Chapter 3: Cell Biology (Concepts)

thinkwell homeschool; based on incorrect answers + my notes

prokaryotes: no nuclear membrane

eukaryotes: has nuclear membrane

prokaryotes vs eukaryotes

1000

how many microns in 1mm

* involved in secretion and excretion of proteins
* individual components of membrane can migrate relative to each other
* selectively permeable (regulates which contents of interstitial fluid can enter cell)

plasma membrane

* phospholipid bilayer w/ floating proteins (bc of hydro-versatility)
* hydrophobic interior + hydrophilic exterior on both sides
* protein orientations:
* on surface (peripheral)
* partially embedded in surface
* through both layers
* between both layers

describe the basic membrane structure using the fluid mosaic model

* DNA carries code
* RNA carries message
* Protein carries out work

in simple terms, how do DNA, RNA, and proteins work together in the cell?

* as a cell gets larger, its volume increases at a much faster rate than its surface area

the plasma membrane cannot keep up with the needs of the interior of the cell if it is too large

why is a higher surface-area-to-volume ratio more efficient than a lower one? (rephrase)

* structure and function are related

simple, most important concept throughout subchapter

* pseudopods surround food item of cell and fuse together to form a vesicle, allowing food to enter the cell

pseudopod purpose?

* microfilaments:
* responsible for shape and contraction of cell
* when contracting, pseudopods form
* actin proteins w/ two anchor points
* when actin is removed from substance or some other pressure causes shrinkage, anchor points will move closer by contracting cell
* \~7nm
* intermediate filaments:
* most belong to keratin family (or the substance in hair and fingernails)
* similar structure to microfilaments, but larger (8-10nm)
* microtubules:
* allows for flexibility of cell
* tubulin dimers stack spirally, forming hollow tube
* makes up centrioles, cilia, and flagella (all of which are able to accomplish movement)

explain the purposes and describe the structures of each of the following cytoskeleton components: microfilaments, intermediate filaments, and microtubules.

* microtubules are flexible
* protein motor molecules bind to adjacent pairs of microtubles
* sets rigid point and provides force for bending and movement

explain how microtubles and protein motor molecules work together to allow for the movement of cells. how do they relate to the cytoskeleton of the cell?

* primary: allows expansion + cell wall formation after cell division (bc flexible in initial stage)
* secondary I: primary wall hardened by pectin, which binds cellulose together, forming a rigid structure
* secondary II-III: 2-3 more walls may form between primary and secondary I walls for extra shape support and rigidity

describe primary and secondary cell walls in a plant cell (how can new cell walls form after cell division?)

* found only in animal cells
* components:
* glycoproteins (like collagen; primarily proteins)
* proteoglycans (mostly carbs)
* fibronectins (anchors proteins to others)
* plasma membrane (integrin helps “lock” extracellular matrix and actin)
* **work together to provide cellular support**

where is the extracellular matrix found? list its four components and describe their collective function

1. transport (tunnel-like structures form through integrated proteins)
2. enzymes (molecules transformed along metabolic pathway)
3. signal transduction (can convey signals across membranes, and may undergo conformational changes as a result)
4. junctions (connections between cells)
5. cell-cell recognition (oligosaccharide can identify its cell to protein of another cell)
6. anchors (collagen and extracellular matrix)

name the six protein functions in the ‘mosaic’ of the cell membrane

* exocytosis: release of materials through the plasma membrane
* endocytosis: import of materials to cell by infoldings of plasma membrane

what are exocytosis and endocytosis?

* phagocytosis (cell eating)
* pinocytosis (cell drinking)
* receptor mediated endocytosis (receptors bind with specific materials; pit forms vesicle)

describe the methods in which a cell may import materials into itself

they are limited to white light, or the range of values visible to the human eye

why are light microscopes limited to a magnification of around 1000x?

* filament-excited electrons (instead of light) pass through materials to minimize wavelength
* lenses = electromagnets
* phosphorescent dyes glow when electron beam hits object
* differs from scanning bc:
* image = 2D (not 3D)
* electrons pass through object, whereas in scanning they bounce off of object

dexplain how a transmission electron microscope works and the type of image it produces. how does it differ to the scanning electron microscope?

* object mounted on gold stub, specimen coated in metal
* electrons **bounce off** object and energy levels of electrons computed to form 3D image
* differs from scanning bc:
* image = 3D (not 2D)
* electrons bounce off object, where in transmission they pass through it

explain how a scanning electron microscope works and what type of image it produces. how does it differ to the transmission electron microscope?

* cell/tissue surrounded in ice
* knife inserted, causing cell to rupture
* natural areas that can rupture include **hydrophobic tail of lipid bilayer**
* holes and bumps left over
* **allows for study of interior’s topography**
* differential centrifugation allows you to pick out and study different materials (not layers or interiors)

describe freeze fracture/etching. what kind of observations does it permit and how does its usage vary from that of differential centrifugation?

* liquid suspension = separated and subjected to increasing speeds in a centrifuge
* homogenate ground up + spun in centrifuge
* densest material = put into another tube, spun faster
* liquid layers will **separate materials by density**, allowing one to pick out and study different materials (separates by substance, not layer, whereas etching allows this in a way)

describe differential centrifugation. what kind of observations does it permit and how does its usage vary from that of freeze fracture (or etching)?