Dr. B Ch 02_lecture_presentation

© 2012 Pearson Education, Inc.

2Foundations:The Cell

PowerPoint® Lecture Presentations prepared by

Steven Bassett

Southeast Community College

Lincoln, Nebraska


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

• germ cells or reproductive cells

• Sperm in males and oocytes in females

• Somatic cells

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


The Study of Cells

• Cytology

• Study of cells

• Common techniques used:

• Light microscopy (LM)

• Transmission electron microscopy (TEM)

• Scanning electron microscopy (SEM)


The Study of Cells

• Light Microscopy

• Magnification up to 1000 times

• Sometimes 2000 maximum


Figure 2.1a Different Techniques, Different Perspectives

Cells as seen in light microscopy

(respiratory tract)

LM 400


The Study of Cells

• Transmission Electron Microscopy

• Magnifies more than light microscopy


Figure 2.1b Different Techniques, Different Perspectives

TEM 2400

Cells as seen in transmission

electron microscopy (intestinal

tract)


The Study of Cells

• Scanning Electron Microscopy

• Shows three-dimensional images


Figure 2.1c Different Techniques, Different Perspectives

SEM 14,000

Cells as seen in scanning

electron microscopy

(respiratory tract)


Figure 2.2 The Diversity of Cells in the Body

Smooth

muscle

cell

Blood

cells

Bone

cell

Oocyte Sperm

Neuron in

brain

Fat cell

Cells lining

intestinal tract


Cellular Anatomy

• The cell consists of:

• Cytoplasm

• Cytosol

• Organelles

• Plasmalemma

• Cell membrane


Figure 2.4 A Flowchart for the Study of Cell Structure

CYTOPLASM

CYTOSOL

PLASMALEMMA

ORGANELLES

NONMEMBRANOUSORGANELLES

MEMBRANOUSORGANELLES

THE CELL

• 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

• Nonmembranous organelles

• Cytoskeleton

• Microvilli

• Centrioles

• Cilia

• Flagella

• Ribosomes


Figure 2.3 Anatomy of a Typical Cell

Microvilli

Secretory

vesicles

Cytosol

Lysosome

CentrosomeCentriole

Chromatin

Nucleoplasm

Nucleolus

Nuclear envelope

surrounding nucleus

Cytoskeleton

Plasmalemma

Golgi apparatus

Mitochondrion

Peroxisome

Nuclear pores

Smooth

endoplasmic

reticulumRough

endoplasmic

reticulumFixed ribosomes

Free ribosomes


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


Cellular Anatomy

• Organelles of the cell

• Membranous organelles

• Mitochondria

• Nucleus

• Endoplasmic reticulum

• Golgi apparatus

• Lysosomes

• Peroxisomes


Figure 2.3 Anatomy of a Typical Cell

Microvilli

Secretory

vesicles

Cytosol

Lysosome

CentrosomeCentriole

Chromatin

Nucleoplasm

Nucleolus

Nuclear envelope

surrounding nucleus

Cytoskeleton

Plasmalemma

Golgi apparatus

Mitochondrion

Peroxisome

Nuclear pores

Smooth

endoplasmic

reticulumRough

endoplasmic

reticulumFixed ribosomes

Free ribosomes


Table 2.1-2 Anatomy of a Representative Cell (Part 2 of 2)


Cellular Anatomy

• Plasmalemma

• A cell membrane composed of:

• Phospholipids

• Glycolipids

• Protein

• Cholesterol


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


Figure 2.5 The Plasmalemma

Glycolipids

of glycocalyxPhospholipid

bilayer

Integral protein

with channel

Hydrophobic

tails

Gated

channel

Cholesterol

Peripheral

proteinsHydrophilic

heads

Cytoskeleton

(Microfilaments) 2 nmCYTOPLASM

The plasmalemma

The phospholipid bilayer

Hydrophobic

tails

Hydrophilic

heads

Cholesterol

Integral

glycoproteins

EXTRACELLULAR FLUID


Cellular Anatomy

• Functions of the Plasmalemma

• Cell membrane (also called phospholipid

bilayer)

• Major functions:

• Physical isolation

• Regulation of exchange with the environment

(permeability)

• Sensitivity

• Structural support


Cellular Anatomy

• Membrane permeability of the plasmalemma

• Passive processes

• Diffusion

• Osmosis

• Facilitative diffusion


Figure 2.6 Diffusion across Plasmalemmae

PlasmalemmaChannel

protein

CYTOPLASM

EXTRACELLULAR

FLUID

Lipids, lipid-solublemolecules, and solublegases (O2 and CO2) candiffuse across the lipidbilayer of the plasmalemma.

Water, small water-soluble molecules,and ions diffusethrough membranechannels.

Large molecules thatcannot fit through themembrane channelsand cannot diffusethrough the membranelipids can only crossthe plasmalemmawhen transported by acarrier mechanism.


Membrane permeability: active processes:

Active transport uses enzymes and carrier proteins and ATP.

Ion pumps are carrier proteins for charged particles.

Ions moved regularly by active transport include:

Na+

Ca2+

Mg2+

K+

An ion pump that moves two ions simultaneously in opposite directions is called an

exchange pump.

