Biology Study Guide Exam 3

8/3/2019 Biology Study Guide Exam 3

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Biology Study Guide #3

The Cell

Exa (1E18), Peta (1E15), Tera (1E12), Giga (1E9), Mega (1E6), Kilo (1E3), Hecto (1E2), Deca (1E1), deci

(1E-1), centi (1E-2), mili (1E-3), micro (1E-6), nano (1E-9), pico (1E-12), femto (1E-15), atto (1E-18)

● Size of largest cells- 1-2 millimeters

● Size of Typical Animal Cell 10-100 micrometers (microns)

● Size of typical organelles, bacteria, nucleus: 1-10 microns

Light Microscopy- 100-uM resolution

● Brightfield (unstained)- very little contrast, transparent

● Brightfield (stained)- enhances contrast, cell must be fixed/preserved/killed

● Phase-Contrast- enhances contrast by amplifying varying densities, expensive

● Shows dynamic processes, functions

Electron Microscopy- 1-nanoM resolution

● Scanning Electron Microscope

● Transmission Electron Microscope

● Showed existence of organelles, where LM could not

● Kills cell (can not see dynamic processes/function)



Why must cell be microscopic?

● V:SA ratio- Volume increase is much greater than SA increase, meaning more material from

the cell or the environment will have to wait to be transported through the plasma membrane

(slow transport in/out of cell)

● More stuff to be made to fill the space = inefficient

Prokaryotes vs. Eukaryotes

● Similarities- plasma membrane, cytosol (aqueous part of the cell inside the membrane), DNA,

ribosomes

● Eukaryotes have membrane-bound organelles

● Internal membrane compartments (euk)- allows incompatible processes to occur

simultaneously, specialized proteins can be embedded in membrane

○ lysosomes- apoptosis (release lytic enzymes into cell)-p53 assesses cell damage,

determines to repair or do apoptosis, p53 acts as tumor suppressant unlessmutated by cancer

Prokaryotes

● Pili- attachment structures on surface of prokaryote

● Nucleoid- region where the cell’s DNA is located (not enclosed by membrane)

● Capsule- jelly-like outer coating

● Flagella- locomotion organelles

● May have cell wall

● Plasma membrane- enclose cytoplasm● Ribosomes- synthesize proteins



Plant Cell Unique Organelle- Plasmodesmata, chloroplasts, cell wall, central vacuole/tonop



Fill in the blank



Animal Cell Unique Organelles- Lysosome, centrioles, flagella



Fill-in-the-blank



Organelles

Cell fractionation technique: separate organelles based on weight and size

● Nucleus-houses genetic material

○ chromatin- DNA+associated proteins (histones)

○ nuclear envelope- double membrane that allows histones, mRNA to pass through

○ nucleolus (dark spot)-rRNA synthesized, ribosome subunits assembled

○ Constant levels of rRNA make ideal for ratios of other substances

● Ribosomes-synthesizes proteins

○ Made of large and small subunit (proteins + rRNA)

○ Free ribosomes = cytosolic proteins

○ Bound ribosomes = exported proteins

○ => lots of proteins-making cell = lots of Ribosomes :D

● Endomembrane System○ Endoplasmic Reticulum-invagination of cell membrane, cisternal (a sac or cavity

containing fluid) space contiguous with the intermembrane space of the nucleus

■ Rough ER = synthesis of secretory proteins

■ Smooth ER = detoxification of drugs (lipophilic) by hydroxylating (add

-OH) it (hydrophilic => stick to water => reabsorped => get rid of),

synthesis of lipids, oils, steroids

■ Prokaryotes secrete proteins by binding ribosomes to cell membrane

(making proteins as it is sticking out)○ Golgi Body- allows proteins to be folded correctly (finishes, sorts and ships)

■ Cisternae (folds) - has “cis” (receiving) face (smooth), “trans”

(exporting) face (rough)

■ Sorting function determines different protein and lipid membranes of

endomembrane system

○ Vacuoles- membrane-bound compartments

■ contractile- squirts water out of cell



■ central- growth without new cytoplasm (less materials needed),

disposal sites of metabollic wastes, holds proteins and ions



● Lysosomes- membrane-bound sacs of hydrolytic enzymes (lysozymes)

○ Acidic pH 5 pumps H+ into lumen

○ Phagocytosis- digests macromolecules (other foods/organisms)



○ Autophagy- breaks down damaged or dysfunctional organelles (placed in vesicles)

in the cell● Peroxisomes-break down toxic peroxides, long chains of fatty acids

● Plasmodesmata- holes in cell walls that allow free passing of small molecules from plant cell to

plant cell

● Cell wall

● Mitochondria- generates bulk of ATP

● Chloroplasts- photosynthesis

● Cytoskeleton- mechanical support, anchorage for organelles, transportation of organelles, cell

motility. Constant assembly and disassembly of filaments for movements.



