Concepts of the Cell Theory - PowerPoint Presentation

Slide1

Concepts of the Cell Theory

A cell is the basic structural and functional unit of living organisms.

The activity of an organism depends on the collective activities of its cells.

Continuity of life has a cellular basis.

Slide2

Chemical Components of Cells

Most cells are composed of the following four elements

Carbon

Hydrogen

Oxygen

Nitrogen

Slide3

Anatomy of the Cell

Cells are not all the same.

All cells share general structures.

All cells have three main regions

Nucleus

Cytoplasm

Plasma membrane

Slide4

Figure 3.1a

Nucleus

Cytoplasm

Plasma

membrane

(a)

Slide5

The Nucleus

Control center of the cell

Contains genetic material (DNA)

Three regions

Nuclear envelope (membrane)

Nucleolus

Chromatin

Slide6

Nucleus

Nuclear envelope

Chromatin

Nuclear

pores

Nucleolus

Rough ER

(b)

Figure 3.1b

Slide7

The Nucleus

Nuclear envelope (membrane)

Barrier of the nucleus

Consists of a double membrane

Contains nuclear pores that allow for exchange of material with the rest of the cell

Slide8

The Nucleus

Nucleoli

Nucleus contains one or more nucleoli

Sites of ribosome assembly

Ribosomes migrate into the cytoplasm through nuclear pores

Slide9

The Nucleus

Chromatin

Composed of DNA and protein

Present when the cell is not dividing

Scattered throughout the nucleus

Condenses to form chromosomes when the cell divides

Slide10

Plasma Membrane

Barrier for cell contents

Double phospholipid layer

Hydrophilic heads

Hydrophobic tails

Also contains proteins, cholesterol, and glycoproteins

Slide11

Figure 3.2

Extracellular fluid

(watery environment)

Sugar

group

Polar heads of

phospholipid

molecules

Bimolecular

lipid layer

containing

proteins

Nonpolar tails

of phospholipid

molecules

Glycoprotein

Proteins

Filaments of

cytoskeleton

Cytoplasm

(watery environment)

Channel

Cholesterol

Glycolipid

Slide12

Plasma Membrane

Bimolecular layer of lipids and proteins in a constantly changing fluid mosaic

Plays a dynamic role in cellular activity

Separates intracellular fluid (ICF) from extracellular fluid (ECF)

Interstitial fluid (IF) = ECF that surrounds cells

Slide13

Figure 3.3

Integral

proteins

Extracellular fluid

(watery environment)

Cytoplasm

(watery environment)

Polar head of

phospholipid

molecule

Glycolipid

Cholesterol

Peripheral

proteins

Bimolecular

lipid layer

containing

proteins

Inward-facing

layer of

phospholipids

Outward-

facing

layer of

phospholipids

Carbohydrate

of glycocalyx

Glycoprotein

Filament of

cytoskeleton

Nonpolar

tail of

phospholipid molecule

Slide14

Membrane Lipids

75% phospholipids (lipid bilayer)

Phosphate heads: polar and hydrophilic

Fatty acid tails: nonpolar and hydrophobic (Review Fig. 2.16b)

5% glycolipids

Lipids with polar sugar groups on outer membrane surface

20% cholesterol

Increases membrane stability and fluidity

Slide15

Membrane Proteins

Integral proteinsFirmly inserted into the membrane (most are transmembrane)Functions: Transport proteins (channels and carriers), enzymes, or receptors

Animation: Transport Proteins

PLAY

Slide16

Membrane Proteins

Peripheral proteinsLoosely attached to integral proteins Include filaments on intracellular surface and glycoproteins on extracellular surfaceFunctions: Enzymes, motor proteins, cell-to-cell links, provide support on intracellular surface, and form part of glycocalyx

Animation: Structural Proteins

PLAY

Animation: Receptor Proteins

PLAY

Slide17

Figure 3.3

Integral

proteins

Extracellular fluid

(watery environment)

Cytoplasm

(watery environment)

Polar head of

phospholipid

molecule

Glycolipid

Cholesterol

Peripheral

proteins

Bimolecular

lipid layer

containing

proteins

Inward-facing

layer of

phospholipids

Outward-

facing

layer of

phospholipids

Carbohydrate

of glycocalyx

Glycoprotein

Filament of

cytoskeleton

Nonpolar

tail of

phospholipid molecule

Slide18

Functions of Membrane Proteins

Transport

Receptors for signal transduction

Attachment to cytoskeleton and extracellular matrix

Slide19

Figure 3.4a

A protein (left) that spans the membrane

may provide a hydrophilic channel across the membrane that is selective for a particular solute. Some transport proteins (right) hydrolyze ATP as an energy source to actively pump substances across the membrane.