Endocytosis:

Pinocytosis: Active process for transporting liquid across the plasmalemma.

Phagocytosis: Active process for transporting solid substances across the

plasmalemma.

Exocytosis: Active process to eliminate waste products across the plasmalemma.

Cellular anatomy


Figure 2.7 Phagocytosis

Bacterium

Pseudopodium

Phagosome

Lysosome

Golgiapparatus

Phagosomefuses with alysosome

Secondarylysosome

Phagocytosis

Exocytosis


Figure 2.8 Receptor–Mediated Endocytosis

Electron micrographs showing vesicle formation in receptor-mediated endocytosis

Early vesicleformation

Plasmalemma

Cytoplasm Completed vesicle

TEMs 60,000


Table 2.2 Summary of Mechanisms Involved in Movement across Plasmalemmae


Figure 2.9 The Cytoskeleton

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 special fluorescent

labeling

LM 3200

SEM 30,000

Microvilli

Microfilaments

Plasmalemma

Terminal web

Mitochondrion

Intermediate

filaments

Endoplasmic

reticulum

Microtubule

Secretory

vesicle


Cellular Anatomy

• Nonmembranous Organelles (details)

• Examples of microtubules

• Centrioles

• Cilia

• Flagella


Figure 2.10 Centrioles and Cilia

A centriole consistsof nine microtubuletriplets (9 0 array).The centrosomecontains a pair ofcentrioles oriented atright angles to oneanother.

A cilium contains nine pairs ofmicrotubules surrounding a central pair(9 2 array).

A single cilium swings forward and thenreturns to its original position. During the power stroke, the cilium is relativelystiff, but during the return stroke, itbends and moves parallel to the cellsurface.

Microtubules

Basal body

Plasmalemma

Microtubules

Power stroke Return stroke

TEM 240,000


Table 2.3 A Comparison of Centrioles, Cilia, and Flagella


• Nonmembranous Organelles (details)

• Ribosomes

• Free ribosomes: float in the cytoplasm

• Fixed ribosomes: attached to the endoplasmic

reticulum

• Both are involved in producing protein

Cellular Anatomy


Figure 2.11 Ribosomes

Nucleus 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


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 are double-membraned

organelles:

Cristae are the folds of the inner

membrane.

The inner fluid is the matrix.

They produce ATP.


Figure 2.12 Mitochondria

Inner membrane

Organic molecules

and O2

CO2

ATP

Matrix Cristae Enzymes

Outer

membrane

TEM 61,776

Cytoplasm

of cell Cristae Matrix


Cellular Anatomy


• Nucleus: control center of the cell

• Nucleoplasm

• Nuclear envelope

• Perinuclear space

• Nuclear pores

• Nuclear matrix


Figure 2.13ab The Nucleus

Nuclear envelope

Perinuclear space

Nuclear pore

A nuclear pore and the

perinuclear space

Perinuclear

space

Nucleoplasm

Chromatin

Nucleolus

Nuclear envelope

Nuclear pores

TEM showing important nuclear structures

TEM 4828


Cellular Anatomy

• Membranous Organelles: Nucleus

• Chromosomes:

• DNA wrapped around proteins called histones

• Nucleosomes

• Chromatin


Figure 2.14 Chromosome Structure

Nucleus of nondividing cell

Chromatin in nucleus

Dividing cellVisible chromosome

Supercoiled

region

Nucleosome

Histones DNA double

helix

In cells that are not

dividing, the

nucleosomes are loosely

coiled, forming a tangle

of fine filaments known

as chromatin.


Cellular Anatomy


• Endoplasmic Reticulum (ER)

• There are two types

• Rough endoplasmic reticulum (RER)

• Smooth endoplasmic reticulum (SER)


Figure 2.15 The Endoplasmic Reticulum

Ribosomes

Cisternae

Rough endoplasmic

reticulum with

fixed (attached)

ribosomes

Free

ribosomes

Smooth

endoplasmic

reticulum

Endoplasmic

Reticulum

TEM 11,000


Cellular Anatomy


• Rough endoplasmic reticulum

• Consists of fixed ribosomes

• Proteins enter the ER


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 2.16a The Golgi Apparatus

Vesicles

Maturing

(trans) face

Forming

(cis) face

A sectional view of the Golgi

apparatus of an active secretory cell

TEM 83,520


Figure 2.16b The Golgi Apparatus

EXTRACELLULAR

FLUID

CYTOSOL

Cisternae

Membrane

renewal

vesicles

Lysosome

Secretory

vesicle

Maturing

(trans) face

Forming

(cis) face

Transport

vesicle

This diagram shows the functional link between the

ER and the Golgi apparatus. Golgi structure has been

simplified to clarify the relationships between the

membranes. Transport vesicles carry the secretory

product from the endoplasmic reticulum to the Golgi

apparatus, and transfer vesicles move membrane

and materials between the Golgi cisternae. At the

maturing face, three functional categories of vesicles

develop. Secretory vesicles carry the secretion from

the Golgi to the cell surface, where exocytosis

releases the contents into the extracellular fluid.

