AP BIO CELLULAR RESPONSE LOCK IN

Animal cells communicate by

• Direct contact (gap junctions)

• Secreting local regulators (growth factors, neurotransmitters)

• long distance (hormones)

3 stages of cell signaling

1. reception

2. transduction

3. response

reception

detection of signal molecule (ligan) 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

Reception (image)

Transduction (image)

Response (image)

Reception: Binding between ___ ___ (ligand) + ____ is ____ _____

signal molecule; receptor; highly specific

Types of receptors

1. plasma membrane receptor (water soluble ligands)

2. Intracellular receptors (cytoplasm, nucleus)
   - small or hydrophobic ligan molecules
   - ex: testosterone or nitric oxygen

Reception steps

Ligand binds to receptor protein → protein changes shape → initiates transduction signal

G-Protein-Coupled Receptor (image)

G-Protein Coupled Receptor (image #2)

Receptor Tyrosine Kinase (image)

Ligand-Gated Ion Channel (image)

G-Protein-Coupled Receptor

7 transmembrane segments in membrane. G protein + GTP activates enzyme → cell response

Tyrosine Kinase

Attaches (P) to tyrosine. activate multiple cellular responses at once.

Plasma Membrane Receptors

Signal on receptor changes shape. Regulate flow of specific ions (Ca2+, Na+)

Transduction

• cascades

• protein kinase

• phosphorylation cascade

Cascades

cascades of molecular interactions relay signals from receptors → target molecules

Protein Kinase

enzyme that phosphorylates and activates proteins at next level

Phosphorylation cascade

enhance and amplify signal

Second messengers

• small, nonprotein molecules/ions that can relay signal inside cell

• ex: cyclic AMP (cAMP), calcium ions (CA2+), inositol triphosphate (IP3)

cAMP

• cyclic adenosine monophosphate

• GPCR → adenylyl cyclase (convert ATP → cAMP → activate protein kinase A)

Response

• regulate protein synthesis by turning on/off genes in nucleus (gene expression)

• regulate activity of proteins in cytoplasm

examples of signal transduction pathway problems/defects

• diabetes

• cholera

• autoimmune disease

• cancer

• neurotoxins, poisons, pesticides

• drugs (anesthetics, blood pressure meds)

Cholera

• disease acquired by drinking contaminated water )human feces)

• bacteria: vibrio cholerae

• bacteria colonizes lining of small intestine and produces toxin

• toxin modifies g protein

• g protein stuck in active form

• diarrhea

Apoptosis

• cell suicide

• triggered by signals that activate cascade of suicide proteins (caspase)

• protects neighboring cells from damage

• animal development and maintenance

• may be involved in diseases like alzheimer’s

Cell cycle

life of a cell from its formation until it divides into two cells

Functions of cell division

reproduction, growth, and tissue repair

Genome

all of a cell’s genetic info (DNA)

prokaryote

single, circular chromosome

Eukaryote

more than one linear chromosomes

Human chromosome #

46

each chromosome must be ____ before cell division

duplicated (replicated)

Duplicated chromosomes

2 sister chromatids attached by a centromere

somatic cells

• body cells

• diploid (2n): 2 of each type of chromosome

• divide by mitosis

• Humans: 2n=46

Gametes

• sex cells (sperm/egg)

• Haploid (n): 1 of each type of chromosome

• formed in meiosis

• humans: n=23

the ____ phase alternates with ____

mitotic; interphase

cell cycle phsaes

G1 → S → G2 → mitosis → cytokinesis

Interphase makes up __% of the cell cycle

90

G1 Phase

cell grows and carries out normal functions

S Phase

duplicates chromosomes (DNA replication)

G2 phase

prepares for cell division, organelles copy

M phase (mitotic)

Mitosis + cytokinesis

Mitosis

nucleus divides

cytokinesis

cytoplasm divides

Mitosis phases

Prophase → metaphase → anaphase → telophase

prophase

the nuclear envelope begins to disappear, DNA coils into visible chromosomes, and fibers begin to move double chromosomes towards the center.

metaphase

Fibers align double chromosomes across the center of the cell

anaphase

Fibers separate double chromosomes into single chromosomes (chromatids). chromosomes separate at the centromere. migrate to opposite ends.

telophase

The nuclear envelope reappears and establishes two separate nuclei. each nucleus contains a complete genome. chromosomes will begin to uncoil.