(a) Transport

Slide20

Figure 3.4b

A membrane protein exposed to the

outside of the cell may have a binding

site with a specific shape that fits the

shape of a chemical messenger, such as a hormone. The external signal may cause a change in shape in the protein that initiates a chain of chemical reactions in the cell.

(b) Receptors for signal transduction

Signal

Receptor

Slide21

Figure 3.4c

Elements of the cytoskeleton (cell’s

internal supports) and the extracellular matrix (fibers and other substances outside the cell) may be anchored to membrane proteins, which help maintain cell shape and fix the location of certain membrane proteins. Others play a role in cell movement or bind adjacent cells together.

(c) Attachment to the cytoskeleton

and extracellular matrix (ECM)

Slide22

Functions of Membrane Proteins

Enzymatic activity

Intercellular joining

Cell-cell recognition

Slide23

Figure 3.4d

A protein built into the membrane may

be an enzyme with its active site

exposed to substances in the adjacent

solution. In some cases, several enzymes in a membrane act as a team that catalyzes sequential steps of a metabolic pathway as indicated (left to right) here.

(d) Enzymatic activity

Enzymes

Slide24

Figure 3.4e

Membrane proteins of adjacent cells

may be hooked together in various

kinds of intercellular junctions. Some

membrane proteins (CAMs) of this

group provide temporary binding sites that guide cell migration and other cell-to-cell interactions.

CAMs

(e) Intercellular joining

Slide25

Figure 3.4f

Some glycoproteins (proteins bonded

to short chains of sugars) serve as

identification tags that are specifically recognized by other cells.

(f) Cell-cell recognition

Glycoprotein

Slide26

Plasma Membrane Junctions

Membrane junctions

1.Tight junctions

Impermeable junctions

Bind cells together into leakproof sheets

2.Desmosomes

Anchoring junctions that prevent cells from being pulled apart

3.Gap junctions

Allow communication between cells

Slide27

Plasma

membranes of

adjacent cells

Desmosome

(anchoring

junction)

Tight

(impermeable)

junction

Microvilli

Gap

(communicating)

junction

Extracellular

space between

cells

Underlying

basement

membrane

Connexon

Figure 3.3

Slide28

Membrane Transport

Plasma membranes are selectively permeable

Some molecules easily pass through the membrane; others do not

Slide29

Types of Membrane Transport

Passive processes

No cellular energy (ATP) required

Substance moves down its concentration gradient

Active processes

Energy (ATP) required

Occurs only in living cell membranes

Slide30

Passive Processes

Simple diffusion

Carrier-mediated facilitated diffusion

Channel-mediated facilitated diffusion

Osmosis

Filteration

Dialysis

Slide31

Passive Processes: Simple Diffusion

Nonpolar lipid-soluble (hydrophobic) substances diffuse directly through the phospholipid bilayer from higher concentrations to lower concentrations.

PLAY

Animation: Diffusion

Slide32

Figure 3.7a

Extracellular fluid

Lipid-

soluble

solutes

Cytoplasm

(a) Simple diffusion

of fat-soluble molecules

directly through the phospholipid bilayer

Slide33

Passive Processes: Facilitated Diffusion

Certain

lipophobic

molecules (e.g., glucose, amino acids, and ions) use carrier proteins or channel proteins, to pass through the plasma membrane.