Other vesicles add surface area and integral proteins

to the plasmalemma. Lysosomes, which remain in

the cytoplasm, are vesicles filled with enzymes.


Cellular Anatomy


• Lysosomes

• Fuse with phagosomes to digest solid materials

• Recycle damaged organelles

• Sometimes rupture, thus killing the entire cell

(called autolysis)


Figure 2.17 Lysosomal Functions

Waste products and debris are then ejected from the

cell when the vesicle fuses with the plasma membrane.

Endocytosis

Extracellular

solid or fluid

As digestion

occurs, nutrients

are reabsorbed for

recycling.

Primary

lysosomes

contain

inactive

enzymes.

As the materials

or pathogens are

broken down,

nutrients are

absorbed.

Golgi

apparatus

Function 1: A primary

lysosome may fuse with

the membrane of another

organelle, such as a

mitochondrion, forming a

secondary lysosome.

Function 2: A secondary

lysosome may also form

when a primary lysosome

fuses with a vesicle

containing fluid or solid

materials from outside the

cell.

Function 3: The lysosomal

membrane breaks down

following injury to, or death

of, the cell. The digestive

enzymes then attack the

cytoplasm in a destructive

process known as

autolysis. For this reason

lysosomes are sometimes

called “suicide packets.”


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


Cellular Anatomy

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Membrane flow is the continual movement and recycling of the plasmalemma.

The ER, Golgi apparatus, and vesicles constantly recycle the lipids, protein

channels, and enzymes of the plasmalemma.

Passive transport:

Diffusion: net movement of material from high concentration to low

concentration area. Example: transportation of oxygen and carbon dioxide

across the plasmalemma.

Osmosis: diffusion of water across a membrane.

Facilitated diffusion: diffusion of materials with the aid of carrier proteins.

Example: transportation of glucose and amino acids.

Active transport:

Ionic pump.

Endocytosis

exocytosis


Intercellular Attachment

• Examples of Intercellular Attachment:

• Communicating junctions

• Gap junctions

• Adhering junctions

• Tight junctions

• Anchoring junctions

• Desmosome

• hemidesmosome


Figure 2.18ab Cell Attachments (Part 1 of 4)

Communicating junctions permit

the free diffusion of ions and small

molecules between two cells.

Embedded

proteins

(connexons)

Hemidesmosome

A diagrammatic view of an

epithelial cell shows the

major types of intercellular

connections.

Tight junction

Zonula adherens

Terminal web

Button

desmosome

Communicating

junction

Anchoring junction


Figure 2.18ac Cell Attachments (Part 2 of 4)

Hemidesmosome




connections.

Tight junction

Interlocking

junctional

proteins

Zonula adherens

Terminal web

Button

desmosome

Communicating

junctionAnchoring junction

Tight junction

Zonula

adherens

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 2.18ad Cell Attachments (Part 3 of 4)

Hemidesmosome




connections.

Tight junction

Zonula adherens

Terminal web

Button

desmosome

Communicating

junction

Anchoring junction

Intermediate

filaments

(cytokeratin)

Cell adhesion

molecules

(CAMs)

Dense area

Intercellular

cement

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.


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: DNA replication

• G2: protein synthesis


Figure 2.20 DNA Replication

KEY

Adenine

Guanine

Cytosine

Thymine

Segment 2

DNA polymerase

DNA nucleotide

DNA

polymerase

Segment 1


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


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


The Cell Life Cycle

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Mitosis—the distribution process of genetic

information

Mitosis consists of four stages:

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis:

Separation of daughter cells after mitosis.


Figure 2.19 The Cell Life Cycle

INTERPHASE

THECELL

CYCLE

MITOSIS ANDCYTOKINESIS(See Figure 2.21)

Indefinite periodG0

Specializedcell functions

G1

Normalcell functionsplus cell growth,duplication oforganelles,proteinsynthesis

G2

Proteinsynthesis

SDNA

replication,synthesis

ofhistones

M


Figure 2.21 Interphase and Mitosis

INTERPHASE

MITOSIS BEGINS

EARLY PROPHASE LATE PROPHASE METAPHASE ANAPHASE TELOPHASE INTERPHASE

CYTOKINESIS

Nucleus

Centrioles

(two pairs)

Astral rays Spindle

fibersCentriole Chromosome

with two sister

chromatids

Metaphase

plate

Chromosomal

microtubuleDaughter

chromosomes

Cleavage

furrow

Daughter

cells


Figure 2.21 Interphase and Mitosis (Part 1 of 2)

INTERPHASE

MITOSIS BEGINS

EARLY PROPHASE LATE PROPHASE

Nucleus

Centrioles

(two pairs)

Astral rays Spindle

fibers

Centriole Chromosome

with two sister

chromatids


Figure 2.21 Interphase and Mitosis (Part 2 of 2)

METAPHASE ANAPHASE TELOPHASE INTERPHASE

CYTOKINESISMetaphase

plate

Chromosomal

microtubule

Daughter

chromosomes

Cleavage

furrow

Daughter

cells

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Dr. B Ch 02_lecture_presentation