The CellThe Cell

A cell is the smallest unit of A cell is the smallest unit of livingliving matter. matter.

Don’t confuse this with: atom, Don’t confuse this with: atom, element, proton, etc.element, proton, etc.

Cell SizeCell Size

Three Main PartsThree Main Parts

Plasma membranePlasma membrane NucleusNucleus CytoplasmCytoplasm

These are ALL CELLS!These are ALL CELLS!

Cell TheoryCell Theory

““Theory” is not a casual term in Theory” is not a casual term in science.science.

Tested innumerable times with Tested innumerable times with consistent results.consistent results.

Universally acceptedUniversally accepted One of the most basic, fundamental One of the most basic, fundamental

concepts in the foundation of concepts in the foundation of biology.biology.

Cell TheoryCell Theory

– 1800s; several scientists working 1800s; several scientists working independently had similar results.independently had similar results.

1. All organisms are made of cells.1. All organisms are made of cells.2. A cell is the structural & function 2. A cell is the structural & function unit of organs.unit of organs.

3. All cells come from pre-existing 3. All cells come from pre-existing cells.cells.

4. Cells are capable of self-4. Cells are capable of self-reproduction.reproduction.

There are two types of There are two types of cells:cells:

1.1. Prokaryotic-Prokaryotic- cells that DO NOT have a cells that DO NOT have a nucleus or other cell ORGANELLESnucleus or other cell ORGANELLES

2.2. Eukaryotic-Eukaryotic- cells with a NUCLEUS & cells with a NUCLEUS & cell ORGANELLEScell ORGANELLES

Which is more complicated?Which is more complicated? REMEMBER REMEMBER YOUYOU ARE ARE EUKARYOTIC!EUKARYOTIC!

ProkaryoticProkaryotic vs vs EukaryoticEukaryotic

Pro = beforePro = before Karyote=kernel(nucleKaryote=kernel(nucle

us)us) DNA is NOT contained DNA is NOT contained

within a nucleuswithin a nucleus Most have a cell wall Most have a cell wall

outside the plasma outside the plasma membranemembrane

May have type of May have type of flagella or pilus flagella or pilus

Archaea and BacteriaArchaea and Bacteria

Eu= trueEu= true Karyote=nucleusKaryote=nucleus DNA contained in DNA contained in

double membraned double membraned nucleusnucleus

Only plant cells have Only plant cells have cell wallcell wall

Contains membrane Contains membrane bound organellesbound organelles

Plants, animals, protists,Plants, animals, protists, fungifungi

Types of OrganismsTypes of Organisms

Unicellular organismsUnicellular organisms– Bacteria, Protists, etc.Bacteria, Protists, etc.

Multicellular organismsMulticellular organisms– PlantsPlants– AnimalsAnimals

Muscles, skin, nerves, liver, digestive, bones, Muscles, skin, nerves, liver, digestive, bones, blood, immune system, lungs, etc.blood, immune system, lungs, etc.

Why cells aren’t biggerWhy cells aren’t bigger

If cells get too large in volume compared to If cells get too large in volume compared to their surface area then it’s difficult to their surface area then it’s difficult to distribute nutrients throughout the cell and distribute nutrients throughout the cell and too hard to get rid of build up of wastes.too hard to get rid of build up of wastes.

The Cell MembraneThe Cell Membrane

A phospholipid bilayerA phospholipid bilayer

With proteins embedded in itWith proteins embedded in it

Hydrophillic heads and Hydrophillic heads and Hydrophobic tailsHydrophobic tails

The phospholipid consists of hydrophilic The phospholipid consists of hydrophilic heads, which point towards the outside heads, which point towards the outside environment and the cytoplasm. The environment and the cytoplasm. The hydrophobic tails repel the water and point hydrophobic tails repel the water and point in. Thus, the in. Thus, the phospholipids form a bilayer phospholipids form a bilayer that acts like a barrier between the cell that acts like a barrier between the cell and the environment.and the environment. The phospholipid The phospholipid bilayer also contains bilayer also contains cholesterolcholesterol, which , which makes the bilayer stronger, more flexible and makes the bilayer stronger, more flexible and more permeable. There are a number of more permeable. There are a number of important important proteinsproteins in the plasma membrane in the plasma membrane

Fluid Mosaic Model of the Cell Fluid Mosaic Model of the Cell MembraneMembrane

The purpose of the membrane is to control The purpose of the membrane is to control what goes in and out of the cell. what goes in and out of the cell.

