chapter 2 218/martini ppt...chapter 2 foundations the cell ... •glycolipids and glycoproteins form...

Lecture Presentation by

Steven Bassett

Southeast Community College

Chapter 2

Foundations

The Cell

© 2015 Pearson Education, Inc.

Introduction

• There are trillions of cells in the body

• Cells are the structural “building blocks” of all

plants and animals

• Cells are produced by the division of preexisting

cells

• Cells form all the structures in the body

• Cells perform all vital functions of the body


Introduction

• There are two types of cells in the body:

• Sex cells

• Sperm in males and oocytes in females

• Somatic cells

• All the other cells in the body that are not sex cells


Cellular Anatomy

• The cell consists of:

• Cytoplasm

• Cytosol

• Organelles

• Plasmalemma

• Cell membrane


Figure 2.2 A Flowchart for the Study of Cell Structure


The Cell

Plasmalemma

Cytoplasm

Cytosol Organelles

Nonmembranous

Organelles

Membranous

Organelles

can be divided

into

Divided into

subdivided into

• Cytoskeleton

• Microvilli

• Centrioles

• Cilia

• Flagella

• Ribosomes

• Mitochondria

• Nucleus

• Endoplasmic

reticulum

• Golgi apparatus

• Lysosomes

• Peroxisomes

Cellular Anatomy

• Anatomical Structures of the Cell

• Organelles

• Nonmembranous organelles

• Membranous organelles


Cellular Anatomy

• Organelles of the Cell


• Cytoskeleton

• Microvilli

• Centrioles

• Cilia

• Flagella

• Ribosomes


Table 2.1 Anatomy of a Representative Cell (1 of 2)


Figure 2.1 Anatomy of a Typical Cell


Microvilli

Secretory vesicles

Cytosol

Lysosome

Centrosome

Centriole

Chromatin

Nucleoplasm

Nucleolus

Nuclear envelope surrounding nucleus

Cytoskeleton

Plasmalemma Free ribosomes

Fixed ribosomes

Rough endoplasmic reticulum

Smooth endoplasmic reticulum

Nuclear pores

Peroxisome

Mitochondrion

Golgi apparatus

Cellular Anatomy

• Organelles of the Cell


• Mitochondria

• Nucleus

• Endoplasmic reticulum

• Golgi apparatus

• Lysosomes

• Peroxisomes




Microvilli

Secretory vesicles

Cytosol

Lysosome

Centrosome

Centriole

Chromatin

Nucleoplasm

Nucleolus


Cytoskeleton


Fixed ribosomes



Nuclear pores

Peroxisome

Mitochondrion

Golgi apparatus

Cellular Anatomy

• Plasmalemma

• A cell membrane composed of:

• Phospholipids

• Glycolipids

• Protein

• Cholesterol


Figure 2.3 The Plasmalemma


Hydrophilic

heads

a

b

Hydrophobic

tails

Cholesterol

Glycolipids of glycocalyx

Phospholipid bilayer

Integral protein with channel

Hydrophobic tails

Integral glycoproteins

Cytoskeleton (Microfilaments)

Hydrophilic heads

Peripheral proteins

Cholesterol

Gated channel

CYTOPLASM

= 2 nm

EXTRACELLULAR FLUID

The phospholipid

bilayer

The plasmalemma

Cellular Anatomy

• Functions of the Plasmalemma

• Cell membrane (also called phospholipid

bilayer)

• Major functions:

• Physical isolation

• Regulation of exchange with the environment

(permeability)

• Sensitivity

• Cell-to-cell communication/Adhesion/Structural

support


Cellular Anatomy

• Structure of the Plasmalemma

• Called a phospholipid bilayer

• Composed of two layers of phospholipid

• Hydrophobic heads are at the surfaces (inside lining

and outside lining)

• Hydrophilic fatty acids (tails) “face toward each

other”

