A TOUR OF THE CELL

• All organisms are made of cells

The cell is the simplest collection of matter that can be alive

Cell structure is correlated to cellular function

All cells are related by their descent from earlier cells

CELLS

EUKARYOTIC CELLS – MEMBRANES TO

SEPARATE FUNCTION

Basic features of all cells

Plasma membraneSemifluid substance called cytosol

Chromosomes (carry genes)

Ribosomes (make proteins)

WHAT IS A CELL?

Prokaryotes

EUKARYOTIC VS PROKARYOTIC

Fimbriae

Bacterialchromosome

A typicalrod-shapedbacterium

(a)

Nucleoid

Ribosomes

Plasmamembrane

Cell wall

Capsule

Flagella A thin sectionthrough thebacterium Bacilluscoagulans (TEM)

(b)

0.5 m

FIGURE 6.5

Have plasma membranes

selective barrier

double layer of phospholipids

EUKARYOTIC CELLS

Outside of cell

Inside of cell0.1 m

TEM of a plasmamembrane

Hydrophilicregion

Hydrophobicregion

Hydrophilicregion

Carbohydrate side chains

ProteinsPhospholipid

(b) Structure of the plasma membrane

Surface area increases whiletotal volume remains constant

Total surface area[sum of the surface areas(height width) of all boxsides number of boxes]

Total volume[height width length number of boxes]

Surface-to-volume(S-to-V) ratio[surface area volume]

1

5

6 150 750

1

1251251

1.26 6

FIGURE 6.8A

ENDOPLASMIC RETICULUM (ER)

RoughER

SmoothER

Nuclearenvelope

Nucleolus

Chromatin

Plasmamembrane

Ribosomes

Golgi apparatus

LysosomeMitochondrion

Peroxisome

Microvilli

MicrotubulesIntermediate filaments

Microfilaments

Centrosome

CYTOSKELETON:

Flagellum NUCLEUS

Animal Cell

FIGURE 6.8B

Animal Cells

Cell

NucleusNucleolus

Human cells from liningof uterus (colorized TEM)

Yeast cells budding(colorized SEM)

10

m

Fungal Cells

5 m

Parentcell

Buds

1 m

Cell wall

Vacuole

Nucleus

Mitochondrion

A single yeast cell(colorized TEM)

NUCLEUS

Nuclearenvelope

Nucleolus

Chromatin

Golgiapparatus

Mitochondrion

Peroxisome

Plasma membrane

Cell wall

Wall of adjacent cell

Plasmodesmata

Chloroplast

Microtubules

Intermediatefilaments

Microfilaments

CYTOSKELETON

Central vacuole

Ribosomes

Smoothendoplasmicreticulum

Roughendoplasmic

reticulum

FIGURE 6.8C

Plant Cell

FIGURE 6.8D

Plant Cells

Cells from duckweed(colorized TEM)

Cell

5 m

Cell wall

Chloroplast

Nucleus

Nucleolus

8 m

Protistan Cells

1 m

Chlamydomonas(colorized SEM)

Chlamydomonas(colorized TEM)

Flagella

Nucleus

Nucleolus

Vacuole

Chloroplast

Cell wall

Mitochondrion

THE NUCLEUS

The nucleus contains most of the DNA in a eukaryotic cell

Ribosomes use the information from the DNA to make proteins

THE NUCLEUS: HOME OF GENETIC INSTRUCTIONS

Double membrane of lipid bilayer

Surrounds nucleus

Tightly controlled

NUCLEAR ENVELOPE:SEPARATION OF NUCLEUS AND

CYTOPLASM

Nucleus

Rough ER

Nucleolus

Chromatin

Nuclear envelope:

Inner membrane

Outer membrane

Nuclear pore

Chromatin

Ribosome

Porecomplex

Close-upof nuclearenvelope

FIGURE 6.9A

FIGURE 6.9B

Nuclear envelope:

Inner membrane

Outer membrane

Nuclear pore

Surface of nuclearenvelope

1 m

Pore complexes (TEM)

0.2

5

m1

m

Nuclear lamina (TEM)

Pore complexes regulate entry and exit of nucleus

Nuclear lamina are a matrix of proteins that line the interior of the nuclear membrane

Provide support to the envelope

CHROMATIN TO CHROMOSOMES

DNA is organized into discrete units called chromosomesEach chromosome composed of a single DNA molecule associated with proteins The DNA and proteins of chromosomes together called chromatinThe nucleolus located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis

Made of ribosomal RNA and protein

Carry out protein synthesis in two locations

RIBOSOMES

ENDOMEMBRANE SYSTEM

regulates protein traffic and performs metabolic functions in the cell

continuous or connected via transfer by vesicles

Nuclear envelopeEndoplasmic reticulum

Golgi apparatusLysosomesVacuolesPlasma membrane

ENDOMEMBRANE

Smooth ER

Rough ER

CisternaeRibosomes

Transport vesicle

Transitional ER

Nuclearenvelope

ER lumen

Collectively account for more than ½ the membrane in a cell

Membranous cisternae

Lumen = internal space

Nuclear Envelope continuous with lumen

ER

Smooth ER Rough ER 200 nm

Smooth ER

Synthesizes lipidsMetabolizes carbohydrates

Detoxifies drugs and poisons

Stores calcium ions

Rough ER

Has bound ribosomes, which secrete glycoproteins

Distributes transport vesicles

Is a membrane factory for the cell

SMOOTH VS ROUGH ER

Ribosome

Endoplasmic Reticulum

Lumen

Protein

Made of flattened stacks = cisternae

2 distinct “sides” cis and trans

Modify molecules as they move through

Synthesizes macromolecules

GOLGI APPARATUS

GOLGI APPARATUS

cis face(“receiving” side ofGolgi apparatus)

trans face(“shipping” side ofGolgi apparatus)

