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| What's up when it feels like everything and nothing are both happening... Yeah. |
Seeing as that I received a
* We want to maximize surface area to volume: a.k.a we want a greater surface area, rather than a larger volume, because for each square micrometer of membrane, only a limited amount of a particular substance can cross per second.
*Parallel: If an average-sized person eats the same amount as an over-weight person, neither may lose any weight that day (without exercising). Either way, the average-sized person is better off -when we're considering what's going inside.
Important sidenote: It's currently 3:33 AM. Last time I checked the clock, it was 2:22 AM. Thank you, angels (kow).
*If a cell's volume increases, it's surface area increases, but at a decreased rate. If you continued to increase the cell's volume, it would soon be unable to efficiently exchange materials (ions, gases, nutrients, wastes) w/their environment, and it would die. This is why larger organisms don't generally have larger cells than smaller organisms; they simply have more cells.
* A.K.A. As a cell grows, its Surface Area:Volume decreases; at some point in growth, its surface area is too small to supply its raw materials to its greater volume.
*Parallel: The more you eat, the bigger & hungrier you become = the less food you'll have in your kitchen.
ALL CELLS (have this in common)
Cell Membrane:
* regulates what comes in & out of cell, keeps material on either side* it's fluid, and it's always in movement
Made of 2 Things . . .
~ Phospholipids- keeps water on either side, thus making the structure
- hydrophilic (likes water) head, hydrophobic (hates water) tail
- they float back & forth
- allows the movement of material
~ Proteins
- allows material in
- connects to material outside
Eukaryotic Cells: People, Animals, Plants, Fungi (nice...), Protists
*compartmentalization allows these cells to be larger (by *specialization & *surface area)
* has a nucleus (where DNA is stored)
* organelles (tiny organs that specialize in certain functions -e.g., smooth ER is an organelle)
* linear chromosomes (rather than loops)
* introns (sections of DNA that don't code genes)
* cytoskeleton (gives it structure)
Cytoplasm A.K.A. Cytosol
- Gooey liquid of the cell
- Mostly water, thus dissolves materials and allows for diffusion from one place to another
- Chalk full of enzymes, proteins, ribosomes
Cytoskeleton A.K.A. the Skeleton of the Cell
- Gives structure and shape to the cell
* All three components interact with each other non-covalently.
The cytoskeleton proteins are multifunctional and are also involved in whole-cell movements and movements of substances within the cell.
Three main structural components of the cytoskeleton:
Microtubules (formed be actins)
* found in all eukaryotic cells
* hollow rods about 25 nm in diameter with 15nm lumen
* structure: wall consists of 13 columns of tubulin molecules
* wall of the tube is constructed from a globular protein called tubulin
* each tubulin protein is a dimer (molecule made of 2 subunits) -each consisting of 2 slightly different polypeptides
* microtubules grow in length by adding tubulin dimers
* functions: maintenance of cell shape (compression-resisting); cell motility (as in cilia or flagella); chromosome movements in cell division; organelle movements
Microfilaments (formed by tubulins): two strands of pearls
* two intertwined strands of actin, each a polymer of actin subunits
* 7nm diameter
Functions: maintenance of cell shape (tension bearing); changes in cell shape; muscle contraction; cytoplasmic streaming; cell motility (pseudopodia/fake foot); cell division
Intermediate filaments
* fibrous proteins supercoiled into thicker cables
* 8-12 nm
* one of several proteins (such as keratins) depending on cell type
* functions: maintanence of cell shape (tension bearing); anchorage of nucleus and certain other organelles; formation of nuclear lamina
Endomembrane System includes:
- Rough ER
- Smooth ER
- Transport Vesicles
- Golgi Apparatus
- Lysosomes
- Microbodies
- Peroxisomes
- protein synthesis
- protein modification
- protein sorting
- protein transport
Path of proteins through the Endomembrane System:
Proteins are made on ribosomes bound to the RER and move through the endomembrane syystem, transported in vesicles (I'm so sure/wtf is going on here) to the golgi apparatus, to the plasma membrane, and out, yo.