Slide34

Figure 3.7b

Lipid-insoluble

solutes (such as

sugars or amino

acids)

(b) Carrier-mediated facilitated diffusion

via a protein

carrier specific for one chemical; binding of substrate

causes shape change in transport protein

Slide35

Facilitated Diffusion Using Channel Proteins

Aqueous channels formed by

transmembrane

proteins selectively transport ions or water

Two types:

Leakage channels

Always open

Gated channels

Controlled by chemical or electrical signals

Slide36

Figure 3.7c

Small lipid-

insoluble

solutes

(c) Channel-mediated facilitated diffusion

through a channel protein; mostly ions

selected on basis of size and charge

Slide37

Passive Processes: Osmosis

Movement of solvent (water) across a selectively permeable membrane

Slide38

Figure 3.7d

Water

molecules

Lipid

billayer

Aquaporin

(d) Osmosis

, diffusion of a solvent such as

water through a specific channel protein

(aquaporin) or through the lipid bilayer

Slide39

Passive Processes: Osmosis

Water concentration is determined by solute concentration because solute particles displace water molecules

Osmolarity

: The measure of total concentration of solute particles

When solutions of different

osmolarity

are separated by a membrane, osmosis occurs until equilibrium is reached

Slide40

Figure 3.8a

(a)

Membrane permeable to both solutes and water

Solute and water molecules move down their concentration gradients

in opposite directions. Fluid volume remains the same in both compartments.

Left

compartment:

Solution withlower osmolarity

Rightcompartment:Solution with greater osmolarity

Membrane

H2O

Solute

Solutemolecules(sugar)

Both solutions have the

same osmolarity: volume

unchanged

Slide41

Figure 3.8b

(b)

Membrane permeable to water, impermeable to solutes

Both solutions have identical

osmolarity, but volume of the

solution on the right is greater

because only water is free to move

Solute molecules are prevented from moving but water moves by osmosis.Volume increases in the compartment with the higher osmolarity.

Leftcompartment

Rightcompartment

Membrane

Solutemolecules(sugar)

H

2

O

Slide42

Importance of Osmosis

When osmosis occurs, water enters or leaves a cellChange in cell volume disrupts cell function

PLAY

Animation: Osmosis

Slide43

Tonicity

Tonicity: The ability of a solution to cause a cell to shrink or swell

Isotonic: A solution with the same solute concentration as that of the

cytosol

Hypertonic: A solution having greater solute concentration than that of the

cytosol

Hypotonic: A solution having lesser solute concentration than that of the

cytosol

Slide44

Figure 3.9

Cells retain their normal size and

shape in isotonic solutions (samesolute/water concentration as insidecells; water moves in and out).

Cells lose water by osmosis and shrink in a hypertonic solution (contains a higher concentration of solutes than are present inside the cells).

(a) Isotonic solutions

(b) Hypertonic solutions

(c) Hypotonic solutions

Cells take on water by osmosis until

they become bloated and burst (lyse)

in a hypotonic solution (contains a

lower concentration of solutes than

are present in cells).

Slide45

Summary of Passive Processes

Process

Energy Source

Example

Simple diffusion

Kinetic energy

Movement of O

2

through phospholipid bilayer

Facilitated diffusion

Osmosis

Kinetic energy

Kinetic

energy

Movement of glucose into cells

Movement of H

2

O through

phospholipid

bilayer

or AQPs.

Filteration

Dialysis

Kinetic energy

Kinetic energy

Movement of

filterete

through kidney filters

Use Of Artificial Filters in Kidney failures

Slide46

Passive Processes

B.Filtration

Water and solutes are forced through a membrane by fluid, or hydrostatic pressure

A pressure gradient must exist

Solute-containing fluid is pushed from a high-pressure area to a lower pressure area as in kidney filtration

C. Dialysis, is artificial filtration in kidney failure

Slide47

2.Active Processes

Substances are transported that are unable to pass by diffusion

Substances may be too large

Substances may not be able to dissolve in the fat core of the membrane

Substances may have to move against a concentration gradient

ATP is used for transport

Slide48

Active Processes

Two common forms of active transport

1.Active transport (solute pumping)

2.Vesicular transport, includes:

A.Exocytosis

B.Endocytosis, includes:

a.Phagocytosis

b.Pinocytosis

Slide49

Active Processes

1.Active transport (solute pumping)

Amino acids, some sugars, and ions are transported by protein carriers called solute pumps

ATP energizes protein carriers

In most cases, substances are moved against concentration gradients

E.g. movement of Na, & K in nerve transmission of impulses

Slide50

Figure 3.11

Extracellular fluid

ADP

ATP

Binding of cytoplasmic

Na+ to the pump proteinstimulates phosphorylationby ATP, which causes thepump protein to change itsshape.

The shape change expelsNa+ to the outside.Extracellular K+ binds,causing release of thephosphate group.