0.1 m

TEM of Golgi apparatus

Cisternae

Membranous sac of enzymes

Used to digest macromolecules

Contents and membranes of lysozymes synthesized in ER

ER protected by 3D structure

LYSOSOMES

Phagocytosis – engulf “food”

Lysosomes fuse with food vacuoleCreate nutrients for cell

Autophagy – recycling cell’s own materialsDamage organelle taggedSurrounded by membraneLysosome fuses

INTRACELLULAR DIGESTION

Nucleus

Lysosome

1 m

Digestiveenzymes

Digestion

Food vacuole

LysosomePlasma membrane

(a) Phagocytosis

Vesicle containingtwo damagedorganelles

1 m

Mitochondrionfragment

Peroxisomefragment

(b) Autophagy

Peroxisome

VesicleMitochondrion

Lysosome

Digestion

© 2011 Pearson Education, Inc.

Animation: Lysosome Formation Right-click slide / select “Play”

Membranous vesicle from ER

Many functions: food, contractile, storage

Function varies based on cell structure

VACUOLE DIVERSE MAINTENANCE CHAMBERS

Central vacuole

Cytosol

Nucleus

Cell wall

Chloroplast

Centralvacuole

5 m

FIGURE 6.15-1

Smooth ER

Nucleus

Rough ER

Plasmamembrane

FIGURE 6.15-2

Smooth ER

Nucleus

Rough ER

Plasmamembrane

cis Golgi

trans Golgi

FIGURE 6.15-3

Smooth ER

Nucleus

Rough ER

Plasmamembrane

cis Golgi

trans Golgi

MITOCHONDRIA AND CHROLOPLASTS

Mitochondria are the sites of cellular respiration

Turn O2 into ATPHave own DNADouble membraneContain free

ribosomesGrow

independently of rest of cell

MITOCHONDRIA

FIGURE 6.17A

Intermembrane space

Outer

DNA

Innermembrane

Cristae

Matrix

Freeribosomesin themitochondrialmatrix

(a) Diagram and TEM of mitochondrion0.1 m

membrane

FIGURE 6.17AA

Outermembrane

Innermembrane

Cristae

Matrix

0.1 m

FIGURE 6.17B

(b)Network of mitochondria in a protistcell (LM)

MitochondrialDNA

Nuclear DNA

Mitochondria

10 m

CHLOROPLASTS

Chloroplasts are the sites of photosynthesis

Thylakoids are membranous sacs stacked into granum

Contain chlorophyll and other enzymes necessary for photosynthesis

FIGURE 6.18A

RibosomesStroma

Inner and outermembranes

Granum

1 mIntermembrane spaceThylakoid(a) Diagram and TEM of chloroplast

DNA

FIGURE 6.18AA

Stroma

Inner and outermembranes

Granum

1 m

FIGURE 6.18B

(b) Chloroplasts in an algal cell

Chloroplasts(red)

50 m

ENDOSYMBIONT

THEORY

NucleusEndoplasmicreticulum

Nuclear envelope

Ancestor ofeukaryotic cells(host cell)

Engulfing of oxygen-using nonphotosyntheticprokaryote, whichbecomes a mitochondrion

Mitochondrion

Nonphotosyntheticeukaryote

Mitochondrion

At leastone cell

Photosynthetic eukaryote

Engulfing ofphotosyntheticprokaryote

Chloroplast

Peroxisomes are specialized metabolic compartments bounded by a single membrane

Peroxisomes produce hydrogen peroxide and convert it to water

How peroxisomes are related to other organelles is still unknown

PEROXISOME

FIGURE 6.19

ChloroplastPeroxisome

Mitochondrion

1 m

CELL SEPARATION

FIGURE 6.4 TECHNIQUE

Homogenization

Tissuecells

Homogenate

Centrifugation

Differentialcentrifugation

Centrifuged at1,000 g

(1,000 times theforce of gravity)

for 10 min Supernatantpoured intonext tube

20,000 g20 min

80,000 g60 min

Pellet rich innuclei andcellular debris

150,000 g3 hr

Pellet rich inmitochondria(and chloro-plasts if cellsare from a plant)

Pellet rich in“microsomes”(pieces of plasmamembranes andcells’ internalmembranes) Pellet rich in

ribosomes

FIGURE 6.4A

TECHNIQUE

Homogenization

Tissuecells

Homogenate

Centrifugation

Differentialcentrifugation

Centrifuged at1,000 g

(1,000 times theforce of gravity)

for 10 min Supernatantpoured intonext tube

20 min

60 minPellet rich innuclei andcellular debris

3 hr

Pellet rich inmitochondria(and chloro-plasts if cellsare from a plant)

Pellet rich in“microsomes”

Pellet rich inribosomes

20,000 g

80,000 g

150,000 g

TECHNIQUE (cont.)FIGURE 6.4B