Structure and Function Cells Structure and Function

What We Will Learn How were cells discovered? What are the basic differences between types of cells? How are cells structured? What are the functions of different cell structures – how do they work?

Cellular Basis of Life Cell Smallest living unit of any organism Capable of carrying out all life functions Uni-cellular life – single cell Multi-cellular life – many cells with different functions

History of Cell Discovery Most cells too small to see with naked eye Invention of microscope enabled scientists to discover and study cells

Scientists and Cell Study Leewenhoek: Simple microscope Observed organisms in pond water, blood cells, bacteria Hooke: Crude compound microscope Observed cell walls of cork Coined term “cells”

Schleiden: (Botanist) Stated all plants are made of cells Schwann: (Zoologist) Stated all animals made of cells

Virchow: Brown: Stated all cells come from pre-existing cells First to identify an internal cell structure (nucleus) From this research and observation of living things a scientific theory was developed (took over 200 years!)

Cell Theory All living things made up of cells Cells are the basic units of structure and function in living things New cells come from existing cells

Exceptions to Cell Theory Viruses: Need host cell to carry out life processes

Exceptions to Cell Theory Mitochondria & Chloroplasts: Organelles that reproduce inside cell Have own unique genetic material Can’t survive outside of cell

Exceptions to Cell Theory The First Cell Where did it come from? What was it like?

2 Basic Types of Cells Prokaryotes Eukaryotes Both Types: Contain DNA Are surrounded by cell (plasma) membrane Carry out all life functions

Prokaryotes No nucleus Lack internal membrane bound organelles DNA in cytoplasm Metabolic functions take place in cytoplasm Smaller, simpler more primitive cells Ex: bacteria

Eukaryotes Nucleus encloses DNA Specialized membrane bound organelles (more compartmentalized) Larger, more complex Ex: protists, plants, animals, fungi

Cell Structure and Organelles

The Cell as a Factory Each organelle carries out a specialized function. Ex: Oversee cell activities Provide energy Produce products Get rid of wastes

Cell as Factory

Cell Membrane Also called “plasma membrane” Separates inside of cell from outside environment

Made of lipid and protein bi-layer Called the “fluid mosaic model” Controls substances going in and out of cell (selectively permeable) http://youtu.be/Rl5EmUQdkuI

Channel Proteins: allow for selective movement of materials in and out of cell membrane

Phospholipids: molecules that line up in a bi-layer (two layers) to make cell membrane Hydrophilic = “water loving” end Hydrophobic = “water fearing” end

Cell Wall Found in plants, fungi, some bacteria and protists NOT in animal cells Inflexible structure Made of cellulose fibers woven together In fungi made of chitin Protect cell and give it support and shape

Cytoplasm Liquid, gel-like substance inside cell membrane (75% water) Many substances dissolved in it Most chemical reactions take place here.

“Cyclosis”: the movement of materials through cytoplasm http://youtu.be/7jw-N82tHjc

Cytoskeleton Internal framework inside cytoplasm Made of fibrous rods microfilaments microtubules Maintains cell shape Supports and moves organelles

Images of Cytoskeleton

Nucleus Directs cell activities Eukaryotic Cells ONLY!! Control center for metabolic functions and reproduction Provides instructions for making proteins and other molecules for the cell

Structure of the Nucleus

Nuclear envelope: membrane surrounding nucleus Nuclear pores: allow materials to leave or enter Nucleolus: dark inner area. Ribosomes formed here

Chromatin: coiled DNA, in the nucleus contains instructions for building proteins unwound and spread out

Communicates with rest of cell by movement of molecules through nuclear pores During cell division, chromatin condenses to form chromosomes that replicate and divide

Endoplasmic Reticulum (E.R.) Channels to move materials inside cell Highly folded (increases surface area)

Rough ER: “bumpy” with ribosomes attached to surface Smooth ER: doesn’t have ribosomes on surface

Ribosomes Site of protein synthesis Small round structures Cell has a lot of them (needs proteins!) May be free floating in cytoplasm or attached to the “rough” E.R.

Golgi Bodies Stack of membranes (like pancakes) Involved in modifying, packaging, storing and releasing products

Vesicles: packages containing proteins that are pinched off to be used inside cell or transported out.

Lysosomes Membrane enclosed vesicles Hydrolytic digestive enzymes Breaks down food and worn out cell parts Formed by Golgi Bodies http://youtu.be/ekdIEpSf-1I

Vacuoles Stores water, food, wastes Much larger in plant cells Used to help give cell shape, structure

Food Vacuoles: merge with lysosomes to digest food

Contractile Vacuoles: Found in single celled freshwater organisms like paramecium “contract” to pump out excess water from cell

Energy and the Cell

Mitochondria Powerhouse of the cell Site of cellular respiration Makes usable energy (ATP)

Simple sugars are broken down to release energy as ATP The more energy a cell needs the more mitochondria it has!

Cristae: Highly folded inner membrane that allows for increased surface area for cellular respiration reactions

Chloroplasts FOUND IN PLANT CELLS ONLY!! Site of photosynthesis Light energy is transformed to chemical energy in the form of sugar Chlorophyll: (green pigment) that captures sunlight

Grana: Inner membranes in “coin” stacks containing chlorophyll Stroma: enzyme filled fluid surrounding grana

Endosymbiotic Theory Mitochondria and chloroplasts have own DNA and can reproduce on their own. Perhaps they were a primitive type of prokayotic cell that became incorporated into another Symbiotic relationship = both cells benefit Evolution of Complex Life http://youtu.be/q71DWYJD-dI

Centrioles FOUND IN ANIMAL CELLS ONLY!! Pair of small cylindrical organelles found near nucleus Function in cell division to pull chromosomes apart

Cell Movement Cilia: short hair like projections used for locomotion

Flagella: long whip-like tail used for locomotion http://youtu.be/QGAm6hMysTA

Pseudopods: “false foot” Projections of the cell membrane Used for locomotion Used to surround and engulf food

Limitations of Cell Size Size is limited by the cell’s need to intake nutrients and excrete wastes Smaller the cell is, the closer all parts are to the external environment. Surface area to volume ratio

http://www. youtube. com/watch http://www.youtube.com/watch?v=rnNAcLJNc3s&feature=share&list=ULrnNAcLJNc3s http://youtu.be/LP7xAr2FDFU Passive transport http://youtu.be/JShwXBWGMyY Osmosis http://youtu.be/XclGRjnilsk Membrane http://youtu.be/GW0lqf4Fqpg

Cellular Organization In multicelluar organisms cells are just the start of how things are organized. Cells Tissues: groups of cells that function together to perform an activity Organs: groups of tissues performing one main function Organ Systems: organs working together Organism