CELLS!

What are cells? Robert Hooke in 1665 first called the tiny chambers he saw in a microscope cells. All living things are made out of cells! Cells contain living matter. CELLS MAKE UP EVERY LIVING THING! Plants are made of CELLS! Animals are made of CELLS! Bacteria are CELLS! Can we see them? Most cells are very small so we can’t see them without a microscope BUT a chicken egg is just one large cell.. 

Let’s talk about scale…

The Cell Theory What do cells have to do with life? All living things are composed of cells (you, me, plants, bugs, fish, Spiderman, Colonel Sanders, Jimmy Neutron, Bacteria, Yeast, Jackie Chan) Cells are the basic units of structure and function in living things (what keeps us upright and helps us live, basically small workers responsible for how we function!) New cells are produced from existing cells (they can’t just appear out of thin air…cells make new cells by dividing!)

All living things Prokaryotes Eukaryotes Protists (unicellular eukaryotes) Plants Animals Fungi

Why are cells named that way? From Greek words… EU means TRUE PRO means BEFORE KARYON means NUCLEUS Eukaryote = TRUE NUCLEUS Prokaryote = BEFORE NUCLEUS All cells have DNA, in eukaryotes it is stored in the nucleus Prokaryotes don’t have a nucleus, and it floats around in the cytoplasm the nucleoid region Only eukaryotes have membrane-bound organelles

Classifications of Life: All life is classified into three Domains… Bacteria Archaea Eukarya Each domain is divided into Kingdoms. There are six different kingdoms… Eubacteria Archae-bacteria Protista Plantae Fungi Animalia Everyday bacteria. Helpful bacteria that live in our bellies as well as streptococcus, the bacterium that causes strep throat. Prokaryotic Bacteria found in extreme environments such as hot boiling water and thermal vents with no oxygen or highly acid environments. Prokaryotic Eukaryotes that are not plants, fungi, or animals. Amoeba, paramecia, euglena, etc. Eukaryotic Flowering plants, cone-bearing plants, mosses, and ferns Eukaryotic Mushrooms, mold, yeast, mildew Eukaryotic Invertebrates: worms, insects, mollusks, etc. Vertebrates: fish, amphibians, reptiles, birds, mammals (including humans). Eukaryotic It’s important to note that both Eubacteria and Archaebacteria are Prokaryotes. All Prokaryotes are single-celled and include all types of bacteria. Eubacteria and Archaebacteria are much more genetically varied than Protists, Plants, Fungus, and Animals, which is why bacteria are divided into two kingdoms. Let’s look at some examples of organisms in each kingdom…

Prokaryotic cells (prokaryotes) Do not have a nucleus--their DNA is spread through the cell Do not have membrane-bound organelles (no vacuoles, no lysosomes, no Golgi, etc.) Known as BACTERIA!!! Are always UNICELLULAR

Eukaryotic Cells (eukaryotes) Larger and more complex than prokaryotes They have a NUCLEUS that separates the cell’s genetic material from the rest of the cell They also have membrane-bound organelles like Golgi apparatus, ER, lysosomes, etc. Eukaryotes: plants, animals, fungi, protists (unicellular eukaryotes)

Types of Eukaryotes: Animal vs. Plant Cells Animal cells Plant cells No cell walls (only cell/plasma membrane) No chloroplasts Many small vacuoles for storage Cell wall (gives rectangular shape) and cell/plasma membrane Chloroplasts for photosynthesis One large central vacuole

Test Yourself! Statement Prokaryotic Eukaryotic 1. Have a nucleus 2. Have membrane-bound organelles 3. Contain genetic material (DNA) 4. Can be single or multi-celled 5. Can only be single-celled. 6. Have a plasma membrane and cytoplasm

How is life organized for MULTI-CELLULAR Organisms? Cells make up tissues which make up organs which make up organ systems which make up organisms We can also take it back to the atomic level..

QUESTIONS? Stem Cells

Why are all cells so small? Cells are usually 2-200 micrometers in diameter Micrometer= one millionth of a meter! (too small to be seen with the naked eye) Why am I not just one big cell? Would I be able to function if I were just one big cell? What advantages does being unicellular offer? What advantages does being multicellular offer?

Amoeba proteus– one of the largest cells ever found Mycoplasma—one of the smallest cells ever found

There are limits to cell size!!! 1. The process of diffusion limits cell growth Diffusion: movement of materials (like food or waste) from high concentration to a low concentration Why?? A. Cells need constant supplies of materials to perform their duties. They get supplies through diffusion into the cell. B. Cells also need to get rid of waste. They get rid of waste by diffusion out of the cell.

A cell 20 cm would require MONTHS for nutrients to get to the center! So what’s the problem? Diffusion is only efficient when it is used over short distances Larger the distance = slower the diffusion rate A cell 20 cm would require MONTHS for nutrients to get to the center!

There are limits to cell size!!! 2. The amount of DNA a cell has limits its size. Most cells have only one nucleus that contains DNA Larger cells need more DNA—and more of everything else! If a cell grows larger than its organelles and DNA can support, the cell’s processes will not meet the demands of the cell Very large cells have more than one nucleus to allow them to function…but there are still size limits

There are limits to cell size!!! 3. And finally…a cell’s surface area-to- volume ratio limits its size. As a cell’s size increases, its volume increases much faster than its surface area Volume = 4/3pr3 Surface area = 4pr2 If the cell membrane is not big enough, oxygen, nutrients, and wastes would not be able to move in and out of the cell quickly enough…and the cell would die!

Cell size doubles, 8x as much volume, but only 4x as much surface area

So what’s the solution to size limit?!

Our cells DIVIDE! A cell divides into two daughter cells Before a cell divides, it replicates all of its DNA, so each daughter cell gets one complete set of genetic information.

The Cell Cycle During the cell cycle: The cell grows (G1 of Interphase) DNA is replicated (S of Interphase) Cell prepares for division (G2 of Interphase) Nucleus divides (Mitosis!) Cytoplasm divides (Cytokinesis) G1, S, G2 are together known as INTERPHASE, the time between cell divisions.