The Cell

The history of the Cell Theory

Before microscopes were invented, people believed that diseases were caused by curses and supernatural spirits

As scientists began using microscopes, they quickly realized they were entering a new world- one of microorganisms

Microscopes enables scientists to view and study cells, the basic units of living organisms

Development of Light Microscopes

The first person to record looking at water under a microscope was Anton van Leeuwenhoek

The microscope van Leeuwenhoek used is considered a simple light microscope because it contained one lens and used natural light to view objects

Compound light microscopes use a series of lenses to magnify objects in steps

These microscopes can magnify objects to 1500 times

The Cell Theory

Robert Hooke was an English scientist who lived at the same time was van Leeuwenhoek

Hooke used a compound light microscope to study cork, the dead cells of oak bark

Cells are the basic building blocks of all living cells

The Cell Theory is Made Up of Three Main Ideas

All organisms are composed of one or more cells The cell is the basic unit of structure and function of

organisms All cells come from preexisting cells

Three Scientists Contributed to the Cell Theory

1838- Schleiden: Plants are made of one or more cells 1855- Virchow: New cells are produced from the

division of old cells 1939- Schwann: Animals are made of cells

Development of Electron Microscopes

The electron microscope was invented in the 1940’s This microscope uses a beam of electrons to magnify

structures up to 500,000 times their actual size There are two basic types of electron microscopes

The scanning electron microscope scans the surface of cells to learn three dimensional shape

The transmission electron microscope allows scientists to study the structure contained within a cell

Two Basic Cell Types

Prokaryotic Cells Cells that do not contain internal membrane-bound structures

and do not have a nucleus

Organisms with these cells are called unicellular, for example bacteria

They still carry out all of life's activities such as respiration, cell reproduction, growth, etc.

Eukaryotic Cells containing membrane-bound structures and a nucleus

Organisms with these cells can be unicellular or multicellular; plan or animal

Organisms that are multi-cellular have specialization in their cells

Eukaryotic Cell Structures:Organelles

The membrane-bound structures within eukaryotic cells

Each “little organ” has a specific function that contributes to cell survival

Separation of organelles into distinct compartments benefits the eukaryotic cells

Biologists divide the cells into two major parts

The nucleus is the central membrane-organelle that manages cellular functions

Everything between the cell membrane and the nucleus is called the cytoplasm (cell goo) , where the rest of the organelles are

Nucleus

Nuclear Envelope- Double layered membrane surrounding the nucleus, contains small pores

Nuclear Pores- Holes in the envelope that allows for transport of materials in an out of the nucleus

Chromatin- Grainy material visible in the nucleus, made of DNA tightly coiled around proteins

Chromosomes- Threadlike structures within the nucleus containing the genetic information that is passed from one generation of cells to the next

Nucleolus- Dense material in nucleus; makes ribosomes which make proteins

Ribosomes Ribosomes are made in the nucleolus out of RNA and

proteins They travel in and out of the nucleolus through the

nuclear pores Ribosomes are small particles within the cell on which

proteins are assembled The can be free (found in the cytoplasm), or attached

to the rough endoplasmic reticulum

Endoplasmic Reticulum The endoplasmic reticulum (ER) is

responsible to assembly, transport, and storage of molecules within a cell

There are two types of ER Rough ER- Contains ribosomes and makes

proteins

Smooth ER- Lacks ribosomes; has enzymes that make membrane lipids and detoxifies drugs

Liver cells contain many smooth ER for detoxification

Golgi Apparatus

Stacks of membranes in the cell that modifies, sorts, and packages proteins from the ER (UPS of cells)

The golgi apparatus is like a customization shop where finishing touch's are added to proteins

Lysosomes Organelles that contain digestive enzymes Digest excess or worn out organelles, food particles,

and engulfed viruses or bacteria Are the clean up crew of the cell Tay-Sachs disease is causes by excess lipid

accumulation on the brain. The cause has been traced to lysosomes that failed to function properly

Vacuoles

A membrane-bound space used for temporary storage materials (water, salts, proteins, and carbohydrates)

Plant cells have much larger vacuoles to be able to stand up rights vs. animal cells

Paramecium have contractile vacuole that pumps excess water of of the cell, which is homeostasis

Mitochondria

Membrane-bound organelles in plant and animal cells that transform energy for the cell

A mitochondria has a highly folded inner membrane The fold increase the surface area of the mitochondria

of cells Cellular respiration takes place in the mitochondria of

cells Cellular respiration in the process that converts

chemical energy stored in food into ATP energy fro the cell to use

Muscles cells (needed for movement) contain a large number of mitochondria for energy production

Chloroplasts

Found in cells of plants and some protists Organelles that capture light energy and produce

glucose to store for a later time Photosynthesis takes place in chloroplasts Contain green pigment called chlorophyll Chlorophyll traps lights energy and gives leaves

and stems their green color Chloroplasts act like a solar power plant

Cytoskeleton

Cells have a support structure called the cytoskeleton within the cytoplasm

It is a network of proteins that help maintain cellular shape and movement

Is composed of microtubules ad microfilaments

Microtubules are thin, hollow cylinders made of protein that maintain cell shape

Microfilaments are thin solid protein fibers that help cells more (amoeba)

Centrioles

Made of microtubules One of two tiny protein structures located

in the cytoplasm of animal cells near the nuclear envelope

Help to organize cell division (helps split cells in two)

Only found in animal cells

Movement:Cilia and Flagella

Some cells surfaces have cilia and flagella, which are structures that aid in locomotion or feeding

Cilia are short, numerous hair like projections that move in a wave like motion

Flagella are long projectiles that move in a whip like motion

Cilia and flagella are the major means of locomotion in unicellular organisms

The Plasma/ Cell Membrane All living cells must maintain a balance regardless of

internal and external conditions. Survival depends on the cell’s ability to maintain the proper conditions within itself

The plasma membranes job is to: Allow a steady supply of glucose, amino acids, and lipids to

come into the cell no matter what the external conditions are

Remove excess amount of these nutrients when levels get so high that they are harmful

Allow waste and other products to leave the cell

Selective permeability is a process used to maintain homeostasis in which the plasma/cell membrane allows some molecules into the cell while keeping others out

Structure of the Plasma Membrane The plasma membrane is composed of two layers of

phospholipids back-to-back called a bilayer Phospholipids are lipids with a phosphate attached

to them The phospholipids are lipids with a phosphate

attached to them The phospholipids in a plasma membrane have a

glycerol backbone, two fatty acid chains, and a phosphate group

The phosphates hydrophilic, and the lipid hydrophobic

Make Up of the Phospholipid Bilayer

The phosphate group is critical for the formation and function of the plasma membrane

The fluid mosaic model describes the plasma membrane as a flexible boundary of a cell

The phospholipids move within the membrane

Other Components of the Plasma Membrane

Proteins are embedded in the phospholipid bilayer Some proteins form channels for mumps to move

material across the membrane Carbohydrates attached to proteins. They act as

signals or identification cards, allowing cell recognition Cholesterol plays the important role of preventing the

patty acid chains of the phospholipids from sticking together

Cell Walls

The cell was is a fairly rigid structure located outside the plasma membrane that provides additional support and protection

Found in plant cells, (protists) algae, and some prokaryotes, but not in animal cells

Plant cells walls are made of cellulose (carb)