intro to cell Test 1 Flashcards
Cell were first made visible by what device? In what year?
Microscope
17th Century
Used visible light to illuminate specimens
Light Microscope
The properties of light itself set a limit to what?
The fineness of detail they can reveal
Uses beams of electrons instead of beams of light as the source of illumination , expanding the ability to the fine details of cells; making some of the larger molecules visible individually.
Electron Microscope
When was the electron microscope invented?
1930s
The development of the light microscope depended on the advances of what?
glass lenses
By this century, lenses were refined to the point that they could be used to make simple microscopes
17th
Examined a piece of cork and in what year reported to the Royal Society of London that the cork was composed of a mass of minute chambers which he called ____________?
Robert Hooke
Cells
Along with Hooke,__________ was able to observe living cells
Antoni can Leeuwenhoek
For almost__________ years the light microscope remained an exotic instrument available to only a few __________.
200
wealthy individuals
It was not until the __________ century that microscope began to be widely used to look at cells
19th
The birth of cell biology was signaled by what?
Two publications
The two publications that signaled the birth of cell biology were? And who wrote them?
1838, botanist Matthias Schleiden
1839, zoologist Theodor Schwann
What did Scheliden and Schwann discover? What did lead to?
Cells were the universal building blocks of living tissues.
All living cells are formed by the division of existing cells.
Cells are either closely packed together or separated from one another by __________,a dense material often made of_________
extracellular matrix
protein fibers embedded in a polysaccharide gel
Each cell is typically about __ to ____ in diameter?
5,20 micrometer
To see the internal structure of a cell is difficult because?
The parts are small, transparent, and mostly colorless
One can exploit that cell components differ slightly from one another in ________________________
refractive index
Filling the cell’s interior is what?
The cytoplasm
Structures smaller than ____________cannot be resolved by light microscope.
0.2 micrometers
For the highest magnification and the best resolution, what must be used?
Electron microscope
The electron microscope can reveal details down to a few_______
nanometers
Cell samples for the electron microscope require________
painstaking
For a light microscope a tissue has to be________
fixed, supported by embedding in a solid wax or resin, cut of sections into thin slices and stained before it is viewed.
There is no possibility of looking at ______ when using an electron microscope
living, wet cells
The external membrane is called what?
Plasma Membrane
The membranes surrounding organelles are called?
Internal membranes
Transmits a beams o f electrons rather than a beam of light microscope
Transmission Electron Microscope
Scatters electrons off the surface of the sample and is used to look at the surface detail of cells and other structures
Scanning Electrons Microscope
Biological membranes are only _ thick
two molecules
Used to determine the three dimensional structure of protein molecules
x-ray crystallography
Have the simplest structure and comes closest to showing essentially no organelles
Bacteria
Basis of classification of all living things
Presence of a nucleus
Organisms who have a nucleus are called?
Organisms with a nucleus are called?
Eucaryotes
Procaryotes
Procaryotes are usually what shape?
Spherical, Rodlike, Cork-screw , small
Some procaryotes perform?
Photosynthesis
Procaryotes are divided into what two domains?
Bacteria and Archaea
Bigger and more elaborate than bacteria and archea
Eukaryotic celss
Eucaryotes posses what?
Nucleus and membrane bound nucleus
Most prominent organelle in a eucaryotic cell
nucleus
Two concentric membranes form what?
Nuclear Envelope
The nuclear envelope contains what
Molecules of DNA
Giant DNA molecules become visible as _____________?
individuals chromosomes
Among the most conspicuous organelles in the cytoplasm
Mitochondria
What two organelles were formed by the endosymbiosis?
Mitochondria and Chloroplasts
How many membranes does a mitochondria have?
two
Mitochondria harness energy from what?
Oxidation of food molecules
What is the basic chemical fuel that powers most the of the cell’s activities?
ATP
The mitochondria consumes what and releases what?
oxygen
carbon dioxide
What process occurs in the mitochondria?
cellular respiration
An anaerobic eucaryote that lacks a mitochondria
Giardia, intestinal parasite
Organelles that are found in the cells of plants and algae
Chloroplasts
Chloroplasts possess internal sacks of membranes containing what?
