Intro toCELLS

What are cells?

A cell is the basic unit of structure and function in a living thing.

Your body is composed of billions of cells.

Today a lot is known about cells. But that wasn’t always the case…

Here’s how we got to where we are today

Some of The History Behind Cells

The first lenses were used in Europe in the late 1500s by merchants who needed to determine the quality of cloth. They used their magnifying lenses to examine the quality of the thread and the precision of the weave in a bolt of cloth. From these simple glass lenses, combinations of lenses were put together.

In Holland in the early 1600s, two useful instruments were constructed: the telescope and the microscope.

Lenses and Microscopes

English scientist Robert Hooke (1635–1703) was the first to record his observations of cells.

In 1665, he took a thin slice of cork and placed it under a microscope that he built himself.

Robert Hooke

Cork Cells - Then and Now

Anton van Leeuwenhoek

One of the first people to use a microscope to study nature

1674 - made detailed drawings of living things in pond water, which he called ‘animalcules’

Anton van Leeuwenhoek

Matthias Schleiden

In 1838, German botanist Matthias Schleiden concluded that all plants are made of cells.

Theodor Schwann

In 1839, another German scientist, Theodor Schwann, concluded that animals are also made of cells.

Rudolf Virchow, a German physician, studied cell reproduction. In 1855, he summarized years of research by stating, “Where a cell exists, there must have been a preexisting cell.…” or cells come from cells

Rudolf Virchow

The Cell TheoryThe cell theory explains the relationship

between cells and living things:

All organisms are composed of one or more cells.

The cell is the basic unit of structure and function in living things.

All cells come from preexisting cells.

What Do Cells Look Like?

What Do Cells Look Like?

How BigAre Cells?

Why so small?Cells need to get materials in (nutrients) and out (waste) through their cell membrane.

As cells get bigger, the ratio of SA to V decreases. At some point, there isn’t enough surface area of membrane to manage the processes.

A high ratio means a cell can easily manage these exchanges.

Each cell in your body shares the characteristics of all living things.

Cells are Living Units

Similarities among cells

In many-celled organisms like you, there are many different specialized cells.

All cells share certain common characteristics.

Similarities among cells

1. All cells are surrounded by a cell membrane.

2. All cells contain organelles.

3. All cells contain cytoplasm.

4. All cells contain DNA.

Classifying cells

Prokaryotic cells do not have a nucleus.Scientists believe that all life on Earth came from ancient cells of this type.Only bacteria have this type of cell.

Classifying cells

Eukaryotic cells have a nucleus and membrane-covered organelles.They tend to be about ten times larger than prokaryotic cells.Animals, plants, fungi, and protists all have eukaryotic cells.

Comparing cell types

Eyepiece

Observation tube

Nosepiece

Low power objective lens

Arm

Medium power objective lens

High power objective lens

Stage Clips

Iris diaphragm

Light Source

Stage

Course Adjustment Knob

Fine Adjustment Knob

Base

Using a Microscope

Always carry with two hands

Only use lens paper for cleaning

Start on the lowest power objective

Use the coarse focus, then the fine focus

Switch to higher power, then only use the fine focus

Preparing a SlideYour sample has to be very thin. Use a razorblade to help obtain a sample.

BE CAREFUL - cut away from yourself! No messing around!

Use an eyedropper or plastic pipet to put a drop of water on your sample

Cover the sample with a cover slip or a second slide.

Clean-UpThrow samples in trash. Rinse your slides with water and arrange them in drying rack.

Put away water beakers and pipets.

Take care of microscope:

Turn to lowest objective, put stage down.

Turn off light. Unplug. Neatly wrap cord around base.

Parts of Cells:Cell Structures

andOrganelles

Basic Cell Structures

Cell membrane - a thin flexible barrier around the cell; regulates what goes in and out of the cell

Nucleus - large structure that contains the cell’s genetic material (DNA) and controls the cells activities

Basic Cell Structures

Cytoplasm - the material inside the cell membrane not including the nucleus

Cytosol - the semifluid substance that fills the cytoplasm

Cell Structures

Cell Wall - cell walls are found in many organisms, including plants, algae, fungi, and nearly all prokaryotes; they are important for structural support

- animal cells do not have cell walls

Cell Structures

Cytoskeleton - a network of protein filaments that helps the cell to maintain its shape; is also involved in cell movement

Parts of cytoskeleton - microtubules and microfilaments

Cell Structures

Microtubules - hollow tube of protein that maintains cell shape and can also serve as a “track” along which organelles are moved

Microfilaments - long, thin fiber that functions in the movement and support of the cell

Cell Structures

Cell Structures - the Nucleus

Nuclear envelope - double membrane layer that surrounds the nucleus

Nucleolus - small, dense region within most nuclei in which the assembly of ribosomes begins

