intro to cells. what are cells? a cell is the basic unit of structure and function in a living...
TRANSCRIPT
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