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151 Cards in this Set

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What English scientist first observed plant cells in the late 1600's, documented in his 1665 book "Micrographia?"
Robert Hooke
What two German scientists first insisted that all living things are made up of cells in the 1830's?
Matthias Schleiden and Theodor Schwann
What are the four concepts that "Cell Theory" comprises?
1) A cell is the basic structural and functional unit of living organisms, so when you define cell properties you are in fact defining the properties of life.

2) The activity of an organism depends on both the individual and the collective activities of its cells.

3) According to the "Principle of Complementarity," the biochemical activities of cells are dictated by the relative number of their specific sub-cellular structures.

4) Continuity of life has a cellular basis.
What are the largest cells in the body?
Nerve cells, which can be well over a meter.
A cell's shape reflects its ______.
Function
What four elements are the most plentiful in living cells?
Carbon, hydrogen, nitrogen, and oxygen.
What are the three main parts of a human cell?
The cell membrane, the cytoplasm, and the nucleus
The plasma membrane separates _____ ____ (the fluid inside the cell) from _____ ____ (the fluid outside the cell)
Intracellular fluid, Extracellular fluid
What is the "fluid mosaic model?"
A depiction of the structure of the membranes of a cell as phospholipid bilayers in which proteins are dispersed.
Which part of a phospholipid molecule is "hydrophilic," meaning that it's attracted to water?
The head
Which part of a phospholipid molecule is "hydrophobic," meaning that it's repelled by water?
The tail
The majority of membrane phospholipids are _____, a condition which kinks their tails and increases membrane fluidity.
Unsaturated
Where do you find glycolipids incorporated into the plasma membrane?
You only find glycolipids on the outer layer, where they compose about 5% of the total lipid content.
Roughly 20% of membrane lipids are ______.
Cholesterol
What are lipid rafts?
Lipid rafts compose about 20% of the outer plasma membrane, and they are tightly packed and dynamic assemblies of saturated phospolipids that are less fluid than the rest of the membrane.
What are the two distinct populations of plasma membrane proteins?
Integral proteins and peripheral proteins
Most integral proteins are what?
Most integral proteins are transmembrane proteins that span the entire width of the membrane and protrude on both sides.
All integral proteins have ______ and ______ regions.
Hydrophobic and hydrophilic
What is the main function of most transmembrane proteins?
Transport
What are three different ways that transmembrane proteins act as molecular transports?
1) Clustering together and forming channels through which small, water-soluble ions or molecules can move

2) Acting as carriers that bind to a substance and move it through the membrane

3) Working as receptors for hormones or other chemical messengers and passing messages to the cell interior (signal transduction)
How are peripheral proteins attached to the cell membrane?
Peripheral proteins are not embedded in the lipid. Rather, they are loosely attached to integral proteins or membrane lipids.
What's a glycocalyx?
The glycocalyx is a carbohydrate-rich layer on the exterior of a cell which is unique from cell to cell, allowing cells to recognize one another.
What do peripheral proteins do?
Peripheral proteins act along with a filament network to support the plasma membrane from the intercellular side. Some are enzymes and some assist in mechanical functions.
What are microvilli?
Microvilli are finger-like extensions of the plasma membrane that increase surface area and are most abundant in absorptive cells. They have a core of actin filaments.
What are the three types of cellular junctions?
1) Tight junctions

2) Gap junctions

3) Desmosomes
What's a tight junction?
It's an impermeable junction formed by integral proteins in the membranes of several cells fusing together, encircling the cell.
What's a gap junction?
A gap junction is a communicating junction in which two cells are very close to one another and connected by connexons made up of transmembrane proteins. They are selectively permeable and common in cells that are excited electrically.
What's a desmosome?
It's a cellular junction in which adjacent cells are connected by protein filaments that interdigitate like the teeth of a zipper. The filaments are anchored to thickened plaques. On the intracellular cide, protein filaments then run the width of the cell and anchor again to the other side of the membrane. Common in cells that undergo great mechanical stress.
What's another name for extracellular fluid?
Interstitial fluid
From what is the interstitial fluid derived?
Blood
In ____ _____, substances cross the plasma membrane without any energy input from the cell.
Passive processes
In ____ _____, the cell provides the energy necessary for moving substances across the plasma membrane in the form of ATP.
Active processes
What are the two main types of passive transport in cells?
Diffusion and filtration
_____ is an important means of passive transport in every cell of the body.
Diffusion
_____ is a means of passive transport that generally only occurs in capillary walls.
Filtration
In diffusion, substances travel along their _____ ______.
Concentration gradient
What two factors influence the speed of diffusion?
Temperature and molecule size
Molecules will diffuse through the plasma membrane if the molecule meets one of the following criteria...
1) The molecule is lipid soluble

