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def: a molecule that is present in very large amounts in the plasma membrane where it constitutes approximatly 20% of the lipids in the membrane by weight. (not sure what that means, actually. hrmmm)

info: cholesterol molecules are short and rigid, they fill in the spaces between neighboring phosphlipid molecules left by the kinks in the unsaturated tails. By filling in the space, cholesterol stiffins the bilayer, making it more rigid and less permiable.

Cell membrane fluidity

def: how flexible and fluid the cell membrane or lipid bilayer is.

what it does:

  • enables membrane proteins to diffuse rapidly in the plane of the bilayer and to intereact with one another (such as for cell signalling)
  • permits membrane lipids and proteins to diffuse from sites where they are inserted into the bilayer after thier synthesis to other regions of the cell.
  • it allows membranes to fuse with one another and mix their molecules

it ensures the membrane molecules are distributed evenly between daughter cells when a cell divides.

Cell Cortex

def: a mesh work of fibrous proteins. determines the shape of the cell and the mechanical properties of the plasma membrane.

Carbohydrate layer

def: a sugar coating (yum)

info: protects cell surface from mechanical and chemical damage. it absorbs water, making a slimy surface. (not yum) he slimy layer helps cells move through narrow spaces and stops cells from sticking to each other and the cell walls.


description: thread like substance found in the nucleus of the eucaryotic cell that are visible when the cell divides.

Contents: The contain both DNA and protein.

What Do:

  • A chromosome's most important job is to carry the genes
  • They fit readily inside the cell's nucleus but are also easily apportioned into two daughter cells in cell division.
  • There are different types of chromosomes and those found in eukaryotic cells are multiple in number
  • I.E. a male primate has an XY paired chromosome, while a female is homologous for the XX chromosome (in reptiles and birds, it's reversed: where males are homologous for ZZ and females are heterologous for ZW).

Cell cycle (chapter 5)

def: Reproductive cycle of the cell: the orderly sequence of events by which a cell duplicates its contents and divides in two.

What do:
The process of creating daughter cells from the original cell.


  • Resting (G0) Phase
  • Interphase (where the cell collects nutrients and prepares to separate)
  • G1 Phase ("growth phase")
  • S Phase (starts when DNA synthesis commences. At the end of this cycle, sister chromatids are formed)
  • G2 Phase (Protein synthesis occurs along with the production of microtubules in this phase)
  • Mitosis (prophase, metaphase, anaphase, telophase, cytokinesis)
  • (and then the cell goes back to the top of the list: G0 Phase)

Centromere (chapter 5)

def: Constricted region of a mitotic chromosome that holds sister chromatids together; also the site on the DNA where the kinetochore forms and then captures microtubules from the mitotic spindle.

What do:
It is a third specialized gene sequence that allows one copy of each chromosome to be placed in the newly formed daughter cells.

Chromatin (chapter 5)

def: Complex of DNA, histones and nonhistone proteins found in the nucleus of a eukaryotic cell. The material of which chromosomes are made.

What Do:
Uhmmmmm…..they make chromosomes. And are comprised of histones and nonhistones, as well as their respective nuclear DNA. ..I think the definitions says it all (plus, there doesn't seem to be much of a blurb in the book about it).

Chromatin-Remodeling Complex (chapter 5)

def: Enzyme (typically multi-subunit) that uses the energy of ATP hydrolysis to after histone-DNA interactions in eukaryotic chromosomes; the resulting alteration changes the accessibility of the underlying DNA to other proteins, including those involved in transcription.

Protein machines that use the energy of ATP hydrolysis to change the position of DNA.

think of it like this:
Michael Scott ("ATP hydrolysis") has taken over the warehouse again and stolen their forklift ("protein machine") in order to knock over a line up of shelves containing new Sabre printers and paper ("change the position of DNA").

