Chapter 3 Study Guide Flashcards
Name the 3 major parts of the cell
The Plasma Membrane (serves as a selective barrier), the Cytoplasm (consists of organelles in a fluid portion called cytosol), and the nucleus (a large organelle housing most of the cell’s DNA)
Describe the fluid mosaic model of the plasma membrane.
Proteins embedded in a sea of fluid lipids. The plasma membrane is described to be fluid because of its hydrophobic integral components such as lipids and membrane proteins that move laterally or sideways throughout the membrane. That means the membrane is not solid, but more like a ‘fluid’.
Know the three major lipid components of the membrane and their relative percentages
75% phospholipids, 20% chloresterol (a steroid), and about 5% glycolipids (lipids with carbohydrate attached)
Draw the structure of the lipid bilayer
the fatty acid tails are together in the interior of the membrane, with the heads pointed outward to the extracellular fluid and in the intracellular fluid. Double bonds put a kink in the fatty acid tails, preventing tight packing.
Describe the term amphipathic
Containing polar and non-polar regions
While part of a phsopholipid is polar and hydrophilic and which part is non-polar and hydrophobic?
the head, a phosphate group and glycerol, is hydrophilic, and the fatty acid tail is hydrophobic.
What is an integral membrane protein?
a protein that extends into and through the membrane bilayer
What is a peripheral membrane protein?
a protein that is loosely attached to the lipid bilayer on the outside of the cell
Know the functional classes of membrane proteins
ion channels, transporters, receptors, enzymes, linker proteins, cell identity markers
What is a cell identity marker?
Proteins unique to an individual’s cells. These are important in the immune system and are also a factor in transplantation of tissue from one person to another
What is an ion channel?
some integral proteins form ion channels, pore or holes that specific ions, such as potassium ions, can flow through to get into or out of the cell. most ion channels are selective; they allow only a single type of ion to pass through
What is a transporter?
In biology, an ion transporter, also called an ion pump, is a transmembrane protein that moves ions across a plasma membrane against their concentration gradient, in contrast to ion channels, where ions go through passive transport.
What is a receptor?
integral proteins called receptors sere as cellular recognition sites. each type of receptor recognizes and binds to a specific type of molecule. For instance insulin receptors bind the horomore insulin. A specific molecule that binds to a receptor is called a ligand of that receptor.
What is an enzyme?
some integral proteins are enzymes that catalyze specific chemical reactions at the inside or outside surface of the cell.
What is a linker protein?
an integral protein that anchors proteins in the plasma membranes of neighboring cells to one another or to the protein filaments inside and outside the cell.
What is meant by the term membrane fluidity?
double bonds put a kink in the fatty acid tails preventing tight packing => in motion
What is meant by the term membrane permeability?
the degree to which a substance can permeate (enter or pass through) the membrane.
What is meant by the term selective permeability?
Selective permeability allows for different concentrations of substances on either side of the membrane (concentration gradients). Selective permeability means that some substances can get through and others cannot.
Define the term: active transport
Transport requiring the assistance of ATP
Definet the term: passive transport
Transport done by virtue of a molecules own kinetic energy (without aid of ATP), like with water through the membrane down it’s concentration gradient
Define the term: concentration gradient
and area from highest to lowest concentration on a substance
Define the term: electrical gradient
There is a difference in distribution of postively charged ions across the membrane. This causes an electical gradient refferent to as the membrane potential.
Define the term: membrane potential
Electical gradient
Define the term: electrochemical gradient
Both concentration gradients and membrane potentials are set up as a result of selective transport across the membrane. The combined influence of concentration gradient and membrane potential (electical gradient) on movement of an ion is referred to as it’s electrochemical gradient.
Define the term: diffusion
movement of molecules or ions down a concentration gradient due to their kinetic energy until they reach equilibrium
Define the term: osmosis
passive movement of water molecules across a selectively permeable membrane from an area of higher to lower water concentration until equilibrium is reached
Define the term: facilitated diffusion
passive movement of a substance down its concentration gradient through the lipid bilayer by transmembrane proteins that function as channels or carriers
Define the term: endocytosis
material moves into cell in vesicles
Define the term: exocytosis
material moves ouf of cell in vesicles e.g. secretory vesicles releasing a horomore or enzyme
Define the term: receptor-mediated endocytosis
highly selective type of endocytosis by which cells take up specific ligands (recall that ligands are molecules that bind to specific receptors). A vesicle forms after a receptor protein itn he plasma membrne recognized and binds to a particular particle in the extracellular fluid.
Define the term: phagocytosis
Endocytosis by white blood cells, major phagocytic cells are two types of white blood cells - neutrophils and macrophages
Define the term: bulk-phase endocytosis (a.k.a. pinocytosis)
the plasma membrane folds inward, forming a vesicle. Nonselective uptake of tiny droplets of extracellular fluid.