Green pigment chlorophyll
Plants can get their energy directly from?
sunlight
What is photosynthesis?
Trap energy of the sunlight in chlorophyll molecules and use this energy to drive the manufacture of energy-rich sugar molecules. Oxygen is released as a by product
Chloroplasts generate what?
Food molecules and oxygen that all mitochondria use
An irregular maze of interconnected spaces enclosed by a membrane.
Endoplasmic Reticulum
What happens in the ER?
most cell components and materials destined for export from the cell are made here
Stacks of flattened membrane enclosed sacs
Golgi Apparatus
What happens in the Golgi Apparatus
Receives and chemically modifies the molecules made in the ER, then directs them to the exterior of the cell or to carious locations inside the cell
Small, irregularly shaped organelles in which intracellular digestion occurs, releasing nutrients from food particles and breaking down unwanted molecules for recycling or excretion
Lysosomes
Small. membrane enclosed vesicles that provide a contained environment for reactions in which hydrogen peroxide is generated and degraded
Peroxisomes
Membranes also form different types of small _______ involved in the transport of materials between one membrane enclosed organelle and another
vessicles
A continual exchange of materials takes place between ____
ER, Golgi Apparatus, Lysosomes, outside of the cell
How are vessicles made?
Plasma membrane tucks inwards and pinches off
Vessicles fuse with what?
Membrane enclosed endosomes
Animal cells can engulf very large particles or even entire foreign cells by what process?
endocytosis
Vessicles from the inside of the cell fuse with the plasma membrane and release their contents into the external medium is done by what process?
exocytosis
The part of the cytoplasm that is not partitioned off within intracellular membranes
cytosol
What is the largest single compartment of the cell?
cytosol
The site of many chemical reactions that are fundamental to the cells existence
the cytosol
Where does the manufacture of proteins take places/
Cytosol
The molecular machines that make the protein molecules, that are visible with the electron microscope
ribosomes
What are the filaments that possess the cytoplasm?
actin filaments, intermediate filaments, microtubles
The thinnest filaments which are present in the muscle cells where they serve as part of the machinery that generates contractile forces
actin filaments
the thickest filaments that form hollow tubes that helps pull duplicate chromosomes to opposite directions and distributes them equally to the daughter cells
microtubles
Serve to strengthen the cell mechanically
intermediate filaments
According to one theory the ancestral eucaryotic cell was a _________ that fed on capturing other cells.
predator
Single celled eucaryotes can prey upon and swallow other cells is borne out by the behavior of many of the free living actively motile microorganism called?
protozoan
Life is based on what compounds?
carbon
Life depends on almost exclusively?
Chemical reactions that take place in watery, solution and in a narrow range of tetmperatures
Life is enormously
complex
Life is dominated and coordinated by what?
collections of enormous polymeric molecules that are formed from chains of chemical subunits linked end to end
Life is tightly?
regulated
What is the center of an atom?
dense, positively charged nucleus surrounded at some distance by a cloud of negatively charged electrons
What are the two kinds of subatomic particles
protons and neutrons
What determines the atomic number?
the number of protons present in an atomic nucleus
The electric charge carried by each proton is exactly _______ and ___________ to the charge carried by a single ________
equal
opposite
electron
The whole atom is electrically what?
neutral
An element can exist in several physically distinguishable but chemically identical forms called what?
isotopes
Isotopes have a different number of what?
neutrons
The molecular weight of a molecule is relative to?
hydrogen atom
The mass of an atom or molecule is specified in?
daltons
One proton or neutron weighs what?
1/ avogrado’s number
The key scale factor describing the relationship between everyday quantities and the numbers of individual atoms or molecules
Avogadro’s Number
What four elements make up 96.5% of an organism’s weight?
C, O, N , H
In living tissues only___________ undergo rearrangements
electrons of an atom
What binds atoms to one another?
chemical bonds
This type of bond is formed when electrons are donated by one atom to another
ionic bond
When atoms share electrons
covalent bonds
Pair of electrons often shared unequally with one atom attracting the shared electrons more than the other
polar covalent bond
The state of the outer electron shell determines what?