○ microtubules- thickest, compression resistant, transport rail (made of tubulin) -

prevent squishing

○ microfilaments- thinnest, pulling resistant (made of actin) - prevent being

stretched

○ intermediate filaments- holds things together (made of proteins such as keratin)

○ desmosomes- made of intermediate filament

○ cell movement- actin filaments xtracellular Matrix- matrix of fibrous proteins and

polysaccharides outside of cell

○ cell held to ECM by integrins (bind to ECM proteins and cytoskeleton)

○ glycoproteins- charged because of carbohydrates, which attracts water and forms

a protective “goo”

○ cell undergoes apoptosis when rid of ECM (unless cancerous)



○ Similarities between cell wall and ECM- highly permeable, allows transfer of

information between cell and environment, synthesized by the cell

○ highly permeable for H20 & small molecule exchange + information exchange

between environment and cytoplasm

○ materials = largely intracell-synthesized

● Centrosome- makes mitotic spindle, cilia, and flagella (microtubules organizing center)

○ composed of two centrioles surrounded by an amorphous (without shapes/form)

mass of pericentriolar (around centriole) material

● Cilia, Flagella-

○ important for motility (movement of liquids and materials)

○ motor proteins that cause microtubules to move relative to each other

● Intracellular Junctions (joining two cells)

○ plasmodesmata (plant) - huge space

○ tight junctions (animal)- impermeable

○ desmosomes (animal)- cell-to-cell adhesions



○ gap junctions (animal)- tightly regulated cell-to-cell channels for ions and small

molecules



Membranes

Fluid Mosaic Model- proteins embedded in a bilayer

Plasma membrane- separates cell from environment (made of phospholipids and proteins)

Membrane Lipids

● selective permeability- hydrophilic molecules can be passively transported through membrane,

hydrophobic molecules must be actively transported through membrane

● receptor protein location- on surface or intracellular

○ depends on passive (intracellular) or nonpassive (surface) nature of molecule

● movement

○ lateral movement (not tethered to proteins (only weak hydrophobic interactions)

○ rare “flip-flop” (exchange of sides by phospholipid (energetically unfavorable for

phosphate head to travel through nonpolar region)



Membrane Asymmetry

● Phospholipids synthesized in smooth ER (causes insertion of phospholipid on one side only)

● Flippases- flip phospholipids to other side of membrane for symmetric growth of bilayer

○ Causes asymmetry because it only flips certain types of phospholipids (enriched in

a certain type on one side, another on the other side)



Saturated Vs. Unsaturated Phospholipids● Phospholipids with unsaturated FA tails form “kinks” (double bonds which force adjacent lipids

further apart causing the membrane to be more fluid)● Phospholipids with saturated FA tails are more viscous



● Bacterial Cells maintain constant membrane fluidity by changing the amount of saturated vs

unsaturated phospholipids○ If temperature rises, phospholipids speed up => more fluid, amount of saturated goes up =>

more solid => even out○ If termperature lowers, phospholipids slow down => more solid, amount of saturated goes

down => more fluid => even out● Animals use cholesterol (wedged in membrane) as a buffer (phospholipids bump into it and slow

down if temp too high, keeps phospholipids from sticking together if temp low)

Membrane Proteins● Drift laterally, not as fast as phospholipids



● integral proteins- require detergents (polar stuff that separates membrane n proteins) to separate

from membrane. IMP helps transport stuff across selectively○ single pass: go through membrane once○ multipass: curves around and go through membrane multiply times. Most common = 7

● peripheral proteins- don’t cross membrane● Functions- transport, enzyme activity, signal transduction, intercellular joining (osmosomes), cell-

cell recognition (glycoproteins), cytoskeleton-ECM (integrins)



● What can pass? Polar and small hydrophobic molecules○ Small hydrophobic molecules can pass freely○ Polar require transport proteins- proteins only discriminate what passes it, not direction (which

is based off of concentration gradient)

