exam 3 bsc 114 daryl lam

cell communication

one cell, or group of cells, releases a chemical signal that is received by and changes the behavior of another cell, or group of cells

local signaling

substances that are secreted from one cell and then influence cells in the vicinity

paracrine signaling

- type of local signaling

- signaling and target cells are very close

- signals are called growth factors, cytokines, etc.

synaptic signaling

- type of local signaling

- signal from nerve to another nerve, muscle, organ, etc.

- signals are neurotransmitters

- similar in mechanism to paracrine

long-distance signaling

signaling between cells separated by some distance (exocrine (through the blood))

reception (cell communication)

a signaling molecule binds to receptors on target cell(s) causing it to change shape

- binding is specific for signal, and binding matches shape of signal with weak bonds (hydrogen, ionic, van der waals)

- 2 types (membrane and intracellular)

ligand

a molecule that binds specifically to another molecule, usually a larger one

membrane receptors

integral membrane proteins with a ligand-binding site on the outside surface

intracellular receptors

receptors located inside the cell rather than on its cell membrane (so cytoplasmic)

signal transduction

intermediate steps between cellular reception and cellular response

- usually amplifies the signal to give a robust response

signal transduction- protein phosphorylation and dephosphorylation

activated protein, activates other proteins, activates other proteins, etc. after a few or many steps, cellular response is activated

phosphorylation cascade

a series of enzyme-catalyzed phosphorylation reactions commonly used in signal transduction pathways to amplify and convey a signal inward from the plasma membrane.

kinase

an enzyme that adds a phosphate group to another molecule

protein kinase

adds a phosphate group to a protein

phosphorylation

act of attaching a phosphate group

phosphatases

enzymes that remove phosphate groups

protein phosphatases

enzymes that remove phosphate groups from a protein

where does cellular response take place

in nucleus, cytoplasm, or combos of both

apoptosis

the response of a cell to signaling is to die

epinephrine signaling

Causes liver cells to break down glycogen into glucose and send the glucose into the blood stream

tissue

collection of cells that work together to perform a specific function

organ

two or more tissues combined and functioned together

cytoskeleton

provides internal structural support and enables movement of substances within the cell

how is the cytoskeleton formed

formed from long chains of protein subunits joined together

microtubule

a hollow tube formed from tubulin dimers

microfilaments

a double helix of actin monomers (the thinnest of the cytoskeletal structures)

- extremely branched and found just below the cell membrane

microfilament function

help reinforce and organize the proteins associated with the cell membrane

- transport of materials inside cells

- shortening of muscle cells during contraction

- separation of daughter cells at the end of animal cell division

microtubule/microfiliment growth

occurs more quickly at the plus ends

- microtubules are positioned near the centrosome and plus ends projecting toward the cell membrane

- microtubules are important for cell division and can go through rapid cycles of shortening followed by slower growth

intermediate filaments

provide mechanical strength to the cell

- made up of different proteins depending on the cell type

subunit of microfilaments

actin monomers

subunit of intermediate filaments

diverse (changes)

subunit of microtubules

tubulin dimers

microfilaments major functions

- cell shape and support

- cell movement

- cell division

- vesicle transport

- muscle contraction

intermediate filaments major functions

cell shape and support

microtubules major functions

- cell shape and support

- cell movement

- cell division

- vesicle transport

- organelle arrangement

integrins

provide a way for cells to attach to the extracellular matrix (important for structural integrity of tissues under physical stress)

cell junctions

connect cells to other cells or to the basal lamina and are reinforced by the cytoskeleton

five types of cell junctions

adherens, desmosomes, hemidesmosomes, tight, gap

gap junctions

allow two cells to communicate through joined rings of integral membrane proteins

plasmodesmata

communication channels that can cross the cell wall of plant cells because the cell membranes of the plants are continuous

basal lamina

provides support for epithelial tissues (collagen in the basal lamina provides flexibility to the tissue and scaffolding for other proteins to associate with it)

dna synthesis

two strands seperate and each strand acts as the template for synthesis of the complementary strand

where does addition occur in dna synthesis

only at the 3' end of the growing strand (!!!!!!)

dna synthesis: replication fork

@ the replication fork:

- dna must be unwound by helicase

- topoisomerase relieves overwinding strain

- single-strand binding proteins keep strands from re-pairing

dna synthesis: rna primers

- made by the enzyme primase

- starts when a single rna nucleotide is added complementary to the dna template strand

- additional rna nucleotides added one at a time

dna polymerase

adds dna nucleotides to the 3' end of the rna primer (when dna polymerase hits a rna primer it removes rna nucleotdies and replaces then with the correct dna nucleotides)

proofreads

if incorrect base is inserted dna polymerase backs up and cuts it out

difference between leading and lagging strand

- leading- strand being copied from the 5'-3' end continuously away from the replication fork

