BIO 120 Smith- WKU - Exam 2: Cell Biology prep

Unit 2: Ch 6(last part), 7, 11, 12

Ch 6: Phospholipid bilayer

6.3 How do things cross

- concentration gradient (moves from high to low) - Diffusion - until equilibrium

- passive transport —> automatic, down its conc gradient

- osmosis —> the water moves not the solutes, until equilibrium, ex: if ions can’t go through the bilayer, water moves instead

• Hypertonic solution —> hyper = overactive = over = more = higher solute concentration outside than inside the cell —> vesicle shrinks

• Hypotonic solution —> opposite of hyper = lower solute concentration outside than inside = more solute conc inside —> vesicle bursts

• isotonic solution —> inside is the same as outside —> no change

- active transport —> needs energy, goes against its concentration gradient

Chemical evolution —> protocell - 1st bilayer protects og RNA

6.4 Proteins alter membrane structure and function

- proteins can be amphipathic (both hydrophobic and hydrophilic)

- sandwich model

- fluid-mosaic model —> the correct one

• integral proteins = integrated in —> nonpolar, hydrophobic —> trans-membrane proteins

• peripheral proteins = outer —> polar, hydrophilic

how to get other stuff (ions, etc) through into the cell? needs help - facilitated diffusion

• channel protein —> charged/ions

• carrier protein —> changes chape to fit molecule —> large molecules

electrochemical gradient: charged, for ions

• electro gradient part - difference in charge across the membrane

• chemical gradient part - difference in solute concentration across a membrane

channels = proteins (amino acids w/ peptide bonds) —> ex: cystic fibrosis (lungs fill with mucus = hard to breath) is caused by defects in a transmembrane protein for Cl- ions

Ex: aquaporins (water-hole/water-pore)

some channels can be gated (regulation)

Ch 7: Inside the Cell

- all cells have: proteins (does most of cell’s functions), nucleic acids (store, transmit, process info), carbs (store energy, support, identity), plasma membrane (selectively permeable, membrane barrier)

eukaryotes —> nucleus

prokaryotes —> no nucleus

Domains: bacteria (prok), archaea (prok), Eukarya (euk)

Endosymbiosis Theory or Symbiosis

—> bacteria were engulfed, mutually beneficial relationship evolved

Evidence

1) mitochondria, chloroplasts contain own DNA

7.1 Prokaryotic Structure

1. DNA) —> circular (plasmids), single chromosome in nucleoid region

2. Ribosomes manufacture proteins) —> large subunit, small subunit, protein synthesis

3. photosynthetic membranes) —> sunlight energy to chemical energy, folds of the plasma membrane

4. organelles = not alot) —> specialized functions —> store calcium ions, magnetic crystals = compass

5. cytoskeleton) —> protein fibers

6. plasma membranes) —> separates life from nonlife, phospholipid bilayer, proteins, cytoplasm(fluid)

7. cell wall) —> glucose, peptidoglycan, protective exoskeleton

8. external stuff for movement/attachment) —> flagella (propels cell), fimbriae (attachment)

7.2 Eukaryotic Structure

—> large surface to volume ratio = more organelles

—> compartmentalization based on purpose —> efficiency

1. nucleus) —> holds nucleic acids, double-membrane nuclear envelope, nucleolus - where rRNA is synthesized

2. ribosomes) —> large + small subunit, protein manufacturers, some are free floating some are attached

Endomembrane System — golgi, rough ER, smooth ER, lysosomes

3. Rough ER ) —> rough bc studded with ribosomes-produce proteins

   Smooth ER) —> packaging lipids

4. Golgi Apparatus) —> polarity, “post-office of the cell”, mods and sends proteins, cis = receives, trans = ships

5. Lysosomes) —> “stomach of the cell”, breaks things apart, recycles, special enzymes, lower pH —> proton pumps to maintain it

   synth in ER, processed in golgi, shipped to lysosomes

6. Vacuoles) —> only in plant cells, store water + ions etc, storage of the cell

7. Peroxisomes) —> redox reactions prod hydrogen peroxide, liver detox alcohol

8. Mitochondria) —> “powerhouse of the cell” = prod ATP, has its own DNA (mtDNA), own ribosomes

   • cristae = inner folds

   • matrix = solution around it

   - all mitochondria is from the female side ( egg not sperm)

9. Chloroplast) —> plants only, photosynthesis, 3 membranes

   • stroma = juice

   • thylakoid = folding, membrane

   • granum = thylakoids stacked

10. Cytoskeleton) —> protein fibers, cells shape + structure, cell movement, transport

11. Eukaryotic Cell Wall) —> plants only, structural support, cellulose → plants, fiber →humans

Plants vs Animals:

- plants have all

- animals don’t have vacuoles, chloroplast, or cell wall

Lysosome Recycling

1. endocytosis → particles bind to receptors on plasma membrane, cell engulfs to form vesicle