• Outer layer consists of glycolipids and glycoproteins

• Glycolipids and glycoproteins form a glycocalyx

coating

• Inner layer does not consist of glycolipids or

glycoproteins




Hydrophilic

heads

a

b

Hydrophobic

tails

Cholesterol




Hydrophobic tails



Hydrophilic heads

Peripheral proteins

Cholesterol

Gated channel

CYTOPLASM

= 2 nm

EXTRACELLULAR FLUID

The phospholipid

bilayer

The plasmalemma

Cellular Anatomy


• Composed of protein molecules

• Peripheral proteins: attached to the glycerol

portions of the fatty acids

• Integral proteins: embedded within the cell

membrane

• Form channels such as gated channels

• Channels open and close




Hydrophilic

heads

a

b

Hydrophobic

tails

Cholesterol




Hydrophobic tails



Hydrophilic heads

Peripheral proteins

Cholesterol

Gated channel

CYTOPLASM

= 2 nm

EXTRACELLULAR FLUID

The phospholipid

bilayer

The plasmalemma

Cellular Anatomy


• Composed of sterol molecules

• Function to maintain fluidity of the membrane

• An example is cholesterol




Hydrophilic

heads

a

b

Hydrophobic

tails

Cholesterol




Hydrophobic tails



Hydrophilic heads

Peripheral proteins

Cholesterol

Gated channel

CYTOPLASM

= 2 nm

EXTRACELLULAR FLUID

The phospholipid

bilayer

The plasmalemma

Cellular Anatomy

• Membrane Permeability of the Plasmalemma

• Passive processes

• Diffusion

• Osmosis

• Facilitative diffusion

• Active processes

• Active transport

• Endocytosis

• Exocytosis


Cellular Anatomy


• Passive process: diffusion

• Movement of molecules from an area of high

concentration to an area of low concentration

• Permeablity, concentration gradient, molecule size

and charge, temperature affect the rate of

movement

• Small inorganic ions and small molecules are

involved


Figure 2.4 Membrane Permeability: Active and Passive Processes (1 of 6)


Plasmalemma

Diffusion

CO2 Extracellular

fluid

Example:

When the concentration of CO2

inside a cell is greater than outside

the cell, CO2 diffuses out of the cell

and into the extracellular fluid.

Diffusion is the movement of molecules

from an area of higher concentration to an

area of lower concentration. The difference

between the high and low concentrations is

a concentration gradient. In diffusion,

molecules move down a concentration

gradient until the gradient is eliminated.

Factors Affecting Rate:

Membrane permeability; magnitude of the

concentration gradient; size, charge, and

lipid solubility of the diffusing molecules;

presence of membrane channel proteins;

temperature

Substances Involved (all cells):

Gases, small inorganic ions and molecules,

lipid-soluble materials

Cellular Anatomy


• Passive process: osmosis

• Movement of water molecules from an area of high

concentration of water to an area of low

concentration of water

• Permeability, concentration gradient, and opposing

pressure affect the rate of movement

• Only water molecules are involved




Water

Osmosis

Example:

If the solute concentration outside

a cell is greater than the inside the

cell, water molecules will move

across the plasmalemma into the

extracellular fluid.

Osmosis is the diffusion of water molecules

(rather than solutes) across a selectively

permeable membrane. Note that water

molecules diffusing toward an area of lower

water concentration are moving toward an area

of higher solute concentration. Because solute

concentrations can easily be determined, they

are used to determine the direction and force

of osmotic water movement.


Size of the solute concentration gradient;

opposing pressure

Substances Involved:

Water only

Solute

Cellular Anatomy


• Passive process: facilitated diffusion

• Solutes are passively transported by a carrier

protein

• Concentration gradient, size and charge of the

solute, temperature, and number of carrier proteins

affect the rate of movement

• Glucose and amino acids are involved




Glucose Facilitated diffusion

Example:

Nutrients that are insoluble

in lipids or too large to fit

through membrane

channels may be trans-

ported across the plasma-

lemma by carrier proteins.

Many carrier proteins move

a specific substance in one

direction only, either into or

out of the cell, after first

binding the substance at a

specific receptor site.

In facilitated diffusion, solutes are

passively transported across a

plasmalemma by a carrier protein. As

in simple diffusion, the direction of

movement follows the concentration

gradient.


