Cell Structure and its Environment.ppt

8/14/2019 Cell Structure and its Environment.ppt

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Cell Structure and

its Environment


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Early Discoveries

During 1665, Robert Hooke observed and

described cells in cork

Tiny compartments = cellulae

Small rooms


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Early Discoveries

Antonie Van Leeuwenhoek

- improves microscope

- first to observe and describe the single-

celled organisms

(animalculesmicroorganisms)


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Early Discoveries

Robert Brown (1831)published observationsreporting the discovery and widespreadoccurrence of nuclei in the cells

Matthias Schleiden (1838)Discovered thatplant parts are made of cells

Theodore Schwann (1839)Discovered that

animal parts are made of cells Rudolph Virchow (1855)Stated that all living

cells come only from other living cells


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Cell Theory

1) Every organism is composed of one or

more cells2) Cell is smallest unit having properties of

life

3) Continuity of life arises from growth and

division of single cells


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Cell

Smallest unit that lives on its own

Each cell is structurally organized for

metabolism

Potential to reproduce


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Types of Cell

Prokaryotic cell

Eukaryotic cell


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Prokaryotic cell

Smallest known cell

Tiny volume of cytoplasm

Membranes dont enclosed DNA


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Parts

Or capsule


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Eukaryotic cell

Present in plants, animals and fungi

Has organelles and nucleus

Animal cell Plant cell


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Structural Organization of Cells

Plasma membrane

Nucleus

Cytoplasm


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Plasma Membrane

Selectively isolates the cells contents from

the external environment

Regulates the exchange of essentialsubstances between the cells contents

and the external environment

Communicates with other cells


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Plasma MembraneLipid Bilayer


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Membrane Proteins

Proteinpump across

bilayer

Proteinchannel

across bilayer

Protein pump

Recognitionprotein

Receptorprotein

extracellularenvironment

cytoplasm

lipid bilayer

Figure 4.4Pa e 57


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Membrane Proteins

proteins

double layer of lipids


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Why arent all cells big?

The smaller or narrower the cell, the more

efficiently materials cross its surface and

become distributed through the interior.


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Common Features of Eukaryotic

Cells Nucleuslocalizing the cells DNA

Endoplasmic reticulumprotein and lipid

synthesis Golgi bodysorting and shipping proteins

Lysosomes/Peroxisomestransporting or

storing a variety of substance

Mitochondriaproducing many ATP molecules

in highly efficient fashion


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The Nucleus

Control center of

eukaryotic cells

The organelle thatphysically separates

DNA from cytoplasmic

machinery


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Components of Nucleus

nuclear envelope

nucleoplasm

nucleolus

chromatin

Figure 4.11b

Page 62


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Components of the Nucleus

Nuclear Envelopepore riddled double

membrane system that selectively controls

the passage of various substances intoand out of the nucleus


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Nuclear Envelope

Two outer membranes (lipid bilayers)

Innermost surface has DNA attachment sites

Nuclear pore bilayer facing cytoplasm Nuclear envelope

bilayer facingnucleoplasm

Figure 4.12bPa e 63


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Nucleoplasmfluid interior portion of the

nucleus

NucleolusConstruction site wherecertain RNAs and proteins are combined

to make ribosomal subunits


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ChromatinTotal collection of all DNA

molecules and their associated proteins in

the nucleus ChromosomeOne DNA molecule and

many proteins that are intimately

associated with it



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Series of functionally connected

organelles in which lipids are assembled

and new polypeptide chains are modified. Products are sorted and shipped to

different destination

Endomembrane System


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Components of Endomembrane

System

Endoplasmic Reticulum

Golgi Bodies

Vesicles


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Endoplasmic Reticulum

In animal cells, continuous with nuclear

membrane

Extends throughout cytoplasm

Two regions - rough and smooth


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Endoplasmic Reticulum and the Ribosomes: protein

production machine

Endoplasmic Reticulum (ER)

source: http://cellbio.utmb.edu/cellbio/ribosome.htm


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Golgi Body

Puts finishing touches on proteins and

lipids that arrive from ER

Packages finished material for shipment tofinal destinations

Material arrives and leaves in vesicles

buddingvesicle

Figure 4.15Pa e 65


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Vesicles

Membranous sacs that move through

cytoplasm

Lysosomes

Organelle of intracellular digestion

Peroxisomes

Breaks down fatty acids and amino acids


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Lysosomes Rich in digestive enzymes (that work at low

pH)

Digest bacteria that invade a cell

Recycling of membrane components

Repair damage to plasma membrane

Get rid of toxic substances Many in the liver

Peroxisomes

lysosome


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Mitochondrial Origins

Mitochondria resemble bacteria

Have own DNA, ribosomes

Divide on their own

May have evolved from ancient bacteriathat were engulfed but not digested


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Mitochondria

Contain their own genome

(distinct from nuclear

genome)

Self-replicating

Critical role in generation of

energy (called ATP):

-

Glycolysis (without oxygenuse)

- Krebs cycle (in presence of

oxygen)


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Non-membranous Structures and

their Functions RibosomesAssembling polypeptide

chains

CytoskeletonImparting overall shapeand internal organization to the cell;

locomotion

MicrotubulesMicrofilaments


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Cytoskeleton

Reinforce, organize, and move internal cell

parts

MicrofilamentsTwo polypeptide chains of actin monomers

Structural support

MicrotubulesProteins cylinders (tubulin monomers)

move cell interior


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Cytoskeleton

Intermediate filaments

Help strengthen and maintain the shape of

cells and cell parts


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The cytoskeleton: a cell's


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The cytoskeleton: a cell sscaffold


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Specialized Plant Organelles

Chloroplasts

Chromoplasts

Amyloplasts Central Vacuole


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Chloroplast

Use sunlight energy to drive the formation

of ATP and NADPH.

Used to assemble sugars and some otherorganic compounds


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Chloroplast


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Thylakoid membrane

The first stage of photosynthesis starts

where many light-trapping pigments,

enzymes and other proteins areembedded


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Plastids

Chromoplast

- Lacks chlorophyll, but they have an

abundance in carotenoids

Amyloplast

- Lacks pigments, often they store starch

grains and are abundant in cells of stems,potato tubers, and seeds


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Central Vacuole

Fluid-filled organelle surrounded by singlemembrane

Stores amino acids, sugars, ions and toxic

wastes Helps the cell grow

It expands during growth

Blue or purple pigments stored in the central

vacuoles are responsible for the colors of theflower


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How Do Cells Move?

Cilia

Flagella


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Cell Surface Specializations

Cell wall

- structural component that wraps

continuously around the plasmamembrane

- it is porous

Cell Junction- where a cell sends and receives signalsand materials, and where it recognizesitself to cells of the same type


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Plant Cell Walls

Primary cell wall

Secondary cell wall

(3 layers)

Thin and pliable

Permits the cell to continue to

enlarge under the pressure of

incoming water

reinforces cell shape


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Animal Cell Junctions

tight

junctionsadhering

junctiongap

junction


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Cell Communication

- one cell signals another to change its

activities

Cell Surface Specializations

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Cell Structure and its Environment.ppt