- lagging- strand being copied in a series of segments towards the replication fork

when does dna replication occur

during the S phase of the cell cycle

dna repair: excision

a nuclease recognizes and removes the mispaired region

dna ligase

seals the free ends

telomere

end of a chromosome

telomerase

linear chromosomes get shorter with each replication, but the enzyme telomerase elongates them

chromatin

combination of dna and proteins

histones

small basic proteins

nucleosome

complex of eight histone proteins

why is cell division important

we are what we are because of cell division; to generate the large number of cells in the body, and to replenish cells that die or turn over

asexual reproduction

each new cell is a new individual

genome

genetic information in a cell

chromosome structure

when a cell is not dividing, each chromosome is in a long, thin chromatin fiber

centromere

region of the chromosome where the two sister chromatids are most closely attached (generally located in the middle of the chromosome)

cohesions

protein complexes that hold sister chromatids together

centrosomes

organize microtubules of spindle apparatus

kinetochore

protein structure on chromatids where spindle microtubules attach, located at the centromere region

cell cycle

regular sequence of cell growth and division

mitosis

division of the genetic material

cytokinesis

division of the cytoplasm; organelles

what phases are in the interphase of the cell cycle

G1, S phase, G2

what phases are in the m phase of the cell cycle

mitosis (and its phases), cytokinesis

g1 phase: what happens

basically just growing, organelles are synthesizing proteins and producing energy, longest phase of the cell cycle

s phase: what happens

synthesis: makes an exact copy of dna via replication

g2 phase: what happens

still growing and preparing to split (specifically making enough organelles for two cells for the split)

phases of mitosis (in order)

prophase, prometaphase, metaphase, anaphase, telophase

prophase

chromosomes condense

- nucleolus disappears

- still has nuclear envelope

- centrosomes split and move to each side of nucleus

- mitotic spindle forms (spindle fibers made of microtubules connect centrosomes)

prometaphase

nuclear envelope breaks apart

- chromosome condensation complete

- microtubules of the spindle now invade the nucleus and interact with the chromosomes

- centrosomes on opposite sides of nucleus

metaphase

chromosomes line the metaphase plate (the middle)

- each kinetochore from sister chromatids is attached to kinetochore microtubules from the opposite pole

- chromosomes are still 2 chromatids

anaphase

sister chromatids separate and travel to opposite poles

- cohesion protein cleaved by the enzyme separase

- at the end of anaphase, the two poles of the cell have equivalent and complete collections of chromosomes

telophase

2 daughter nuclei form (nuclear envelope re-froms and chromosomes decondense)

- daughter nuclei are genetically identical

how do the cell split in cytokinesis (animal cells)

a cleavage furrow forms, pinching the cytoplasm (actin microfilaments and myosin)

binary fission

type of asexual reproduction in which an organism replicates its dna and divides in half, producing two identical daughter cells

how do cells know when to stop dividing

Cells regulate their division by communicating with each other using chemical signals from special proteins called cyclins when they get too close to each other

checkpoints in the cell cycle

there are multiple checkpoints throughout the cell cycle that would pause it if it found the dna to be damaged or something else to be wrong

cancer

loss of cellular control mechanisms (they are not regulated and just grow/divide grow/divide etc.)

when cells communicate by the signaling process, one cell produces a ______ that must be recieved by the _______ on or in the responding cell

signaling molecule; signal receptor

a receptor that is inside the cell would require a ________ signal molecule that can ________ the plasma membrane

nonpolar; pass through

a _______ expresses a gene or genes that direct the production of the signaling molecule, and the _______ expresses a gene or genes that direct the production of the _______

signaling cell; responding cell; receptor protein

the types of cellular communication from shortest to longest distance traveled by the signaling molecule to reach its responding cell

autocrine, paracrine, endocrine

what signaling molecule would you expect must travel the longest distance from a signaling cell to a responding cell

testosterone (chemical signal with multiple targets throughout the body)

growth factors such as platelet-derived growth factor (pdgf), when trageting adjacent cells to induce proliferation

paracrine signaling

the basal lamina is

a specialized form of the extracellular matrix found beneath all epithelial tissues

how does an adherens junction differ from a desmosome

whereas both adherens junctions and desmosomes connect cells using cadherin proteins, adherens junctions connect to microfilaments in the cytoplasm and desmosomes connect to intermediate filaments

components found in the extracellular matrix

collagen, laminim, and elastin

the extracellular matrix is

a network of proteins and polysaccharides outside the cell that plays a role in structural support

motor proteins cause movement by

binding to the cytoskeleton, undergoing a conformational change, harnessing energy from atp

cell movement can be facilitated by microfilaments in what way

by dynamic growing and shrinking at the ends

what is the first thing to occur in dna replication

the strands of the dna double helix and seperated

which of the strands uses a template for dna replication

both strands use a template during replication

on which strand are new nucleotides being added continuously in the same direction as the replication form is opening

the leading strand

on which strand is dna synthesis discontinuous, occuring in fragments that are later connected

the lagging strand

a cell that is not actively dividing is in what phase of the cell cycle

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