Chap 1 Cell and Tissue Function

8/4/2019 Chap 1 Cell and Tissue Function

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Copyright © 2007 Lippincott Williams & Wilkins.

Chapter 1

Cell Structure and Function




Cell Structure

Endoplasmicreticulum

Golgi apparatus

Nucleolus

Lysosome

Ribosomes

Mitochondrion

Cell membrane

Nucleus




Cell Components

• Nucleus and nucleolus

• Cytoplasm and cytoplasmic organelles

– Ribosomes

– Endoplasmic reticulum

– Golgi complex

–

Lysosomes, peroxisomes– Mitochondria

• Cytoskeleton

– Microtubules, microfilaments




Red Blood Cells Start Out withAll the Organelles

• As they mature, they:

– Lose their lysosomes

– Produce hemoglobin

– Have small Golgi bodies

– Have enlarged endoplasmic reticulum

•

When they are mature, they:– Lose their endoplasmic reticulum

– Lose their mitochondria

How does this relate to their function?




Anaerobic Energy Metabolism—Glycolysis

• In the cytoplasm, molecules are broken into 2-carbonchunks

– Glycolysis breaks sugar 2 ATP molecules formed

– Other pathways break fatty acids or amino acids

– Breaking molecules involves removing electrons

º Handed to electron carriers like NAD and FAD

º H+ follows the electrons

– Afterwards, they are put back on the 2-carbonchunks

º Forming lactic acid




Aerobic Energy Metabolism—Krebs Cycle

• 2-carbon moleculesenter themitochondrion

matrix space

– Krebs cyclebreaks themdown 1 ATPmoleculeformed

– Carbon is lostas CO2




Krebs Cycle Occurs within Mitochondria

• Breaking molecules involves removing electrons

–Handed to electron carriers like NAD and FAD

– H+ follows the electrons

– Many of these electron carriers are loaded upwith electrons by the Krebs cycle


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Aerobic Energy Metabolism—

Oxidative Phosphorylation

Inside mitochondrion matrix:

Many electron carriers carryelectrons

Many H+ ions follow them,attracted to the negative

electrons

In innermitochondrialmembrane:

Proteins that cancarry electronscross themembrane

And that canmake ATP whenH+ ions passthrough them




Oxidative Phosphorylation (cont.)

• Electron carrierspass electrons tothe membraneproteins

• H+ ions follow theelectrons across

the membrane,but the electrons are passed backinto themitochondrion

electrons

electrons

H+

H+

H+

H+

H+

H+





• H+ ions areattracted to theelectronsbut can only getback into themitochondrion bygoing through the

ATP-producingprotein

• This is how mostATP is made

electrons

electrons

H+

H+

H+

H+

H+

H+

H+





• Now the H+ ions are

reunited withthe electrons

inside themitochondrion

•

They combinewith oxygen toform H2O

electrons

electrons

H+

H+

H+

H+

H+

H+

H+H+oxygen



Basic Energy Metabolism—What ThreePoints Would You Add to This Diagram?



Diffusion Is Movement of Molecules

• Passive diffusion: molecules move randomly

away from the area where they are mostconcentrated

• Facilitated diffusion: molecules diffuse acrossa membrane by passing through a protein

• Osmosis: diffusion of water molecules



Osmosis: Which Way Will Water Move?

Blood:

Few solutes

Lots of water Cell:

Manysolutes

Less water



Water Diffuses from the Place with Lots of Water to the Place with Less Water

Blood:

Few solutes

Lots of water Cell:

Manysolutes

Less water



“Water Follows Solutes”

Blood:

Few solutes

Lots of water Cell:

Manysolutes

Less water



Na+

Diffuses into a Cell— What Will Water Do?

Na+



The Cell’s Na+

/K+

ATPase Pumps the Na+

Back Out—What Will Water Do Now?

3 Na+

2 K+



Cell Communication

• A messenger molecule attaches to receptorproteins on cell surface

• Receptor proteins cause cell to respond by:

– Opening ion channels to let ions in or out

– Causing a second molecule to be releasedinside the cell

– Turning on enzymes inside the cell

– Stimulating the transcription of genes in thenucleus



The Basics of Cell Firing

• Cells begin with anegative charge:

resting membranepotential

• Stimulus causessome Na+

channels to open

• Na+ diffuses in,making the cellmore positive

Thresholdpotential

RestingMembranepotential Stimulus

Actionpotential



The Basics of Cell Firing (cont.)

• At thresholdpotential, moreNa+ channelsopen

• Na+ rushes in,making the cellvery positive:

depolarization• Action potential:

the cell responds(e.g., bycontracting)

Thresholdpotential


Actionpotential



The Basics of Cell Firing (cont.)

• K+ channels open

• K+ diffuses out,making the cellnegative again:repolarization

• Na+/K+ ATPase

removes the Na+from the cell andpumps the K+back in

Thresholdpotential


Actionpotential



Acetylcholine (Ach)Starts Contraction

• What will happen

if Ach receptors

are destroyed?

• What will happen

if you blockacetylcholinesterase?

Acetylcholine

released from

motor neuron

attaches to receptor

on muscle cell

opens Na+

gates

acetylcholinesterase

destroys

acetylcholine and

stops the firing

Na+ enters cell

and muscle cell

depolarizes



Na+ enters cell

and muscle cell

depolarizes

Ca2+ released

from sarcoplasmic

reticulum into the

sarcoplasm

Ca2+

attaches to

troponin



Ca2+

attaches to

troponin

troponin and

tropomyosin move

off actin binding site

myosin attaches

to actin binding

site



Contraction UsesEnergy

• Myosin uses

ATP to pullactin

• It also needsATP to let goof actin

• Why does adead bodybecome stiff?

myosin attachesto actin binding

site

myosin uses

energy from ATP

to pull actin

myosin picks up a

new molecule of

ATP

myosin lets go of

actin and reaches

forward

Chap 1 Cell and Tissue Function

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