2. phagocytosis (“eat-cell-act”) → swallows it and digests it

3. autophagy (“same-eating”) → damaged organelles are recycled

7.6 Cytoskeleton

→ network of fibers, cell shape/structural support, not static, alters cell shape

3 types (actin filaments/microfilaments, intermediate filaments, microtubules)

1. microfilaments → smallest, actin molecules into long coiled strands

   → dense networks

   - cell shape

   - cell movement (w/ motor protein myosin)

   - uses ATP → muscle contractions, cytokinesis (split cell), cytoplasmic streaming, cell crawling

2. intermediate filaments → in keratin (nails, hair), mid size, structural support not movement, gives nucleus its shape

   - nuclear lamins

3. microtubules → largest, large hollow tubes of tubulin (protein), structure, polarity, railroad tracks (vesicle transport), movement, stability

   • animal cells - the center is centrosome

     • 2 bundles of microtubules called centrioles

     • a wagon wheel of 9 triplets

     • “9+2”

   • uses motor proteins → kinesin = hydrolyzes ATP, allows vesicle to move

flagella → euk and prok, movement

cilia → movement, in respiratory tract (mucus), digestive (food)

axoneme → “9+2” → 2 central microtubules, 9 pairs all around

dynein → motor protein, moves cilia and flagella, b/ween 2 pairs of doublets

Ch 11: Cell Surface

11.1 Cell surface

• cell-cell interactions

• extracellular layer → outside membrane, protective, cell shape

  • concrete/ground substance = resists compression, steel rods/fibers = resist tension

  • Animals: ECM(extracellular matrix) → bone + cartilage have large ECM

    • collagen → binds together (like rebar), flexible

    • proteoglycans → cement → attracts water + forms gel

  • integrins → integrate

  • lamins → glycoproteins

  • Plants: primary cell wall (cellulose - #1 polymer in plants)

    • microfibrils → bundled into cellulose

    • pectin →absorb water (like the proteoglycans) → used in jam/jelly

    • cell shape is rectangular → ECM/cell wall counteracts turgor pressure from osmosis

      • turgor pressure = important for young growing plant cells, the pressure exerted by the fluid inside a plant cell against its cell wall, essentially the force that keeps a plant cell firm and upright due to the influx of water through osmosis

    • secretes expansins (proteins) → helps to stretch/grow so it doesn’t rupture

  • secondary cell wall → between plasma membrane and primary cell wall

    • in some mature plant cells

    • form follows function: leaf cells → waxes, wood→ lignin (2nd most polymer after cellulose)

    • thicker than primary cell wall

11.2 ADJACENT cells connect + communicate

• multicellularity

Connect

• plant cells → middle lamella (made of pectin, give) connects plant cells together, like glue

• animal cells → tight junctions, desmosomes, gap junctions

  • tight junctions = keep things watertight, ex: stomach tissue (no acid leak), bladder (no urine leak), blood vessels (no blood leak)

    • can open and close

    • like a quilt

  • desmosomes = like rivets = snapping → connect cytoskeletons → anchor

Communicate

• animal cells contd.

  • gap junctions → form channels, flow between cells

• plant cells

  • plasmodesmata → smooth ER, hole/pore

11.3 DISTANT Cell-Cell Signaling

1. neurotransmitters → open and close channels in distant cells, EX: brain controls the body

2. hormones → produced by the body, get into blood stream from head to toe, bind to signal receptors, info carrying molecules

   • lipid-based/soluble → can go through membrane + bind to receptor inside the cell

   • lipid-insoluble → can’t go through, binds to receptors outside the cell

signal receptors → can be blocked, change shape and activity after binding to a hormone, dynamic

signal transduction (cascade - domino effect)

1. G-protein-coupled receptors → sends 2nd messengers

2. phosphorylation → adds a phosphate (gets 3 from ATP) → turning on a light switch

   • kinase → an enzyme that adds a phosphate

   • (phosphatase → opposite of kinase, removes a phosphate)

11.4 Unicellular Organisms Signaling

• based on changes in environment

• quorum sensing → signaling pathways, respond to population density

  • response varies across species

  • bacteria release molecules (species-specific) when #’s reach a certain threshold

Ex of quorum sensing responses: plaque on teeth, light-producing reactions, slime mold cells become a slug-like body

Ch 12: The Cell Cycle

start as embryos

Meiosis = prod reproductive cells → gametes (cells with ½ the amount of hereditary material)

Mitosis = prod other cells = somatic cells (Copied and divided equally between 2 cells)

• both use cytokinesis

replication steps

1. copy DNA

2. separate the copies

3. divide the cytoplasm → 2 complete cells

4 phases → G1, S, G2, M

G1 = growth, S = synthesis, G2 = growth, M = mitosis(division)

