CELLS:

THEIR STRUCTURE & FUNCTION

THE CELL THEORY(DEVELOPED AFTER THE DISCOVERY OF THE MICROSCOPE

AND THE CELL)

HAS THREE PARTS:

1. ALL ORGANISMS ARE COMPOSED OF CELLS.

2. CELLS ARE THE BASIC UNIT OF LIFE – they are the smallest structures that show all the characteristics of life.

3. CELLS ARISE FROM OTHER PRE-EXISTING CELLS.

1. ALL ORGANISMS ARE COMPOSED OF CELLS.

DOES THIS MEAN ALL ORGANISMS – EVEN BACTERIA, VIRUSES, PLANTS & ANIMALS?

Most organisms are MULTICELLULAR = composed of many cells. These are the two types ---

THE TWO TYPES OF CELLS:

PROKARYOTIC EUKARYOTIC

1. THEY ARE COMPOSED OF ONLY A PROTEIN COAT AND DNA or RNA.

2. THEY CANNOT LIVE WITHOUT A HOST (ANOTHER PROKARYOTIC OR EUKARYOTIC CELL).

3. THEY CAN PERFORM ONLY SOME OF THE CHARACTERISTICS NECESSARY FOR LIFE.

THE VIRUS DEBATE

HERE’S THE INFO……………..YOU DECIDE!!!

1. MOVEMENT – Must be able to move food into its body, distribute it to all parts of the body, and eject wastes.

2. METABOLISM AND HOMEOSTASIS – Must be able to make energy from compounds and build tissues. Must know how much is required to keep

the body in balance.

3. RESPONSIVENESS – Must be able to respond to the environment – “fight or flight”.

4. GROWTH AND DEVELOPMENT – Grow by taking in raw materials and using them to synthesize new cells.

5. REPRODUCTION – Ability to produce offspring to produce new generations.

6. ADAPTATION – Features that fit them into their environment and help them survive.

WHAT ARE THE CHARACTERISTICS OF LIFE?What makes some things living and others nonliving?

ALL CELLS HAVE CERTAIN CHARACTERISTICS:

1. Surrounded by a membrane = PLASMA OR CELL MEMBRANE

This membrane separates them from the outside environment.

BUT…. It does allow some things in….this makes it SEMI-PERMEABLE.

WHAT ARE SOME THINGS IT LETS IN?

2. CELLS ARE THE BASIC UNIT OF LIFEWHAT IS A CELL COMPOSED OF?

THE PLASMA MEMBRANE “ALSO KNOWN AS THE CELL MEMBRANE”

STRUCTURE:

- Two layers (bilayer) of PHOSPHOLIPIDS AND PROTEINS

- Semi- permeable: allows in/out oxygen, carbon dioxide, proteins, glucose, water – some with the use of ENERGY other without

FUNCTION:

-Separate cell from external environment

-Barrier to keep some materials out and allow others in; controls what enters and leaves

2. ALL CELLS INCLUDE – DNA - Since they must reproduce and make proteins for their functioning.

The DNA in cells is SEGREGATED into a DNA- containing region.

3. All cells contain – CYTOPLASM

Cytoplasm is a “jello” (jelly) like substance

It contains:

Water, salts and organic compounds

It is located inside the CELL MEMBRANE and between the cell membrane and NUCLEAR MEMBRANE.

It is in constant motion – bathing and moving the cell structures.

Cell Functions/Jobs

A.    Digestion

B.   Secretion – release enzymes and other chemicals

C.     Metabolism or Respiration

D.    Excretion

E.     Absorption

F.     Reproduction

G.    Response To Stimulus

H. Synthesis – making of proteins and other substances

Cells contain subparticles known as

ORGANELLES.

WHICH ORGANELLES AND THE NUMBER A CELL CONTAINS DEPENDS UPON THE TYPE OF CELL THAT IT IS.EACH ORGANELLE HAS ITS OWN SPECIFIC STRUCTURE AND FUNCTION.

THE CELL ORGANELLES NUCLEUS

STRUCTURE -CONTAINS THE GENES (DNA)

ALSO KNOWN AS CHROMATIN (NONDIVIDING CELL) OR CHROMOSOMES (DIVIDING CELL)

- -SURROUNDED BY A DOUBLE LAYERED MEMBRANE WITH PORES CALLED THE NUCLEAR MEMBRANE

- - CONTAINS THE NUCLEOLUS

FUNCTION

- CONTROLS THE MAKING OF NEW CELLS

- -CONTROLS THE MAKING OF PROTEINS

- - ALSO KNOWN AS THE “BLUEPRINTS”

NUCLEOLUS

STRUCTURE

- Located within the nucleus, spherical

- Contains RNA and proteins

FUNCTION

- Produces ribosomes (l0,000/min.)

