Unit 2 Set A

Cells, Membranes, and Energy(!)

Test: 7/14

Chapters: 4 - 7

Human height

Length of somenerve andmuscle cells

Chicken egg

Frog egg

Un

aid

ed e

ye

Lig

ht m

icro

sco

pe

Ele

ctro

n m

icro

scop

e

10 m

1 m

100 mm(10 cm)

10 mm(1 cm)

1 mm

100 m

10 m

1 m

100 nm

10 nm

1 nm

0.1 nmAtoms

Proteins

Small molecules

Lipids

Viruses

Ribosome

Nucleus

Mycoplasmas(smallest bacteria)

Most plant andanimal cells

Most bacteria

Mitochondrion

Figure 4.2A

Cell Size Demonstration

Microscopes

• Light Microscope– Passes visible light

through the organism

• Scanning Electron Microscope (SEM)– Reflects electrons– Surfaces

Microscopescon’t

• Transmission Electron Microscope (TEM)– Goes through the

cells– Allows us to see

organelles and proteins

Why are cells so small?• Cells must interact with the outside

environment

• The closer the outside is, the easier it is to interact

• More surface area = more interaction

• Volume vs. surface area

– A small cell has a greater ratio of sur face area to volume than a large cell of the same shape

30 m 10 m

30 m 10 m

Surface areaof one large cube 5,400 m2

Total surface areaof 27 small cubes 16,200 m2

Figure 4.2B

The Domains of Life

• Eubacteria– “New bacteria”

• Archaebacteria– “Old bacteria”

• Very, very rare

• Eukaryota– Everything else

What determines the Domain?• The general type of cell.

• Eubacteria and archbacteria are very simple cells that form simple organisms

• Eukaryotes are more complex cells that CAN (but not always) for complex organisms

Prokaryotes

• Pro = before

• Karyo = kernel

• “Before the kernel”– Without a nucleus

• The simplest organisms– Bacteria

• E. coli

– Prokaryotic cells are small, relatively simple cells • That do not have a nucleus

• They do not have membrane-bound organelles

Figure 4.3B

Prokar yoticflagella

Ribosomes

Capsule

Cell wall

Plasmamembrane

Nucleoid region (DNA)

Pili

Prokaryotes do have…

• “Free” DNA and RNA• Flagella (for moving)• Pilli (for “sexual”

reproduction)• Cell walls (protection)• Ribosomes (to create

proteins)• Capsule (for really good

protection)• A plasma membrane (to

create the internal environment)– Lipid bi-layer!

Eukaryotes

• Eu = new/good• Karyo = kernel• “New/Good kernel”

– Evolved a nucleus• Protects DNA

– More recent

• The “big” organisms– Plants, Animals– Fungus, Protists

Prokaryotic cells are structurally simpler than eukar yotic cells

Prokaryotic cell

Nucleoidregion

Nucleus

Eukar yotic cell Organelles

Co

loriz

ed

TE

M 1

5,0

00

Figure 4.3A

Eukaryotes

• Have membrane-bound organelles– Mitochondria, chloroplasts, etc.

• Have a nucleus, or many nuclei

– A typical animal cell• Contains a variety of membranous organelles

• This picture is very important!

NucleusSmooth endoplasmicreticulum

Roughendoplasmicreticulum

Ribosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Flagellum

Not in mostplant cells Lysosome

Centriole

Microtubule

CytoskeletonIntermediatefilament

Microfilament

Peroxisome

Figure 4.4A

– The nucleus is the cellular control center• Containing the cell’s DNA, which directs cellular activities

• The library/city design and planning department

NucleusChromatin

Nucleolus

Pore

Ribosomes

Roughendoplasmicreticulum

Two membranesof nuclearenvelope

Figure 4.5

– Rough endoplasmic reticulum is where proteins are made

– Ribosomes on the sur face of the rough ER• Produce proteins that are secreted,

inser ted into membranes, or transpor ted to other organelles

Transport vesiclebuds off

Sugar chain

3

Rough ER

Glycoprotein2Polypeptide

Ribosome

1

Figure 4.8

• Smooth endoplasmic reticulum has a variety of

functions – Smooth endoplasmic reticulum, or smooth ER

• Synthesizes lipids

• Sorts, stores, and is a place for stuff to go initially

• “Post office”Smooth ER

Rough ER

Nuclearenvelope

Rough ER

Ribosomes

Smooth ER

TE

M 4

5,00

0

Figure 4.7

Figure 4.9

Golgi apparatus

TE

M 1

30

,00

0

Transportvesicle fromthe Golgi“Shipping” side

of Golgi apparatus

Golgiapparatus

“Receiving” side ofGolgi apparatus

Transportvesiclefrom ER

New vesicleforming

The Golgi apparatus finishes, sorts, & ships cell products– Stacks of membranous sacs receive and modify ER products

then ship them to other organelles or the cell surface

– Packaging/processing plant

Vacuole

• Vacuoles move around material– “Bubbles” in the cell– Like the mail trucks

• Kinda

– Lysosomes are sacs of enzymes– Enzymes = break down stuff (from lab)

