Cell Structure and FunctionCell Structure and Function

Chapter 4

Robert Hooke (1635-1703)Robert Hooke (1635 1703)

Discovered “cells” byDiscovered cells by studying the cork layer of bark from an oak tree.

Found cells when studied tree stemsstudied tree stems, roots, and leaves.

Antony van Leeuwenhoek (1632-1723)

Learned how to make excellent lenses & placed them into simple microscopessimple microscopes.

He was the first person to observe living cells.

Vorticella

spirogyra

Matthias Schleiden & Theodor S hSchwann

Schleiden (botanist) &Schleiden (botanist) & Schwann (zoologist) developed the Cell Theory.

Rudolf Virchow (1821-1902)Rudolf Virchow (1821 1902)Noted that cells

come from other cells ffrom studying humanhuman diseases.

The Cell TheoryThe Cell Theory

1 All organisms are made up of one or1. All organisms are made up of one or more cells.

2 Cells are the basic unit of structure2. Cells are the basic unit of structure and function of organisms.

3 N ll f i ti ll b3. New cells come from existing cells by cell reproduction.

MicroscopesMicroscopesLight: light wavesLight: light waves

pass through a small organism, or thin slices of a larger organism, & th t tthe structures are magnified through the lens systemthe lens system.

Phase contrast:Phase contrast: modifies differences in light waves so that transparent cell structures appear as li ht & d k ilight & dark regions.

Electron: enables usElectron: enables us to see cell parts at very high magnifications by using an electron b i t d fbeam instead of a light beam to illuminate theilluminate the object.

Transmission ElectronTransmission Electron Microscope: (TEM)

Cell structures can be enlarged as much as 1,000,000x & provides photographs that show remarkableshow remarkable detail.

apoptosis

CellsCellsBasic unit of living organisms.Basic unit of living organisms.2 basic types:

prokaryotes: do not have a membraneprokaryotes: do not have a membrane enclosing their DNA. Do not contain membrane-bound organelles.e b a e bou d o ga e es

Prokaryotes are divided into two o a yotes a e d ded to t odomains:Bacteria: includes organisms that areBacteria: includes organisms that are similar to the first cellular life-forms.

Archae: includes organisms that are gthought to be more closely related to

eukaryotic cells found in all other ykingdoms of life.

eukaryotes: usually have at least oneeukaryotes: usually have at least onemembrane enclosed structure, the nucleus, which contains DNA; contain membrane-;bound organelles.

unicellular: consists of a single cell which carries out all the many activities of that organism.

multicellular: contain from dozens to billions of cells Organisms have a number of differentcells. Organisms have a number of different types of cells; each type of cell has a certain role to play.role to play.

Colonies: a collection of genetically identical cells that live together in a collected group.g g p

Colonies are not truly multicellular since few of their activities are coordinated.

Volvox

Levels of OrganizationLevels of Organization

Cells tissue (group of similar cells thatCells tissue (group of similar cells that carry out a specific function) organs(group of tissues that perform a particular job in an organism) organ system(group of organs that accomplish related t k ) i (th bi i ftasks) organism (the combining of organ systems)

OrganellesOrganelles

Structures that carry out specific functions.

Plasma MembranePlasma Membrane• Outer membrane that encloses the cell contents• Controls the passage of materials in & out of the cell• Made of 2 thin layers of lipid molecules.• Protein molecules floating on & within the lipid

layers help molecules move in & out of the cell.

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1 - cell-surface marker: glycoprotein that identifies cell type.2 - receptor protein: recognizes and binds to substances outside of cell.3 – intergral protein: enzyme that assists chemical reactions inside cell3 – intergral protein: enzyme that assists chemical reactions inside cell.4 – transport protein: helps substances move across cell membrane.5 – peripheral proteins: lie on only one side of membrane and not

embedded in itembedded in it.The cell membrane is a fluid mosaic model. The bilayer behaves like a fluid more than a solid. The membrane’s lipids and proteins can move laterally within the bilayer.

