BIO-110 Quiz 6 Flashcards

Unicellular organisms

sense environment around them, there are other cells to cooperate or compete w/ nearby

multicellular organisms

cell-cell interactions are the basis for developing specialized tissues that must interact in coordinated ways for the organism to benefit

how do cells mostly in multicellular organisms secrete macromolecules into the extracellular environment?

thru exocytosis

why do we need rigid structural support

to help maintain the shape of the tissue

why do we need cushiony support

to pad around individual cells

how do animal cells make extracellular matrix

by secreting components

What is the rigid component of the ECM composed of?

collagen fibrils

What is the cushiony component of the ECM composed of?

proteoglycan complexes

how do collagen fibrils form

by collagen proteins combining

what does each collagen protein consist of

3 polypeptide chains which wind around each other to form fibrous component of animal ECM

collagen proteins are…

• trimeric (3 polypeptide subunits) and wind together to form a long strand

• then associate with each other into a bundle (the fibril)

what are proteoglycan complexes?

huge groupings of proteins w/ many carbohydrates attached

what forms the ground substance of the animal ECM

complexes of gelatinous proteoglycans

what are individual proteoglycans composed of

a protein backbone w/ many short carb chains attached

cell walls provide what

the rigid support in plants + fungi

what do carbs provide

the cushion

what are cell walls made of

cellulose (plants) or chitin (fungi)

the pectin acts as a cushion that

separates the cell wall and the plasma membrane + solidifies the lamella between neighboring cell walls

how are plant cell walls formed?

by cellulose fibrils (like collagen fibrils but less flexible

what happens when plants stop growing

they make a secondary cell wall in between the original cell wall and the plasma membrane

what does the secondary cell wall contain

other molecules like waxes (waterproofs leaves) or lignin proteins (adds structure to woody plants)

what do animal cells use to interact and communicate w/ each other

proteins embedded in the plasma membrane

what are desmosomes

plaques of proteins in plasma membrane of two neighboring cells

what happens when desmosomes associate w/ each other

they firmly attach the cells together

what are tight junctions

proteins arranged in a line in the membranes of neighboring cells

what happens when tight junctions associate?

they sew the membranes very close together to form a watertight seal

what are gap junctions?

• plaques of proteins that have many small channels running thru them that connect the cytoplasm of neighboring cells

• this allows them to communicate by sending small molecules thru

what are the large gaps in the cell wall of plant cells called

plasmodesmata

what can neighboring cells in the plasmodesmata do

they can share plasma membrane and can send even large molecules from one cell to the other

tight junctions

seals cells together

desmosomes do what?

connects the cytoskeletons of cells

gap junctions

act as channels between cells

what do desmosomes provide

a strong structural attachment point between cells

what do desmosomes consist of

• transmembrane cadherin proteins that associate w/each other to attach two cells

• as well as a scaffold of anchoring proteins on both intracellular sides

what does the scaffold provide

an attachment point for the actin cytoskeleton, which firmly anchors the desmosome in place

what do tight junctions do

form a seal in the extracellular space to prevent the diffusion of molecules

what are tight junctions used to do

create a barrier between two cells which seals the opposite sides from each other

what do the tight junctions help to determine

what can enter or leave whole tissues or organs

what do gap junctions allow

allows neighbors to send signals to one another w/ small molecules

what do gap junctions create

pores between neighboring cells so small molecules can selectively diffuse directly thru into the neighbor’s cytoplasm

what do these pores in the gap junctions do

allows the sharing of important signals carried by messengers (like ions)

gap junctions can electrically synchronize…

neighboring cells

plasmodesmata are…

large enough for plant cells to share large stuff

what is plasmodesmata

large channels between neighboring plant cells that pass thru holes in the cell wall and are large enough for bulk sharing of cytoplasm

neighboring cells share..

endoplasmic reticulum

what are the benefits of neighboring cells sharing endoplasmic reticulum

saves energy not having to send molecules across a membrane

what are the cons of neighboring cells sharing endoplasmic reticulum

restricts how autonomously neighboring cells can act

what does communication between distant cells require

• a signal molecule to be released from one cell

• a receptor molecule on the distant cell (to detect the signal)

