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CELL AS A UNIT OF LIFE

Cell theory Prokaryotic and Eukaryotic cells

Microscopic structure of plant and animal cells

Cells as basic units of living organisms are grouped into tissue and organs

about this chapter

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Definition of Cell

A cell is the smallest unit that is capable of performing life

functions.

Examples of Cells

Amoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria

3.1 Early Discoveries

Mid 1600s •Robert Hooke observed and described cells in cork

Late 1600s •Antony van Leeuwenhoek observed sperm, microorganisms

1820s •Robert Brown observed and named nucleus in plant cells

Developing Cell Theory

Rudolf Virchow

Theodor

Schwann

Schlieden “Plant growth, he stated in 1837, came about through the production of new cells,

which, he speculated, were propagated from the nuclei of old cells,” i.e., all plants

are composed of cells.

Matthias Schleiden

CELL THEORY

Living things are made up of cells

The cell is the basic unit of structure

Cells come only from preexisting cells

Cell

Smallest unit of lifeCan survive on its

own or has potential to do so

Is highly organized for metabolism

Senses and responds to environment

Has potential to reproduce

Two types of cells :

Prokaryotic cells No true nucleus or organelles e.g : Eubacteria and cyanobacteria

Eukaryotic cells Nucleus and organelles that

surrounded by a membrane e.g: protozoa, algae, fungi, plants

and animals

Microscopes Create detailed images of something

that is otherwise too small to see

Light microscopes Simple or compound

Electron microscopes Transmission EM or Scanning EM

ocular lens

objective lens

stage

condenser

illuminator

prism

source of illumination

Figure 4.6bPage 58

Slide 1

ocular lens

objective lens

stage

condenser

illuminator

prism

source of illumination

Figure 4.6bPage 58

Click to view animation.

Light microscopy animation.

Animation

viewing screen

projector lens

intermediate lens

objective lens

specimencondenser lens

accelerated electron flow (top to bottom)

Figure 4.7Page 58

frog egg3 mm

typical plant cell10-100 µm

mitochondrion1-5 µm

chloroplast2-10 µm

human redblood cell7-8 µmdiameter

Trypanosoma(protozoan)25 µm long

Chlamydomonas(green alga)5-6 µm long

polio virus30 nm

HIV(AIDS virus)100 nm

T4 bacteriophage225 nm long

tobacco mosaic virus300 nm long

DNA molecule2 nm diameter

Unaided Vision

Electron Microscope (Down To 0.5 Nm)

Light Microscope (Down To 200 Nm)

Escherichia coli (bacterium)1-5 µm long

1 centimeter (cm) = 1/100 meter, or 0.4 inch

1 millimeter (mm) = 1/1,000 meter

1 micrometer (µm) = 1/1,000,000 meter

1 nanometer (nm) = 1/1,000,000,000 meter

1 meter = 102 cm = 103 mm = 106 µm = 109 nm

1 mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm 0.5 nm

Figure 4.8Page 59

Limitations of Light Microscopy

Wavelengths of light are 400-750 nm

If a structure is less than one-half of a wavelength long, it will not be visible

Light microscopes can resolve objects down to about 200 nm in size

Electron Microscopy

Uses streams of accelerated electrons rather than light

Electrons are focused by magnets rather than glass lenses

Can resolve structures down to 0.5 nm

PROKARYOTIC CELLS &

EUKARYOTIC CELLS

The prokaryotic cell is much simpler in structure, lacking a nucleus and the other membrane-enclosed organelles of the eukaryotic cell.

1. Organisms2. Cell size3. Cell division4. Cell walls5. Organelles6. Genetic material7. Flagella8. Respiration9. Photosynthesis10.Nitrogen fixation

* refer handout

prokaryotes vs eukaryotes

MICROSCOPIC STRUCTURE OF PLANT

AND ANIMAL CELLS

animal cells

plant cells

CELLS AS BASIC UNITS OF LIVING ORGANISMS

ARE GROUPED INTO TISSUE AND ORGANS

CELLS ARE GROUPED INTO TISSUE AND

ORGANS

THE PLANT

Plant PlantGymnosperm- seed-bearing plantAngiosperm-flower-producing plant

TISSUES

Cells in plants and animals are grouped together in tissues.

