Cell Structure and Function - Welcome to Biology! - Mt ...cherylchowbiology.weebly.com/uploads/1/7/1/7/17179396/lecture_3.pdf · The Cell Theory •All organisms are composed of one

Chapter 3 Cell Structure and

Function

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

3.1 The Cellular Level of

Organization

• The cell is the structural and functional unit

of an organism.

• Smallest structure capable of performing

all the functions necessary for life.

3.1 The Cellular Level of

Organization

• Prokaryotic cells lack membrane-enclosed

structures.

• Eukaryotic cells possess membrane-

enclosed structures.

The Cell Theory

• All organisms are composed of one or

more cells.

• Cells are the basic living unit of structure

and function in organisms.

• All cells come only from other cells.

Sizes of Living Things

10 m 1 m 0.1 m 1 cm 1 mm 100 µm 10 µm 100 nm 10 nm 1 nm 0.1 nm

mouse frog egg

human egg most bacteria

virus

protein

atom ant

electron microscope

light microscope

human eye

human

blue whale

chloroplast rose

1 km 100 m 1 µm

amino

acids

plant and

animal

cells

ostrich

egg


Surface Area / Volume Ratio

• The amount of surface area affects the

ability to get materials in and out of a cell.

• A cells increase in volume, the

proportionate amount of surface area

decreases.

Surface Area / Volume Ratio

• All three have the same volume, but the

group on the right has four times the

surface area.

One 4-cm cube Eight 2-cm cubes Sixty-four 1-cm cubes


• All cells are surrounded by a plasma membrane.

• The material inside of a cell is the cytoplasm.

• The plasma membrane regulates what enters and exits a cell.

protein

molecules

phospholipid

bilayer


3.2 Prokaryotic Cells

• Lack a membrane-bounded nucleus

– Eukaryotic cells have a nucleus

• Domain Bacteria and Archaea

• Generally unicellular

– May be single, strings or clusters

• Not all bacteria cause disease

– Some are beneficial

• Cell Wall

– Peptidoglycan

• Capsule

– Or slime layer

• Flagellum

– Movement

• Fimbriae

– Attachment

• Nucleoid

– NO membrane

– Single chromosome

• Ribosomes

– Protein synthesis

Fimbriae:

hairlike bristles that

allow adhesion to

surfaces

Flagellum:

rotating filament present

in some bacteria that

pushes the cell forward

Ribosome:

site of protein synthesis

Nucleoid:

location of the bacterial

chromosome

Plasma membrane:

sheath around cytoplasm

that regulates entrance

and exit of molecules

Cell wall:

covering that supports ,

shapes, and protects cell

Capsule:

gel-like coating outside

cell wall


• Prokaryotes

are:

– Structurally

simple

– Metabolically

diverse

– Adapted to

most types of

environments

Ribosome:


Nucleoid:


chromosome

Plasma membrane:




Cell wall:



Capsule:


cell wall


© Ralph A. Slepecky/Visuals Unlimited

Fimbriae:

hairlike bristles that

allow adhesion to

surfaces

Flagellum:

rotating filament present

in some bacteria that

pushes the cell forward

Ribosome:


Nucleoid:


chromosome

Plasma membrane:




Cell wall:



Capsule:


cell wall


© Ralph A. Slepecky/Visuals Unlimited

3.3 Eukaryotic Cells

• Eukaryotic cells:

– Are structurally complex

– Have a nucleus

– Possess membrane-bound organelles

– Animals, plants, fungi and protists

• Cell walls

– Some eukaryotic cells have cell walls.

– Plant cells may have a primary and secondary

cell wall.

• Cellulose a constituent of primary cell wall.

– Also found in algae (protist) cell walls

• Lignin found in secondary cell walls.

– Fungi cell walls

• Some cellulose

• Some chitin (also found in insect exoskeletons)

Cytoskeleton:

Actin filaments

Nucleus:

Rough ER

Ribosomes

Golgi apparatus

Centrioles*

Cytoplasm Peroxisome

*not in plant cells

Intermediate filaments Smooth ER

Endoplasmic Reticulum:

Microtubules

Centrosome

Mitochondrion

Polyribosome

Nucleolus

Chromatin

Nuclear envelope

Lysosome*

Vesicle



Central vacuole*

Smooth ER

Cytoplasm

*not in animal cells

Cell wall*

Cell wall of adjacent cell

Chloroplast*

Mitochondrion

Microtubules

Plasma membrane

Actin filaments

Granum*

Ribosomes

Rough ER

Endoplasmic

Reticulum:

Centrosome

Nucleus:

Nuclear envelope

Chromatin

Nuclear pore

Golgi apparatus

Peroxisome

Nucleolus

The Nucleus

• Stores DNA

– Every cell in an individual contains the same DNA

• Chromatin

– DNA and associated proteins

– Usually divided into chromosomes

• Nucleolus

– Where ribosomal RNA (rRNA) made

• Nuclear Envelope

– Nuclear pores

nuclear pore

Nuclear envelope:

inner membrane

outer membrane chromatin

nucleoplasm

nucleolus

phospholipid

nuclear

pore

nuclear

envelope


Ribosomes

• Site of protein synthesis

– Use messenger RNA (mRNA) as template

• Two subunits (large and small) – Subunits consist of rRNA and protein molecules

