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83 Cards in this Set
- Front
- Back
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what is science?
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Statement of fact or knowledge
• A way of asking questions about the world • Branch of knowledge or study • A search for unifying principles about the world around us |
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what is biology?
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• Biology is a branch of science-life forms
and life processes • Guided by natural law • Explanatory by reference to natural law • Testable against the empirical world • Conclusions are tentative (not necessarily the final word) • Falsifiable |
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Seven Characteristics of Life
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1. Information storage and retrieval (DNA)
2. High level of order and complexity 3. Energy conversion and metabolism 4. Responsiveness to environment 5. Capacity for growth and development 6. Reproduction 7. Evolution |
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DOING SCIENCE
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• Hypothesis testing for theory invalidation (the
scientific method) • Establishing causality • Discovery and characterizing natural systems (human genome project-brute force technology) • Serendipity • Trial and error • Reducing uncertainties in natural constants (speed of light, gravitational constant) |
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scientific method
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• Observations in nature
– Lead to questions about why? when? how? etc. • Theories – A large set of observations or data may lead to the development of a theory through inductive reasoning – A central feature of a “science” • Hypotheses – Scientific questions to test the validity of a theory • Tests or experiments – Design experiments and collect data to answer the hypothesis • Data analyses and explanations – Support or falsification of underlying theory (deductive process) – Modify or abandon theory |
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DEDUCTIVE REASONING
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uses general premises to make specific
predictions • For example, if organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans are composed of cells (deductive prediction) |
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INDUCTIVE REASONING
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• Inductive reasoning draws conclusions
through the logical process of induction • Repeat specific observations can lead to important generalizations – For example, “the sun always rises in the east |
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a theory is:
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– Broader in scope than a hypothesis
– General, and can lead to new testable hypotheses – Supported by a large body of evidence in comparison to a hypothesis |
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Models are...
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representations of natural
phenomena and can take the form of: – Diagrams – Three-dimensional objects – Computer programs – Mathematical equations |
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• Discovery science
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describes natural structures
and processes • This approach is based on observation and the analysis of data |
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Limitations of Science
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• In science, observations and experimental
results must be repeatable • Science cannot support or falsify supernatural explanations, which are outside the bounds of science |
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goal of technology
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to apply scientific
knowledge for some specific purpose |
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cells
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All organisms are composed of cells.
The cell is the fundamental unit of life. – Cells acquire and use energy – Cells organize molecules – Cells grow and reproduce – Cells live independently |
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cell theory
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-All living things are made up of one or more cells
-cells are the basic structural and functional units of life -Cells arise from pre-existing cells. |
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Common Features of Cells
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• A barrier or boundary that separates the internal
milieu of the cell from the environment. • A set of genes that encode all the proteins necessary to reproduce itself. • A cytoplasm (the material inside the cell; also called cytosol) where cellular biochemistry occurs |
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Prokaryotes
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• Bacteria and Archaea
• Tend to be less complex - single celled organisms • Commonly known as bacteria • Single circular chromosome • Have cell walls |
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Eukaryotes
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• Animals, plants, fungi, and protists
• Cells of plants, animals, fungi, and protists • Possess organelles, cellular structures that perform specific functions • Have a nucleus, a special compartment containing the chromosomes |
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Why Are Cells So Small?
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• Volume determines amount of chemical
activities a cell can carry out • Surface area determines rate that material enters and leaves cell • As volume increases, surface area also increase but not at same rate • If cell is too large chemical activities in cell cannot be supported by rate of material exchange across cell membrane |
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Antonie van Leeuwenhoek
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expert at making lenses.