The chemical properties of an element
When atoms become electrically charged
ions
An attraction that occurs between oppositely charged atoms
electrostatic attraction
Cluster of atoms held together by covalent bonds
molecule
What holds the nuclei together by opposing the mutual repulsion between like charges during a covalent bond?
electron density
The measured amount of energy that must be supplied to break a bond
bond strength
Can covalent bonds be broken by heat?
no, only during chemical reactions with other atoms and molecules
Crucially important in the cell in the many situations where molecules have to associate and disassociate readily to carry their functions
non covalent bonds
The nucleus of an atom is held in orbit by what?
Electrostatic attaraction
If there are too many or too few neutrons in a nucleus what can happen?
the nucleus may disintegrate by radioactive decay
4th and 5th electron shells can hold up to how many electrons?
18
Atoms with more than four shells are
rare in biological molecules
Negative ions are called?
anions
Positive ions are called?
cations
Polar covalent bonds are important in biology because they allow molecules to?
interact through electrical forces
Bonds that are easily broken by the random thermal motions due to the heat energy of the molecules
hydrogen bond
Water loving including DNA,RNA, majority of proteins
hydrophilic
Water hating
hydrophobic
Cell membranes are constructed from what ?
hydrocarbon tails of molecules
substances that release protons when they dissolve in water
acids, form hydronium ion
What is pH?
the measure of hydronium ions in a solution
Strong acids lose
protons easily
Weak acids
hold onto their protons
Many of the acid important in the cell are held together by what
molecules that contain carboxyl group
Molecule capable of accepting a proton
base
Weak acids and bases that can release or take up proton near a pH of 7
buffers
What property above all living things seem almost miraculously different from non living matter?
they create and maintain order in a universe that is tending always towards greater disorder
A living organism requires what sources?
a source of atoms in the form of food and a source of energy
Both the atoms and the energy must come from where?
the nonliving envrionment
The total sum of all chemical reactions needed to carry out to survive, grow, and reproduce
metabolism
The two opposing streams of chemical reaction occur in cells
anabolic
catabolic
What does the catabolic pathway do?
breaks down food stuff into smaller molecules; making useful form of energy and some of the small molecules that the cell needs as building blocks
What does the anabolic pathway do?
Uses the energy harnessed during the catabolic pathway to drive the synthesis of the many molecules that form the cell
The second law of thermodynamics
in the universe or in any isolated system the degree of disorder can only increase
What is entropy
the measure of a system’s disorder
Cells take in energy how?
in the form of food, photons of light, inorganic molecules
The most disordered form of energy
heat
Animals and plants extract energy from food molecules by a process called?
oxidation
When carbon and hydrogen atoms in molecules combine with oxygen is called what?
cellular respiration
Atoms of what move between the living and non living world
nitrogen, sulfur, phosphorus
The metabolism carries the molecules through a large number of reactions by the use of what?
enzymes
Oxidation
electrons transferred from one atom to another
Reduction
addition of electrons
A molecule requires a boost over an ____________before it can undergo a chemical reaction
energy barrier
Enzymes bind to one or two molecules called
Substrates
A substance that can lower the activation energy of a reaction is called
catalyst
Each ‘enzyme has a what ? This is where the substrates fit.
active site
K is commonly employed as a measure of what?
the binding strength of a noncovalent interaction between two molecules
The binding strength is very useful because?
it indicates how specific the interaction is between the two molecules
Energy released in the binding interaction
binding energy
What is entropy
the measure of a system’s disorder
Cells take in energy how?
in the form of food, photons of light, inorganic molecules
The most disordered form of energy
heat
The stronger the binding of an enzyme and substrate, the
slower their rate of disassociation
The concentration of a substrate at which the enzyme works at half its maximum speed
Km,
Micahelis’ constant
Atoms of what move between the living and non living world
nitrogen, sulfur, phosphorus
The metabolism carries the molecules through a large number of reactions by the use of what?
enzymes
Oxidation
electrons transferred from one atom to another
Reduction
addition of electrons
A molecule requires a boost over an ____________before it can undergo a chemical reaction
energy barrier
Enzymes bind to one or two molecules called
Substrates
A substance that can lower the activation energy of a reaction is called
catalyst
Each ‘enzyme has a what ? This is where the substrates fit.
