AP Bio Unit 4 - Cellular Communication

Animal Cells Communicate by

Direct contact, secreting local regulators, long distance

Direct contact

gap junctions

Secreting local regulators

Growth factors, neurotransmitters

Long distance

hormones

3 stages of cell signaling

reception, transduction, response

Reception

Detection of a signal molecule (ligand) coming from outside the cell

Transduction

Convert signal to a form that can bring about a cellular response

Response

specific cellular response to the signal molecule

Types of receptors

Plasma membrane receptor, intracellular

Plasma membrane receptor

Water soluble ligands (polar)

Intracellular receptors

Small or hydrophobic ligand molecules, Eg. Testonsterone or nitric oxide (N O). Ligand bonds to protein

3 plasma membrane receptor systems

G-protein-coupled Receptor (GPCR), Receptor Tyrosine Kinase, Ligand-gated Ion channel

Cascades of molecular instructions…

relay signals from receptors to target molecules

Protein kinase

enzymes that phosphorylates and activates proteins at next level

Phosphorylated cascades

enhance and amplify signal

Charge gradient

Neuron membrane is polarized, negative inside, positive outside

Open Na+ channels

Na+ diffuse into cell

signal

action potential

Synapse-between neurons

Switch from electrical to chemical signal

Release neurotransmitters

Binds with protein receptor, quickly degraded

Homeostasis

Keeping balance

Animals rely on 2 systems for regulation

Endocrine system, nervous system

Endocrine system

Glands secrete chemical signals, slow, long-lasting response

Nervous system

Neurons transmit “electrical” signal, fast, short-lasting response

Typically lipids

nonpolar, can go through phospholipid bilayer, simple diffusion

Metabolism

Digestion, processing glucose

Solute levels in blood

Potassium, sodium, chloride ions

Types of feedback

Negative feedback, positive

Negative feedback

changing conditions back to target set point, most common

Positive feedback

Amplify response, very few examples (childbirth, uterine connections).

Prophase

Visible chromosomes, centrioles at poles, nucleus breaks down

Anaphase

Chromatids separate at kinetochores

Telephase

Chromosomes arrive at opposite poles, daughter nuclei form

Metaphase

Chromosomes in middle

Cytokinesis

Animals - cleavage furrow forms. Plants - cell plate forms, new cell wall

Chromosome

How DNA is organized, double helix DNA wrapped around histone proteins

Interphase

90% of the cell cycle - G1, S, G2. The cell doing its “everyday job”

Prophase

Visible chromosomes, centrioles at the poles, nucleus breaks down

Anaphase

Chromatids separate at kinetochores

telephase

Chromosomes arrive at opposite poles, the daughter nuclei forms.

Metaphase

Chromosomes in the middle

Cytokinesis

Animals - cleavage furrow forms. Plants - cell plate forms (new cell wall).

CHromosome

How DNA is organized. Double helix DNA wrapped around histone proteins.

CHromatin

DNA and protein together. Appears as threads on microscope - long thin fiber

Homologous chromosomes

One from each parent, same “genes” on them. Come in pairs (one from mom, one from dad)

Sister chromatids

Contain identical copies of original DNA

Centromere

narrow part in the middle where they’re connected

Why do cells divide

Reproduction, repair (or renewal), growth

Cell growth

from fertillized egg to multi-celled organism

Cell reproduction

Asexual reproduction, one celled organism

Cell repair and renewal

Replace cells that die from normal wear and tear or from injury.

In interphase, the nucleus is

Well-defined, with DNA loosely packed in long chromatin fibers

G1

1st gap (growth) - the cell grows larger, creating new proteins and organelles

S

Synthesis - when the cell replicates DNA, creating two identical sister chromatids

G2

2nd Gap (growth) - the cell continues to grow, producing more proteins and making sure the cell is ready for mitosis

Centrioles

In animal cells - a pair of centrioles organize spindle fibers made of microtubules

Evolution of mitosis

Evolved from Binary fission in bacteria. A single chromosome replicates, the cell pinches in two

Frequency of cell division in mature nerve cells

No division, permanently in G0

G0

Cell that has moved out of the cycle completely or non dividing cell

Checkpoint control system

Cell cycle controlled by STOP and GO chemical signals at critical points. Check to see if everything has performed normally

Checkpoint locations

G1 checkpoint, M checkpoint, G2 checkpoint

What do cell cycle signals control

Cyclins and Cdks

Cyclins and Cdks

Regulatory proteins (cyclins), build up until they reach a certain amount and are ready to move on (like an hourglass)

Cdks

Cyclin-Dependent Kinase - partner with cyclin to control transitions between phases by phosphorylating target proteins.

Development of cancer

unlimited growth/divisions, ignore checkpoints, escape apoptosis, promotes blood cell growth, overcome anchor and density dependence.

Apoptosis

Cellular suicide genes

What causes hits

Mutation in cells by - UV rays or radiation, chemical exposure, radiation exposure, age, pollution, genetics, heat

Tumors

Mass of abnormal cells

benign tumor

abnormal cells remain at original site

malignant tumor

cells leaving site

Metastasis

Start more tumors or the spread of tumors

Treatments for cancer

Target rapidly dividing cells - immunotherapy, high energy radiation, chemotherapy

High energy radiation

kills rapidly dividing cells

Chemotherapy

stop DNA replication, stop mitosis and cytokinesis

Secondary messengers

molecules that relay signals from receptors to target molecules within the cell, acting as internal signal transducers