Cell Discovery, Theory, & Organelles

Direct InstructionSynthesize Notes on 26R

Cell Diversity and Size

First Sightings of Cells

Around 1590, the invention of the microscope made it possible for people to discover and learn about objects on the micro (µ) scale. Micro = 10-6

One of the first people to observe cells was Robert Hooke. He looked at cork samples and named what he saw “cells”.

Robert Hook’s composite microscope

Anton von Leeuwenhoek was the first person to observe what are now called bacteria. 

Matthias Schleiden found that all plants are made of cells.

Theodor Schwann, found that all animals are made up of cells.

Rudolf Virchow proposed that new cells are formed only from existing cells

The Cell Theory

One of the fundamental ideas of modern biology

Includes 3 principles: 1. All living organisms are composed of

one or more cells 2. Cells are the basic unit of structure

and organization of all living organisms 3. Cells arise only from previously

existing cells

Remember 2 major cell types

EukaryotesProkaryotes

Prokaryotic cells Cells that do not

contain a nucleus & membrane bound organelles

Prokaryotes contain DNA, but only a single, circular molecule

Which kingdoms contain living organisms with only prokaryotic cells?

PROKARYOTES

• UNICELLULAR ORGANISMS

• EXAMPLE= cyanobacteria

Fossil 2 billion years old (left) and living (right). Note the similarities in

appearance. Interspersed among the cyanobacteria colonies are chains of rod-

shaped bacteria.

Eukaryotic cells Contain a nucleus

and membrane-bound organelles

More advanced – organelles allow specialized cell functions to take place in different parts of the cell at the same time

Which kingdoms contain eukaryotic cells?

INTERNAL ORGANIZATION

• ORGANELLES:– CELL COMPONENT THAT PERFORMS SPECIFIC

FUNCTIONS FOR THE CELL

Parts of the cell that both eukaryotes and prokaryotes have

Most cells have a: Cell Wall

Cell wall Thick, rigid, mesh of fibers that

surrounds the outside of the plasma membrane, protecting the cell and giving it support

Which Kingdom does NOT have a cell wall??

Make sure you know what each kingdom’s cell wall is composed of!!

All cells have a: Plasma membrane PLASMA MEMBRANE

Plasma membrane – flexible boundary that controls the movement of substances into and out of the cell

Plasma Membrane The plasma membrane has selective

permeability: Allows some substances to pass through while

keeping others out

Structure of the plasma membrane

The plasma membrane can have this selective permeability because it is composed of a phospholipid bilayer Phospholipid bilayer = two layers of phospholipid

molecules arranged with polar heads facing outside and nonpolar tails facing inside

Plasma membrane – phospholipid bilayer

Plasma membrane continued… Proteins are embedded

in the phospholipid bilayer Held in place by polar

(charged)/non-polar attractions

Help cells recognize each other

Recognize & bind specific substances

Move substances in and out of cell

The phospholipids create a “sea” in which other molecules can float, like apples floating in a barrel of water.

All Cells HaveCYTOPLASM:

– CELL GOO INSIDE CELL

– WHERE THE ORGANELLES ARE LOCATED

– ALSO CALLED CYTOSOL

Cytoplasm Cytoplasm=

semifluid material inside the cell’s plasma membrane

In prokaryotes, all of the cell’s functions take place directly in the cytoplasm

In eukaryotes, all of the cell’s functions take place within organelles in their cytoplasm Cytoplasm

Cytoskeleton Supporting network

of long, thin protein fibers that form a framework for the cell and provide an anchor for the organelles inside the cells

CYTOSKELETON• NETWORK OF LONG

PROTEIN STRANDS IN THE CYTOSOL

• NO MEMBRANE• AIDS IN MOVEMENT OF

ORGANELLES • MICROFILAMENTS:

– THREADS OF A PROTEIN CALLED ACTIN.

– SMALLEST STRAND MAKES UP CYTOSKELETON

MICROTUBLES:• LARGEST STRANDS • HOLLOW TUBES• WHEN CELL IS ABOUT TO DIVIDE BUNDLES COME TOGETHER AND EXTEND ACROSS THE CELL

SPINDLE FIBERS:

• THICK BUNDLES

• ASSISTIN MOVEMENT OF CHROMOSOME DURING CELL DIVISION

All cells have: RIBOSOMES• MAKES PROTEINS

• MOST NUMEROUS ORGANELLE IN THE CELL

• NO MEMBRANE

• 60% RNA AND 40% PROTEINS MAKE UP RIBOSOME'S

• PRODUCED & ASSEMBLED IN THE NUCLEOLUS

• Many Proteins are produced by a specialized cell, e.g. antibodies– transported and used

elsewhere in the organism• WHEN RIBOSOMES ARE

ATTACHED TO ER:– PROTEINS INSERTED TO

MEMBRANES

– PROTEINS EXPORTED FROM CELL

    

Electron Micrograph of ribosomes. The ribosomes operate in chains when translating a

mRNA.

                                       

 

   

                               

Proteins (AA chains) being made by ribosomes from mRNA

Once amino acids bond together to form a chain, it is now a protein, and can be used by the body.

