Cells & Cell Organelles

Cell Theory• The cell theory is the unifying

theme in biology because it emphasizes the similarity of all living things.– All organisms are composed of one or

more cells.– Cells are the smallest living units of all

living organisms.– Cells arise only by division of a

previously existing cell.

Cell Characteristics• Cells contain specialized structures to

perform functions necessary for life.

• Cellular activities necessary for life include chemical reactions that facilitate:– acquiring energy– reproduction– adaptation– maintaining homeostasis

Cell Characteristics• The basic processes necessary for living

things to survive are the same for a single cell as they are for a more complex organism.

• A single-celled organism has to conduct all life processes by itself.

• A multi-cellular organism has groups of cells that specialize to perform specific functions.

Cell Characteristics• All cells contain:• Genetic material

– single circular molecule of DNA in prokaryotes

– double helix located in nucleus in eukaryotes

• Cytoplasm jelly-like substance that fills the cells interior

• Plasma membrane encloses the cell– – phospholipid bilayer

Phospholipids

Membraneproteins

Cell Types• Cell structure is one of

the ways in which organisms differ from each other.– 2 Types of Cells

•Prokaryote•Eukaryote

Prokaryotic Cells

• Earth’s first cells were prokaryotes.

• The simplest life forms are the prokaryotes.

• Prokaryotic cells exist in two major forms: eubacteria and archaebacteria.

Prokaryotic Cells

Prokaryotes are cells that lack a nucleus and membrane bound organelles.

• Bacteria and related microorganisms are prokaryotes

Generalized Prokaryotic Cell

Eukaryote•Eukaryotes arose from

prokaryotes and developed into larger more complex organisms.

•Eukaryotes are cells that contain a nucleus and organelles surrounded by a membrane, such as mitochondria and chloroplasts.

Eukaryote• Can be both

unicellular or multi-cellular

• Examples of eukaryotes are:

– All fungus, plant, and animal cells

Generalized Eukaryotic Cell

Cell size comparison

Bacterial cell

Animal cell

micron = micrometer = 1/1,000,000 meter diameter of human hair = ~20 microns

most bacteria 1-10 microns

eukaryotic cells 10-100 microns

Visualizing Cells

Why study cells?

• Bodies Cells – bodies are made up of cells– cells do all the work!

• What jobs have to be performed for an organism to live…– breathe– eat– make energy– remove wastes – respond to environment– growth & development– reproduction

The Work of Life

these are the same jobs your cells have to do!these are the same jobs your cells have to do!

Cells gotta live! • What jobs do cells have to do?

– make energy• for daily life

• for growth

– build more cells• growth

• reproduction

• repair

– make proteins• proteins control every

cell function

Making Proteins

Proteins do all the work!

cellsDNA proteins

one of the major job of cells is to make proteinsone of the major job of cells is to make proteins

proteins do all the work!proteins do all the work!

Building Proteins• Organelles involved

– nucleus– ribosomes– endoplasmic reticulum

(ER)– Golgi apparatus– vesicles

nucleus ribosome ERGolgi

apparatusvesicles

Nucleus• Stores genetic material• Contains DNA• site where RNA is made• Nucleolus: Chromatin and ribosomal

subunits• Nuclear envelope:

– Double membrane with pores• Largest organelle• BRAIN of the cell – controls protein

synthesis

Nucleus

smallsubunit

largesubunit

Ribosomes

Ribosomes

• Function– protein factories: build proteins

• Structure – RNA & proteins– 2 subunits

RibosomesThey can be found alone

in the cytoplasm or attached to the endoplasmic reticulum.– Alone in cytoplasm-

makes proteins for use within the cell

– Attached to RER- makes proteins for export out of the cell

Endoplasmic Reticulum• Function

– duct work or hallways of cell

– processing of proteins– membrane factory

• Structure– rough ER

• ribosomes attached

– smooth ER

Endoplasmic reticulum– transports materials through the cell

•Rough ER - studded with ribosomes–Attached to nuclear membrane–site of protein synthesis and processing