2) The molecule is small enough to pass through membrane channels

3) The molecule is assisted by a carrier molecule
What special name is given to the unassisted transport of a solvent -- usually water -- across the plasma membrane?
Osmosis
What are the two main types of diffusion?
Simple diffusion and facilitated diffusion
Describe simple diffusion
Non-polar and lipid soluble substances diffuse directly across the plasma membrane. Such substances include oxygen, carbon dioxide, and fat-soluble vitamins.
Describe facilitated diffusion.
Certain molecules, notably glucose and other sugars, amino acids, and ions are transported passively by either binding to protein carriers in the membrane and being ferried across or by traveling through water-filled protein channels.
What's a carrier?
A carrier is an integral transmembrane protein that binds to a specific group or class of molecules such as glucose or amino acids,and transports it passively through the membrane.
What are the two types of protein channels?
Leakage channels and gated channels
The total concentration of solute particles in a solution is described by what word?
Osmolarity
Define tonicity.
Tonicity is the ability of a solution to change the shape or tone of cells by altering their internal water volume.
Solutions with the same concentration of non-penetrating solutes as those found in cells are called:
isotonic (the same tonicity)
Solutions with a higher concentration of non-penetrating solutes than the concentrations found in cells are called:
Hypertonic
What happens to cells immersed in a hypertonic solution?
They give off water according to the concentration gradient and shrink (crenate).
A solution with a concentration of solutes less than those concentrations found within cells is called:
Hypotonic
What's the most extreme example of hypotonicity?
Distilled water
What happens to cells immersed in a hypotonic solution?
The cells swell rapidly and could possibly burst, or "lyse."
How do osmolarity and tonicity differ?
Osmolarity only takes into account relative solute concentrations, ignoring membranes' permeability (or lack thereof) to said solutes.
Osmosis will continue until when?
Osmosis will continue until osmotic pressure and hydrostatic pressure are equal.
What's hydrostatic pressure?
The back-pressure of intracellular water pushing against the plasma membrane
Define filtration.
Filtration is a process by which hydrostatic pressure exerted against capillary walls forces solutes and water through. Whereas diffusion occurs along a concentration gradient, filtration occurs along a pressure gradient.
Are capillary walls selectively permeable?
No -- they just don't allow blood cells or large molecules through due to their size.
Whenever a cell uses ATP to move solutes across the membrane, the process is referred to as an:
active process
What are the two major mechanisms of active membrane transport?
Active transport and vesicular transport
What's the difference between facilitated diffusion and active transport?
Active transporters called solute pumps move molecules against the concentration gradient while facilitated diffusion moves with the concentration gradient
Active transport requires carrier proteins that combine _____ and _____ with transported substances.
specifically, reversibly
What are the active transporters called?
solute pumps
What is the difference between primary and secondary active transport?
Primary active transport depends on energy derived directly from ATP. Secondary active transport is made possible by the energy stored in ionic gradients created by the operation of primary active transport pumps.
Why do we say that secondary active transport systems are "coupled systems?"
We say this because secondary active transport systems always move more than one substance at a time
What are the two classifications of coupled active transport systems?
Symport and antiport
What's a symport system?
A symport system is a coupled active transport system in which transported molecules all move in the same direction through channels.
What's an antiport system?
An antiport system is a coupled active transport system in which transported molecules move in opposite directions through channels.
Is the sodium-potassium pump a symport system or an antiport system?
antiport
What transport mechanism is used for exocytosis and endocytosis?
Vesicular transport
What two compounds are generally responsible for providing energy for vesicular transport?
ATP (adenosine triphosphate) and GTP (guanosine triphosphate)
Describe the process of exocytosis
1) Substance to be removed from cell is enclosed in a membranous sac (vesicle)

2) In most cases, the vesicle migrates to the plasma membrane, fuses with it, then ruptures into the extracellular space. The vesicle/membrane fusion is helped along by vesicle transmembrane proteins called v-Snares and cellular transmembrane called t-Snares

3) In some cases, such as in neurotransmitter secretion in the brain, the membranes don't fuse. Instead, a fusion pore flickers open, part of the vesicle contents are released, then the pore closes. This conserves energy since the vesicles can be reused and is called "kiss and run."
What type of vesicles provide the main route for endocytosis and transocytosis?
Clathrin-coated vesicles
What type of vesicles are most frequently hijacked by pathogens to gain entry to the cell?
Clathrin-coated vesicles
Describe endocytosis.
1) The substance to be taken in is enclosed in a "coated pit" in the plasma membrane. Clathrin assists in selecting cargo and deforming the membrane.