Prophase (image)

metaphase (image)

Anaphase (image)

Telophase and Cytokinesis

Cytokinesis

cytoplasm of cell divided

Animal cells cytokinesis

pinch at the cleavage furrow

Plant cells cytokinesis

cell plate forms and cuts cells apart

chromosomes are walked to poles by ____ during anaphase

motor proteins

Kinetochore microtubules shorten at ends as they ______

depolymerize

bacteria cells divide by ________

binary fission

other types of asexual reproduction used by other organisms

• budding - yeast

• sporation - mushrooms

• regeneration - lizard, starfish

• tubers - potatoes

• runners - strawberries

• bulb - onions or tulips

• grafting - skin

cell cycle checkpoint

control point where stop/go signals regulate the cell cycle

G1 checkpoint 

• most important

• controlled by cell size, growth size, growth factors, environment

• go → completes whole cell cycle

• stop → cell enters nondividing state (G0 phase)

G2 checkpoint

controlled by DNA replication completion, DNA mutations, cell size

M-spindle (metaphase) checkpoint

check spindle fiber (microtubules) attachment to chromosomes at kinetochores (anchor sites)

kinetochore

proteins associated with DNA at centromere

Kinases

(cyclin-dependent kinase, cdk), protein enzyme controls cell cycle; active when connected to cyclin

Cyclins

proteins which attach to kinases to activate them; levels fluctuate in the cell cycle

MPF

• maturation-promoting factor

• specific cyclin-Cdk complex which allows cells to pass G2 and go to M phase

anchorage dependence

cells must be attached to another cell or ECM to divide

density dependent inhibition

crowded cells normally to stop dividing; cell-surface protein binds to adjoining cell to inhibit growth

growth factor

proteins released by other cells to stimulate cell division

Cancer

disorder in which cells lose the ability to control growth by not responding to regulation.

multistep process of about 5-7 genetic changes for a cell to transform

what regulatory factors are affected by cancer

loses anchorage dependency and density-dependency regulation

transformation

process that converts a normal cell to a cancer cell

tumors

mass of abnormal cells

benign tumor

lump of cells remain at original site

malignant tumor

invasive - impairs functions of I+ organs (Called cancer)

metastasis

cells separate from tumor and travel to other parts of body

protein phosphates

remove phosphate groups from specific proteins to stop the signal or reset the pathway

Flow of ions into a cell

1. Ligand-gated ion channel receptor remains closed util bound by receptor. closed to stop ions from going in when they do not need to

2. the ligan-gated ion channel opens after being bounds to, specific ions can flow through and change the concentration

3. ligan dissociates from the receptor, causing the channel to close again, ending the cellular response

nerve cells are also called ___

neurons

parts of a neuron

dendrite, cell body, nucleus, schwann cell, myelin sheath, node of ranvier, axon terminal, axon.

endocrine distruptor

a natural or man-made chemical that mimics or interferes with the endocrine system

Multiple Sclerosis

a chronic autoimmune disease that affects the brain and spinal cord by damaging the protective myelin sheath around nerve fibers and disruption communication between the brain and body. T cells and B cells damage the nervous system.

example of an endocrine disruptor

phytostrogens, soy food

DDT

a synthetic insecticide that is largely outlawed because causes deformities in animals and hormonal signaling and reproduction.

Heroin

located on neurons of the brain which affects dopamine, the pleasure system, and endorphins. a part of the morphine group.

two hormones that regulate blood sugar

insulin and glucagon

what endocrine gland produces the glucose controlling hormones

the pancreas

when blood sugar is low, what hormone is secreted

glucagon

when blood sugar is high, what hormone is secreted

insulin

Type 1 diabetes

lowers blood sugar levels

Type 2 diabetes

cells struggle to use insulin

feedback mechanisms

used by organisms to maintain their internal environments and respond to environmental changes. increase or decrease cellular response to a certain event.

homeostasis

the maintenance of a stable internal environment

two examples of homeostasis

blood temperature and pH of blood

negative feedback

homeostasis is maintained by regulating a physiological process and returning a system back to its target set point.