Semi-permeableSemi-permeable means certain means certain molecules can be transported across the molecules can be transported across the membrane while others are kept out.membrane while others are kept out.

Proteins that are found in the bilayer are Proteins that are found in the bilayer are receptor proteinsreceptor proteins,, which deal with which deal with communication, communication, recognition proteinsrecognition proteins and and transport proteinstransport proteins that regulate the that regulate the movement of water and soluble molecules movement of water and soluble molecules through the membrane. through the membrane.

Transport of molecules across the Transport of molecules across the membranemembrane

Transport is either Transport is either activeactive or or passivepassive.. Active transportActive transport is moving molecules is moving molecules

against the concentration gradientagainst the concentration gradient and and energy is required in the form of ATP. energy is required in the form of ATP.

Passive transportPassive transport is moving molecules is moving molecules down the concentration gradientdown the concentration gradient and and no energyno energy is required. is required. – diffusiondiffusion, which moves from , which moves from high high

concentration to low concentration concentration to low concentration – osmosisosmosis, which is the , which is the diffusion of waterdiffusion of water

molecules molecules

Cell membrane interactiveCell membrane interactive

cell membrane interactivecell membrane interactive file:///C:/Documents%20and%20Settifile:///C:/Documents%20and%20Setti

ngs/nancy/My%20Documents/tdc02_ings/nancy/My%20Documents/tdc02_int_membraneweb/tdc02_int_membrant_membraneweb/tdc02_int_membraneweb.htmlneweb.htmlfile:///C:/Documents%20andfile:///C:/Documents%20and%20Settings/nancy/My%20Settings/nancy/My%20Documents/%20Documents/tdc02_int_membraneweb/tdc02_int_membraneweb/tdc02_int_membraneweb.htmltdc02_int_membraneweb.html

The OrganellesThe Organelles

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The Nucleus- DNA containerThe Nucleus- DNA container

Nucleus Nucleus cellular cellular control centercontrol center

– Controls cellular activityControls cellular activity contains contains hereditaryhereditary material (DNA material (DNA

in chromosomes) in chromosomes) self duplicatingself duplicating structure -divides structure -divides

when the cell divides when the cell divides

Structure of NucleusStructure of Nucleus

Nuclear Envelope (membraneNuclear Envelope (membrane):):– Double lipid bilayerDouble lipid bilayer: keeps DNA : keeps DNA

separated from the rest of the cellseparated from the rest of the cell– Continuous with Endoplasmic ReticulumContinuous with Endoplasmic Reticulum

NucleolusNucleolus: : assembly of ribosomesassembly of ribosomes for protein synthesisfor protein synthesis

Nuclear poresNuclear pores: holes that allow : holes that allow stuff in and outstuff in and out

Endoplasmic ReticulumEndoplasmic Reticulum

Rough Endoplasmic Rough Endoplasmic ReticulumReticulum

““HIGHWAY” for cell transportHIGHWAY” for cell transport consists of a network of interconnected, flattened consists of a network of interconnected, flattened

sacs whose walls are formed of a sacs whose walls are formed of a single single membranemembrane. The outer surface is ". The outer surface is "roughrough" because " because it is studded with small particles called it is studded with small particles called ribosomesribosomes. .

The ribosomes The ribosomes synthesize proteinssynthesize proteins and discharge and discharge them into the sacs where they are packaged in them into the sacs where they are packaged in membranes which travel through the cytoplasm membranes which travel through the cytoplasm to other organelles……. to other organelles…….

