Life is based on chemistry, and chemistry takes place in cells The Living Cell Life is based on chemistry, and chemistry takes place in cells
Outline The Nature and Variety of Cells How Does a Cell Work? Metabolism: Energy and Life Cell Division
The Nature and Variety of Cells
The Cell Theory All living things are composed of cells The cell is the fundamental unit of life All cells arise from previous cells
Observing Cells: The Microscope
How Does a Cell Work?
Cell Membranes Cell Membranes Transport Receptors Cell Wall Isolate cell Separates cell parts Transport Individual molecules Specific materials channels Receptors Bind molecules Cell Wall Plants
Plant Cell
There are two types of cells on Earth: Prokaryotic and Eukaryotic There are two types of cells on Earth: Prokaryotic and Eukaryotic. The former appeared first, and strong evidence indicates that the latter evolved from the former via endosymbiotic relationship. Prokaryotic cells include all bacteria and the blue-green algae. Fossil evidence shows that they have lived on earth for at least 3.8 billion years. The DNA in prokaryotic cells is not enclosed within a membrane-bound nucleus as is the DNA in eukaryotic cells.
Schematic of a Eukaryotic Cell The information required for producing all of the constituents of a cell is contained in the DNA in the chromosomes in the nucleus
The Nucleus Nucleus Prokaryotes Eukaryotes Double Membrane Contains genetic material Prokaryotes No nucleus Eukaryotes Double Membrane
Cell, the factories of life You have about 10 trillion cells. Factories have: Front office- paperwork Building- Bricks and Mortar- loading docks Production Units Power Plant
Cell, the factories of life Paperwork- the plan- DNA Building- cell walls. Protein & Receptors- loading dock
Cell, the factories of life Production- organelles- perform the chemical functions Power Plant- Mitochondria receive carbohydrates, fats and proteins and “burn” to produce energy Synthesis- site of protein synthesis (controlled by RNA next chapter)
Photograph of a cell of maize rust Photograph of a cell of maize rust. The dark boundary is the cell wall, made from cellulose. The nucleus takes up almost half the area of the central part of the cell.
Mitochondria “Sausage“ shaped organelles (specialized structures in cells) where molecules derived from glucose react to produce the cells energy
An organelle- mitochondria.
The Energy Organelles: Chloroplasts and Mitochondria Specialized structure in cell Chloroplasts Energy transformation chlorophyll Plant cells only Double membrane Mitochondria Produces cells energy Own DNA
Cytoskeleton Cytoskeleton Structure Gives cell shape Anchors Allows movement Transport system Within cell Structure Strong filaments Complex web
Metabolism: Energy and Life
Cells Energy Cells store energy in various ways. The most common is in a molecule adenosine triphosphate or ATP. Making ATP is endothermic so cells can make ATP and then release that energy when it’s needed.
The Cell’s Energy Currency Adenosine triphosphate (ATP) Provides energy Structure 3 phosphate groups Sugar molecule: ribose adenine Function Removal of phosphate group provides energy
The ATP reaction The tri-phosphate becomes a di-phosphate
Photosynthesis Photosynthesis Process Colors Convert sunlight to energy Process Energy + CO2 + H2O carbohydrate + O2 Colors
Glycolysis: The First Step in Energy Generation in the Cell Respiration Oxidation of carbohydrate Retrieves energy in glucose Aerobic Process Glycolysis Split glucose Result Pyruvic acid 2 ATP 2 energy carriers Convert energy carriers to 2-3 ATP 1 molecule glucose = 6-8 ATP
Fermentation: A Way to Keep Glycolysis Going Anaerobic Inefficient Yeast alcohol Animal cells Lactic acid
The Final Stages of Respiration Krebs cycle Glucose broken down CO2 produced ATP Energy-carrying molecules Result 36-38 ATP
Cell Division
Mitosis Mitosis Chromosomes Process Cell division Not for sexual reproduction Chromosomes Process Copy chromosomes Spindle fibers Migration of chromosomes Nuclear membrane reforms
Meiosis Meiosis Process Result Sexual reproduction 1 cell forms 4 gametes Gametes are genetically unique Process Copy chromosomes Crossing over Segregation Segregation again Result 4 daughter cells ½ normal chromosomes
Meiosis
VIRUS Virus occupy a twilight zone between the worlds of living and nonliving things. Criteria commonly applied for living things include (1) independent motility, (2) irritability (the ability to respond to certain environmental stimuli), (3) the ability to reproduce, and (4) the ability to specify the genetic composition of progeny.
Viruses can have a wide variety of shapes and sizes Viruses can have a wide variety of shapes and sizes. This diagram of a bacterial virus shows the protein coat containing DNA at the head. The tail fibers at the bottom attach the virus to the cell wall. DNA is then injected into the cell through the cylindrical core.
A diagram of the HIV virus A diagram of the HIV virus. The reverse transcriptase is the enzyme that initiates reverse transcription in the virus.
THE AIDS VIRUS Human immunodeficiency virus (HIV) was shown in 1984 to be the cause of the dreaded condition called immune deficiency syndrome (AIDS). In 2004 40 million people lived with it (1.1 million Americans) 5 million people acquired HIV 3.1 million people died of it
The central dogma of molecular biology
HIV is a human retrovirus, the third such virus to be identified HIV is a human retrovirus, the third such virus to be identified. Retroviruses (retro--from Latin means "turning back" are named after the crucial step in their growth cycle that involves the reversal of transcription, the first half of the "central dogma of biology"
Organic Molecules
Four Basic Characteristics Most molecules based on chemistry of carbon Organic molecules Life’s molecules form from few elements H, O, C, N97.5% of body weight Molecules composed of simple building blocks Arranged differently Shape determines behavior Determines ability for bonding
Chemical Shorthand No H atoms or bonds to H are shown C atoms are not shown explicitly Shorthand