Duquesne University Advanced General Biology 115 Exam 3

Plasma Membrane

selectively permeable phospholipid bilayer including embedded proteins that is selectively permeable and controls flow in and out of the cell

Extracellular Layer

Region right above the outer side of the plasma membrane

Extracellular layer function

1, helps define cell shape, 2 attaches the cell to other cells, 3 acts as a first defense

Extracellular Layer Structure

fiber composite of cross- linked network of long filaments that resist tension

What is a plant cell wall made of?

long strands of cellulose

• bundled into microfibrils

• crisscross network

What keeps the plant cell wall moist?

hydrophilic gelatinous polysaccharides such as pectin

Turgid Cell

water enters by osmosis, vacuole swells and pushes against cell wall

Flaccid Cell

water lost from cell, vacuole shrinks, cell loses shape

What is the role of expansins?

disrupt hydrogen bonds that cross- link the microfibrils in the wall, allowing the microfibrils to slide past one another to allow growth

Secondary Plant Cell Wall

between plasma membrane and the primary wall

and the structure correlates with the specific cell function

Lignin

the secondary cell wall in cells that form wood

What is the extracellular matrix?

fiber composite secreted by cells and provides structural support

What does the ECM consist of?

collagen and proteoglycans

Collagen

a network of protein fibers

Proteoglycans

a ground substance formed of gelatinous polysaccharide

What does collagen make up?

tendons, ligaments, and skin (elastic)

What does the ECM help cells do?

1. stick together

2. form protein- protein attachments

3. link the ECM directly to the cell's cytoskeleton

What strengthens ECM?

connections to transmembrane proteins

Integrin

actin protein filaments in the cytoskeleton bind to these transmembrane proteins

Laminins

ECM proteins in which integrins bind to

Metastasis

The spread of cancer cells beyond their original site

What can the breakdown of ECM lead to?

metastasizing of cancer cells

Multicellularity

physical connections between cells

What are tissues made of?

groups of similar cells performing similar functions

What is the extracellular space between adjacent plant cells made of?

1. primary cell wall

2. Middle lamella

3. primary cell wall of another plant cell

What glues plant cells together?

middle lamella

What is the middle lamella made of?

gelatinous pectins

Epithelial tissue

sheets of cells that cover organs and line body cavities

What structures connect neighboring epithelial cells?

tight juntions and desmosomes

Gap Junctions

in animals and plants allow communication between cells

Tight Junctions

stitch the two cells together to form a watertight seal

Desmosomes

link the cytoskeleton of adjacent cells

Cell-Cell Gaps

direct connections between cells in a tissue and allows cells to communicate and work together

Selective adhesion

The tendency of cells of one tissue type to adhere to other cells of the same type.

What is the difference in adhesion in cell types?

adhesion proteins

Antibodies

Specialized proteins that aid in destroying infectious agents

Cadherins

adhesion proteins in desmosomes and there are many different types

What are the fundamentals of cell adhesion proteins?

anchor in the plasma membrane, form selective attachments with other adhesion proteins on the surface of adjacent cells, and link to the cytoskeleton

Hormone

long distance messenger that carries information, is secreted from a cell, circulates in the body, and also acts on target cells far from the signaling cell

How do distant cells communicate?

hormones

What size and concentration are hormones?

small molecules and low concentration

4 steps of Cell-Cell signaling

1. signal reception

2. signal processing

3. signal response

4. signal deactivation

What are signal receptors bound by?

• hormones

• cell-cell signals

G Proteins Trigger…

the production of an intracellular messenger

Enzyme-linked receptors trigger…

the activation of a series of proteins inside the cell

What are G proteins?

membrane anchored proteins that are activated when they bind to GTP

What deactivates G proteins?

when they hydrolyze the bound GTP to GDP

Second Messengers

small molecules that diffuse rapidly throughout the cell and amplify the hormone signal

Protein kinases

transfer phosphates from ATP to protein, a process called phosphorylation

How do second messengers work?

by activating protein kinases

Phosphorlate

kinases add a phosphate group to other proteins

Amplified signal

when an enzyme in a cascade catalyzes the phosphorlation of many copies of the downstream enzyme

Phosphorylation cascade

A series of enzyme-catalyzed phosphorylation reactions commonly used in signal transduction pathways to amplify and convey a signal inward from the plasma membrane

What is the response to a cell-cell signal?

change which genes are being expressed in the target cells and activate or deactive a particular target protein that already exists in the cell

How do cells recognize signal deactivation?

automatic and rapid mechanisms

What certain signals scan automate signal deactivation?

concentration of hormones and the number and activity of signal receptors

What do phosphates do?

remove phosphate groups

Crosstalk

interactions between different signal transduction pathways

How can crosstalk occur?

1. one pathway inhibits steps in a second pathway reducing cell's response to first pathway

2. one pathway stimulates steps in a second pathway leading to 2 different responses to a signal

3. multiple steps in a signaling pathway

What is signaling about in unicellular organisms?

changes in enviroment

Quorum sensing

signaling pathways that respond to population density

What type of macromolecule is the animal cell ECM?

Protein (Collagen) and polysaccharide (Proteoglycan)

What type of macromolecule is the plant cell wall?

Polysaccharide (Celulose and pectin)

What subunits make up the plant cell wall?

sugars

What subunits make up the animal cell ECM?

sugars and amino acids

Of the components in the animal cell ECM and plant cell wall, which correspond to steel rods and which correspond to concrete in the reinforced concrete analogy?

fibers are the steel rods and the ground substance is the concrete

Why is the reinforced concrete model such a good analogy for the function of cell walls and the ECM?

How does collagen produced in the inside of the cell transported to the outside of the cell? (be prepared to draw the pathway)

From the rough ER to the golgi out to the membrane because collagen is a protein

List the four key components of a cell signaling event

1, reception, 2, processing, 3, response, 4, deactivation

What happens to a cell after receiving a lipid soluble signal (be prepared to draw an example of this)

the signal will be able to enter the cytoplasm easily, the receptor can change shape, then it will be able to enter the nucleus will be able to turn on or off genes. in order to deactivate the signal, the receptor can be removed entirely or an enzyme can break down the steroid

What happens to a cell after receiving a lipid insoluble signal? (be prepared to draw an example of this)