Cell Biology Chapter 2

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Flashcards for Cell Biology Chapter 2

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Compounds Combinations of matter that consists of chemical elements in pure form
element properties depend on the structure of its atoms
the formation and function of molecules depends on chemical bonding between atoms
Chemical bonds are made and broken down by chemical reactions
Formic acid When threatened, wood ants shoot volleys of __________ _______ into the air from their abdomens, and acid rains on the predators or micro parasites also a herbicide to prevent other trees from growing there
Chemicals in relation to insects they play a major role in communication, attracting mates, and defense
Matter - makes up organisms - anything that takes up space has mass -consists of chemical elements in pure form and in combinations (compounds)
Element - a substance that cannot be broken down into other substances by chemical reactions - makes up matter - there are 92 different elements
compound - a substance that consist of two or more different elements combined into a fixed ratio - has different characteristics than those of its elements
Essential elements - varies from organism to organism - the elements that an organism needs to live a healthy life and reproduce - 20-25% of the 92 elements are essential
Essential elements that are 96% of living matter O - Oxygen N - Nitrogen H - Hydrogen C - Carbon
Essential elements that are 4% of living matter Ca - Calcium P - Phosphorus K - Potassium S - Sulfur
trace elements required by organisms in minute quantities
what is the trace element that is needed by all forms of life? Fe - Iron
What is Goiter? it makes the thyroid gland grow to an abnormal size because of an iodine deficiency
What causes Goiter to happen? The thyroid gland's main job is to concentrate iodine from the blood to make thyroid hormone. Without enough iodine, it cannot do this. Therefore, the individual becomes hypothyroid. Then the pituitary gland in the brain senses the low thyroid level and signals the thyroid to produce more thyroid hormone and to grow in size. This signal is the Thyroid Simulating Hormone (TSH).
What are the essential elements that are needed by humans? O - Oxygen C - Carbon H - Hydrogen N - Nitrogen They make up 96.3% of a humans body mass.
What are the trace elements that are needed by humans? Ca - Calcium P - Phosphorus K - Potassium S - Sulfur Na - Sodium Cl - Chlorine Mg - Magnesium They make up 3.7% of a human's body mass.
What is the chemical connection to biology? Biologists specialize in the study of life, but organisms and their environments are natural systems to which the concepts of chemistry and physics apply.
What are the elements of life? Essential elements and trace elements
How did the tolerance to toxic elements evolve? evolution by natural selection which causes adaptations.
Atom - smallest unit of matter that still retains the properties of an element - each element consists of a certain type of atom that's different from atoms of other elements
What are subatomic particles? - tiny bits of matter (atoms) that are composed of smaller parts - there are three kinds: 1. Protons 2. Neutrons 3. Electrons
Proton has one unit of positive charge
Neutron is electrically neutral
Electron has one unit of negative charge
atomic nucleus - a core at the center of an atom where neutrons and protons are tightly packed - protons make the nucleus positive
Where are electrons found? in a 'cloud' around the nucleus where they move rapidly
Proton and neutron mass 1.7X10^-24 g OR 1 Dalton (d) OR 1 Atomic Mass Unit (amu)
atomic number - the number of protons a specific element has - written as a subscript to the left of the symbol for the element - tells the number of protons and electrons in an atom
mass number - sum of protons and neutrons in the nucleus - written as a superscript to the left of an elements symbol
atomic mass approximation of the total mass of an atom
What are isotopes? - different atomic forms of the same element (more or less neutrons) - they have slightly different masses but react identically in reactions
stable isotopes the nuclei do NOT have a tendency to lose subatomic particles
decay to lose subatomic particle
radioactive isotope - the nucleus decays spontaneously giving off particles and energy (giving off heat and energy - unstable isotope
radioactive isotopes as diagnostic tools in medicine they are incorporated into biologically active molecules then used as tracers to track atoms during metabolism, the chemical processes of an organism
tracers - radioactive isotopes that are often used as diagnostic tools in medicine - also used with sophisticated imaging instruments (PET scanners - monitor growth and metabolisms of cancers) (Positron - emission tomography)
What is radiometric dating? - researchers date fossils by measuring radioactive decay - scientists measure the ratio of different isotopes and calculate how many half-lives (in years) have passed since an organism was fossilized or a rock was formed
half-life of an isotope - the time it takes for 50% of the parent isotope to decay - the parent isotope decays into the daughter isotope at a fixed rate which is NOT affected by any environmental variables)
energy the capacity to cause change (example: doing work)
Potential energy the energy that matter possesses because of its location or structure
Does matter tend to move towards the lowest or highest possible state of energy? lowest state of energy
potential energy of an electron - this is due to the distance from the nucleus - the farther away from the nucleus, the greater the potential energy
can electrons exist between energy levels? no. electrons can only exist at certain energy levels, not between them.