A tissue is a group of similar cells that are organised to do a specific job

Angiosperm Body Plan

VASCULAR TISSUES

GROUND TISSUES

SHOOT SYSTEM

ROOT SYSTEM

EPIDERMIS

•Ground tissue system

•Vascular tissue system

•Dermal tissue system

shoot tip(terminal bud)

lateral (axillary) bud

flower

EPIDERMIS

leaf

seeds(inside fruit)

witheredcotyledon

root hairs

root tiproot cap

node

nodeinternode

VASCULAR TISSUES

GROUND TISSUES

SHOOT SYSTEM

ROOT SYSTEM

primary root

lateral root

Overview of the plant body

Ground tissue

Vascular tissue

Meristems• Regions where cell divisions produce

plant growth• Consist of unspecialised, dividing

cells.• Apical meristems

– Lengthen stems and roots– Responsible for primary growth

• Lateral meristems– Increase width of stems– Responsible for secondary growth

activity atmeristems

new cellselongateand start todifferentiateinto primarytissues



Figure 29.4Page 507

Root apical meristem

Shoot apical meristem



ROOT APICAL MERISTEMApical meristem near all root tips gives rise to protoderm, ground meristem, and procambium

These give rise to the root’s primary tissue systems: epidermis, ground tissues, and

vascular tissues

SHOOT APICAL MERISTEMSource of primary growth (lengthening)

THREE PRIMARY MERISTEMSProtoderm epidermis

Ground meristem ground tissueProcambium primary vascular tissues



Figure 29.4Page 507

Apical Meristems

vascular cambium

cork cambium

secondaryphloem

secondaryxylem

thickening

LATERAL MERISTEMSTwo lateral meristems in older stems and roots of woody plants produce secondary growth (increases in diameter):

Vascular cambium secondary vascular tissuesCork cambium periderm (replaces epidermis)

Figure 29.4Page 507

LATERAL MERISTEMS

Ground tissue system

• -serves basic functions:

• Food and water storage

Vascular tissue system

• -distributes water and solutes

Dermal tissue system

• Covers and protect plant surfaces

Three Plant Tissue system

GROUND TISSUE SYSTEM

Predominantly cells in the leaf, stem, roots and storage organs

e.g., potato tuber e.g., celery stem e.g., cherry seed

VASCULAR TISSUE SYSTEM

The xylem and phloem made up the plant vascular tissue system

Food, water, and other substances are transported and is continuous throughout the plant.

DERMAL TISSUE SYSTEM (OR EPIDERMIS)

Single layer of tightly packed cells covering and protecting the young parts of plant

E.g., the waxy cuticle that help plant retain water in leaves and stems

Tissue Differentiation

Protoderm Ground meristemProcambium

Epidermis

Ground tissuePrimary vascular tissue

Simple Tissues• Made up of only one

type of cell

Parenchyma

Collenchyma

Sclerenchyma

Parenchyma: A Simple Tissue

• Most of a plant’s soft primary growth

• Pliable, thin walled, many sided cells

• Cells remain alive at maturity and retain capacity to divide

• Mesophyll is a type that contains chloroplasts

Parenchyma: A Simple Tissue

• Most of a plant’s soft primary growth

• Pliable, thin walled, many sided cells

• Cells remain alive at maturity and retain capacity to divide

• Mesophyll is a type that contains chloroplasts

• Ground tissue for fruits, stems and leaves.