2) The vesicle closes and enters the cell, losing the clathrin coating and fuses with an endosome

3) The endosome does one of three things: a) recycles the vesicle contents back to the membrane. b) combines with a lysosome, which digests or releases (if iron or cholesterol) the contents, or c) moves across the cell and dumps the contents out the other side (transcytosis), common in endothelial cells lining blood vessels
What are the three types of endocytosis that use clathrin-coated vesicles?
phagocytosis, pinocytosis, and receptor-mediated endocytosis
What's phagocytosis?
Phagocytosis occurs when a cell forms pseudopods, engulfs a large mass, creates a phagosome (eaten body), and usually digests the contents using a lysosome. Think of WBCs and macrophages.
What word describes the movement of phagocytes, characterized by moving by use of temporary pseudopods?
Amoeboid motion
Describe pinocytosis
1) A bit of infolding plasma membrane surrounds a very small volume of extracellular fluid containing dissolved molecules, which then enters the cells and fuses with an endosome. Common in most cells, especially important in nutrient-absorbing cells
Describe receptor-mediated endocytosis
receptor-mediated endocytosis is the main mechanism for SPECIFIC endo/transcytosis of macromolecules. The receptors are very specific plasma membrane proteins. Both the receptor and vesicle are "ingested" and dealt with.
What molecules are taken up by receptor-mediated endocytosis?
enzymes, insulin, low-density lipoproteins, iron, flu viruses, diptheria, and cholera toxins
What type of vesicles are responsible for almost all "vesicular trafficking," e.g. sending proteins from the Rough ER to the Golgi apparatus?
vesicles coated with coatomer (COP1 and COP2) proteins
Besides clathrin-coated vesicles, what other type of vesicle is responsible for receptor-mediated endocytosis?
Caveolae, or caveolin-composed vesicles.
What is the typical range of a resting membrane potential?
-50 to -100 mV (millivolts)
All cells are ____ since the inside of a cell is generally negatively charged compared to the outside environment.
polarized
A cell displays voltage, or a difference in potential, in what one place?
at the plasma membrane
What ion is found in greater concentration inside a cell than outside?
K+
What ion is found in greater concentration outside a cell than inside?
Na+ and Cl-
What gives a cell membrane its negative charge?
negatively charged protein anions and the work of the Na+/K+ ATPase enzyme located in the plasma membrane. For every two K+ ions accepted into the cell, 3 Na+ ions are ejected, and this is accomplished using ATP for energy
What's another word for the Na+/K+ ATPase?
NA+/K+ pump
What purpose, besides maintaining a membrane potential, does the Na+/K+ pump serve?
It keeps the Na+ osmolarity low inside the cell, thus reducing osmotic pressure into the cell, and keeping water from flowing into the cell and causing it to burst
What ion is the cell membrane most permeable to?
Potassium (K+)
What kind of gradients do ions travel along?
electrochemical gradients
What are the two main families of glycocalyx molecules?
1) cell adhesion molecules
2) plasma membrane receptors
What part of the cell is always involved in cellular interaction?
the glycocalyx
Cellular glycoproteins that act as cell adhesion molecules (CAMs) fall into what two main categories?
cadherins and integrins
What are CAMs?
Cell adhesion molecules are glycoproteins such as cadherin and integrin that are found on almost every cell in the body
In what tasks to CAMs assist?
embryonic development, wound repair, immunity, and more
What 5 main roles roles do CAMs play?
1) Molecular "velcro" that helps cells bind to each other and the extracellular space

2) "Arms" that migrating cells use to haul themselves around

3) SOS signals protruding from injured or infected blood vessel linings that rally WBCs

4) Mechanical sensors responding to local tension by stimulating synthesis or degradation of adhesive membrane junctions