Magnitude of the concentration

gradient; size, charge, and solubility of

the solutes; temperature; availability

of carrier proteins


Glucose and amino acids

Extracellular

fluid

Receptor

site Carrier

protein

Cytoplasm

Carrier protein releases

glucose into cytoplasm

Plasmalemma

Cellular Anatomy


• Active process: active transport

• Solutes are actively transported by a carrier protein

regardless of the concentration gradient

• ATP, number of carrier proteins affect the rate of

movement

• Sodium, potassium, calcium, and magnesium ions

are involved




Extracellular

fluid

Active transport

Example:

One of the most common

examples of active transport

is the sodium–potassium

exchange pump. For each

molecule of ATP consumed,

three sodium ions are

ejected from the cell and two

potassium ions are reclaimed

from the extracellular fluid.

Using active transport, carrier proteins can move

specific substances across the plasmalemma despite an

opposing concentration gradient. Carrier proteins that

move one solute in one direction and another solute in

the opposite direction are called exchange pumps.


Availability of carrier proteins, solutes, and ATP


Na+, K+, Ca2+, Mg2+ (all cells); other solutes in special

cases

Sodium–potassium

exchange pump

Cytoplasm

3 Na+

2 K+ ATP ADP

Cellular Anatomy


• Active process: endocytosis

• Pinocytosis: vesicles bring small molecules into the

cell

• A variety of stimuli affect the rate of movement (not

fully understood)

• Extracellular fluid is involved

• Phagocytosis: vesicles bring solid particles into the

cell

• Presence of extracellular pathogens affects the rate

of movement

• Bacteria, viruses, foreign matter, and cell debris are

involved




Endocytosis is the packaging of extracellular materials into a vesicle (a membrane-bound sac) for importation into the cell.

Pinocytotic

vesicle

forming

Endocytosis

Example:

Water and small

molecules within a

vesicle may enter

the cytoplasm

through carrier-

mediated transport

or diffusion.

In pinocytosis, vesicles form at the

plasmalemma and bring extracellular fluid

and small molecules into the cell. This

process is often called “cell drinking.”

Cell Pseudopodium

extends to

surround object

Cell

Phagocytic vesicle

Extracellular fluid Target molecules

Receptor

proteins

Cytoplasm

Vesicle

containing

target

molecules

Example:

Large particles are

brought into the cell

when cytoplasmic

extensions (called

pseudopodia) engulf

the particle and form

a phagocytic vesicle.

Example:

Each cell has

specific sensitivities

to extracellular

materials, depend-

ing on the kind of

receptor proteins

present in the

plasmalemma.

In phagocytosis, vesicles form at

the plasmalemma to bring solid

particles into the cell. This process is

often called “cell eating.”


Stimulus and mechanism not under-

stood


Extracellular fluid and its associated

solutes

Pinocytosis Phagocytosis Receptor-mediated endocytosis


Presence and abundance of

extracellular pathogens or debris


Bacteria, viruses, cell debris, and

other foreign material

In receptor-mediated

endocytosis, target molecules

bind to specific receptor proteins

on the membrane surface,

triggering vesicle formation.


Number of receptors on the

plasmalemma and the concentration of

target molecules (called ligands)


Many examples, including cholesterol and

iron ions

Cellular Anatomy


• Active process: exocytosis

• The release of intracellular material to the

extracellular area

• Requires ATP and calcium ions for movement

• Fluid and cellular waste and secretory products are

involved




Cell

Exocytosis

Example:

Cellular wastes that

accumulate in vesicles

are ejected from the cell.

Exocytosis is the release of

fluids and/or solids from cells

when intracellular vesicles fuse

with the plasmalemma.