Collenchyma: A Simple Tissue

• Specialized for support for primary tissues

• Makes stems strong but pliable• Cells are elongated• Walls thickened with pectin• Alive at maturity

Scelerenchyma : A Simple Tissue

• Supports mature plant parts• Protects many seeds• Thick, lignified walls • Dead at maturity• Two types:

– Fibers: Long, tapered cells– Sclereids: Stubbier cells

Complex Tissues

Xylem

Phloem

Epidermis

Composed of a mix of cell types

Xylem

•Conducts water and dissolved minerals•Conducting cells are dead and hollow at maturity

vessel membertracheids

Phloem: A Complex Vascular Tissue

• Transports sugars • Main conducting

cells are sieve-tube members

• Companion cells assist in the loading of sugars

sieve plate

sieve-tubemember

companioncell

Epidermis: A Complex Plant Tissue• Covers and protects plant

surfaces• Secretes a waxy, waterproof

cuticle• In plants with secondary

growth, periderm replaces epidermis

Monocots and Dicots:

Parallel veinsNetlike veins

3 pores1 pore

4 or 5 floral parts

3 floral parts

1 cotyledon 2 cotyledons

Vascular bundles dispersed

Vascular bundles in ring

Monocots and Dicots:

Parallel veinsNetlike veins

3 pores1 pore

4 or 5 floral parts

3 floral parts

1 cotyledon 2 cotyledons

Vascular bundles dispersed

Vascular bundles in ring

Shoot Development

immature leaf

ground meristem

primary phloem

primary xylempith

procambium

cortex

procambium

protoderm

shoot apical meristem

procambium

epidermis

Figure 29.11 Page 510

Internal Structure of a Dicot Stem

Outermost layer is epidermisCortex lies beneath epidermisRing of vascular bundles separates

the cortex from the pith The pith lies in the center of the

stem

Internal Structure of a Monocot Stem

• The vascular bundles are distributed throughout the ground tissue• No division of ground tissue into cortex and pith

Ring of vascular bundlesdividing ground tissue into cortex and pith Vascular bundles distributed

throughout ground tissue

Dicot Monocot

Internal structure of Stems

Common Leaf Forms

petiole

blade

axillarybud

node

blade

sheath

node

DICOT MONOCOT

Adapted for Photosynthesis

Leaves are usually thin High surface area-to-volume ratio Promotes diffusion of carbon dioxide in,

oxygen outLeaves are arranged to capture sunlightAre held perpendicular to rays of sunArranged so they don’t shade one another

Leaf Structure

UPPEREPIDERMIS

PALISADEMESOPHYLL

SPONGYMESOPHYLL

LOWEREPIDERMIS

one stoma

cuticle

O2CO2

xylem

phloem

Root Systems

Taproot system of a California poppy

Fibrous root system of a grass plant

Figure 29.17Page 514

VASCULAR CYLINDER:

endodermispericyclexylem

phloemcortexepidermis

fully grown root hair

Vessels have matured; root hairs and vascular cylinder about to form

Cells elongate; sieve tubes form and mature; vessel members start to form

Most cells have stopped dividing

Cells are dividing rapidly at apical and primary meristems

quiescent center

root cap

Root Structure

Root cap covers tip

Apical meristem produces the cap

Cell divisions at the apical meristem cause the root to lengthen

Farther up, cells differentiate and mature

AnimalCell specialization

ANIMAL TISSUES AND ORGAN SYSTEMS

Take a rest

Animal tissue

HOMEOSTASIS

Stable operating conditions in the internal environment

Brought about by coordinated activities of cells, tissues, organs, and organ systems

TISSUE A group of cells and intercellular

substances that interact in one or more

tasks

Four typesEpithelial tissue

Muscle tissue

Connective tissue

Nervous tissue

ORGANSGroup of tissues organized to perform

a task Heart is an organ that pumps blood

through body Heart consists of muscle tissue, nervous

tissue, connective tissue, and epithelial tissue

ORGAN SYSTEMS

Organs interact physically, chemically, or both to perform a common task

Circulatory system includes the heart, the arteries, and other vessels that transport blood through the body

EPITHELIAL TISSUE

Lines the body’s surface, cavities,

ducts, and tubes

One free surface faces a body

fluid or the environment

simplesquamousepithelium

basementmembrane

connective tissue

SIMPLE EPITHELIUM

Consists of a single layer of cells

Lines body ducts, cavities, and tubes

Cell shapes:

