Introduction to Cells

What is a cell? …membrane bound structure, it is the smallest unit of life.

Important people who helped discover cells Robert Hooke – looked at a thin slice of cork cells named the structure “cell” Anton von Leeuwenhoek looked at pond water, was 1st to look at living cells! Given what these two scientist as well as others knew about cells they came up with the Cell theory

Microscopes Only been around for about 250 years. Several types: Light microscope Electron microscope (SEM & TEM)

Light microscope

What are the 3 parts to the Cell Theory? All living things are made of at least 1 cell. Cells are the basic unit of structure & function of life. Cells only come from other living cells.

Are there differences between cells? Different shapes Different sizes Different internal organization Cells range from being tiny microscopic bacteria to very large cells.

Different cell shapes

How is the internal organization different? Cells are either Prokaryotic or Eukaryotic!!

Eukaryote Has nucleus Has linear DNA & rod shaped chromosomes Has many membrane-bound organelles Can be 1 celled (unicellular) or many celled (multicelled). Ex: fungus, plants, us

Typical Eukaryote (animal cell)

Prokaryote No nucleus Has DNA & circular chromosome No membrane-bound organelles Can only be unicelled Ex: bacteria

Typical prokaryote

Cell Organelles …small structures within the cell, each has a specific job. Not all cells will have every organelle!

THE ORGANELLES

1) Nucleus The nucleus is considered the control center of the cell It contains the DNA The nucleus Controls all the cell functions The nucleus is surrounded by a double membrane called the nuclear membrane The nuclear membrane allows substances to move in and out of the nucleus Some have a nucleolus inside

Nucleus

Endoplasmic Reticulum AKA: ER – Is considered to be the “highway of the cell” 2 types: smooth (no ribosomes and is the site of lipid synthesis) & rough (has ribosomes attached and is the site for protein synthesis) Snuggles up to the nucleus Helps with movement of substances within the cell, Smooth ER also helps make steroids & break down toxins.

ER

Golgi Apparatus The “post office” of the cell. The golgi apparatus modifies, sorts, and packages proteins into storage sacs called vesicles. Vesicles then ship the proteins out of the cell.

Golgi Apparatus

Ribosomes Make proteins. Can be “free” in the cytoplasm or attached to rough ER.

Ribosomes

Lysosomes Recycler of the cell (garbage disposal) Contain substances that digest excess or worn-out organelles and food particles. When a cell “lysis” (breaks down) the lysosomes are usually the reason.

Mitochondria “power plant” Most of the energy cell’s need is made here! (cell respiration) The mitochondria have an outer membrane and a folded inner membrane that provides a large amount of surface area. **has its own DNA Produces energy by breaking the bonds in sugar molecules.

Mitochondria

Cytoplasm/Cytoskeleton Cytoplasm = jelly like substance in the cell Cytoskeleton = made up of microtubules & microfiliments Both are important for providing structural support in intracellular movement.

Cytoplasm/Cytoskeleton

Cell Membrane/Plasma Membrane Acts like the door of the cell by allowing things into and out of the cell. Double layer of lipids with carbs & proteins. Helps maintain cell shape and homeostasis. Is selectively permeable, which means it allows some substances to pass freely through the membrane while keeping other substances out.

Cell membrane

Plant cells have the same organelles & a few new ones!

Plant cells

Chloroplast Organelles that capture light energy and convert it to chemical energy. This process is know as photosynthesis **has its own DNA Cells in plant leaves have LOTS of chloroplasts! Contains chlorophyll that give plant leaves and stems their green color.

Chloroplasts

Cell Wall Is a thick Rigid organelle that surrounds the outside of the cell membrane. mostly made of cellulose. Protects the cell and gives the cell support.

Cell wall

Some other cell parts to be aware of… Cilia – hair-like structures used for cell movement. 2) Flagella (flagellum) – whip-like tail that is used for cell movement . Can have one or two flagella.

Vacuoles – used for temporary storage of wastes, water, and food. Plants usually have 1 large vacuole called the Central Vacuole. Animal cells have many smaller vacuoles called vesicles. 4) Centrioles – only found in animal cells, aid in cell division

Cells – general information Cell size is limited by the ratio of surface area to volume. Cells that have particular functions may have more of some organelles & less of other organelles. Ex: Muscle cells have more Mitochondria. Why might this be?