Material ejected from cell


Stimulus and mechanism incompletely

understood; requires ATP and calcium

ions


Fluid and cellular wastes; secretory

products are released by some cells

Cellular Anatomy

• Extensions of the Plasmalemma: Microvilli

• Fingerlike projections of the plasmalemma

• Absorb material from the ECF

• Increase the surface area of the plasmalemma

• Microvilli can bend back and forth in a waving

manner

• This movement helps to circulate extracellular fluid

• This movement helps absorb nutrients




Microvilli

Secretory vesicles

Cytosol

Lysosome

Centrosome

Centriole

Chromatin

Nucleoplasm

Nucleolus


Cytoskeleton


Fixed ribosomes



Nuclear pores

Peroxisome

Mitochondrion

Golgi apparatus

Cellular Anatomy

• The Cytoplasm

• Term for all of the intracellular material

• Cytosol

• Consists of the ICF (intracellular fluid)

• Consists of nutrients, protein, and waste products

• Organelles

• These are intracellular structures that perform

specific functions




Microvilli

Secretory vesicles

Cytosol

Lysosome

Centrosome

Centriole

Chromatin

Nucleoplasm

Nucleolus


Cytoskeleton


Fixed ribosomes



Nuclear pores

Peroxisome

Mitochondrion

Golgi apparatus

Cellular Anatomy

• The Cytoplasm

• Cytosol

• Contains a higher concentration of potassium ions

and a lower concentration of sodium ions as

compared to the ECF

• Consists of a net negative charge

• Contains a high concentration of protein

• Contains a small quantity of carbohydrates

• Contains a large reserve of amino acids and lipids

• Contains large amounts of inclusions


Cellular Anatomy

• The Cytoplasm

• Organelles


• Cytoskeleton Centrioles Cilia

Flagella Ribosomes


• Mitochondria Nucleus Endoplasmic

reticulum

Golgi apparatus Lysosomes Peroxisomes


Cellular Anatomy

• Nonmembranous Organelles (details)

• The cytoskeleton consists of:

• Microfilaments

• Intermediate filaments

• Thick filaments

• Microtubules


Cellular Anatomy


• Microfilaments: consist of actin protein

• Anchor cytoskeleton to integral proteins

• Stabilize the position of membrane proteins

• Anchor plasmalemma to the cytoplasm

• Produce movement of the cell or a change in the

cell’s shape


Cellular Anatomy


• Intermediate filaments

• Provide strength

• Stabilize organelle position

• Transport material within the cytosol


Cellular Anatomy


• Thick filaments: composed of myosin protein

• Found in muscle cells: involved in muscle

contraction


Cellular Anatomy


• Microtubules: composed of tubulin protein

• Involved in the formation of centrioles

• perform a function during cell reproduction

• Involved in moving duplicated chromosomes to

opposite poles of the cell

• perform a function during cell reproduction

• Involved in anchoring organelles

• Involved in moving cell organelles

• Involved in moving the entire cell

• Involved in moving material across the surface of

the cell


Figure 2.5 The Cytoskeleton


Microvilli

a

b

Microfilaments

Plasmalemma

Terminal web

Mitochondrion

Intermediate

filaments

Endoplasmic

reticulum

Microtubule

Secretory

vesicle

SEM × 30,000

LM × 3200

c

The cytoskeleton provides

strength and structural

support for the cell and its

organelles. Interactions

between cytoskeletal elements

are also important in moving

organelles and in changing

the shape of the cell.

A SEM image of the

microfilaments and microvilli

of an intestinal cell.

Microtubules in a living

cell, as seen after

fluorescent labeling.

Cellular Anatomy


• Examples of microtubules

• Centrioles

• Cilia

• Flagella


Table 2.2 A Comparison of Centrioles, Cilia, and Flagella


Figure 2.6 Centrioles and Cilia


Microtubules

Microtubules

Plasmalemma

Basal body

Power stroke Return stroke

a A centriole consists of nine microtubule triplets (9 + 0 array). The centrosome contains a pair of centrioles oriented at right angles to one another.

b

c

A cilium contains nine pairs of microtubules surrounding a central pair (9 + 2 array).

TEM × 240,000 A single cilium swings forward and then returns to its original position. During the power stroke, the cilium is relatively stiff, but during the return stroke, it bends and moves parallel to the cell surface.

