CellsCellsThe Building The Building Blocks of LifeBlocks of Life

How did Cells Form?How did Cells Form?

• Several Theories of How Cells Formed:– Cells arose in shallow pools containing “soup”

of chemicals. These chemicals become combined and formed cells.

– Cells formed in beds of clay that allowed substances (chemicals) to be contained and produce living things – cells.

– Meteors and asteroids carried water, containing life (cells) to the Earth.

Which Cell Theory Is True?Which Cell Theory Is True?

• We still do not know for sure how cells formed.

Spontaneous Generation?Spontaneous Generation?

• The Theory of The Theory of Spontaneous GenerationSpontaneous Generation states that life could arise from non-living states that life could arise from non-living matter.matter.

– This theory was disproved in 1668 by This theory was disproved in 1668 by Francesco Redi who used raw meat for his Francesco Redi who used raw meat for his experiments.experiments.

Francesco RediFrancesco Redi

Redi’s ExperimentRedi’s Experiment

Characteristics of Living ThingsCharacteristics of Living Things

• All living things share characteristics, they:– Are made of cells– Are able to move– Perform complex chemical activities– Are able to grow and develop– Are able to respond to their environment– Are able to reproduce

What is a Cell?What is a Cell?

• The cell is the basic building block of The cell is the basic building block of all living things.all living things.

– The first cells on Earth are thought to have The first cells on Earth are thought to have evolved ~3.5 billion years ago.evolved ~3.5 billion years ago.

– These cells could not produce their own These cells could not produce their own food.food.

All living things are made of cellsAll living things are made of cells

Plant Cells Animal Cells

All living things are able to moveAll living things are able to move

All living things perform All living things perform complex chemical activitiescomplex chemical activities“building up and breaking “building up and breaking

down”down”

• Metabolism is the sum total of all the chemical reactions that occur in a living thing.– In humans these chemical reactions are

ingestion, digestion, respiration, and excretion.

What are the Needs of Living What are the Needs of Living Things?Things?

• In order to survive all living things need:– Energy– Food– Water– Oxygen– Living space– To maintain a proper temperature

Cell TheoryCell Theory• The current cell theory

states that:

– All living things are made of cells.

– Cells are the basic unit of structure and function in living things.

– Living cells only come from other living cells.

What Are Cells Made Of?What Are Cells Made Of?

• OrganellesOrganelles, or “tiny organs”, are , or “tiny organs”, are the structures that make up a cell.the structures that make up a cell.

• OrganellesOrganelles were discovered by were discovered by Robert Hooke in 1665 while looking Robert Hooke in 1665 while looking at cork cells.at cork cells.

How Do Cells Function?How Do Cells Function?

• Each of the organelles in a cell has a defined function.

• There are many organelles that make up a cell.– These include the cell wall, cell membrane,

nucleus, cytoplasm, endoplasmic reticulum, ribosomes, lysosomes, mitochondria, vacuoles, chloroplasts.

• All organelles working together create the cells structure.

Cell Organelles – Cell WallCell Organelles – Cell Wall

• The cell wallcell wall provides supportsupport and protectionprotection for the cell.

• The cell wallcell wall is rigid.

• Cell wallsCell walls are only found in plant cells.

Cell Wall – only in plantsCell Wall – only in plants

Cell Organelles – Cell MembraneCell Organelles – Cell Membrane

• The cell membrane is the “doorway” of the cell.• Cell membranes control the movement of

materials into and out of the cell.– Pores are the openings in the cell membrane.

• Cell membranes provide support and protection. – In plant cells the cell membrane is found just

inside the cell wall.– In animal cells the cell membrane is the

outermost organelle.

Cell MembraneCell Membrane

Cell Organelles - NucleusCell Organelles - Nucleus

• The The nucleusnucleus is the is the “control center”,“control center”, or or “brain” of the cell which controls all “brain” of the cell which controls all activities in the cell.activities in the cell.

• The The nucleusnucleus has three parts: has three parts:– Nuclear membraneNuclear membrane– ChromosomesChromosomes– NucleolusNucleolus

Cell Organelles - NucleusCell Organelles - Nucleus

• The nuclear membranenuclear membrane controls the movement of materials into and out of the nucleus.

• The chromosomeschromosomes direct the activities within the cell and also pass on genetic traits to the next generation.

• The nucleolusnucleolus, or “little nucleus” is the site of ribosome production.

Cell Organelles - Cell Organelles - CytoplasmCytoplasm

• CytoplasmCytoplasm is the clear, is the clear, thick jelly-thick jelly-like like substance substance that that contains all contains all the the organelles.organelles.

Cell Organelles – Endoplasmic Cell Organelles – Endoplasmic ReticulumReticulum

• The The endoplasmic endoplasmic reticulumreticulum, or , or ER, is the ER, is the tubular tubular transportationtransportation system system throughout the throughout the cell.cell.

Endoplasmic ReticulumEndoplasmic Reticulum Smooth and Rough Smooth and Rough

Cell Organelles - Cell Organelles - RibosomesRibosomes

• Ribosomes are the protein factories of the cell.

• Most ribosomes are found attached to the outside of the endoplasmic reticulum.– This location helps the cell with efficiency of

production and transport.

RibosomesRibosomes

Cell Organelles - LysosomesCell Organelles - Lysosomes

• Lysosomes are the “clean up crew” of the cell.

• Lysosomes are involved in the digestive process of the cell.– Enzymes break down large food into smaller

bits for the mitochondria to use.– Lysosomes are not common in plant cells.

Cell Organelles - MitochondriaCell Organelles - Mitochondria

• Mitochondria are the “powerhouse” of the cell and supply most of the energy for the cell.

Cell Organelles - VacuolesCell Organelles - Vacuoles

• VacuolesVacuoles are the “storage tanks” of the cell.

• VacuolesVacuoles can store food, water, or waste.– In plant cells vacuolesvacuoles are common.

• Usually one large vacuole per cell.

– In animal cells vacuolesvacuoles are not common.

• Usually several small vacuoles per cell.

Cell Organelles - Cell Organelles - ChloroplastsChloroplasts

• ChloroplastsChloroplasts are the “energy producers”“energy producers” of plant cells.

• ChloroplastsChloroplasts are only found in plant cellsonly found in plant cells.

• ChloroplastsChloroplasts contain green chlorophyllchlorophyll that captures energy from the sun.

What Is Cell Specialization?What Is Cell Specialization?

• In multicellular organisms, cells not only In multicellular organisms, cells not only complete its own life activities, but also complete its own life activities, but also performs a function that contributes to the performs a function that contributes to the life of the organism.life of the organism.

• Within multicellular organisms there is Within multicellular organisms there is division of labor or specialization.division of labor or specialization.– The work of keeping the organism alive is The work of keeping the organism alive is

divided up among different parts of the divided up among different parts of the organism.organism.

Levels of SpecializationLevels of Specialization

Cells combine to form

Tissues combine to form

Organs combine to form

Organ systems combine to form

Organism

More SpecializationMore Specialization

StudentsStudents combine to form combine to form

ClassesClasses combine to form combine to form

GradesGrades combine to form combine to form

SchoolsSchools combine to form combine to form

DistrictDistrict