Viewed many microscopic things in water, mud and gunk between his teeth, called these things ‘animalcules. 1683 he was first to see bacteria |
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Rudolf Virchow
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studies cells in disease
Cells never arise from non-cellular matter. • Pasteur (1822-1895) proved that spontaneous generation did not occur • Diseases arise from changes in specific cells. • We summarize the work of Virchow, Schlieden and Schwann as the Cell Theory |
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Cell wall
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in prokaryotes, supports the cell and determines its shape
bacteria cell walls contain peptidoglycan |
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flagella
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means for cells to move
in prokaryotes its made of protein called flegellin works by spinning on its axis lik a propeller |
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pili
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threadlike structures, shorter than
flagella, which project from the surfaces of some bacteria. help bacteria to adhere to one another during mating, as well as to animal cells for protection and food |
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capsule
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some bacteria have them around their cell wall
composed of polysaccharides aid bacteria by protecting them from white blood cells keeping them from drying out helping them attach to other cells |
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nucleus
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• The nucleus is the site of DNA storage
and replication. • It is the site of genetic control of the cell’s activities. • A region within the nucleus, the nucleolus, begins the assembly of ribosomes from specific proteins and RNA |
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nuclear functions
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• DNA replication - duplicates genome for cell
division, • DNA maintenance and repair to prevent mutation • DNA transcription - to make the proteins that carry out cellular functions • Pores form channels that connect the nucleoplasm to the cytoplasm. – Important for protein synthesis |
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Nucleolus
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Located inside the
nucleus. • Composed of DNA and RNA. • Ribosomes are assembled here and exported to the cytoplasm. |
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Endoplasmic Reticulum (ER)
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elaborate folded membrane in cell
entrance into cell secretory system |
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Rough ER
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• Rough ER is covered
with ribosomes. • Modify proteins – especially those destined for export from the cell. |
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Smooth ER
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• No ribosomes.
• Involved in the synthesis and metabolism of lipids. • Sends packages (vesicles) to the Golgi complex |
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Golgi Complex
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• The “traffic director” of
the cell. • Biomolecules – protein, lipids and carbohydrates – are processed for export by exocytosis. – Forms vesicles that eventually fuse with the plasma membrane to release contents. • Golgi complex receives proteins from the rough ER and “directs” them with molecular tags to different locations inside the cell. |
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Lysosomes
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• Membrane-enclosed
vesicles. • Garbage disposal • Contains enyzmes called hydrolases that digest biomolecules. • Degrades food, cellular debris, and old organelles. |
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Mitochondria
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• The cell’s
powerhouse • Has it’s own DNA! • converts nutrients into energy: adenosine triphosphate or ATP • Production of ATP using fuel molecules and O2 is cellular 2 respiration |
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The Chloroplast
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• Double membrane, inner membrane is continuous
with stacked membranes called thylakoids that contain chlorophyll and are the site of the photosynthesisOnly in plants and certain protists • Has own DNA! • Contain the green pigment chlorophyll • Site of photosynthesis • Photosynthesis uses light energy and converts it into chemical energy |
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Peroxisomes
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• Peroxisomes are organelles that collect
toxic peroxides (such as hydrogen peroxide) that result from chemical reactions within the cell. They have a single membrane and a granular interior containing specialized enzymes |
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Vacuoles
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•Vacuoles are membrane-bound sacs filled with
aqueous solutions and dissolved substances. •Most eukaryotic cells can have small vacuoles that are formed as required, but plant cells and certain protists have specialized vacuoles as well. |
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microfilament
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Microfilaments can exist as single filaments, in bundles, or in
networks. They are assembled from actin monomers, which come together to form long, double helix chains. Microfilaments have two main roles: 1. They help parts of the cell or the entire cell to move. 2. They stabilize cell shape |
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intermediate filaments
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found only in multicellular organisms.