Cellular Anatomy


• Ribosomes

• Free ribosomes: float in the cytoplasm

• Fixed ribosomes: attached to the endoplasmic

reticulum

• Both are involved in producing protein




Microvilli

Secretory vesicles

Cytosol

Lysosome

Centrosome

Centriole

Chromatin

Nucleoplasm

Nucleolus


Cytoskeleton


Fixed ribosomes



Nuclear pores

Peroxisome

Mitochondrion

Golgi apparatus

Figure 2.6 Centrioles and Cilia


Microtubules

Microtubules

Plasmalemma

Basal body

Power stroke Return stroke

a A centriole consists of nine microtubule triplets (9 + 0 array). The centrosome contains a pair of centrioles oriented at right angles to one another.

b

c

A cilium contains nine pairs of microtubules surrounding a central pair (9 + 2 array).

TEM × 240,000 A single cilium swings forward and then returns to its original position. During the power stroke, the cilium is relatively stiff, but during the return stroke, it bends and moves parallel to the cell surface.

Cellular Anatomy

• Membranous Organelles (details)

• Double-membraned organelles

• Mitochondria: produce ATP

• Nucleus: contains chromosomes

• Endoplasmic reticulum: network of hollow tubes

• Golgi apparatus: modifies protein

• Lysosomes: contain cellular digestive enzymes

• Peroxisomes: contain catalase to break down

hydrogen peroxide


Cellular Anatomy


• Mitochondria

• Consist of cristae

• Consist of mitochondrial matrix

• Produce ATP


Figure 2.8 Mitochondria


Inner membrane

Organic molecules and O2

CO2

ATP

Matrix Cristae

Outer membrane

Enzymes

Cytoplasm of cell Cristae Matrix

TEM × 61,776

Cellular Anatomy


• Nucleus: control center of the cell

• Nucleoplasm

• Nuclear envelope

• Perinuclear space

• Nuclear pores

• Nuclear matrix


Figure 2.9ab The Nucleus


Perinuclear

space

a

TEM × 4828

Nucleoplasm

Chromatin

Nucleolus

Nuclear envelope

Nuclear pores

TEM showing important nuclear structures.

Nuclear

envelope

Perinuclear

space

Nuclear

pore

A nuclear pore and the

perinuclear space.

b

Figure 2.9c The Nucleus


SEM × 9240

Inner membrane of

nuclear envelope

Broken edge of

outer membrane

Outer membrane of

nuclear envelope

The cell seen in this SEM was frozen and then broken apart so that internal structures could be seen. This technique, called freeze-fracture, provides a unique perspective on the internal organization of cells. The nuclear envelope and nuclear pores are visible; the fracturing process broke away part of the outer membrane of the nuclear envelope, and the cut edge of the nucleus can be seen.

c

Cellular Anatomy

• Membranous Organelles: Nucleus

• Chromosomes:

• DNA wrapped around proteins called histones

• Nucleosomes

• Chromatin


Figure 2.10 Chromosome Structure


Nucleus of nondividing cell

a

Chromatin in nucleus Loosely coiled

nucleosomes,

forming chromatin.

Sister chromatids

Centromere

Kinetochore

Dividing cell

Visible chromosome

Supercoiled

region

In cells that are not dividing, the DNA is loosely coiled,

forming a tangled network known as chromatin.

b When the coiling becomes tighter, as it does in preparation for cell division, the DNA

becomes visible as distinct structures called chromosomes. Chromosomes are composed

of two sister chromatids which attach at a single point, the centromere. Kinetochores are

the region of the centromere where spindle fibers attach during mitosis.

DNA double

helix

Histones

Nucleosome

Cellular Anatomy


• Endoplasmic reticulum (ER)

• There are two types

• Rough endoplasmic reticulum (RER)

• Smooth endoplasmic reticulum (SER)


Cellular Anatomy


• Rough endoplasmic reticulum

• Consists of fixed ribosomes

• Proteins enter the ER


Figure 2.11 The Endoplasmic Reticulum


Ribosomes

Cisternae

Rough endoplasmic

reticulum with fixed

(attached) ribosomes

Free

ribosomes

Smooth

endoplasmic

reticulum

Endoplasmic

Reticulum

TEM × 11,000

Figure 2.7 Ribosomes


Nucleus

a

Free

ribosomes

Endoplasmic

reticulum with

attached fixed

ribosomes

Small ribosomal

subunit

Large ribosomal

subunit

TEM × 73,600

Both free and fixed ribosomes can

be seen in the cytoplasm of this cell.