G1 + S + G2 = interphase

G1 → 4 unreplicated chromosomes

S → synthesis

G2 → 2 sister chromatids per each of the 4 replicated chromosomes

M → split, dividing

Gap phases allow cells to grow and organelles to replicate

chromosomes are double helix

homologous chromosomes → not exact copies but same types of genes, code for same genes but potentially different alleles, ex: both chromosomes have the eye color gene (but allele could be brown for one and blue for another), during S phase

sister chromatids → each one is the exact copy of each other, same, duplicated

centromere → each chromosome is attached here, middle part

cohesions → proteins that attach to each other

23 pairs of chromosomes in humans

XX- female, XY - male

can be abnormalities, ex: down syndrome has 3 pairs not 2 pairs of chromosome 21

M phase

1. Mitosis - division of the replicated chromosomes (split the chromatids)

2. cytokinesis - division of the cytoplasm

diploid → 2 copies of each homologous chromosome

Mitosis has 5 subphases

IPPMAT (interphase - not part of M phase - G1 + S + G2, prophase, prometaphase, metaphase, anaphase, telophase)

prophase → chromosomes condense, spindle apparatus forms = made of microtubules

prometaphase → nuclear envelope breaks down, microtubules attach to chromosomes at kinetochores (at the centromere)

metaphase → chromosomes are lined up in the middle

anaphase → sister chromatids are pulled apart by microtubules with motor proteins, shortens the distance bc tubulin is lost = pulls it back

telophase → 2 independent nuclei form

cytokinesis → cytoplasm divides

animals → actin, myosin rings pinch off, cleavage furrow

plants → don’t pinch off so easily = cell wall = cellulose = tough to break, vesicles fuse to form a cell plate

bacteria → split via binary fission

Control of the Cell Cycle

- variations in cell length based on cell types

- there are checks before moving onto the next phase (ex: enough cytoplasm, etc)

cyclin, cyclin-dependent kinase (Cdk) → fluctuates up and down(amounts)

Checkpoints:

• cells that divide without control → can form a tumor

  cancer = unregulated cell division

• G1 checkpoint → cell size is large enough, DNA undamaged

• G2 checkpoint → DNA undamaged, MPF present, chromosomes replicated correctly

• M checkpoint → MPF is absent, fully separated

p53 = a protein found in most cancer cells, its a tumor suppressor, if damaged = cell keeps replicating, G1 checkpoint

• apoptosis = programmed cell death

deletion = missing a chromosomal segment, G2 checkpoint

duplication = extra segment, G2 checkpoint

2 genes

• oncogenes → speed up growth, promote cancer, gas pedal of car

• tumor suppressor → slows down, not promote cancer, breaks of car

tumor types

• Benign → harmless, can remove

• Malignant → can spread to other parts of the body

Review of Everything so far

plants vs animal cells: plants are surrounded by cell walls → plasmodesmata allows for communication and nutrient distribution

integrins = integral membrane proteins, often attached to cytoskeletal proteins + ECM molecules

tight junctions = only found in epithelial cells that need to be watertight vs desmosomes = in a wide array of cells

hormones function as signal molecules

proteins in animal cells ECM → has fibronectin, fibrillin, collagen (not actin)

desmosomes primary function → bind animal cells together

gap junctions → coordinate activities of adjacent animal cells

mitosis = during M phase, shortest phase of the cell cycle

sister chromatids = 2 recently replicated DNA strands that are joined together by cell division

chromosomes become visible during prophase

prometaphase → mitotic spindle fibers attach to kinetochores (part of centromere)

during metaphase → chromoseomes are lined up in the middle of the cell, held by spindle fibers

anaphase → sister chromatids are pulled to opposite poles of cell

telophase → mitotic spindles disintegrates, new nuclear envelope forms

cytokinesis often (not always) accompanies telophase

Overview of all the phases

prophase

• spindle begins to form

• centrosomes begin to move apart

• chromosomes begin to condense - first visible with light microscope

prometaphase

• mitotic spindle is completed

• it penetrates the nuclear envelope (into fragments)

• centrosomes are on opposite sides of the nucleus

metaphase

• alignment of chromosomes along metaphase plate (in a ~line in the middle)

anaphase

• cell elongates

• 2 sister chromatids separate

telophase

• chromosomes reach the poles

• spindles disassembles

• chromosomes are less condensed

• new nuclear envelopes form

cytokinesis

• cytoplasm divides

• 2 separate daughter cells form

carcinogens = cause cancer:

cigarette smoke → lung cancer, bladder cancer, uterine cancer

UV light → skin cancer

fat → uterine cancer, prostate cancer, colon + rectum cancer, breast cancer

testosterone → prostate cancer

estrogen → uterine cancer, breast cancer

viruses → lymph nodes/lymphomas

tumor suppressors → prevent cell from enter S phase after DNA damage, regulatory

centrosome → microtubular organizing center, animal cells, all phases of the cell cycle, organizes microtubules, has centrioles, near cell nucleus in animal cells, related to the spindle apparatus

vs

centromere → center of chromosome that holds sister chromatids together