•Smooth ER - lacks ribosomes–site of synthesis of phospholipids and the packaging of proteins into vesicles

• rough ER– ribosomes

attached

• smooth ER

Types of Endoplasmic Reticulum

transport vesicles

secretoryvesicles

• Function– like UPS headquarters

• “shipping & receiving department”

– finishes, sorts, tags & ships proteins– ships proteins in vesicles

• membrane sacs• “UPS trucks”

Golgi Apparatus

proteins

transportvesicle

Golgiapparatus

vesicle

smooth ER

rough ER

nuclear porenucleus

ribosome

cellmembrane protein secreted

cytoplasm

Making proteins

Making Energy

ATP

Cells need power! • Making energy

– take in food & digest it

– take in oxygen (O2)

– make ATP– remove waste

ATP

Lysosomes• Function

– little “stomach” for cell• digests food

– “clean up crew” of the cell• cleans up broken down

organelles

• Structure– pockets of digestive

enzymes

Lysosomes

white blood cells attack & eat invading germs =

digest them in lysosomes

Lysosome function• Lysosomes fuse with food vacuoles

– digest nutrients for the cell

vacuole

When things go bad… • Diseases of lysosomes are fatal

– digestive enzyme not working in lysosome– picks up food, but can’t digest it

• lysosomes fill up with undigested material

– grow larger & larger until disrupts cell & organ function

• example:Tay-Sachs diseasebuild up undigested fat in brain cells

But sometimes cells need to die…• Lysosomes can be used to kill cells when they

are supposed to be destroyed– some cells have to die for proper development in an

organism• ex: tadpole tail gets re-absorbed when it turns into a frog

• ex: getting rid of webbing between your fingers during fetal development

– “auto-destruct” process• lysosomes break open and kill cell

• cell “suicide”

Making energy • Mitochondria

– make energy from sugar

• sugar (glucose) ATP

• Chloroplasts– make energy & sugar from sunlight

• sunlight ATP & sugar– ATP = active energy

– sugar = stored energy

ATP

ATP

Mitochondria• "Powerhouse of the cell" - cellular

metabolism• Structure- outer and inner

membranes, cristae• Found in both plant and animal

cells• Very active cells have more

mitochondria

Chloroplasts•Chloroplasts are larger and more complex than mitochondria

•Contain green pigment called chlorophyll that absorbs sunlight in the first step of photosynthesis

•Found ONLY in PLANTS

The Great ENERGY Circle of Life

sun

ATP

Photosynthesis

Respiration

O2glucosesugarCO2 H2O+ +

plants

animals & plants

Food & water storageplant cellsplant cells

central vacuole central vacuole

contractilevacuole

contractilevacuole

food vacuoles food vacuoles

animal cellsanimal cells

Major organelles• Nucleus

• Ribosomes

• Endoplasmic reticulum

• Golgi apparatus

• Vacuoles & vesicles

• Lysosome

• Mitochondria

• Chloroplast

Cell Membrane•controls what enters and leaves the cell

•Found in ALL cells

•Phospholipid bilayer with transport proteins, and cholesterol (for flexibility)

Cell Wall

•provides support

•Found in PLANT and BACTERIA cells

•Made from cellulose

Centrioles•Cylindrical structures found near the nucleus •Made of hollow, tubular structures arranged in bundles •Important in cell division•Found ONLY in ANIMAL cells

Plant vs. Animal CellsPLANT CELL

ANIMAL CELL

Cell membraneMitochondria

Golgi apparatusNucleus

CytoskeletonRibosomes

Endoplasmic reticulum

Lysosomes

HAVE:Cell Wall

LARGE vacuolesChloroplasts

DO NOT HAVE:Centrioles

HAVE:Centrioles

DO NOT HAVE:Cell Wall

LARGE vacuolesChloroplasts

Cell Differentiation• Cell specialization occurs during the

development of a multi-cellular organism.

• The genetic information necessary for all cellular functions remains in each cell but may not be used.