An individual

ribosome,

consisting of small

and large subunits.

b

Cellular Anatomy


• Smooth endoplasmic reticulum

• Synthesizes lipids, steroids, and carbohydrates

• Storage of calcium ions

• Detoxification of toxins


Cellular Anatomy


• Golgi apparatus

• Synthesis and packaging of secretions

• Packaging of enzymes (modifies protein)

• Renewal and modification of the plasmalemma


Figure 2.12 TEM of the Golgi Apparatus


Vesicles

Maturing

(trans) face

Forming

(cis) face

Golgi apparatus TEM × 83,520

Cellular Anatomy


• Lysosomes

• Fuse with phagosomes to digest solid materials

• Recycle damaged organelles

• Sometimes rupture, thus killing the entire cell

(called autolysis)


Cellular Anatomy


• Peroxisomes

• Consist of catalase

• Abundant in liver cells

• Convert hydrogen peroxide to water and oxidants


Cellular Anatomy

• Membrane Flow

• This is the continuous movement and recycling of

the cell membrane

• Transport vesicles connect the endoplasmic

reticulum with the Golgi apparatus

• Secretory vesicles connect the Golgi apparatus

with the plasmalemma

• Vesicles remove and recycle segments of the

plasmalemma


Figure 2.13 Functions of the Golgi Apparatus (1 of 3)


Cytoplasm

Transport vesicle

Rough ER

mRNA Ribosome Endoplasmic Reticulum

Golgi Apparatus Synthesis and

Packaging of

Secretions: Steps

2 Secretory products are

packaged into transport

vesicles that eventually

bud off from the ER.

These transport vesicles

then fuse to create the

forming (cis) face of the

Golgi apparatus.

Protein and glycoprotein

synthesis occurs in the

rough endoplasmic

reticulum (RER). Some

of these proteins and

glycoproteins remain

within the ER.

Cisterna Forming (cis) face

1

Figure 2.13 Functions of the Golgi Apparatus (2 of 3)


Secretory vesicle

TEM × 75,000

The maturing (trans) face

generates vesicles that

carry materials away

from the Golgi apparatus.

Secretory material

Plasmalemma

Secretory vesicle

Plasmalemma

Exocytosis at the

surface of a cell

Cytoplasm

Lysosome

Cytoplasm

Maturing (trans) face

Forming (cis) face

Cisterna

Golgi Apparatus

Packaging of Enzymes for Use

in the Cytosol

Renewal or Modification of

the Plasmalemma

Synthesis and Packaging

of Secretions

Synthesis and

Packaging of

Secretions: Steps

4

Each cisterna physically

moves from the forming

face to the maturing

face, carrying with it its

associated proteins.

This process is called cisternal progression.

3

Intercellular Attachment

• Many cells form permanent or temporary

attachment to other cells

• Attach via cell adhesion molecules (CAMs)

• Attach via cellular cement (proteoglycans)

• Examples of Intercellular Attachment

• Communicating junctions

• Adhering junctions

• Tight junctions

• Anchoring junctions



• Communicating Junctions

• Also called gap junctions

• Two cells held together via protein called

connexon

• This protein is a type of channel protein

• Attach via cell adhesion molecules (CAMs)

• Attach via cellular cement (proteoglycans)


Figure 2.14ab Cell Attachments


Embedded

proteins

(connexons)

a

Hemidesmosome

Tight junction

Terminal web

Button

desmosome

Communicating junction b Communicating

junctions permit

the free diffusion

of ions and small

molecules

between two cells. A diagrammatic view of an

epithelial cell showing the major

types of intercellular connections.