• some mechanism to transport the signal

receptors are almost always…

proteins specialized for the task

some signal-receptor complexes cause what

changes to a cell directly (like turning a gene off or on)

what should the signal-receptor complexes must be able to do

to cross the plasma membrane

the signal-receptor complexes also has to

be transduced (it is how the cell will respond to effect changes, based on what signal it got)

signal transduction is mediated by

second messenger molecules that get produced inside target cells as a result of the signal binding to the receptor

lipid-soluble signals can do what

they can directly cross a cell’s plasma membrane

what can the signal-receptor complex do if there is an appropriate protein receptor

it can directly alter the physiology (functioning) of the cell

most signals are not able to do what

directly cross the membrane

how do these signals then cross the membrane?

• they bind to the extracellular domain of a protein receptor embedded in the membrane

• from this the intracellular domain of the receptor protein is activated

what two types of enzymes might the receptor protein be

• enzyme that catalyzes the creation and release of second messengers

• enzyme that activates another molecule

what are some 2nd messengers created by

the activated transduction pathway

what can ATP be converted into

the second messenger cyclic AMP (cAMP)

2nd messengers can also be released from

intracellular stores

2nd messengers are

intracellular amplifiers of the first messengers (extracellular) signal

2nd messengers often cause

multiple responses at multiple levels of cellular function

what are the levels of cellular function

• gene transcription

• mRNA translation

• protein activation

gene transcription

slower, longer-term

protein activation

quick, short-term changes

signaling pathways do not exist in

isolation within a cell

a cell fine-tunes its function based on what

whatever signals its receiving at a given moment in time

what is cell division

any process where 1 parent cell splits into 2 daughter cells

growth

multicellular organisms don’t start life at full size

repair or replace

damaged tissue often requires new cells to become functional again, worn out cells must be replaced

reproduction

single celled organisms reproduce by dividing

multicellular organisms need to make new cells to pass on genetic information and reproduce

mitosis

one eukaryotic parent cell gives rise to two clone daughter cells

what is mitosis used for in unicellular organisms

asexual reproduction for unicellular organisms

what is mitosis used for in multicellular organisms

used to grow and replace in multicellular organisms

meiosis

one parent cell gives rise to four daughter cells w/ half normal genetic material

what is meiosis used for

for sexual reproduction in multicellular organisms

binary fission

similar to mitosis, but for prokaryotes

what is binary fission used for

asexual reproduction

what is the most important part of mitosis

replication of genome

why do u have to copy cytoplasm and not only genome in mitosis

because it would be too small

G1 (1st gap phase)

the cell performs its normal functions while gathering nutrients to grow, make organelles, etc

S (synthesis phase)

the cell duplicates its genome

G2 (2nd gap phase)

the cell performs its normal functions while gathering nutrients to grow, make organelles, etc

M phase (mitosis)

the cell divides into two

G0 (not in cell cycle)

mature cells that have no need to divide exit the cell cycle into G0

what is the only phase chromosomes become visible in

m phase

when can u not use chromosome term

if it hasn’t been condensed (then u use chromatin)

interphase includes

G1,S, G2

what happens in interphase

4 replicated chromosomes, each consisting of two sister chromatids

what happens during mitosis

one eukaryotic parent cell gives rise to two clone daughter cells

why do we need to separate the sister chromatids

so that each daughter cell gets 1 copy of each chromosome

what are chromosomes and their cloned copy held together by

a protein scaffold

why do chromosomes condense as tightly as possible

it makes organizing and moving them much easier

when do replicated chromosomes condense

at the start of mitosis

what is eukaryotic DNA organized into

chromosomes

chromatid

refers to a single copy of the duplicated strand

what are the two copies of chromatid referred to

sister chromatids

what is the complex protein which holds together the sister chromatids of a condensed chromosome called

the centromere

how many chromosomes do human somatic cells have

46 chromosomes from 23 pairs