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Chapter 3 SIMILARITIES AND DIFFERENCES BETWEEN CELLS
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Life Must Be Dynamic
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Selectivity We are a community of living creatures (cells) in a “pond of water” –Specialized members of the community –Outlaw cells (cancer) –Invaders
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The Cell, The Smallest Living Unit
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Specialization in the Society
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Blood Stream Each group of cells have unique barriers (capillaries) for exchange with the blood which allows them to create a special environment for that group of cells
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Different Cell Types Common Processes: Processes all cells must do. Qualitative Differences: Unique processes that all types of cells do not do Quantitative differences: Some cells do more or less of some processes
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Energy The production of high potential energy molecules such as ATP All cells need to do this
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Cell Types Differ in their use of Energy Glucose + 2 ADP + 2 Pi + 2 NAD+ ---> 2 Pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H 2 O Small amount of energy (ATP) Acetyl-CoA + 3 NAD+ + FAD + GDP + Pi + 3 H 2 O ---> 3 NADH + FADH2 + CoA-SH + GTP + 3 CO 2 Large amount of energy Without Oxygen With Oxygen Use of Fat and pyruvate Use of Sugar
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Variation in energy Extremes in energy use Skeletal muscle. Brain
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Reproduction (Stem Cells) Skin and lining of digestive system (replacement) Liver and muscle (damage) Immune system (replacement and attack) Nervous system ???
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Cell Division (proliferation) A complex process involving many reactions (proteins) Signals for and against –Inhibition –Stimulation Copy DNA (check for mistakes: repair or apoptosis) Mutations: mistakes that escape Separate into two cells
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Protein Synthesis and Degradation Both Carried out by proteins Synthesis depends on mRNA Degradation depends on proteins Highly controlled and selective
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Turnover
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The Cell Membrane Charge barrier Molecular ports (channels) Information ports (receptors) They often work together
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The cell
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Channels Ion channel Glucose channel
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Relationships between Cells Communications: a language of chemical messages Coordinates functions involving many cells Signals and Receptors: A cell can’t respond to a signal that it can’t see
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Signals Chemical messages made by one cell that gives directions to another cell or cells Two types: water soluble and fat soluble –Insulin –Glucocorticoids Frequency and intensity modulated signals Every hormone is a different “voice” talking to those cells in the community that can listen
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Receptors A cell can only respond to the “voices” that it can hear Receptors mediate many things –Open channels through the membrane –Alter gene expression –Signals often cascade and feedback
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Receptors
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Respond to the signal Adjust and remember Tolerance Dependence
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Other Forms of Life in the Community Viruses Bacteria Fungi Parasites
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