((GOLGI BODIESGOLGI BODIES) where they are further ) where they are further processed. processed.

Golgi BodiesGolgi Bodies

Add carbohydrates component to  Add carbohydrates component to 

        the protein and the protein and package the package the 

        finished productfinished product before it leaves  before it leaves 

        the cell.the cell.     Form the plasma membrane and Form the plasma membrane and

        membranes of lysosomesmembranes of lysosomes

LysomesLysomes produced by the produced by the Golgi apparatusGolgi apparatus contain powerful contain powerful protein digesting enzymesprotein digesting enzymes responsible for the responsible for the breakdown and breakdown and

absorptionabsorption of materials taken in by the cell. of materials taken in by the cell. Often, a cell engulfs a foreign substance Often, a cell engulfs a foreign substance

through through ENDOCYTOSISENDOCYTOSIS, another form of , another form of active transportactive transport. During endocytosis, the cell . During endocytosis, the cell membrane puckers up, forms a pouch around membrane puckers up, forms a pouch around materials outside the cell, and pinches off to materials outside the cell, and pinches off to become a vesicle. If the contents need to be become a vesicle. If the contents need to be destroyed, lysosomes combine with the destroyed, lysosomes combine with the vesicle and release their enzymes.vesicle and release their enzymes.

vacuolesvacuoles fluid-filled, membrane-surrounded cavities fluid-filled, membrane-surrounded cavities

inside a cell. The vacuole fills with food inside a cell. The vacuole fills with food being digested and waste material that is being digested and waste material that is on its way out of the cell. on its way out of the cell.

removing unwanted structural debris removing unwanted structural debris surrounding the cell surrounding the cell

sequestering materials that might be toxic sequestering materials that might be toxic to the cell to the cell

containment of waste products containment of waste products maintaining internal maintaining internal hydrostatic pressurehydrostatic pressure or or

turgorturgor within the cell (especially plant cells) within the cell (especially plant cells) storing small molecules storing small molecules exporting unwanted substances from the exporting unwanted substances from the

cell. cell.

vacuolesvacuoles

MitochondriaMitochondria Mitochondria are the cells' Mitochondria are the cells' power sourcespower sources. . They are distinct organelles with They are distinct organelles with two two

membranes. membranes. Usually they are rod-shaped, however they Usually they are rod-shaped, however they

can be round. can be round. The outer membrane limits the organelle. The outer membrane limits the organelle. The inner membrane is thrown into folds or The inner membrane is thrown into folds or

shelves that project inward. These are shelves that project inward. These are called "called "cristae mitochondrialescristae mitochondriales

Contain their own DNA which can be passed Contain their own DNA which can be passed onon

Endosymbiosis Endosymbiosis

It is theorized that mitochondria and It is theorized that mitochondria and chloroplasts were once free living chloroplasts were once free living bacteria that got caught in evolutionbacteria that got caught in evolution

Both are double membraned, contain Both are double membraned, contain their own DNA and can self replicatetheir own DNA and can self replicate

Quick checkQuick check What is meant by the phrase "the cell is What is meant by the phrase "the cell is

the functional unit of life"?the functional unit of life"? How are the organelles in a cell like the How are the organelles in a cell like the

organs in a human body?organs in a human body? Why do you think cells that produce large Why do you think cells that produce large

numbers of proteins have more rough numbers of proteins have more rough endoplasmic reticulum (ER) than cells that endoplasmic reticulum (ER) than cells that produce fewer proteins?produce fewer proteins?