Squamous Cuboidal Columnar

STRATIFIED EPITHELIUM

Two or more layers thick

Functions in protection, as in skin

Cells in the layers may be squamous,

columnar, or cuboidal

Glands Secretory organs

derived from epithelium

Exocrine glands have ducts or tubes

(secrete mucus, saliva, earwax)

Endocrine glands are ductless

Product-hormone

Section through the glandular epithelium of a frog.

pore that opens at skin surface

mucous gland

poison gland

pigmented gland

CELL JUNCTIONS

a type of structure that exists within the tissue of a

multicellular organism. They consist of protein

complexes and provide contact between

neighbouring cells, between a cell and the

extracellular matrix, or

Tight junctions prevent leaks

Gap junctions connect abutting cytoplasms

Adhering junctions cement cells together

TightJunction

AdheringJunction

GapJunction

http://en.wikipedia.org/wiki/Multicellular

http://en.wikipedia.org/wiki/Cell_(biology)

CONNECTIVE TISSUE

Most abundant tissue in the bodyCells are scattered in an

extracellular matrixMatrix is collagen and/or elastin

fibers in a polysaccharide ground substance

collagenous fiberfibroblast

elastic fiber

Loose connective tissue

cartilage cell(chondrocyte)

Cartilage

collagenous fibers

collagenous fibers

fibroblast

Dense, regular connective tissue

ground substance with collagen fibers

cell bulging with fat droplet

nucleus

Adipose tissue (fat storage) Dense, irregular connective tissue

compactbone tissueblood vessel

bone cell(osteocyte)

Bone

SOFT CONNECTIVE TISSUESSPECIALIZED CONNECTIVE TISSUES

location of cartilage on knobby end of along bone

bone tissue

Figure 33.6Page 571

Blood

Classified as a connective tissue because blood cells arise in bone

Serves as the body’s transport medium

Red cells, white cells, and platelets are dispersed in a fluid medium called plasma

MUSCLE TISSUE

Composed of cells that contract when

stimulated

Helps move the body and specific body parts

Types of tissue- Skeletal, cardiac, smooth

SKELETAL MUSCLE

Located in muscles that attach to bones

Long, cylindrical cells are striated

Cells are bundled closely together in parallel arrays

Figure 33.8, page 572

SMOOTH MUSCLE

In walls of many internal organs

(stomach, lungs etc) and

some blood vessels

Cells are not striped and taper

at the ends

Figure 33.8, page 572

one muscle cell

one bundle of musclecells in its own sheath

outer connective tissue sheath around one muscle

one whole muscle, a biceps

Figure 33.9Page 572

CARDIAC MUSCLE

Present only in the heart

Cells are striated and

branching

Ends of cells are joined by

communication junctions

nucleus

NERVOUS TISSUE

Detects stimuli, integrates information, and

relays commands for response

Consists of excitable neurons and supporting

neuroglial cells

NEUROGLIA

Constitute more than half of the nervous

tissue

Protect and support the neurons, both

structurally and metabolically

Major Organ Systems

IntegumentaryMuscularSkeletalNervousEndocrine

•Lymphatic•Respiratory•Urinary•Circulatory•Reproductive

IntegumentarySystem

MuscularSystem

SkeletalSystem

NervousSystem

EndocrineSystem

CirculatorySystem

Fig. 33.11(1)Page 574

LymphaticSystem

RespiratorySystem

DigestiveSystem

UrinarySystem

ReproductionSystem

Fig. 33.11(2)Page 575

Organ systems carry out the major body functions of most animals. Each organ system consists of several organs and has

specific functions.

Thank you for your attention

^_^

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perbezaan antara mereka yang berjaya dengan yang lain bukanlah kerana kekurangan kekuatan atau ilmu,tetapi lebih kepada kekurangan kesungguhan dan kemahuan