• That function in digestion within a cell• Lysosomes also recycle damaged organelles

Figure 4.10AFigure 4.10A

GolgiapparatusPlasma

membrane

“Food”

Foodvacuole

Lysosomes

2Lysosomeengulfingdamagedorganelle

5

Digestion4

3

Engulfmentof particle

Transport vesicle(containing inactivehydrolytic enzymes)

1

Rough ER

Enzymes

• Catalyst for cells– Break down or put

together materials– Made of proteins– “Active site”

• Where things happen

– Based on SHAPE

• The various organelles of the endomembrane system are interconnected structurally and functionally– They really are the same thing, just with different jobs– They’re all part of the processing and shipping business

Nucleus

Smooth ER Nuclear envelope Golgi apparatus

Lysosome

Vacuole

Plasmamembrane

Rough ERTransport vesiclefrom ER to Golgi

Transport vesicle fromGolgi to plasma membrane

Figure 4.13

THE CYTOSKELETON AND RELATED STRUCTURES

The cell’s internal skeleton helps organize its structure and activities– A network of protein fibers make up the

cytoskeleton.

Actin subunit

Microfilament

7 nm

Fibrous subunits

10 nm

Intermediate filament Microtubule

25 nm

Tubulin subunit

Cilia and flagella move when microtubules bend and straighten– Eukaryotic cilia and flagella are locomotive

appendages that protrude from certain cells• Sperm cells (flagella)• Intestine cells (cilia)

LM

60

0

Co

loriz

ed

SE

M 4

,10

0

Figure 4.17A Figure 4.17B

Mitochondria harvest chemical energy from food– Mitochondria carry out cellular respiration which

uses the chemical energy in food to make ATP for cellular work (the powerhouse of the cell)

• ATP= energy for cells

Figure 4.15

Mitochondrion

Outermembrane

Intermembranespace

Matrix

Innermembrane

Cristae

TE

M 4

4,8

80

– ATP powers nearly all forms of cellular work– The energy in an ATP molecule lies in the

bonds between its phosphate groups

Phosphategroups

ATP

EnergyP P PP P PHydrolysis

Adenine

Ribose

H2O

Adenosine diphosphateAdenosine Triphosphate

++

ADP

Figure 5.4A

– ATP drives reactions by phosphorylation• Transferring a phosphate group to make molecules

more reactive

Figure 5.4B

ATP

Chemical work Mechanical work Transport work

P

P

P

P

P

P

P

Molecule formed Protein moved Solute transported

ADP +

Product

Reactants

Motorprotein

Membraneprotein Solute

+

Cellular respiration

• C6H1206 + O2 -> CO2 + H2O + ATP

• Occurs in the mitochondria

• Turns sugars and oxygen into carbon dioxide and water– Turns sugar into energy

– Plant cell has structures that an animal cell lacks• Such as chloroplasts and a rigid cell wall

CentralvacuoleNot in

animalcells

Chloroplast

Cell wall

Golgiapparatus

Nucleus

Microtubule

CytoskeletonIntermediatefilament

Microfilament

Ribosomes

Smoothendoplasmicreticulum

Mitochondrion

Peroxisome

Plasma membrane

Roughendoplasmicreticulum

Figure 4.4B

Chloroplasts conver t solar energy to chemical energy– Chloroplasts, found in plants and some protists

conver t solar energy to chemical energy in sugars

TE

M 9

,750

Chloroplast

Stroma

Intermembranespace

Inner and outermembranes

Granum

Figure 4.14

Photosynthesis

• CO2 + H2O -> C6H1206 + O2

• Occurs in the chloroplast

Vacuoles function in the general maintenance of the cell– Plant cells contain a large central vacuole,

• Which has lysosomal and storage functions

Chloroplast

Centralvacuole(not seen in animals)

Nucleus

Col

oriz

ed T

EM

8,7

00

Figure 4.12A

Plant cells • Are suppor ted by rigid cell walls made largely of cellulose

• Connect by plasmodesmata, which are connecting channels

Plasma membrane

Cytoplasm

Plasmodesmata

Vacuole

Layers of one plant cell wall

Walls of two adjacent plant cells

Figure 4.18A

Fungi

• Share traits with animals and plant cells– Do not have chloroplasts

• Don’t produce their own energy

– Do have cell walls• Made of chitin

– More closely related to animals then plants– Release enzymes into the environment

around them• Digest outside of their body!

By July 14th

• You should be able to fill in the chart by memory.

• By now you should understand some of the general trends.

A little encouragement…

• If I see a dramatic positive trend in your grade, especially your final, I will increase your letter grade.