There are at least 50 kinds of intermediate filaments, often specific to a few cell types. Intermediate filaments are made up of fibrous subunits organized into tough, ropelike assemblages. They help to stabilize a cell’s structure and maintain its shape. |
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microtubules
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Microtubules are long, hollow, unbranched cylinders assembled from
molecules of the protein tubulin. Tubulin is a dimer made up of the monomers α-tubulin and β-tubulin. Thirteen chains of tubulin dimers surround the central cavity of the microtubule. Microtubules are dynamic structures, whose length may change rapidly by the addition of removal of tubulin dimers. Microtubules have two roles in the cell: 1. They form a rigid internal skeleton for some cells. 2. They act as a framework along which motor proteins can move structures in the cell. |
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Cytoskeleton
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• Maintains cell
shape and support • Movement – Cilia – flagella • Move things within a cell |
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cilia
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Cilia - shorter and found in large
numbers -found in protists and in tissues such as those in mammalian respiratory system. -beat stiffly in one direction and recover in the other |
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stem cells
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Stem Cells
• Cell with the potential for self-renewal and the capacity to generate more specialized cells • SCs at different developmental stages appear to have different capacities for self-renewal and differentiation • Use of SCs in medicine to treat diseases linked to a lot of hope, hype and moral controversy |
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Functions of
“Fluid” Membranes |
•Essential boundaries that separate the inside from the outside
•Regulate the contents of the spaces they enclose •Serve as a “workbench” for a variety of biochemical reactions |
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Physical Properties of Lipids
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•Determine physical properties of membranes
•Lipids are heterogeneous, but share one property they are hydrophobic they do not dissolve in water •Functions: •energy reserves in cells •structural - part of membranes •messengers eg. some hormones |
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three classes of lipids
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•Three classes:
•simple lipids •complex lipids • steroids |
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Fluid Mosaic Model
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Fluid Mosaic Model
• 1972 Singer and Nicolson • Major Features 1) lipids are in a bilayer, which have two roles - a solvent for membrane proteins and a barrier 2) proteins and lipids diffuse laterally within the bilayer, 3) the bilayer is asymmetrical |
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Mammalian red blood cells:
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•have no internal membranes,
•no nucleus, no organelles and few macromolecules other than hemoglobin. • Scientists obtained almost pure plasma membrane by lysing these cells. • Found primarily phospholipids, also protein and other lipids and carbohydrates. • There was enough phospholipid to go around cellsTWICE • Conclusions: membrane is a lipid bilayer and contains many biomolecules-a molecular mosaic |
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Simple Diffusion
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• Membrane is considered permeable
• Small molecules pass through the lipid bilayer of the membrane. • The hydrophobic inner core of the membrane allows nonpolar, lipid-soluble molecules to diffuse more rapidly across the membrane than other molecules. • Only water and the smallest of molecules seem to deviate from this rule, passing through much more quickly than their lipid solubilities would predict. • Rate of diffusion determined by: – Concentration gradient – Exchange surface (membrane) and diffusing species characteristics (e.g., lipid solubility) • Requires no energy |
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Isotonic solutions
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have equal solute concentrations.