Loss of phosphaterestores the originalconformation of the pumpprotein. K+ is released to thecytoplasm and Na+ sites areready to bind Na+ again; thecycle repeats.

Na+

Na+

Na+

Na+

Na+

Na+

K+

K+

P

P

K+

K+

3

3

2

1

2

1

Cytoplasm

Slide51

Figure 3.11, step 1

Extracellular fluid

ADP

ATP

Binding of cytoplasmic

Na+ to the pump proteinstimulates phosphorylationby ATP, which causes thepump protein to change itsshape.

Na+

Na+

Na+

Cytoplasm

1

P

1

Slide52

Figure 3.11, step 2

Extracellular fluid

Cytoplasm

ADP

ATP

Binding of cytoplasmic

Na+ to the pump proteinstimulates phosphorylationby ATP, which causes thepump protein to change itsshape.

The shape change expelsNa+ to the outside.Extracellular K+ binds,causing release of thephosphate group.

Na+

Na+

Na+

Na+

Na+

Na+

K+

K+

2

1

P

P

1

2

Slide53

Figure 3.11, step 3

Extracellular fluid

ADP

ATP

Binding of cytoplasmic

Na+ to the pump proteinstimulates phosphorylationby ATP, which causes thepump protein to change itsshape.

The shape change expelsNa+ to the outside.Extracellular K+ binds,causing release of thephosphate group.

Loss of phosphaterestores the originalconformation of the pumpprotein. K+ is released to thecytoplasm and Na+ sites areready to bind Na+ again; thecycle repeats.

Na+

Na+

Na+

Na+

Na+

Na+

K+

K+

K+

K+

3

3

Cytoplasm

1

2

P

P

1

2

Slide54

Active Processes

2.Vesicular transport, includes:

A.Exocytosis

Moves materials out of the cell

Material is carried in a membranous vesicle

Vesicle migrates to plasma membrane

Vesicle combines with plasma membrane

Material is emptied to the outside

Slide55

Extracellular

fluid

Moleculeto besecreted

Secretoryvesicle

Cytoplasm

Fusion pore formed

FusedSNAREs

(a) The process of exocytosis

The membrane-bound vesiclemigrates to theplasma membrane.

There,v-SNAREs bindwith t-SNAREs, thevesicle and plasmamembrane fuse,and a pore opensup.

Vesiclecontents arereleased to thecell exterior.

3

2

1

Vesicle

SNARE

(v-SNARE)

Plasma

membrane

SNARE

(t-SNARE)

Figure 3.12a

Slide56

Figure 3.12b

Slide57

Active Processes

Vesicular transport (continued)

B.Endocytosis

Extracellular substances are engulfed by being enclosed in a membranous vescicle

Types of endocytosis:

a.Phagocytosis—“cell eating”for solids, e.g. bacteria

b.Pinocytosis—“cell drinking” for liquids as hormones

Slide58

Extracellular

fluid

Vesiclefusing withlysosomefor digestion

Ingestedsubstance

Pit

Membranes andreceptors (if present)recycled to plasmamembrane

Detached vesiclecontaining ingestedmaterial

Transport to plasmamembrane and exocytosisof vesicle contents

Release ofcontents tocytosol

Cytosol

Plasmamembrane

Lysosome

2

1

3

Vesicle

Figure 3.13a

Slide59

Extracellular

fluid

Vesiclefusing withlysosomefor digestion

Ingestedsubstance

Plasmamembrane

1

Figure 3.13a, step 1

Slide60

Extracellular

fluid

Vesiclefusing withlysosomefor digestion

Ingestedsubstance

Detached vesiclecontaining ingestedmaterial

Transport to plasmamembrane and exocytosisof vesicle contents

Release ofcontents tocytosol

Cytosol

Plasmamembrane

Lysosome

Vesicle

2

1

Figure 3.13a, step 2

Slide61

Extracellular

fluid

Vesiclefusing withlysosomefor digestion

Ingestedsubstance

Pit

Membranes andreceptors (if present)recycled to plasmamembrane

Detached vesiclecontaining ingestedmaterial

Transport to plasmamembrane and exocytosisof vesicle contents

Release ofcontents tocytosol

Cytosol

Plasmamembrane

Lysosome

2

1

Vesicle

3

Figure 3.13a, step 3

Slide62

(b)