● Principles of Diffusion- random, movement down concentration gradient, passive transport (diffusion

across biological membrane due to going down the concentration gradient)



● Osmosis- Water moves from an area of higher free water concentration to an area of lower free

water concentration



● Relative terms to compare solutions (hypertonic-greater conc., isotonic-equal conc., hypotonic-lower

conc.)○ Animal cells prefer isotonic solutions, Plant cells prefer hypotonic (do not burst due to cell wall,

turgid)

○

○ Contractile vacuoles used in osmoregulation (expendature of energy to release fluid from cell)● Facilitated diffusion- must be helped by proteins but follow the concentration gradient (cofactors,

channel proteins, carrier protein)



● Active transport- go against concentration gradient (use ATP)



● Cotransport- cotransport



Endocytosis- phagocytosis (cell eating), pinocytosis (cell drinking - H2O accepting only), receptor-

mediated endocytosis○ RMEC- triggers endocytosis only when ligand binds receptor, brings in other molecules plus

ligand○

Pinocytosis only brings H20, RMEC brings other molecules too.

○

● uses LDL receptor (cholesterol hey). Defected LDL receptor = can't recognize LDS =>

hypercholesterolemia (high chol. in blood)



Mitosis-growth and repair, spread DNA evenly

● Genome- entire genetic code of an organism (packed into chromosomes, in humans = 46

chromosomes). Homologous pair = 2 chromosomes coupled together.

● Karyotype- taken during pregnancy to test for genetic disorders

o shows 22 homologous pairs (autosomes)- similar, but not identical (locus is the same, but gene

code may not be the same)

o 1 pair of sex chromosomes (XX,XY)

o Dad determines sex of child- Mom gives X or X, Dad gives X or Y

● FACs analysis- Fluorescence-Activated Cell sorting, tags sperms and separates them (choose

child gender)

● Somatic cells- all cells besides germ cells (diploid)

● Germ cells- sperm, egg (haploid)

● Cell division- mitosis, cytokinesis



Stages of Mitosis- (24

hours)

● Interphase- DNA

Replication (23 hours)

o Chromosomes are

diffuse, centrosomes

begin building up

spindle fibers

● Prophase- mitotic

spindle forming

o Condensed

chromosomes pairs of

sister chromatids(exactly alike unless

mutated), mitotic

spindle forming

● Prometaphase-

mitotic spindle

completed

o Nuclear envelope

disintegrated,

complete polar

separation of

centrosomes

o Chromosomes are

exposed to spindle fibers, attach onto spindle by kinetochores



● Metaphase-

chromosomes

aligned in middle

o Metaphase

plate forms(centerline)

● Anaphase-

sister

chromatids pull

apart

o In plants,

membranevesicles align at

metaphase plate

to form cell wall

o

Chromosomes

pulled apart by

“reeling: (fibers

pulled in by

centrosomes) or

“pac man”

(enzyme

“chomps” along spindle fibers, turning microtubules into tubulin subunits)

o Experiment- cut mitotic spindle between centrosome and sister chromatid. Segment attached to

centrosome shortens, reeling; if segment attached to chromatid shortens, by “pac man”

● Telophase- 2 sets of identical genetic code at opposite poles



o In animal cell, cleavage furrow- contractile ring of cytoskeletal elements

● Cytokinesis- separation of cells



Cell Cycle- G (growth), S (DNA synthesis), M (mitosis)

● G1, S, G2 = interphase

● Checkpoints - G-S transition, G2-M transition

o G-S – checks DNA for damage (fix or apoptosis) and for environment favorability (affected bygrowth factors). If not passed, cell goes out of cycle into G0 (non-growth phase)

o G2-M – finished DNA Replication?

● Cancer Cells = transformation (process of normal turning cancer)

o evade checkpoints (don’t need growth factors)



o Don’t exhibit density-dependent inhibition (normal cells grow on a plate until they cover the

bottom), so they grow on top of each other

o Stop dividing at random points

o IMMORTAL

● Types of tumors

o Benign- has stopped growing, is well-defined, easily removed

o Malignant- is growing and invading, no defined boundary, bulk of tumor cut out and area

irradiated

Metastatic- moved from one location to another (low-probability event, but only one cell needed for

spread)

Biology Study Guide Exam 3

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