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hypertonic solution
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has a higher solute concentration
than the solution to which it is being compared. |
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A hypotonic solution
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has a lower solute concentration
than the solution to which it is being compared. |
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uniport
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move single solute in one direction
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symport
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moves two solutes in the same direction
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antiport
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move two solutes in opposite direction ex soduim-potassuim pump
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Primary active transport
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requires the
direct participation of ATP, whose hydrolysis supplies the necessary energy. |
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Secondary active transport
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does not use
ATP directly. Instead, it uses the energy supplied by an ion concentration gradient established by primary active transport |
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phagocytosis
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cellular eating
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pinocytosis
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cellular drinking
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endocytosis
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wht cell brings in
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process of exocytosis
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A membrane protein protruding from the cytoplasmic side of the
vesicle binds with a membrane protein on the cytoplasmic side of the target site on the plasma membrane. 2. The phospholipid regions of the two membranes merge. 3. An opening to the outside cell develops. 4. The contents of the vesicle are released to the environment. 5. The vesicle membrane is smoothly incorporated into the plasma membrane. |
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Tight Junctions
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Tight junctions link adjacent epithelial cells that line the lumen (cavity)
of organs such as the intestine. They result from the mutual binding of strands of specific membrane proteins, which form a series of joints encircling each epithelial cell. They prevent substance from moving through the spaces between cells and restrict the migration of membrane proteins and phospholipids from one region of the cell to another. |
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Desmosomes
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Desmosomes hold adjacent cell firmly together, acting like spot
welds or rivets. Each desmosome has a dense structure called a plaque on the cytoplasmic surface of the plasma membrane. The plaque is attached to special cell adhesion proteins, which stretch through the plasma membrane of one cell, across the intercellular space, and through the plasma membrane of the adjacent cell. Each desmosome also has a cytoskeleton made of keratin, which connects the plaque one side of the cell with the plaque on the other side of the cell. These keratin fibers provide great mechanical stability to epithelial tissues. |
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Gap Junctions
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Gap junctions facilitate communication between cells. Each gap junction
is composed of specialized protein channels, called connexons, which span the plasma membranes of two adjacent cells and the intercellular space between them. Dissolved molecules and electric signals are passed from cell to cell through these junctions. |
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Systems of Cell Reproduction
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Unicellular organisms use cell division primarily to
reproduce • Multicellular organisms: cell division also plays important |
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Four events of cell reproduction:
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signal to reproduce
– Replication of DNA and cell components. – DNA must be distributed to new cells. – The cell membrane must separate the two new cells. |
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Fission in Prokaryotes
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One circular chromosome.
– As DNA replicates, each of the two resulting DNA molecules attaches to the plasma membrane. – As the cell grows, new plasma membrane is added between the attachment points, and the DNA molecules are moved apart. – Cytokinesis separates the one cell into two, each with a complete |
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Cell Division in Eukaryotic Cells
three steps |
– The replication of the DNA within the nucleus
• MANY chromosomes – Packaging and segregation of the replicated DNA into two new nuclei (nuclear division) – Division of the cytoplasm (cytokinesis) • Eukaryotic cells divide by mitosis or meiosis. |
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four phases of cell cycle
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M, G1, S and G2
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G1, S and G2 are collectively
called... |
interphase
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what is an exception to growth factors of cells?
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cancer
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Control Points in the Cell Cycle
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• DNA damage checkpoints in
late G1 and S • DNA replication checkpoint in late G2 • Spindle checkpoint in M checks for proper spindle attachment • Failures at checkpoints alter progression through cell cycle until repairs made |
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Transitions from G1 to S and G2 to
M depend on activation of a protein called... |
cyclin-dependent
kinase, or Cdk |
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function of Cyclin-Cdk complexes
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Cyclin-Cdk complexes allow or
prevent the passage to the next cell cycle stage, depending on the extra- and intracellular conditions |
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Rb prevents progression into wht phase
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interphase
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how is Rb inactivated?
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Cyclins D and E activate
Cdk 4 and 2, which in turn inactivate RB by phosphorylating it. then the cell can progress into s phase |
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Cell cycle control system regulated by two key families of
proteins |
– 1) cyclin-dependent kinases (Cdk)
– 2) cyclins - bind to Cdk proteins and regulate their function |
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Two main classes of cyclins
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G1 and mitotic cyclins
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Cyclin D-Cdk4 acts during...
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G1 - regulates the restriction
point or Start, after a cell passes the restriction point it must continue the cell cycle or die |
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Cyclin E-Cdk2 acts at the
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G1-S boundary, this initiates
DNA replication |
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Cyclin A -Cdk2 act at
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S, also initiates DNA replication
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Cyclin B-Cdk1 acts at the
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G2-M boundary, initiates the
transition to chromosome condensation and mitosis |
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Retinoblastoma
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• Mutation of RB gene
(tumor suppressor gene) • Rb protein is a key to cell cycle control • Mutated RB protein leads to uncontrolled cell division |
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when do DNA chromosomes replicate
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S phase
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