Housekeeping

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Housekeeping

• Test Tuesday
• Cover through today
• Presentation meetings
• Today at end of class

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Different cells

• Adaptation
• Cell needs

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Who are we?

• We need structure
• We need to reproduce
• We need to grow and develop
• We need energy
• We need to interact with the environment

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What need to interact with the environment
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What need to interact with the environment
Cellular level
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The cell membrane!
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Proteins in the membrane

• Integral
• Transmembrane
• Peripheral

What distinguishes between extracellular and
intracellular membrane
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Functions of these proteins
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Question 4Why does the cell need transport
proteins? What can the lipid bilayer allow into
the cell and why?
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Membrane permeability

• Permeable to hydrophobic molecules and some small
  ions (water)
• Transport proteins
• Hydrophilic channels
• Binding helps physically move them
• Very specific
• Selectively permeable

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Question 5 Judy is at a really tough aerobic
class and is breathing pretty hard. She is sure
glad that her cells dont need to work that hard
to take up the necessary oxygen she needs to keep
going in aerobics. How do her cells do it?
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Diffusion

• Movement along its concentration gradient

NO WORK NECESSARY!Passive diffusion
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Question 6A cell is introduced to a new
environment with the concentrations seen below.
The cells membrane is permeable to
monosaccharides (glucose and fructose) but not to
disaccharides (sucrose). Answer the following
questions based on the picture.
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Cell equilibrium

• Solute balance
• Water balance (osmosis movement of water)

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Water balance important for cell maintenance
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Cells learn to adapt!
Vacuole
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Question 8 What mechanism does a proton pump
use in our body to transfer protons (Hydrogen)
out of the cell? Hydrogen then often enters the
cell through the use of cotransport with another
solute. What mechanism is often used here?
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Proton pump
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Facilitated diffusion
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Question 8What is the difference between
active transport, facilitated diffusion,
electronegative transport, and passive transport?
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Definitions

• Electrogenic pump transport creating a voltage
• Electrochemical gradient diffusion along a
  electrochemical gradient (charge)
• Passive transport transport along its
  concentration/electrochemical gradient
• active transport needs energy

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Question 8A macrophages role in the immune
system is usually to gobble up bacteria so they
are not able to circulate in the body. What type
of endocytosis does it utilize?
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Who are we?

• We need structure
• We need to reproduce
• We need to grow and develop
• We need energy
• We need to interact with the environment

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We need to interact with the environment
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Cells interact with each other to coordinate
responses in the body
What do cells need to communicate about?
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Cell-Cell communication
Sporulation
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Cell-Cell communication
Sexual reproduction
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Signal transduction
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Send a signal
What is a signal?
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How close? How far?

• Local signaling
• Long distance
• Direct contact

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Local and long distance signalling
Hormones
affects neighboring cells
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Direct contact
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The signal is sent
How do we get a response?
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3 stages of Cell talking

• Reception
• Initial interaction
• Transduction
• Uncoding the message
• Response
• Reaction to the message

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Key Process is specific to the right cells, at
the right time, to get the right response
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Reception

• Signal ligand
• Signal receptor
• Plasma membrane
• How do you control who gets the message?
• How do you react to the message?

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Types of receptors

• G protein linked receptors
• Tyrosine kinase receptor
• Ion-channel receptor
• Intracellular receptor

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G-protein-linked receptors

• Multiple types of G protein receptors
• seven ?-helices

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G protein-linked receptors

• Receptor activated
• GTP displaces GDP
• Binds/activates another protein (enzyme)
• Activated enzyme continues signal pathway

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G-protein linked receptors

• Development
• Sensory reception
• Medicinal purposes

Key Widespread throughout the cell and involved
in many different types of cell talk
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Tyrosine kinase receptors

• Tyrosine kinase
• Phosphorylate tyrosine

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• 2 receptors bind together (dimer)
• Tyrosine kinase activated
• Phosphate group added
• Relay proteins activated
• Cell response

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Tyrosine kinase receptors

• Growth factors
• Cell reproduction
• Activate several pathways at once

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What is the key difference in the signaling
pathway between G-protein linked receptors and
tyrosine kinase receptors??
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Ion channel receptors

• Protein pores
• Signal binds
• Pore opens or closes
• Change in chemical concentration
• Cellular response

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Intracellular receptors

• Signal must pass through membrane
• Binds to intracellular protein
• Cellular response

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Message (Signal) sent and received
Now what?
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3 stages of Cell talking

• Reception
• Initial interaction
• Transduction
• Uncoding the message
• Response
• Reaction to the message

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Transduction

• Relay molecules
• Proteins
• Different paths

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Transduction

• Protein phosphorylation
• Secondary messengers (nonproteins)
• cAMP
• Calcium and inositol trisphosphate

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Protein phosphorylation

• Protein kinase
• Protein phosphatase

How does this differ from the tyrosine kinase
receptors?
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Secondary messengers cAMP
Cyclic adenosine monophosphate
In plasma membrane
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cAMP

• Adenyl cyclase activated
• ATP to cAMP
• Activation of protein kinase A

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Second messengers Ca

• Affect intracellular calcium concentration

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• Use diacylglycerol (DAG) and Inositol
  trisphosphate (IP3)

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Message (Signal) sent, received, processed
Now what?
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3 stages of Cell talking

• Reception
• Initial interaction
• Transduction
• Uncoding the message
• Response
• Reaction to the message

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The response

• Activation of enzymes
• Synthesis of enzymers (proteins)turning on
  genes!

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Why such an ornate pathway??
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Why so ornate?

• Signal amplification
• Signal specification
• Different cells have different proteins

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Key Process is specific to the right cells, at
the right time, to get the right response