In which kinds of human cells would you In which kinds of human cells would you expect to find the most mitochondria? The expect to find the most mitochondria? The most lysosomes? The most ribosomes? most lysosomes? The most ribosomes? Explain your answers. Explain your answers.

centriolescentrioles

CentriolesCentrioles

Found only in animal cellsFound only in animal cells,, these paired these paired organelles are typically located together organelles are typically located together near the nucleus, near the nucleus,

centrioles are positioned so that they are centrioles are positioned so that they are at right angles to each other, Each at right angles to each other, Each centriole is made of centriole is made of nine bundles of nine bundles of microtubules (three per bundle) microtubules (three per bundle) arranged in a ringarranged in a ring..

Centrioles play a Centrioles play a notable notable role in cell role in cell division.division.

cytoskeletoncytoskeleton ELEMENTS OF THE CYTOSKELETONELEMENTS OF THE CYTOSKELETON

All of the All of the microfilaments and microtubulesmicrofilaments and microtubules combine to form the combine to form the cytoskeletoncytoskeleton of the cell. of the cell.

The cytoskeleton is The cytoskeleton is different from cytoplasmdifferent from cytoplasm. . The The cytoskeleton provides structurecytoskeleton provides structure. Cytoplasm . Cytoplasm is just a fluid. is just a fluid.

The cytoskeleton connects to every organelle The cytoskeleton connects to every organelle and every part of the membrane. Think about an and every part of the membrane. Think about an amoeba. All of the pieces work together so that amoeba. All of the pieces work together so that the foot might reach out towards the food. Then the foot might reach out towards the food. Then the lysosomes and peroxisomes are sent to the lysosomes and peroxisomes are sent to begin digestion. The movement of the organelles begin digestion. The movement of the organelles and and cytoplasmcytoplasm is all related to the tubules. is all related to the tubules.

Plant CellPlant Cell

Plant cell wallPlant cell wall rigidity of the cell wall renders plants rigidity of the cell wall renders plants

sedentarysedentary Made of Made of CelluloseCellulose animals lack of wall allows their cells more animals lack of wall allows their cells more

flexibility, which is necessary for locomotion. flexibility, which is necessary for locomotion. protectsprotects the intracellular contents the intracellular contents provides a porous medium for the circulation provides a porous medium for the circulation

and distribution of water, minerals, and other and distribution of water, minerals, and other nutrients, and nutrients, and

houses specialized molecules that regulate houses specialized molecules that regulate growth and protect the plant from disease. growth and protect the plant from disease.

Cell wallCell wall

The main chemical components of The main chemical components of the primary plant cell wall include the primary plant cell wall include cellulosecellulose (in the form of organized (in the form of organized microfibrilsmicrofibrils; a complex ; a complex carbohydrate made up of several carbohydrate made up of several thousand glucose molecules linked thousand glucose molecules linked end to end. end to end.

Plant cell wallPlant cell wall

ChloroplastsChloroplasts

Chloroplasts are specialized organelles Chloroplasts are specialized organelles found in all higher plant cells. These found in all higher plant cells. These organelles contain the plant cell's organelles contain the plant cell's chlorophyllchlorophyll, hence provide the green , hence provide the green color. They have a color. They have a double outer double outer membranemembrane. Within the stroma are other . Within the stroma are other membrane structures - the thylakoids and membrane structures - the thylakoids and grana (singular = granum) where grana (singular = granum) where photosynthesisphotosynthesis takes place. takes place.

  

ChloroplastsChloroplasts

DIFFERENCES BTW PLANT AND DIFFERENCES BTW PLANT AND ANIMAL CELLSANIMAL CELLS

ANIMAL CELLANIMAL CELL• Can change shape.Can change shape.• No Cellulose cell wallNo Cellulose cell wall• No Chlorophyll or No Chlorophyll or

chloroplastschloroplasts• Small or no vacuolesSmall or no vacuoles• Has centrioles Has centrioles

PLANT CELLPLANT CELL• Fixed structure.Fixed structure.• Has a cellulose cell Has a cellulose cell

wall and a cell wall and a cell membrane membrane

• Chlorophyll in Chlorophyll in chloroplastschloroplasts

• large vacuoleslarge vacuoles