CytoplasmCytoplasm• Jellylike material found within the cell.y• Contains the organelles.• cytosol: includes molecules and small particles but

not membrane-bound organelles.• Many of the chemical reactions of a cell take place in

the cytosolthe cytosol.

NucleusNucleus• Control center of the cell• Contains most of the cell’s genetic information in

DNA• Contain one or more nucleoli, sites of synthesis &

assembly of rRNA & tRNA• genes: control the basic functions of the cell• genes: control the basic functions of the cell• chromosomes: contain DNA & proteins

Nuclear Envelope & NucleolusNuclear Envelope & Nucleolus

• Double membrane surrounding nucleusg• It is continuous at several pts. w/a complex network

of other membranes in the cytoplasm• The nucleolus manufactures ribosomes. It is a knot

of chromatin.

The portion of the cell nucleus which contains all of the DNA of theall of the DNA of the nucleus in an animal or plant cell.

Endoplasmic Reticulum• Provide passageways for the movement of materials

throughout the cell2 t• 2 types:

RER – Rough Endoplasmic ReticulumSER Smooth Endoplasmic ReticulumSER – Smooth Endoplasmic Reticulum

RERRER

• Produces phospholipids and proteinsProduces phospholipids and proteins• The ribosomes produce digestive enzymes

SERSER

• Builds lipids like cholesterol.p• Produces estrogen and testosterone.• Releases calcium in skeletal and heart muscle,

which stimulates contractions.• Detoxify drugs and poisons in the liver and kidney

cellscells.

RibosomesRibosomesResponsible for protein synthesis.p p yMade of protein and RNA molecules and do not have a

membrane.

Mitochondria• Powerhouse of the cell• Transfer energy from organic molecules to

Ad i T i h h t (ATP) hi h tAdenosine Triphosphate (ATP) which powers most of the cell’s chemical reactions.

• Consists of an outer membrane & a folded innerConsists of an outer membrane & a folded inner membrane

cristae

VacuoleVacuoleStore & transport nutrients & waste productsp p

Golgi ComplexGolgi Complex• Helps package cell products for export from the cellp p g p p

VesiclesVesicles• Small, spherical shaped sac that are surrounded by , p p y

a single membrane.• Classified by their contents.• Often migrate to and merge with the plasma

membrane.• Release their contents to the outside of the cell• Release their contents to the outside of the cell.• “shuttle service”• Include lysosomes and peroxisomesy p

LysosomesLysosomesContain digestive enzymes which help break down g y p

large molecules & worn-out cell parts

Peroxisomes• Similar to lysosomes but contain different enzymes

and not produced by Golgi Apparatus.• Abundant in liver and kidney cells• Abundant in liver and kidney cells.• Break down fatty acids, which is then used by

mitochondria.• Produce hydrogen peroxide when breaking down

alcohol and killing bacteria.

CentriolesCentriolesPresent in pairs and play an important role in mitosis.p p y p

Cytoskeleton (Microtubules & Microfilaments)Tiny tubes composed of proteins.Form the cell’s skeletonEnable the cell to maintain its distinct shape & internal

organization.Microfilaments contribute to cell movementMicrofilaments contribute to cell movement.

Cell WallCell WallProvides strength and protectionProvides strength and protectionFormed by living plant cells of cellulose fibers.

Central VacuoleCentral Vacuole

• Reservoir that stores large amounts of water.Reservoir that stores large amounts of water.• Also stores enzymes, metabolic waste, and

other materials.

PlastidsPlastids• Organelles surrounded by a doubleOrganelles surrounded by a double

membrane and contain their own DNA.2 types:yp

CHLOROPLASTSCHROMOPLASTSCHROMOPLASTS

ChloroplastsChloroplastsContain the pigment chlorophyll, essential for

capturing the light energy of the suncapturing the light energy of the sun.Contain complicated membranes where

photosynthesis takes place calledphotosynthesis takes place called thylakoids.

ChromoplastsChromoplasts• Contain colorful pigments that may or mayContain colorful pigments that may or may

not take part in photosynthesis.Carotene: orange pigment found in carrot root g p g

cells.Flower petal cells contain red, purple, yellow. p , p p , y

or white pigments.