active site
K is commonly employed as a measure of what?
the binding strength of a noncovalent interaction between tow molecules
The binding strength is very useful because?
it indicates how specific the interaction is between the two molecules
acetyl CoA
used to add two carbon units in the biosynthesis of the hydrocarbon tails of fatty acids
The larger K is,
the greater the drop in free energy between the disassociated and associated states, the more tightly the molecules will bind
NADH is the transfer of what
electrons and hydrogen
What happens when enzymes and substrates have collided with one another?
multiple weak bonds are formed until they are disassociated by thermal motion
The stronger the binding of an enzyme and substrate, the
slower their rate of disassociation
The concentration of a substrate at which the enzyme works at half its maximum speed
Km,
Micahelis’ constant
Store energy in exchangeble forms either as transferable chemical groups or as high energy electrons
activated carriers
Most widely used activated carrier
ATP
reaction that involves the transfer of phosphate goup
phophorylation
Phosphorylation reactions are an example of what kind of reaction?
condesation
Phosphorylation reactions are important cellular functions such as
activate substrates, facilitate exchange of chemical energy, help control cell signaling processes
The most abundant energy carrier in cells
ATP
Coupled reactions
energetically favored reaction drives an nonenergetically favored reaction to produce an activated carrier molecule or other useful molecule
NADH is used for whtat?
Ananbolic reactions
NADPH is used for what
catabolic reactions in which ATP is formes
Can carry only an acetyl group in a readily transferable linkage
coenzyme A
acetyl CoA
used to add two carbon units in the biosynthesis of the hydrocarbon tails of fatty acids
ATP is the transfer of what
phosphate
NADH is the transfer of what
electrons and hydrogen
A protein is made from?
Long chain of amino acids
Proteins are linked together by ?
covalent polypeptide bonds
Amino acids are present in a unique order called
amino acid sequence
Polypeptide backbone
sequence of core atoms of the amino acid that form the chain
side chains
parts of amino acids that are not involved in the forming of peptide bonds
proteins fold into a conformation of
lowest energy
What happens when proteins fold incorrectly
aggregates form that can damage cells and whole tissues
Protein folding is assisted by whom?
proteins called molecular chaperones
What are the two common folding patterns of proteins
a helix and b helice
The first protein foldings were discovered by what?
hair and silk studies
What are the two common folding patterns of proteins
a helix and b helice
When was the 2nd protein folding found
B sheet
protein fibroin
Foldings in the proteins originate from where
hydrogen bondings in the N-H and C=O groups in polypeptide backbone
When was the 2nd protein folding found
B sheet
protein fibroin
Foldings in the proteins originate from where
hydrogen bondings in the N-H and C=O groups in polypeptide backbone
Helices are formed how?
by placing similar subunits next to each other
A helix is generated how
single polypeptide chain turns around itself to form a structurally rigid cylinder
WHat kind of bond is made within an a helice and between what elements?
hydrogen
every fourth amino acid
links one C=O of one peptide bond to another N-H
polypeptide bond is hydro philic or phobic?
philic and separated from hydrophobic membrane by non polar side chain
Produce a very rigid, pleated structure
b sheets
B sheets are made how
hydrogen bonds formed between segments of polypeptide chains lying side side
Produce a very rigid, pleated structure
b sheets
Protein domain
any segment of a polypeptide chain that can fold independently into a compact stable structure
Primary structure of protein
amino acid sequence
Quaternary structure of protein
a particular protein molecule is formed as a complex of more than one polypeptide chain
teteriary structure of protein
a helices, b sheets, random coils, loops formed between n and c termini,
Quaternary structure of protein
a particular protein molecule is formed as a complex of more than one polypeptide chain
The most common covalent cross link
disulfide bonds
Two identical folded polypeptide chains form a symmetrical complex of two protein subunits
dimers
The most common covalent cross link
disulfide bonds
Disulfide bonds are formed when
proteins are being exported from the cell, catalyzed in ER by enzyme that links -SH groups from cystenin side chain