Pseudopod

Bacterium

or otherparticle

Cytoplasm

Extracellularfluid

Figure 3.13b

Slide63

(c)

Membrane

receptor

Figure 3.13c

Slide64

Cytoplasm

The material outside the nucleus and inside the plasma membrane

Site of most cellular activities

Slide65

Cytoplasm

Contains three major elements

Cytosol

Fluid that suspends other elements(PH,7)

Organelles

Metabolic machinery of the cell

“Little organs” that perform functions for the cell

Inclusions

Chemical substances such as stored nutrients or cell products

Slide66

Ribosomes

Golgi apparatus

Secretion being released

from cell by exocytosis

Microtubule

Centrioles

Mitochondrion

Lysosome

Cytosol

Smooth endoplasmic

reticulum

Chromatin

Nucleolus

Nuclear envelope

Nucleus

Plasma

membrane

Rough

endoplasmic

reticulum

Intermediate

filaments

Peroxisome

Figure 3.4

Slide67

Cytoplasmic Organelles

A.Mitochondria

“Powerhouses” of the cell

Change shape continuously

Carry out reactions where oxygen is used to break down food

Provides ATP for cellular energy

Slide68

Cytoplasmic Organelles

B.Ribosomes

Made of protein and RNA

Sites of protein synthesis

Found at two locations

Free in the cytoplasm

As part of the rough endoplasmic reticulum

Slide69

Cytoplasmic Organelles

C.Endoplasmic reticulum (ER)

Fluid-filled tubules for carrying substances

Two types of ER:

1.

Rough endoplasmic reticulum

Studded with ribosomes

Synthesizes proteins

2.Smooth endoplasmic reticulum

Functions in lipid metabolism and detoxification of drugs and pesticides

Slide70

Figure 3.5

In the cistern, the protein folds into its

functional shape. Short sugar chainsmay be attached to the protein (forminga glycoprotein).

The protein is packaged in a tinymembranous sac called a transportvesicle.

The transport vesicle buds from therough ER and travels to the Golgiapparatus for further processing.

As the protein is synthesized on theribosome, it migrates into the rough ERcistern.

3

2

1

Ribosome

mRNA

Rough ER

Transport

vesicle buds off

Protein inside

transport vesicle

Protein

4

3

2

1

4

Slide71

Figure 3.5, step 1

Ribosome

mRNA

Rough ER

Protein

As the protein is synthesized on the

ribosome, it migrates into the rough ER

cistern.

1

1

Slide72

Figure 3.5, step 2

In the cistern, the protein folds into its

functional shape. Short sugar chainsmay be attached to the protein (forminga glycoprotein).

As the protein is synthesized on theribosome, it migrates into the rough ERcistern.

2

Ribosome

mRNA

Rough ER

Protein

2

1

1

Slide73

Figure 3.5, step 3

In the cistern, the protein folds into its

functional shape. Short sugar chainsmay be attached to the protein (forminga glycoprotein).

The protein is packaged in a tinymembranous sac called a transportvesicle.

As the protein is synthesized on theribosome, it migrates into the rough ERcistern.

3

2

1

Ribosome

mRNA

Rough ER

Transport

vesicle buds off

Protein

3

2

1

Slide74

Figure 3.5, step 4

In the cistern, the protein folds into its

functional shape. Short sugar chainsmay be attached to the protein (forminga glycoprotein).

The protein is packaged in a tinymembranous sac called a transportvesicle.

The transport vesicle buds from therough ER and travels to the Golgiapparatus for further processing.

As the protein is synthesized on theribosome, it migrates into the rough ERcistern.

3

2

1

Ribosome

mRNA

Rough ER

Transport

vesicle buds off

Protein inside

transport vesicle

Protein

4

3

2

1

4

Slide75

Cytoplasmic Organelles

D.Golgi

apparatus

Modifies and packages proteins

Produces different types of packages

Secretory

vesicles

Cell membrane components

Slide76

Figure 3.6

Golgi vesicle containing

digestive enzymes

becomes a lysosome

Pathway 3

Pathway 2

Secretory vesicles

Proteins

Secretion by

exocytosis

Golgi vesicle containing

proteins to be secreted

becomes a secretory

vesicle

Golgi

apparatus

Pathway 1

Transport

vesicle

Membrane

Proteins in cisterna

Cisterna

Rough ER

Lysosome fuses with

ingested substances

Golgi vesicle containing

membrane components

fuses with the plasma

membrane

Plasma membrane

Extracellular fluid

Slide77

Cytoplasmic Organelles

D.Lysosomes

Contain enzymes produced by ribosomes

Packaged by the Golgi apparatus

Digest worn-out or nonusable materials within the cell

Slide78

Cytoplasmic Organelles

F.Peroxisomes

Membranous sacs of oxidase enzymes

Detoxify harmful substances such as alcohol and formaldehyde

Break down free radicals (highly reactive chemicals)