RIBOSOMES

STRUCTURE- Made of 2 subunits of protein and RNA

- - No membrane, spherical

- - Located on the Endoplasmic

- reticulum and

in the cytoplasm

FUNCTION- protein synthesis

ENDOPLASMIC RETICULUM STRUCTURE:

- Consists of a network of tubes that are continuous with the nuclear membrane

TWO TYPES:

SMOOTH ER – does NOT contain ribosomes

Function = making lipids, breakdown of carbohydrates, muscle contraction, and detoxification of drugs and poisons

ROUGH ER – contains ribosomes on its surface (outside)

Function = site of PROTEIN production and Transport of proteins

GOLGI BODY OR APPARATUSSTRUCTURE

- A series of flattened, membranous sacs (looks like pita bread)

- - Located near the ER

FUNCTION

- Packages and stores proteins

- - Sends proteins to the cell membrane

for EXPORT in small spherical structures

called VESICLES.

LYSOSOMESALSO KNOWN AS “SUICIDE SACS” - STRUCTURE

Sphere shaped, membrane bound organelles located in the cytoplasm- Contain DIGESTIVE ENZYMES- More commonly found inanimal cells

FUNCTIONBreak down and digest old cell parts, bacteria, food particles- Play a role in early development

MITOCHONDRIA“Powerhouses of a cell”

STRUCTURE:

- Double membrane structure. The outer membrane is smooth, while the inner membrane is folded, these folds are called CRISTAE.

- - The inner most area is called the Mitochondrial matrix.

FUNCTION:

- Cellular Respiration

Glucose is changed to water, carbon dioxide and energy (known as ATP) which the cell can use for its many functions.

PLASTIDSPlastids are PLANT organelles that store chemical energy. They include:

AMYLOPLASTS – which store starch

LEUCOPLASTS – which store starch, proteins, and lipids

CHROMOPLASTS – which contain color pigments

CHLOROPLASTS – which contain the green pigment, CHLOROPHYLL

CHLOROPLASTSSTRUCTURE:

Chloroplasts have a double membrane. The outer membrane is smooth, while the inner membrane forms stacks called THYLAKOIDS. Thylakoids may be joined together to form GRANA.

These membranes are bathed in a fluid called STROMA.

FUNCTION:

PHOTOSYNTHESIS – converting carbon dioxide and water with the help of sunlight into SUGAR and OXYGEN.

VACUOLESSTRUCTURE:

- Found mainly in plant cells

- larger than vesicles

- - Single membrane, spherical

- -May take up to 90% of a plant

cells area

FUNCTION:

- Store food, excess water, toxins, enzymes, and waste products.

- - Digest food and waste

- - Pump excess water out of cells

CYTOSKELETON (Cell Framework)

STRUCTURE:

- Composed of microtubules and microfilaments (protein tubes and threads)

FUNCTION:

-Microtubules – shape, support and help move organelles around the cell

- Microfilaments – muscle contraction, cytoplasmic streaming, and changes in cell shape

CILIA AND FLAGELLA

STRUCTURE:

-Extensions of cell membranes

- Composed of microtubules in a “ 9 + 2” pattern

-Driven by ATP

-Cilia: numerous and short

-Flagella: one or two to a cell and longer

FUNCTION: MOVEMENT OF THE CELL

Cilia - move back and forth like an oar

Flagella – move in a whip-like fashion

CELL WALLFound only in PLANT CELLS

STRUCTURE:

- composed of CELLULOSE

- - Two walls thick

- - contains pores

FUNCTION:

- Protect, strengthen and allow certain materials in and out

PROKARYOTIC CELLS

Include bacteria and some algae

DO NOT contain all the structures found in eukaryotic cells.Size 1-10 microns

Nucleus No, circular DNA

Ribosomes Yes

Cell Wall Yes

Other Organelles No

Cilia/Flagella Yes

EUKARYOTIC CELLS

TWO TYPES:

PLANT CELLS ANIMAL CELLS

  Eukaryotic Prokaryotic

Representative organism

Plant and animal cells

Bacteria and some algae

Size 10-50 microns 1-10 microns

Nucleus Yes No

Ribosomes Yes Yes

Cell Wall Plant only Yes

Other Organelles Yes No

Cilia/Flagella Yes Yes

DIFFERENCES BETWEEN EUKARYOTIC AND PROKARYOTIC CELLS

  Animal  Plant

Size 10-20 microns

30-50 microns

Shape Irregular Square/Rectangular

Cell Wall No Yes

Lysosome Yes Rare

Chloroplast No Yes

Vacuole Small or absent

Large/90% of cell

Cilia/Flagella Both Mostly absent except sperm

DIFFERENCES BETWEEN PLANT AND ANIMAL CELLS

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

Living things can arise from nonliving things.

EXPERIMENTATION

REDI EXPERIMENT – 1600’S

BIOGENESIS

Life comes from life.

SPALLANZANI’S EXPERIMENT- 1700’S

      

      

      

      

      

      

      

                                                  

                                        

PASTEUR’S EXPERIMENT – 1800’s

BIOLOGICAL HEIRARCHYATOMS

MOLECULES/COMPOUNDS

ORGANELLES – subparticles of cells

CELLS

TISSUES – group of cells that perform the same function (Example: Four types - Muscle tissue, epithelial tissue, connective tissue,

nerve tissue)

ORGANS – group of tissues that perform the same function (Example: Stomach – muscle, epithelial, nerve, connective tissue)

ORGAN SYSTEMS – group of organs that work together to perform the same function (Example: Digestive System)

ORGANISM – group of organ systems that work together to perform a function