kinetic energy the energy that matter possesses as it moves
electron shells - where electrons are found - each has a characteristic average distance and energy level - the amount of potential energy: 1st shell - low last shell - high
how do electrons move from one electron shell to another? by absorbing or losing an amount of energy that is equal to the difference in potential energy to the other shell
When an electron ABSORBS energy, does it move toward the nucleus or away from the nucleus? it moves to the next shell (away from the nucleus)
valence electrons - electrons on the outermost shell (valence shell) - these are the electrons that take place in chemical bonding - atoms with the same number of valence electrons behave the same
When an atom has a full valence shell is it reactive or nonreactive? Nonreactive. this is also called inert.
electron orbital 3-d space where an electron spends 90% of its time
S - orbital what is its shape?) spherical shaped orbital
P - orbital (what is its shape?) dumbbell shaped orbital
chemical bonds form because of a tendency of an atom to complete its valence shell
how do atoms with incomplete valence shells acquire complete valence shells? - atoms with incomplete valence shells can interact with other specific atoms and transfer or share electrons so that each atom has a full valence shell - this results in chemical bonds
Valence the binding capacity of an atom = the number of unpaired electrons required to complete its valence shell
What is a covalent bond? a bond formed by the sharing of two electrons by two atoms (two atoms connected by a pair of shared electrons)
Molecule - two or more atoms held together by covalent bonds - H2, O2, H2O, CH4
Lewis dot structure element symbols are surrounded by dots that represent the valence electrons
Structural formula H-H the line represents a single bond
double bond atoms joined by the sharing of two pairs of electrons (4 electrons)
electronegativity - attraction of a particular atom for the electron of a covalent bond - the more electronegative an atom is, the more strongly it pulls shared electrons towards itself
non-polar covalent bond two atoms of the same element, electrons shared equally because the two atoms have the same electronegativity
Polar covalent bond - when an atom is bonded to a more electronegative atom - the electrons of the bond aren't shared equally - polarity varies -gives it a partial negative and a partial positive charge
ion - when two atoms bond by one taking and electron from the other -they become ions - because the more electronegative atom takes an electron which changes their charges (cation and anion) THEN they attract - an electrically charged molecule
cation a positive ion
anion a negative ion
ionic bond when a cation and an anion attract and form a bond
ionic compounds - salts - compounds formed by ionic bonds - does NOT consist of molecules
what effects the strength of ionic bonds? - environment - if it is dry, it is hard - if it is wet, it is soft; will dissolve/dissociate/fall apart
Weak bond - when two molecules in a cell make contact, they may adhere temporarily by these bonds
The reversibility of weak bonds as an advantage two molecules can come together, respond to one another in some way, and then separate
When is an ionic bond weak? when it is in water
hydrogen bonds - bond formed by an attraction between a hydrogen and an electronegative atom - non-covalent - weak bond between two charged molecules
Vander Waals interactions - individually weak - only occurs when atoms and molecules are very close together - result from transient local partial charges
Are electrons evenly distributed when involved in a Vander Waals interaction? not always. the ever changing regions of positive and negative charges enable all atoms and molecules to stick together
where do Vander Waals interactions occur? the can be between molecules or parts of molecules
molecular shape - determined by the positions of the atoms orbitals - bonds also determine the shape
a molecule with only two atoms is what...? ALWAYS linear
tetrahedron - molecular shape - a pyramid with a triangle base
molecular shape - determines how biological molecules recognize and respond to one another with specificity
endorphins - signaling molecules made by the pituitary gland that binds to the receptors, relieving pain and producing euphoria during times of stress
morphine - it is like endorphins - interacts with pain receptors in the brain like endorphins do (same receptors)
Chemical reactions - the making and breaking of chemical bonds which leads to changes in the composition of matter - matter is conserved
reactants - starting materials - the materials that are there before the reaction occurs
products - ending materials - the materials that result from a reaction
Matter is conserved in a chemical reaction. True or False True
Concentration of the reactants affects the rate of reaction. True or False True - the greater concentration of reactant molecules, the more frequently they collide with one another and have an opportunity to react and form products
chemical equilibrium - the point at which the forward and reverse reactions offset one another by occurring at the same rate - reaction rates are equal - this does NOT mean the concentrations are equal - this DOES mean that they have stabilized at a fixed ratio
What is the smallest unit of matter? AND What are its particles? - An atom - Proton, Neutron, Electron
Atomic mass vs. Atomic number - The atomic mass tells the mass of the particle - The atomic number tells the number of protons and electrons within an atom
Ionic bonds vs. covalent bonds -Ionic bonds are formed between a cation and an anion - Covalent bonds are formed between the sharing of a pair of electrons
Name two weak chemical reactions 1. Hydrogen bonds 2. Vander Waals interactions
Why do we care about the shape of molecules in biology? The shape of a molecule determines how it interacts with other molecules outside of itself.
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