BUT IT ALSO is not as destructive as Michael because, instead of just changing the position of the DNA, it can "loosen" the tightly bound DNA and allow other proteins access to the cell. So, very much unlike Michael, it is helpful to other proteins. (I'm sorry, Michael)

Complementary (chapter 5)

def: Describes two molecular surfaces that fit together closely and form noncovalent bonds with each other. Examples include complementary base pairs such as A&T, and the two complementary strands of a DNA molecule.

what do:
(in this case) A always pairs with T/U and C alwayspairs with G. This concept is of major importance when it comes to copying and repairing DNA.

think of it this way: If these base pairs did not pair together in this matter. Say, for example, Thymine decided it was sick of Adenine and they got into a fight and he moved out. Then later, he met Guanine who wanted to leave Cytosine but couldn't think of a way out of the relationship. In the end, Cytosine and Adenine hooked up while Thymine and Guanine decided to give it a try.

So now A is paired with C and T is paired with G.

This is a bad. Like, the whole universe explodes-kind of bad.

Because when the DNA strands get taken apart and copied in transcription, the copy of the strand will produce the wrong base pairing. And when translation comes through, instead of pairing A with C — as suggested above because A and C decided they were in love..blah,blah — you now have a copy of a DNA strand where Adenine is paired with..well…adenine. And you can't pair a base with itself! This isn't the South!

Another reason it's bad: messing with the base pairs can cause the wrong protein to be synthesized.

I hope that makes sense.

Ca2+/calmodulin-dependent protein kinase (CaM-kinase) (chapter 16)

def: Enzyme that phosphorylates target proteins in response to an increase in Ca2+ ion concentration, through its interaction with the Ca2+-binding protein calmodulin.

Calmodulin (chapter 16)

def: Small Ca2+ binding protein that modifies the activity of many target enzymes and membrane transport proteins in response to changes in Ca2+ concentration.

Cell signaling (chapter 16)

def: The molecular mechanisms by which cells detect and respond to external stimuli and send messages to other cells.

Think of it this way:
The cell signal is like an old school switch board operator (like Ms. Morgan's job here at good ol' UM), who has to detect the incoming messages as well as respond to them and send out the information where it is needed.

What Do:
There are 4 different types of stimuli: (A) Hormones produced can then enter the bloodstream and ride the circulatory system; (B) Paracrine signals are released by cells in the extracellular fluid and act locally; (C) Neural signals are transmitted along axons' and (D) Contact-dependent signaling relies on cell-surface-bound signal molecules to bind to a receptor protein of an adjacent cell.

please note that the crucial difference between these cell signals is in the speed and selectivity with which the signals are delivered to their targets.

Cyclic AMP (cAMP) (chapter 16)

def: nucleotide generated from ATP in response to hormonal stimulation of cell-surface receptors. cAMP acts as a signaling molecule by activating protein kinase A; it is hydrolyzed to AMP by a phosphodiesterase.

Cyclic AMP-dependent protein kinase (PKA) (chapter 16)

def: Enzyme that phosphorylates target proteins in response to a rise in intracellular cyclic AMP concentration.

Cytokine (chapter 16)

def: Small protein made and secreted by cells that acts on neighboring cells to alter their behavior. Cytokines act via cell surface cytokine receptors.

Clamp Loader (chapter 6)

what do: it hydrolizes ATP each time a clamp is locked around the DNA.

Centriole (chapter 17)

def: Short cylindrical array of microtubules, usually found in pairs at the center of a centrosome in animal cells. Also found at the base of cilia and flagella (also called basal bodies)

Centrosome (chapter 17)

def: Constricted region of a mitotic chromosome that holds sister chromatids together, also the site on the DNA where the kinetochore forms and then captures microtubules from the mitotic spindle.

Cilium (chapter 17)

def: hairlike extension on the surface of a cell with a core bundle of microtubules and capable of performing repeated beating movements. Cilia, in large numbers, drive the movement of fluid over epithelial sheets, as in the lungs.

Cytoskeleton (chapter 17)

def: System of protein filaments in the cytoplasm of a eukaryotic cell that gives the cell shape and the capacity for directed movement. Its most abundant components are actin filaments, microtubules and intermediate filaments.

Cytosol (chapter 15)

def: Contents of the main compartment of the cytoplasm, excluding membrane-enclosed organelles such as the ER and mitochondria. The cell fraction remaining after membranes, cytoskeletal components and other organelles have been removed.