Cell Structures - the Nucleus

OrganellesRibosome - small particle in the cell on which proteins are assembled; made of RNA and protein

Endoplasmic reticulum (ER) - internal membrane system in cells in which components of the cell membrane are assembled and some proteins are modified

Organelles

Rough ER - the part of the ER involved in protein synthesis

Smooth ER - contains enzymes that perform specialized tasks, such as synthesis of lipids

Organelles

Organelles

Golgi Apparatus - stack of membranes in the cell in which enzymes attach carbohydrates and lipids to proteins

Organelles

Organelles

Lysosomes - organelle filled with enzymes to digest certain materials in the cell

Organelles

Organelles

Centrioles - tiny structures in animal cells near the nuclear envelope; they play a rule in cell division

Organelles

Vacuole - stores materials such as water, salts, proteins, and carbohydrates; large in plant cells

Organelles

Chloroplast - found in plants and some other organisms; used for photosynthesis; contain chlorophyll

Organelles

Organelles

Mitochondria - releases energy from stored food molecules

Organelles

Interesting Info

Mitochondria have their own DNA separate from the cell’s DNA

And you inherit mitochondrial DNA maternally (from you mother), so you actually don’t get half your genetic information from each parent. You technically get more DNA from Mom!

Other Structures

Cilia (sing. cilium) - short hairlike projections that produce movement in many cells

Flagella (sing. flagellum) - whiplike structure on some cells used for movement

Other Structures

Cilia Flagella

Plant Cells vs Animal CellsBoth are eukaryotic cells, have a nucleus, organelles, cell membranes, cytoplasm

Plant and animal cell differences

Plant Cells

Cell wall

Chloroplasts

Large central vacuole

No centrioles

Animal Cells

Have centrioles

No cell wall

No chloroplasts

No large central vacuole

Cell membrane - a thin flexible barrier around the cell; regulates what goes in and out of the cell

Nucleus - large structure that contains the cell’s genetic material (DNA) and controls the cells activities

Cytoplasm - the material inside the cell membrane not including the nucleus

Cytosol - the semifluid substance that fills the cytoplasm

Cell Wall - cell walls are found in many organisms, including plants, algae, fungi, and nearly all prokaryotes; they are important for structural support

Cytoskeleton - a network of protein filaments that helps the cell to maintain its shape; is also involved in cell movement

Microtubules - hollow tube of protein that maintains cell shape and can also serve as a “track” along which organelles are moved

Microfilaments - long, thin fiber that functions in the movement and support of the cell

Nuclear envelope - double membrane layer that surrounds the nucleus

Nucleolus - small, dense region within most nuclei in which the assembly of ribosomes begins.

Ribosome - small particle in the cell on which proteins are assembled; made of RNA and protein

Rough ER - the part of the ER involved in protein synthesis

Smooth ER - contains enzymes that perform specialized tasks, such as synthesis of lipids

Golgi Apparatus - stack of membranes in the cell in which enzymes attach carbohydrates and lipids to proteins, preparing the proteins

Lysosomes - organelle filled with enzymes to digest certain materials in the cell

Centrioles - tiny structures in animal cells near the nuclear envelope; they play a role in cell division

Vacuole - stores materials such as water, salts, proteins, and carbohydrates; large in plant cells

Chloroplast - found in plants and some other organisms; used for photosynthesis; contain chlorophyll

Mitochondria - releases energy from stored food molecules

Plasma Membrane

The cells of all organisms are surrounded by a cell membrane.

Function: separate cell’s contents from the environment and control what enters and leaves the cell

Structure: thin bilayer of phospholipids and proteins

The two ends of a phospholipid molecule have different properties:

Phosphate head - hydrophilic (“water-loving”); dissolves easily in water

Lipid tail - hydrophobic (“water-fearing”); does not dissolve in water

Phospholipid Molecules

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Phospholipid Bilayer

Why are the membranes organized into a bilayer?

There are two “watery” areas that interact with the cell membrane - outside the cell and inside the cell (the cytosol).

Membrane ProteinsThere are proteins embedded in the lipid bilayer that serve a variety of functions.

The proteins in and on the membrane form patterns, or mosaics, on the membrane.

Membrane Proteins

Fluid Mosaic ModelBecause the membrane is fluid (it is felxible and the phospholipids can roll over one another) with a mosaic of proteins,

Our current view of the cell membrane is called the Fluid Mosaic Model.

Crossing the Membrane

Transport of Large Molecules

Endocytosis - in to cell

Exocytosis - out of cell

Transport of Large Molecules

Phagocytosis - endocytosis of large particles (solid)

Pinocytosis - endocytosis of fluid and dissolved soluted (liquid)

Water Balance in Cells