Unit 4 Cell Signaling

Ligand

Molecule that binds to a receptor protein bringing message and Initiates cell response

Receptor protein

Intra-Cellular: Inside of cell in cytoplasm

Extracellular: on the outside

Are ligand specific and cannot change shape

Signal Transduction

Process of which a cell receives a signal, changes to respond to the signal, and finally responds depending on what the signal is asking for

Reception

Ligand Binds to receptor protein to initiate signal transduction, transmits message into cell

Transduction

Message goes through the cell and and is modified for response

Response

Can be anything from cell growth to secretion of molecules or change in gene expression depending on message

Ex) Epinephrine is a response to increased stress in the body and cells and organs respond by increasing glucose levels to provide quick more energy

Signal Transduction pathways

Contact Communication

→ Animal cells gap junctions

• Ex) Immune system T-Cells interacting with antigen

→ Plant cells plasmodesmata

Local Signaling: Known as paracrine signaling

→ Ex) Neurotransmitters

Long Distance signaling: known as endocrine signaling

→ Ex) Insulin production and hormones

Negative Feedback loops

Returning body to original state

→ Blood sugar regulation

Positive feedback loops

Cascade effect amplifying signals

Ex) Childbirth

Cell Cycle

Stage of life, growth and development of cells

Interphase

Comprised of G, S, G0, and G2 stages

G1

Cell grows and functions like normal

G0

If cell fails G1 Checkpoint it goes into G0 where it can stay indefinitely or grow to go onto S phase

S

DNA Replication and creation of Centromeres or points of division on chromosomes

G2

Cell continues to grow and prepares for division

Mitosis

Cell replication
4 Stages

Prophase

Metaphase

Anaphase

Telophase

Results with 2 identical Diploid daughter cells

Cytokinesis

Splitting of cell’s cytoplasm

Prophase

Condensation of Chromatin into Chromosomes and disappearance of nucleic membrane

Metaphase

Chromosomes line up in the middle of the cell and spindle fibers (made from centrosomes and made with miotic spindle) attach to centromere (center of chromosomes)

Anaphase

Sister chromatids of chromosomes are pulled apart to opposite sides of the cell, each daughter cell will receive equal amount of chromatids

Telophase

Nucleic membrane forms around the new daughter cells

Nondisjunction

One daughter cell receives more sister chromatids than the other creating genetic issues for both cells, one is missing genetic information and the other has too many copies of it

Cyclin

Proteins that fluctuate in concentration across the cell and rise and fall at specific stages.

→ these proteins regulate the cell and its functions/growth

→ they bind to CDK’s and CDK’s phosphorylate target proteins involved in cell progression that control the cell cycle.