What Do:
Creates further compartments (inside the internal membrane) within the cell that protect enzymes from outside interference with other enzymes in other compartments.

think of it this way:
You have a huge gated backyard. And I am talking huge like the size of a small island-kinda huge. So, to keep outside animals or people from wandering into your yard, you put up a gate (the "internal membrane"). But then you decide that the gate's lame and not pretty enough so you build an elaborate labyrinth. But you don't want, say, the Goblin King ah, David Bowie with all his spandex'd-pants interfering with the lives of the "everyday labyrinth wanderers[like Hoggle]" so you set up little compartments ("cytosol") that keep everyone separated and shoved into cubicles.

Clathrin (chapter 15)

def: Protein that makes up the coat of one type of transport vesicle. Clathrin-coated vesicles bud from the Golgi Apparatus on the outward secretory pathway and bud from the plasma membrane on the inward endocytic pathway.

What do:
Basically, clathrin-coated vesicles form on the Golgi. Small GTP-binding proteins called dynamins now assemble a ring around the coated vesicles. With the proteins recruited at the neck of the vesicle, the dynamin causes the ring to constrict and pinch off a vesicle from the membrane.

it's good to note Clathrin itself plays no part in the capturing of molecules for transport. (ie. it does none of the rounding up, but still expects them to show up and be transported. It's like a subway)

Coated Vesicle (chapter 15)

def: Small membrane-enclosed organelle with a cage of proteins (the coat) on its cytosolic surface. It is formed by the pinching off of a protein-coated region of a membrane.

What Do:
It doesn't really do anything. It's just a vesicle with a jacket.

Codon (chapter 7)

def: Sequence of three nucleotides in a DNA or messenger RNA molecule that represents the instruction for incorporation of a specific amino acid into a growing polypeptide chain.

Combinatorial Control (chapter 8)

def: Describes the way in which groups of proteins work together in combination to control the expression of a single gene.

Complementary DNA (cDNA) (chapter 10)

def: DNA molecule made as a copy of mRNA and therefore lacking the introns that are present in the genomic DNA. Used to determine the amino acid sequence of a protein by DNA sequencing or to make the protein in large quantities by cloning followed by expression.

Capase (chapter 18)

def: A family of proteases. Members of the family are activated as a part of the pathway leading to apoptosis.

Cyclin-dependent protein kinase (Cdk) (chapter 18)

def: Protein kinase that has to be compelxed with a cyclin protein in order to act. Different Cdk-cyclin complexes trigger different steps in the cell division cycle by phosphorylating specific target proteins.

Cdk Inhibitor Protein (chapter 18)

def: Protein that inhibits cyclin-Cdk complexes, primarily to inhibit progress through the G1 and S phases of the cell cycle.

Cell Cycle (chapter 18)

def: Reproductive cycle of the cell: the orderly sequence of events by which a cell duplicates its contents and divides into two.

Cell-cycle Control System (chapter 18)

def: Network of regulatory proteins that governs progression of a eukaryotic cell through the cell cycle.

Centrosome (chapter 18)

def: Centrally located organelle of animal cells that is the primary microtubule-organizing center and separates to form the two spindle poles during mitosis. In most animal cells it contains a number of centrioles.

Centrosome Cycle (chapter 18)

def: Duplication of the centrosome (during interphase) and separation of the two new centrosomes (at the beginning of mitosis), to form the poles of the mitotic spindle.

Checkpoint (chapter 18)

def: Point in the eukaryotic cell-division cycle where progress through the cycle can be halted until conditions are suitable for the cell to proceed to the next stage.

Chromosome Condensation (chapter 18)

def: Process by which a chromosome becomes packed into a more compact structure prior to M phase of the cell cycle.

Cohesion (chapter 18)

def: Protein complex that forms a ring that holds sister chromatids together after DNA has been replicated in the cell cycle.

Condensin (chapter 18)

def: Protein complexes with a ring-like structure that help carry out chromosome condensation.

Cyclin (chapter 18)

def: Protein that periodically rises and falls in concentration in step with the eukaryotic cell cyle. Cyclins activate specific protein kinases (ie. Cdk) and thereby help control progression from one stage of the cell cycle to the next.

Cytokinesis (chapter 18)

def: Division of the cytoplasm of a plant or animal cell into two, as a distinct from the division of its nucleus (which is mitosis).

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