• Found attached to endoplasmic reticulum

or free in cytoplasm

Endomembrane System

• Consists of the nuclear envelope, the

endoplasmic reticulum, the Golgi

apparatus, and several vesicles (tiny

membranous sacs)

• Essentially the transportation and product-

processing section of the cell

• Compartmentalizes cell

Endoplasmic Reticulum

• Membranous channels and saccules (flattened

vesicles)

nuclear envelope ribosomes

0.08 µm

rough

endoplasmic

reticulum

smooth

endoplasmic

reticulum


© R. Bolender & D. Fawcett/Visuals Unlimited

Endoplasmic Reticulum

• Rough ER

– Studded with ribosomes

– Processing and modification of proteins

• Smooth ER

– No ribosomes

– Synthesizes phospholipids

– Various other functions

Golgi Apparatus

• Post office of the cell

• Collects, sorts, packages, and distributes

materials such as proteins and lipids

• Proteins made in RER have tags that

serve as “zip codes” to direct Golgi

apparatus where to send them


plasma

membrane

secretion

enzyme

lysosome

contains digestive enzymes

that break down worn-out

cell parts or substances

entering the cell at the

plasma membrane

secretory vesicle

fuses with the plasma

membrane as secretion

occurs

Golgi apparatus

modifies lipids and proteins

from the ER; sorts them

and pack ages them in

vesicles

transport vesicle

shuttles lipids to various

locations such as the

Golgi apparatus

lipid

transport vesicle

shuttles proteins to

various locations such as

the Golgi apparatus

protein

ribosome

rough endoplasmic

reticulum

folds and processes proteins

and pack ages them in vesicles;

vesicles commonly go to

the Golgi apparatus

Nucleus

smooth endoplasmic

reticulum

synthesizes lipids and

also per forms various

other functions

incoming vesicle

brings substances into

the cell that are digested

when the vesicle fuses

with a lysosome

Lysosomes

• Produced by Golgi apparatus

• Contain hydrolytic digestive enzymes

• Garbage disposals of the cell

• Break down unwanted, foreign substances

or worn- out parts of cells

Vacuoles

• Large membranous

sacs

• Larger than vacuole

• Most prominent in

plants

• Store substances.

– Water

– Pigments

– Toxins

Peroxisomes • Membrane bound

vesicles

containing

enzymes

• Break down

molecules

producing

hydrogen

peroxide

• Immediately

broken down into

water and oxygen


peroxisome

© EM Research Services, Newcastle University

• Life is possible only because of a constant

input of energy.

• Chloroplasts

• Mitochondria

Energy-Related Organelles

Energy-Related Organelles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

carbohydrate

(high chemical energy)

chloroplast mitochondrion

usable

energy

for cells CO2 + H2O

(low chemical energy)

solar

energy

ATP

• Photosynthesis – Only plants, algae, and cyanobacteria

– Solar energy is the ultimate source of energy for most

cells

• Cellular respiration – All organisms convert chemical energy into ATP

– ATP used for all energy-requiring processes in cells


solar energy + carbon dioxide + water carbohydrate + oxygen

carbohydrate + oxygen carbon dioxide + water + energy


Chloroplasts

• Site of photosynthesis in plants and algae

• Structure:

– Double-membrane

– Stroma

– Grana – stacks of thylakoids • Chlorophyll located in thylakoid membrane

• Single circular DNA molecule

– Make some but not all of its own proteins

– Ribosomes


grana thylakoid stroma

a.

b.

500 nm

double

membrane

outer

membrane

inner

membrane

thylakoid

space

Courtesy Herbert W. Israel, Cornell University

Mitochondria

• Found in all eukaryotic cells

– Including plants and algae

• Site or cellular respiration

• Structure:

– Double-membrane

– Matrix

– Cristae

• Invaginations increase surface area

• Also contain their own DNA


cristae matrix

a.

b.

200 nm

double

membrane

outer

membrane

inner

membrane

Courtesy Dr. Keith Porter

The Cytoskeleton

• Maintains cell shape

• Assists in movement of cell and organelles

• Dynamic – assembled and dissasembled

• Three types of protein components:

– Actin Filaments

– Intermediate Filaments

– Microtubules

Actin Filaments

• Two actin chains twisted in helix

• Roles

– Structural – dense web under plasma membrane

– Found in intestinal microvilli

– Formation of pseudopods


a. Actin filaments

actin

subunit

Chara

a(actin): © M. Schliwa/Visuals Unlimited; a(Chara): © The McGraw-Hill Companies, Inc. /Dennis Strete and Darrell Vodopich, photographers