Simplified translation on the ribosome

JHK

JHK

JHK

PROTEIN CHAIN

JHK

JHK JHK

JHK

JHK

JHK

JHK JHK JHK

JHK

RIBOSOMES Allow PROTEIN CHAINS to be made correctly

Translation = the language of nucleic acids translated to the language of proteins

Eukaryotes have organelles that prokaryotes do not have.

NUCLEUS:– LARGE

– NEAR CENTER OF CELL

– CONTAINS MOST OF CELLS GENETIC INFO

– DIRECTS MOST ACTIVITIES OF CELL

Nucleus In eukaryotic cells, the

central membrane-bound organelle that manages cellular functions and contains DNA

Surrounded by a nuclear envelope – a double membrane that has nuclear pores to allow substances in and out of the nucleus

• NUCLEAR MATRIX= PROTEIN SKELETON

• NUCLEAR ENVELOPE= DOUBLE MEMBRANE AROUND NUCLEUS

• CHROMOSOME= DENSELY PACKED (“X”) CHROMATIN

• CHROMATIN= COMBO OF DNA & PROTEIN (stretched out chromosome)

• NUCLEAR PORE= SMALL HOLES (Doors)

• NUCLEOLUS= RIBOSOME SYNTHESIS, PRODUCTION

nuclear pores

nucleus

ENDOPLASMIC RETICULUM (ER)• A SYSTEM OF MEMBRANE BOUND SACS AND TUBULES• INTRACELLULAR “HIGHWAY”

– MOLECULES MOVE FROM ONE PART OF CELL TO ANOTHER• 2 TYPES OF ER:

– SMOOTH ER= (no ribosomes)

– ROUGH ER= (COVERED W/RIBOSOMES)

Endoplasmic reticulum Highly folded

membrane system in eukaryotic cells that is the site for protein and lipid synthesis

ROUGH ER:• MAKE PROTEINS

• USED FOR EXPORT OUT OF THE CELL

• ALSO TO BE INSERTED INTO THE CELL MEMBRANE

SMOOTH ER: • INVOLVED IN

PRODUCTION (SYNTHESIS) OF STEROID GLAND CELLS

• REGULATION OF CALCIUM LEVELS

• BREAKDOWN OF TOXIC SUBSTANCES BY LIVER CELLS

SMOOTH ER

ROUGH ER

Golgi apparatus “UPS crew” Flattened stacks or sacs of membranes that

modifies, sorts, and packages proteins into sacs called vesicles Vesicles can fuse with the cell’s plasma membrane

to release proteins to the environment outside of the cell

GOLGI APPARATUS• PROCESSING• PACKAGING• SECRETING

ORGANELLE• SYSTEM OF

MEMBRANES “PANCAKES”

• MODIFIES PROTEINS FOR EXPORT BY CELL

Vacuoles “storage crew” Membrane-bound

vesicle for temporary storage of materials such as food, enzymes, and wastes

LYSOSOME “clean up crew”

• SMALL• SPHERICAL ORGANELLE • ENCLOSE ENZYMES in a

SINGLE MEMBRANES• DIGEST PROTEIN, CARBS.,

LIPIDS, DNA, RNA– When needed: OLD

ORGANELLES, VIRUSES, BACTERIA THAT WERE INGESTED

• RARE IN PLANT CELLS

MITOCHONDRIA

• CONTAIN THEIR OWN DNA (circular)

• SURROUNDED BY A DOUBLE MEMBRANE

Mitochondria “Power-house” “Mighty Mouse”

Converts fuel (sugars) into the energy molecule ATP for the rest of the cell

• TRANSFER ENERGY FROM ORGANIC COMPOUNDS (pyruvate) TO ATP VIA CHEMICAL RXN’S

• ATP = (AdenosineTriPhosphate) MOLECULE THAT MOST CELLS USE AS ENERGY CURRENCY

• CAR (MITOCHONDRIA)

• GASOLINE (CHEMICAL RXN)

• GAS + ENGINE = CAR STARTS (ATP MADE)

• CAR RUNS (ENERGY)

MITOCHONDRIA IN HUMAN LIVER CELL

• SURROUNDED BY:

• 2 MEMBRANES– OUTER & INNER

• CRISTAE:– THE LONG FOLDS OF

THE INNER MEMBRANE

• ENLARGE SURFACE AREA

• WHERE CHEMICAL RXNS TAKE PLACE

HOW CELLS MOVE• CELLS USE HAIRLIKE STRUCTURES THAT

EXTEND FROM THE SURFACE OF THE CELL

• SHORT & IN LARGE QUANTITIES = CILIA

• LONG & LESS NUMEROUS = FLAGELLA

Cilia and Flagella Flagella

Long, tail-like projection with a whiplike motion that helps a cell move through a watery environment

Cilia Short, numerous

projections that look like hair and function in cell movement

Plant cells have 3 structures that animal cell lack

1. Cell wall 2. Chloroplasts 3. Central vacuole

Chloroplast Double membrane

organelle that captures light energy and converts it to chemical energy through photosynthesis

Central vacuole Membrane bound space that stores water;

Aids in the rigidity of the cell

Draw/Color Plant Cell

Draw/Color Animal Cell