Zonula adherens


• Adhering Junctions

• Tight junctions, also called occluding junctions

• Prevent the movement of water and other

molecules from passing between the cells



• Anchoring Junctions

• Zona adherens (adhesion belt) is a sheetlike

anchoring material

• Provides strong links that cells can shed from the

body in sheets (ex. dandruff)

• Macula adherens (desmosome) is a small,

localized anchoring junction

• Most abundant in superficial layers of the skin


Figure 2.14ac Cell Attachments


Hemidesmosome

Tight junction

Terminal web

Button

desmosome

Communicating junction

Zonula adherens

Tight junction

Zonula

adherens

Interlocking

junctional

proteins

a A diagrammatic view of an



c A tight junction is formed by the

fusion of the outer layers of two

plasmalemmae. Tight junctions

prevent the diffusion of fluids

and solutes between the cells.

Figure 2.14ad Cell Attachments


a

Hemidesmosome

Tight junction

Terminal web

Button

desmosome


A diagrammatic view of an



Zonula adherens

Intermediate filaments (cytokeratin)

Cell adhesion

molecules

(CAMs)

Dense area

Intercellular cement

d Anchoring junctions

attach one cell to another.

A macula adherens has a

more organized network

of intermediate filaments.

An adhesion belt is a form

of anchoring junction that

encircles the cell. This

complex is tied to the

microfilaments of the

terminal web.


• Anchoring junctions

• Focal adhesions (focal contacts)

• Connect intracellular microfilaments to protein

fibers

• Found in epithelial tissue that migrates during

wound repair

• Hemidesmosomes

• Found in connecting cells that are exposed to a lot

of abrasion

• Examples are the cornea of the eye, skin, vaginal

tissue, oral cavity, and esophagus


a

Hemidesmosome

Tight junction

Terminal web

Button

desmosome


A diagrammatic view of an



Zonula adherens

Clear layer

Dense layer

Basal lamina

e Hemidesmosomes attach an epithelial

cell to extracellular structures, such as

the protein fibers in the basal lamina.

Figure 2.14ae Cell Attachments


The Cell Life Cycle

• Cell reproduction consists of special events

• Interphase

• Mitosis

• Prophase

• Metaphase

• Anaphase

• Telophase

• Cytokinesis

• Overlaps with anaphase and telophase


The Cell Life Cycle

• Cell Reproduction (Interphase)

• Everything inside the cell is duplicating

• Consists of G1, S, and G2 phases

• G1: duplication of organelles and protein synthesis

• S: Chromosome replication and DNA synthesis and

histone synthesis

• G2: protein synthesis


Figure 2.16 DNA Replication


KEY

Adenine

Guanine

Cytosine

Thymine

Segment 2

DNA polymerase

DNA nucleotide

Segment 1

DNA

polymerase

The Cell Life Cycle

• Cell Reproduction (Mitosis)

• Prophase

• The first phase of mitosis

• Metaphase

• Paired chromatids line up in the middle of the

nuclear region

• Anaphase

• Paired chromatids separate to opposite poles of

the cell

• Telophase

• Two new nuclear membranes begin to form


Figure 2.17 Mitosis


Nucleus

Nuclear

membrane

Spindle

fibers

Centrioles

(two pairs)

Astral

rays

Chromosomal

microtubules

Centromere

Chromosome

with two sister

chromatids

Interphase Prophase

Early prophase

Metaphase

Late prophase

Anaphase Telophase Cytokinesis

Chromosomal

microtubules

Metaphase

plate

Daughter

chromosomes

Cleavage

furrow

Daughter

cells

The Cell Life Cycle

• Cell Reproduction (Cytokinesis)

• Cell membrane begins to invaginate, thus forming

two new cells

• Many times this phase actually begins during

anaphase

• This is the conclusion of cell reproduction


Figure 2.15 The Cell Life Cycle


THE

CELL

CYCLE

INTERPHASE

S

DNA

replication,

synthesis

of

histones G2

Protein

synthesis

G1

Normal

cell functions

plus cell growth,

duplication of

organelles,

protein

synthesis

Indefinite period

G0

Specialized

cell functions

M

MITOSIS AND

CYTOKINESIS

(See Figure 2.17)

chapter 2 218/martini ppt...chapter 2 foundations the cell ... •glycolipids and glycoproteins form...

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