• So keep working. You’ll get there!

Quiz #1

• Clear your desks, grab a writing utensil.

• No notes, books, etc.

Enzymes

• Catalyst for cells– Break down or put

together materials– Made of proteins– “Active site”

• Where things happen

– Based on SHAPE– Use ATP

– For a chemical reaction to begin:• Reactants must gain or absorb some energy, called

the energy of activation• Enzymes reduce this energy of activation

Figure 5.5A

EA barrier

Reactants

Products1 2E

nzym

e

– A protein catalyst called an enzyme• Can decrease the energy of activation needed to

begin a reaction

Figure 5.5B

Reactants

EA withoutenzyme

EA withenzyme

Net changein energy

Products

Ene

rgy

Progress of the reaction

Figure 5.6

Enzyme(sucrase)Glucose

Fructose

Active site Substrate(sucrose)

H2O

1 Enzyme availablewith empty activesite

2 Substrate binds to enzyme with induced fit

4 Products arereleased

3 Substrate is converted to products

How enzymes catalyze reactions

The cellular environment affects enzyme activity– Temperature, salt concentration, and pH

influence enzyme activity• Lab *cough* lab!

– Some enzymes require non-protein cofactors• Such as metal ions or organic molecules called

coenzymes– Ex) Coenzyme Q10

• They help it, or tell it to “go”

Inhibitors interfere with an enzyme’s activity – A competitive inhibitor takes the place of a substrate

in the active site– A noncompetitive inhibitor alters an enzyme’s

function by changing its shape

Figure 5.8

Substrate

Enzyme

Active site

Normal binding of substrate

Enzyme inhibition

Noncompetitiveinhibitor

Competitiveinhibitor

Examples of inhibitors• Antibiotics

– Penicillin inhibits bacteria’s ability to produce RNA.

• Poisons– Can stop nerve enzymes from working correctly.

• Viagra– Inhibits a enzyme that reduces blood flow.

• Originally a heart medication.

Membranes

– Phospholipids form a two-layer sheet• Called a phospholipid bilayer, with the heads

facing outward and the tails facing inward

Figure 5.11B

Water

Water

Hydrophilicheads

Hydrophobictails

The membrane is a fluid mosaic of phospholipids, sugars and proteins

Figure 5.12

Fibers of the extracellular matrix

Carbohydrate(of glycoprotein)

Glycoprotein

Microfilamentsof cytoskeleton

Phospholipid

Cholesterol

Proteins

Plasmamembrane

Glycolipid

Cytoplasm

Functions of membrane proteins

Messenger molecule

Receptor

Activatedmolecule

ATP

Enzymes Receptors for messages Transport of substances

Passive transport is diffusion across a membrane– In passive transport, substances diffuse through

membranes without work by the cell spreading from areas of high concentration to areas of low concentration

EquilibriumMembraneMolecules of dye

Equilibrium

Transport proteins may facilitate diffusion across membranes (facilitated diffusion)– Small nonpolar molecules such as O2 and CO2 diffuse easily

through the phospholipid bilayer

– Other molecules do not easily diffuse across the bilayer and transport proteins provide passage through a process called facilitated diffusion

Figure 5.15

Solutemolecule

Transportprotein

Osmosis is the diffusion of water across a membrane– In osmosis water travels from a solution of lower solute concentration to

one of higher solute concentration

Figure 5.16

Lowerconcentration

of solute

Higherconcentration

of solute

Equalconcentration

of solute

H2OSolutemolecule

Selectivelypermeablemembrane

Watermolecule

Solute molecule withcluster of water molecules

Net flow of water

Water balance between cells and their surroundings is crucial to organisms– Osmosis causes cells to shrink in hypertonic solutions

and swell in hypotonic solutions

– In isotonic solutions animal cells are normal, but plant cells are limp (plant cells need LOTS of water)

Figure 5.17

Plantcell

H2O

H2OH2O

H2O

H2O

H2O

H2O

H2OPlasma

membrane

(1) Normal (2) Lysed (3) Shriveled

(4) Flaccid (5) Turgid(6) Shriveled (plasmolyzed)

Isotonic solution Hypotonic solution Hypertonic solution

Animalcell

PP PProtein

changes shapePhosphatedetaches

ATPADPSolute

Transportprotein

Solute binding1 Phosphorylation2 Transport3 Protein reversion4

Cells expend energy for active transport– Transport proteins can move solutes against a

concentration gradient through active transport, which requires ATP

Figure 5.18

Fluid outside cell

Cytoplasm

Protein

Vesicle

Exocytosis and endocytosis transport very large molecules or proteins– To move large molecules or particles through a

membrane a vesicle may fuse with the membrane and expel its contents (exocytosis)

– To move large molecules or particles into the cell is endocytosis

Figure 5.19A

The Inner Life of the Cell

The Harvard Cell Video

The XVIVO Version of the Video