Replicate by pinching in half

Slide79

Cytoplasmic Organelles

G.Cytoskeleton

Network of protein structures that extend throughout the cytoplasm

Provides the cell with an internal framework

Three different types of elements

Microfilaments (largest)

Intermediate filaments

Microtubules (smallest)

Slide80

Figure 3.7a-c

(a) Microfilaments

(b) Intermediate filaments

(c) Microtubules

Actin subunit

7 nm

10 nm

Fibrous subunits

Tubulin subunits

25 nm

Microfilaments form the blue

network surrounding the pinknucleus.

Intermediate filaments formthe purple batlike network.

Microtubules appear as goldnetworks surrounding thecells’ pink nuclei.

Slide81

Cytoplasmic Organelles

H.Centrioles

Rod-shaped bodies made of microtubules

Direct the formation of mitotic spindle during cell division

Slide82

Cellular Projections

Not found in all cells

1.Cilia move materials across the cell surface

Located in the respiratory system to move mucus&

forgein

particles

2.Flagella propel the cell

The only flagellated cell in the human body is sperm

3.Microvilli are tiny, fingerlike extensions of the plasma membrane

Increase surface area for absorption in small intestine

Slide83

Figure 3.8a

Fibroblasts

Rough ER and Golgi

apparatus

No organelles

Nucleus

Erythrocytes

(a) Cells that connect body parts

Slide84

Figure 3.8b

Epithelial

cells

Nucleus

Intermediate

filaments

(b) Cells that cover and line body organs

Slide85

Figure 3.8c

Skeletal

muscle cell

Nuclei

Contractile

filaments

Smooth

muscle cells

(c) Cells that move organs and body parts

Slide86

Figure 3.8d

Fat cell

Lipid droplet

(d) Cell that stores

nutrients

Nucleus

Slide87

Lysosomes

Macrophage

(e) Cell that fights

disease

Pseudo-

pods

Figure 3.8e

Slide88

Figure 3.8f

Processes

Rough ER

Nerve cell

Nucleus

(f) Cell that gathers information and controls body

functions

Slide89

Figure 3.8g

Nucleus

Flagellum

Sperm

(g) Cell of reproduction

Slide90

Cell Life Cycle

Cells have two major periods

A.Interphase

Cell grows,i.e.resting phase

Cell carries on metabolic processes

B.Cell division

Cell replicates itself

Function is to produce more cells for growth and repair processes

Slide91

DNA Replication

Genetic material is duplicated and readies a cell for division into two cells

Occurs toward the end of interphase

DNA uncoils and each side serves as a template

Slide92

Key:

= Adenine

= Thymine

= Cytosine

= Guanine

Old

(template)strand

Newlysynthesizedstrand

Newstrandforming

Old (template)strand

DNA of one chromatid

C

G

T

A

A

C

G

T

G

C

G

C

A

T

A

T

G

C

A

G

T

A

C

C

G

C

G

T

T

A

A

A

T

T

C

G

T

A

A

A

T

T

C

G

T

A

T

A

G

C

G

C

G

C

G

C

A

Figure 3.14

Slide93

B.Events of Cell Division

(1)Mitosis—division of the nucleusResults in the formation of two daughter nuclei(2)Cytokinesis—division of the cytoplasmBegins when mitosis is near completionResults in the formation of two daughter cells

PLAY

A&P Flix

™: Mitosis

Slide94

Stages of Mitosis

a.Prophase

First part of cell division

Early:Centrioles migrate to the poles to direct assembly of mitotic spindle fibers

DNA appears as double-stranded chromosomes attached in the center by the centromere