Actin Filaments

• Actin interacts with motor molecules

• Example: muscle cells

• In the presence of ATP, myosin pulls actin along


tail head

P ADP +

actin filament

membrane

myosin

molecules ATP

Intermediate Filaments • Intermediate in size between actin filaments and

microtubules

• Functions:

– Support nuclear envelope

– Cell-cell junctions, such as those holding skin cells tightly together

– Strengthens human hair

human

fibrous

subunits

b. Intermediate filaments


b(intermediate): © K.G. Murti/Visuals Unlimited; b(humans): © Amos Morgan/Getty RF

Microtubules

• Hollow cylinders made of tubulin (α and )

• Assembly:

– Under control of Microtubule Organizing Center (MTOC)

– Most important MTOC is centrosome

c. Microtubules

tubulin

subunit

chameleon


c(microtubules): © K.G. Murti/Visuals Unlimited; c(chameleon): © Photodisc/Vol. 6/Getty RF

a. Actin filaments

human

actin

subunit

Chara


fibrous

subunits

b. Intermediate filaments

c. Microtubules

tubulin

subunit

chameleon

a(actin): © M. Schliwa/Visuals Unlimited; a(Chara): © The McGraw-Hill Companies, Inc. /Dennis Strete and Darrell Vodopich, photographers; b(intermediate): © K.G.

Murti/Visuals Unlimited; b(humans): © Amos Morgan/Getty RF; c(microtubules): © K.G. Murti/Visuals Unlimited; c(chameleon): © Photodisc/Vol. 6/Getty RF

• Interacts with motor molecules kinesin and

dynein to cause movement of organelles


vesicle moves , not microtubule

ATP

kinesin

vesicle

kinesin

receptor

Centrioles • Found in centrosomes of animals

• Short cylinders with a 9 + 0 pattern of microtubule triplets

one microtubule

triplet


Cilia and Flagella

• Hairlike projections that aid in cell

movement

• In eukaryotic cells, cilia are much shorter

than flagella

• Both are membrane-bound cylinders

– 9 + 2 pattern of microtubules


Flagellum

shaft

Sperm

Cilia

flagellum

Flagellum cross section 25 nm

The shaft of the

flagellum has a ring

of nine microtubule

doublets anchored

to a central pair of

microtubules.

In the presence of

ATP, the dynein side

arms reach out to

their neighbors,

and bending occurs.

ATP

dynein

side arms

The side arms

of each doublet

are composed

of dynein, a

motor molecule.

dynein

side arm

central

microtubules

radial

spoke

outer

microtubule

doublet

plasma

membrane

(cilia): © Dr. G. Moscoso/Photo Researchers, Inc.; (flagellum): © William L. Dentler/Biological Photo Service; (sperm): © David M. Phillips/Photo Researchers, Inc.

3.4 Evolution of the Eukaryotic Cell

• First cells were prokaryotes

• Evidence suggests archaea are more

closely related to eukaryotes

• Evolved in stages

• Endosymbiotic theory

– Mitochondria and chloroplasts are derived

from prokaryotes that were taken up by a

much larger cell


DNA

Original

prokaryotic cell

1. Cell gains a nucleus by the

plasma membrane invaginating

and surrounding the DNA

with a double membrane.

2. Cell gains an endomembrane

system by proliferation

of membrane.


3. Cell gains mitochondria.

protomitochondrion

mitochondrion

Plant cell

has both mitochondria

and chloroplasts.

Animal cell

has mitochondria,

but not chloroplasts.

protochloroplast

chloroplast

4. Cell gains chloroplasts.


DNA

Original

prokaryotic cell

1. Cell gains a nucleus by the

plasma membrane invaginating

and surrounding the DNA

with a double membrane.

2. Cell gains an endomembrane

system by proliferation

of membrane.

3. Cell gains mitochondria.

protomitochondrion

mitochondrion

Plant cell

has both mitochondria

and chloroplasts.

Animal cell

has mitochondria,

but not chloroplasts.

protochloroplast

chloroplast

4. Cell gains chloroplasts.

Supporting evidence

1. Mitochondria and chloroplasts are similar

to bacteria in size and in structure.

2. Both organelles are bounded by a double

membrane— the outer membrane may

be derived from the engulfing vesicle, and

the inner one may be derived from the

plasma membrane of the original

prokaryote.

Evidence (cont.)

3. Mitochondria and chloroplasts contain a limited

amount of genetic material and divide by

splitting.

– Their DNA (deoxyribonucleic acid) is a circular loop

like that of prokaryotes.

4. Although most of the proteins within

mitochondria and chloroplasts are now

produced by the eukaryotic host, they do have

their own ribosomes and they do produce some

proteins.

– Their ribosomes resemble those of prokaryotes.

Evidence (cont.)

5. The RNA (ribonucleic acid) base

sequence of the ribosomes in

chloroplasts and mitochondria also

suggests a prokaryotic origin of these

organelles.

Documents

Cell Structure and Function - Welcome to Biology! - Mt ...cherylchowbiology.weebly.com/uploads/1/7/1/7/17179396/lecture_3.pdf · The Cell Theory •All organisms are composed of one