotic theory
one time mitochondria were free-living prokaryotes and developed an endosymbiotic relationship with current-day eukaryotic cells
only arise from pre-existing mitochondria (reproduce themselves)
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
Chloroplast function
Site of photosynthesis in plant cells
Light energy converted into usable chemical energy
Chloroplast and endosymbiotic theory
applies
Cytoskeleton structure
not an organelle
Network of multiple types of proteins inside cells
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
Extracellular Matrix structure
not an organelle
Network of multiple types of proteins outside of cells
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)
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
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)
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
Fluid mosaic model
- plasma membranes are fluid structures
- The phospholipid bilayer is like a lake
- Molecules are ‘floating’ around in it
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
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
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
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
- If it’s too liquid, phospholipids will become more unsaturated and shorter at the same time, not at different times
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
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
What is the major barrier for molecules crossing a plasma membrane?
the hydrophobic interior
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
What are the types of membrane transport
- passive transport (diffusion): movement of molecules across the membrane from high concentration to low concentration
Does NOT require cellular energy - active transport: movement of molecules across the membrane from low concentration to high concentration
DOES require cellular energy
What are the types of passive transport?
-
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 -
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
How do cells regulate facilitated diffusion
- 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 - Regulating the activity of transport proteins
- Some proteins are always on, so always transporting
- Some have an on-and-off switch
Channel proteins in FD
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
Carrier proteins
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
What are the 3 types of carrier proteins in FD?
- Uniporters: carrier proteins that only transport 1 type of molecule
- Symporters: carrier proteins that transport 2 types of molecules, in the same direction, at the same time
- Antiporters: carrier proteins that transport 2 types of molecules, in opposite directions, at the same time
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)
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
peripheral proteins
attached to surface of lipid layer
integral proteins
integrated into the lipid bilayer in whole or part