Late:Nuclear envelope breaks down and disappears with the nucleolus too

Slide95

Stages of Mitosis

b.Metaphase

Chromosomes are aligned in the center of the cell in the equatorial plane on the metaphase plate

Slide96

Stages of Mitosis

c.Anaphase

Chromosomes are pulled apart and toward the opposite ends of the cell

Cell begins to elongate

Cleavage furrow appears

Slide97

Stages of Mitosis

d.Telophase

Chromosomes uncoil to become chromatin

Nuclear envelope reforms around chromatin

Spindles break down and disappear

Slide98

Stages of Mitosis

(2)Cytokinesis

Begins during late anaphase and completes during telophase

A cleavage furrow forms to pinch the cells into two parts

Slide99

Centrioles

Chromatin

Forming

mitotic

spindle

Centrioles

Chromosome,

consisting of two

sister chromatids

Nuclear

envelope

Plasma

membrane

Interphase

Metaphase

plate

Nucleolus

Early prophase

Fragments of

nuclear envelope

Late prophase

Nucleolus

forming

Spindle

pole

Cleavage

furrow

Nuclear

envelope

forming

Telophase and cytokinesis

Daughter

chromosomes

Anaphase

Sister

chromatids

Spindle

Metaphase

Spindle

microtubules

Centromere

Centromere

Figure 3.15

Slide100

Centrioles

Chromatin

Nuclear

envelope

Plasma

membrane

Interphase

Nucleolus

Figure 3.15, step 1

Slide101

Forming

mitotic

spindle

Centrioles

Chromosome,

consisting of two

sister chromatids

Centromere

Early prophase

Figure 3.15, step 2

Slide102

Fragments of

nuclear envelope

Late prophase

Spindle

pole

Spindle

microtubules

Centromere

Figure 3.15, step 3

Slide103

Metaphase

plate

Sister

chromatids

Spindle

Metaphase

Figure 3.15, step 4

Slide104

Daughter

chromosomes

Anaphase

Figure 3.15, step 5

Slide105

Nucleolus

forming

Cleavage

furrow

Nuclear

envelopeforming

Telophase and cytokinesis

Figure 3.15, step 6

Slide106

Protein Synthesis

Gene—DNA segment that carries a blueprint for building one protein

Proteins have many functions

Building materials for cells

Act as enzymes (biological catalysts)

RNA is essential for protein synthesis

Slide107

Role of RNA

Transfer RNA (tRNA)

Transfers appropriate amino acids to the ribosome for building the protein

Ribosomal RNA (rRNA)

Helps form the ribosomes where proteins are built

Messenger RNA (mRNA)

Carries the instructions for building a protein from the nucleus to the ribosome

Slide108

Transcription and Translation

Transcription

Transfer of information from DNA’s base sequence to the mRNA

Three-base sequences on mRNA are called codons

(A

to

T &

C to G)

Slide109

Transcription and Translation

Translation

Base sequence of nucleic acid is translated to an amino acid sequence

Amino acids are the building blocks of proteins

Slide110

Nucleus

(site of transcription)

mRNA

Nuclear pore

Nuclear membrane

Correct aminoacid attachedto each speciesof tRNA by anenzyme

Aminoacids

mRNA leavesnucleus and attaches toribosome, andtranslation begins.

mRNA specifyingone polypeptide ismade on DNA template.

Cytoplasm(site of translation)

Synthetaseenzyme

Growingpolypeptidechain

Incoming tRNArecognizes acomplementary mRNAcodon calling for its aminoacid by binding via itsanticodon to the codon.

tRNA “head”bearing anticodon

Large ribosomal subunit

Direction of ribosomeadvance; ribosomemoves the mRNA strandalong sequentiallyas each codon is read.

Small ribosomal subunit

Portion ofmRNA alreadytranslated

Released tRNAreenters the cytoplasmicpool, ready to berecharged with a newamino acid.

Peptide bond

As the ribosomemoves along themRNA, a new aminoacid is added to thegrowing protein chain.

DNA

Codon

Ser

Met

Gly

Phe

Ala

lle

U

A

U

A

A

G

A

U

U

U

C

G

C

C

A

A

U

G

U

C

C

C

G

G

A

A

T

C

G

T

T

C

G

C

T

A

U

U

A

G

C

A

AGCGAU

T

T

A

G

C

A

A

G

C

G

A

T

1

2

3

4

5

Figure 3.16