Endoplasmic Reticulum (ER) - folded membrane
Rough ER
- makes proteins
Ribosomes (protein synthesis/a.k.a. where proteins are produced) in the cytoplasm
* Made in the nucleolus
*complexes made of ribosomal RNA and protein
*free ribosomes (suspended in the cytosol)
*bound ribosomes (attached to the outside of the endoplasmic reticulum or nuclear envelope)
Smooth ER
- makes lipids
- makes steroids
- metabolism or breaking-down of carbohydrates
- breaks down toxins inside the cell
Golgi Apparatus (yeah, okay)
* where proteins go (transported in vesicles) to be modified and packaged
* where lysosomes (where material is broken-down) are produced
Lysosomes: a membranous sac of hydrolytic enzymes that an animal uses to digest (hydrolyze) macromolecules
* hydrolytic enzymes and lysosomal membrane are made by rough ER and then transferred to the Golgi apparatus for further processing.
* they also use their hydrolytic enzymes to recycle the cell's own organic material, a process called autophagy
* with the help of lysosomes, the cell continually renews itself
* has enzymes that work in oxygen-poor areas and lower PH
Deals w/Energy:
Mitochondria
- breaks down sugars from photosynthesis
- found in all Eukaryotic Cells
- makes ATP
- same size as bacteria and archaea
-they're folded to increase surface area
- some genes found here
Chloroplasts
- found in plants
- some genes found here
- always present when there's photosynthesis
Nucleus
Quick & Simple Video: All About the Nucleus*contains most of the genes in the eukaryotic cell
*most noticable organelle in a cell (average is 5um in diameter)
Nuclear envelope: double membrane (each a lipid bilayer separated by a space of 20-40 um) enclosing the nucleus; perforated by pores (pore complex lines each pore and regulates the entry and exit of proteins and RNAs in the cell, as well as macromolecules); continuous with ER; separates its contents from cytoplasm
Nuclear lamina (lines the surface of the nuclear envelope): netlike array of protein filaments that maintains the shape of the nucleus by supporting the nuclear envelope; helps organize genetic material so it functions efficiently.
Nuclear matrix: framework of protein fibers; helps organize genetic material so it functions efficiently.
Nucleolus: nonmembranous structure involved in production of ribosomes (ribosomal RNA); a nucleus has one or more nucleoli
Chromatin: material consisting DNA and proteins; visible in a dividing cell as individual condensed chromosomes.
Chromosome: DNA is organized into units called chromosomes. Each chromosome contains one long DNA molecule associated with many proteins
Prokaryotic Cells: Bacteria & Archaea
* all small (to increase surface area)
* evolved before Eukaryotic Cells
* do not have double membrane
* only one "naked" chromosome (circular molecule)
* Cytoplasm
* Their flagella rotate, unlike ours
Plant Cells:
* Thick Cell Wall
* Chloroplast :
* Mitochondria
* Vacuole
VS.
Animal Cells:* Mitochondria
*Centrioles
... Just looked at the clock once again, while feeling sad. 4:44 AM
Peroxisome: a specialized metabolic compartment bounded by a single membrane, holds on to enzymes that require oxygen
- contain (oxidative) enzymes that remove hydrogen atoms from various substrates and transfer them to oxygen (O2), thus producing hydrogen peroxide (H2O2)
- Take H --> O2 --> H202
- some peroxisomes use oxygen to break fatty acids down into smaller molecules that are transported to the mitochondria and used as fuel for cellular respiration
- detoxify alcohol and other harmful compounds by transferring hydrogen from the poisons to oxygen
- they also contain an enzyme that convert H2O2 to water
- play a role in cholesterol synthesis and the digestion of amino acids
- liver cells most likely have a lot of peroxisome
Random Stuff
*Oxygen needs to get into a cell through diffusion (bc it doesn't have a charge)
*Carbon Dioxide is going to get out of a cell (bc it doesn't have a charge)
*Nucleus, Mitochondria, Chloroplasts = They all have double membranes
Chew on this... (maybe while smoking?)
"Goal of life: increase surface area"
Compartmentalization = parts within the parts . . . Think nesting dolls -and, while you're at it, remember love is all you need, at the end of the day -not made-up labels like Golgi Apparatus.
- knock on wood