5) Transmitter of intracellular signals that direct cell migration, proliferation, and specializiation
Integral proteins and glycoproteins that act as membrane receptors engage in one of what two types of signaling?
contact signaling and chemical signaling
Describe contact signaling.
Contact signaling occurs when cells physically touch one another. This is important for development and immunity, and some pathogens can use contact signaling to identify primary targets.
Describe chemical signaling.
Chemical signaling involves a signal chemical (a ligand) such as a neurotransmitter, hormone, or paracrine, binding to a plasma membrane receptor. Invariably, the receptor's structure changes and cell proteins are altered in some way.
Describe a G-protein-linked receptor.
A G protein-linked receptor uses a G-protein as a middleman that activates or inactivates a membrane-bound enzyme or ion channel.
What's a "second messenger?"
A second messenger is an intracellular chemical signal that connects plasma membrane events to the internal metabolic machinery of the cell. Found in conjunction with G protein-linked receptors
What are two of the most important second messengers in the human body?
cyclic AMP and ionic calcium, both of which typically activate protein kinase enzymes
What types of enzymes do cAMP and ionic calcium usually activate?
protein kinase enzymes
What do protein kinase enzymes do?
Protein kinase enzymes transfer phosphate groups from ATP to other proteins, potentially activating a whole series of enzymes, often with exponential results.
What signaling molecule is one of nature's simplest molecules and the first gas identified as a biological messenger?
Nitric oxide (NO)
Describe electrical signaling
During electrical signaling, certain plasma membrane proteins are channel proteins that respond to changes in membrane potential by opening or closing the channel.
What are the three components of cytoplasm?
1) Cytosol
2) Organelles
3) Inclusions
What's cytosol?
Cytosol is the viscous, semitransparent fluid in which the other cytoplasmic elements are susended. It containes proteins, salts sugars, water, and more.
What are organelles?
They are the metabolic machinery of the cell.
What are inclusions?
Inclusions are chemical substances that are present in certain cells -- think of melanin in skin cells or hemoglobin in RBCs.
Which organelles are non-membranous?
1) Cytoskeleton
2) Centrioles
3) Ribosomes
Which organelles are membranous?
1) Mitochondria
1) Peroxisomes
3) Lysosomes
4) Endoplasmic reticulum
5) Golgi apparatus
What's the interactive intracellular system made up of membranous organelles called?
The endomembrane system
What are mitochondria?
Mitochondria are the energy-producers that provide an ATP supply.
Mitochondria have how many membranes?
2
What's inside a mitochondrion?
1) The inner membrane folded into shelflike cristae

2) The matrix (gel-like inner substance)
What's aerobic cellular respiration?
It's the process of mitochondria attaching phosphate groups to ADP to create ADP and thus create energy.
What's a term used to describe the process of creating ATP by attaching phosphate groups to ADP, usually done by mitochondria?
Aerobic cellular respiration
Where are mitochondria believed to have come from?
Ancient bacterial invaders
What are ribosomes?
Ribosomes are protein-synthesizing organelles made of two globular subunits.
How do mitochondria multiply?
By division, and they have their own DNA and RNA
Do ribosomes have their own RNA?
Yes.
Where are ribosomes found?
Some float freely in the cytoplasm while others are attached to membranes, forming a complex called the rough endoplasmic reticulum.
What do free ribosomes create?
Free ribosomes create soluble proteins that function in the cytosol.
What do membrane-bound ribosomes create?
Membrane-bound ribosomes synthesize proteins destined either for incorporation into cell membranes or for export from the cell as well as most of the components of the plasma membrane.
Can ribosomes travel to and from the ER?
Yes.
What is the endoplasmic reticulum?
The endoplasmic reticulum is a system of tubes and membranes enclosing fluid-filled cavities (cisternae) within the cytosol.
Where is the endoplasmic reticulum found?
The endoplasmic reticulum is continuous with the nuclear membrane and winds throughout the cytosol.
What cells have the largest rough ERs?
Cells that synthesize and export proteins: secretory cells
Describe the golgi apparatus
The golgi apparatus is a stack of flattened membranous sacs that modifies, concentrates, and packages proteins and lipids made at the rough ER.
Describe lysosomes
Lysosomes are the digestive 'organs' of cells -- they use acid hydrolases to digest molecules, and also collect and store hydrogen ions using a pump to maintain an acidic pH
What cells have the most lysosomes?
Phagocytes
What do peroxisomes do?
Peroxisomes neutralize free radicals using oxidases, and ultimately molecular oxygen to turn free radicals into hydrogen peroxide.
How do peroxisomes replicate?
By pinching off and dividing.
What's the cytoskeleton?
it's an elaborate series of rods running through the cytosol made up of microtubules, intermediate filaments, and microfilaments
What are centrioles?
Centrioles are barrel-shaped organelles that produce microtubules and organize the mitotic spindle.
What are cilia?
Cilia are whiplike, motile cellular extensions that occur in large numbers. They propel substances away from or down the cell.
What's a flagella?
A big cilia... the tail of a sperm. It propels the cell.
What's the one cell type that lacks a nucleus.
Mature red blood cells.
What are the three components of the nucleus?
1) Nuclear envelope
2) Nucleoli
3) Crhomatin
What's the nuclear envelope?
It's a double-membrane barrier similar to the mitochondrial membrane. The outer membrane is continueous with the rough ER.
What are nucleoli?
They are nuclear subunits that assemble ribosomal subunits.
What is chromatin made up of?
30% DNA, 60% histone proteins, 10% RNA
What are chromosomes made up of?
Chromosomes
What's interphase?
The phase of cell growth between cell formation and cell division.
What are the two phases of the cell life cycle?
Interphase and the mitotic phase.
What are the four phases of mitosis?
Prophase, metaphase, anaphase, telophase
What is the role of RNA?
RNA carries out DNA's instructions for polypeptide synthesis
What are the three types of RNA?
Transfer RNA, Ribosomal RNA, Messenger RNA