Unit 4 Cell Communication

Reception

cells have proteins on the cell membrane that bind to specific signaling molecules

ligand

signaling molecules in cell communication, binds to receptors

Transduction

causes intracellular portion of the receptor to change shape and send a signal in the cell

Cellular response

cell responds in some way

Gap junctions

connect between animal cells when they touch, allowing substances to pass back and forth

local regulator

secretes molecules through exocytosis so local cells can pick it up and respond

hormones

long distance signaling molecules, travels through blood stream to signal different glands in the body, a cell will respond only if they have the right receptor for it

Intracellular receptor

nonpolar ligands diffuse into cells and bind to regulators

G coupled receptor

g proteins are activated by ATP, causing them to transfer a signal from a receptor on the cell membrane to an enzyme somewhere else on the membrane. The binding of the g protein to the enzyme causes a cellular response.

Ion channel receptor

Channel proteins are opened by ligands, causing ions to enter the cell and cause a cellular response.

multiple protein pathways amplify the signal

As a signal is passed during transduction what happens?

phosphorilation

adds phosphate to protein, changing shape

protein kinase

phosphorylates proteins

cross talk

two signals cross and alter each other.

One signal results in one response

One signal results in multiple responses

Two signals combine to make one response

Three ways signals can go through transduction

Apoptosis

Programmed or controlled cell suicide, prevents enzymes from leaking out of a dying cell and damaging neighboring cells. Used to prevent mutated cells from dividing and creating tumors.

Caspases

enzymes that cut up proteins that carry out apoptosis

extracellular death-signaling ligand

DNA damage in nucleus

protein misfolding in endoplasmic reticulum

Apoptosis is triggered by…

Endocrine and nervous system

control and coordination in the body depend on what?

endocrine system

transmits chemical signals to receptive cells throughout the body via blood.

homeostasis

steady state/internal balance regardless of external environment

body temperature, blood pH, and glucose concentration

things in humans that are kept at a constant state

set point

“normal” state that a variable in the body is in.

negative feedback

helps return variables to their set point

positive feedback

moves body away from set point

Mitosis

allows for production of offspring for unicellular organisms (asexual reproduction)

Genome

all DNA in a cell

Chromosomes

packaged DNA, humans have 46 (two sets)

Gametes

reproductive cells (sperm and egg), contains half the chromosomes of other cells

Cell cycle

stages a cell goes through to grow and in some cases divide

interphase

G1, S, and G2 phases of the cell cycle

G1 phase

Phase when the cell grows after division

S phase

Phase when the cell replicates its DNA in preparation for division

G2 phase

Phase when the cell makes final preparations for division

M phase

Mitosis, final stage of the cell cycle

Cytokinesis

occurs after mitosis, final separation of daughter cells

G0 phase

Phase the cell goes into if it stops dividing.

Cell cycle checkpoints

3 signals that regulate the cell cycle

G1 checkpoint

Checkpoint that determines whether cell will divide or enter G0 phase

G2 checkpoint

checkpoint after G2 phase that checks to make sure everything is ready for mitosis

M checkpoint

checkpoint after Mitosis before cytokinesis

Cyclin+cdk (cyclin dependent kinase)=MPF (Mitosis promoting factor)

When enough Cyclin is built up from cell growth, it combines with cdk to make MPF, signaling Mitosis to start.

Breaks down the nucleus for mitosis

What does MPF do?

To stop the nucleus from being broken down when mitosis done

Why does cyclin break down after mitosis?

Growth factor

protein released by certain body cells that stimulates other cells to divide

Density dependent inhibition

cells proliferate until they don’t have enough growth factor or nutrients available for cells to reproduce. Basically, when cells are surrounded on all sides, they stop dividing, regulating cell division.

Anchorage dependence

animal cells must be anchored to reproduce (must be in contact with a specific tissue). Regulates cell division.

Oncogenes

Genes involved in the speeding up of the cell cycle. Mutations to these genes can cause cell division to speed up too much or cease to be controlled. These mutations are required for a cell to become cancerous.

Tumor suppressor genes

Genes that prevent the cell cycle from speeding up. Mutations to this gene are required for a cell to become cancerous. Ex: apoptotic genes

mutations speeds up cell division

mutations prevents cell division

2 types of cancerous mutations

Immortal

What is a cancer cell referred to as because they can always divide as long as nutrients are available?

Transformation

normal cells turning into cancer cells from about 5-7 mutations

Cancer cells

Cells that don’t respond to attempts to control cell growth and often don’t stop at checkpoints.

DNA repair genes

Genes that fix mutated DNA unless mutated themselves.