Understand the describe in detail the operation of the sodium-potassium pump
1) 3 Na+ ions in the cytosol bind to the pump
2) Na+ binding triggers ATPase to convert ATP to ADP. Phosphate binds and changes the shape of the pump. This shape change causes release of NA+ and binding of 2 K+ ions
3) K+ binding triggers release of the phosphate group and another shape change
4) K+ released into cytosol
What is the energy source the the operation of the sodium-potassium pump?
the ATP to ADP conversion done by ATPase and the released phosphate
What reaction takes place to generate energy for the sodium potassium pump?
ATPase breaks the phosphate bond to convert ATP to ADP. the phosphate binds and changes the shape of the pump.
What enzyme catalyses the reaction to create energy for the sodium-potassium pump?
ATPase
What is another name for the sodium-potassium pump?
NA+/K+ ATPase pump
In which direction across the membrane are sodium ions transported by the sodium-potassium pump?
Sodium ions are transported from inside the cell to outside the cell.
In which direction across the membrane are potassium ions transported by the sodium-potassium pump?
Potassium ions are transported from the extracellular fluid into the cell.
Know the structure and major functions of the cytoskeleton:
Serves as a scaffold to help determin cell shape and to organize cellular contents
Aids in movement of organelles within cell, e.g. during cell division or phagocytosis
Three types of filaments
a) Microfilaments – thinnest
b) Intermediate filaments
c) Microtubules - made mostly of a protein, tubulin
Know the structure and major functions of the centrosomes:
Function: to build microtubules needed to form the mitotic spindle during cell division
Located near the nucleus
Consists of two centioles and pericentriolar materials (centriols consist of 9 clusters of 3 microtubules). Pericentriolar matrix is rich is protein called tubulin, needed to make microtubules.
Know the structure and major functions of the ribosomes:
Site of protein synthesis.
Ribsomes associated with endoplasmic reticulum synthesis proteins that will be intersted in the the plasma membrane or recreted
Fre ribosomes synthesize proteins used in the cytosol
Know the structure and major functions of the rough endoplasmic reticulum:
Network of membrane enclosed sacs connected to nuclear envelop and extending through cytoplasm
Rough ER sythesizes glycoproteins and phospholipids
Know the structure and major functions of the smooth endoplasmic reticulum:
no ribosomes on surface. Synthesizes fatty acids and steroids.
What is the difference between the rough and the smooth endoplasmic reticulum?
Rough has ribosomes on surface, smooth does not. Rough sythesizes glycoproteins and phospholipids. Smooth sythesizes fatty acids and steroids.
Know the structure and major functions of the lysosomes:
contain digestive enzymes to destroy unwanted materials in the cell, e.g. malformed proteins, things taken in for disposal. Enzymes only function at very acidic pH.
Know the structure and major functions of the golgi complex:
Modifies, sorts, packages, and transports proteins received from the rough ER.
Forms secretory vesicles that transport secretory proteins from the golgi complex to the plasma membrane for exocytosis or transport proteins to other organelles
Know the structure and major functions of the Mitochondria:
Mitochondria look like kidney beans and generate ATP
Describe the structure and function of the nucleus
The nucleus housese most of the genetic information of the cell (contains chromatin and nucleolus)
Surrounded by a double membrane with specialized pores that allow movement of large substances such as RNA and proteins between nucleus and cytoplams
Contains the cell’s heriditary material (genes), which are arranged along chromosomes.
Define the term: gene chromosome
genes (DNA) are arranged along chromosomes. Each chromosome is a long molecule of DNA coiled together with several proteins. The combination of DNA and chromosomal proteins is called chromatin.
Define the term: chromatin
genes (DNA) are arranged along chromosomes. Each chromosome is a long molecule of DNA coiled together with several proteins. The combination of DNA and chromosomal proteins is called chromatin.
Define the term: nuclear membrane
The nucleus is surrounded by a double membrane with specialized pores that allow movement of large substances such as RNA and proteins between nucleus and cytoplams
Define the term: nuclear pore
specialized pores in the nuclear membrane that allow movement of large substances such as RNA and proteins between nucleus and cytoplams
Define the term: nucleolus
The nucleolus (plural nucleoli) is a non-membrane bound structure found in the nucleus of cells. It is composed of proteins and nucleic acids found within the nucleus of eukaryotic cells. Its function is to transcribe ribosomal RNA (rRNA) and combine it with proteins to form almost-complete ribosomes.
Describe how proteins are synthesized
1) an mRNA molucule binds to the small ribosomal subunit at the mRNA binding site. A special tRNA, called initiator tRNA, binds to the start codon (AUG) on mRNA, where translation beings. the tRNA anticodon (UAC) attaches to the mRNA codon (AUG) by pairing between the complementary bases. Besides being the strat codon, AUG is also the codon for the amino acid methionine. Thus, methionine is always the first amino acid in a growing polypeptide.
2) Next, the large ribsomal subunit attaches to the small ribosomal subunit-mRNA complex, creating a fucnitonal ribosome. The initiator tRNA, with its amino acid (methionine) first in to the P site of the ribosome.
3) The anticodon of another tRNA with its attached amino acid pairs with the second mRNA codon at the A site of the ribosome.
4) A component of the large ribosomal subunit catalyzes the formation of a peptide bond between methionine, which separates from its tRNA at the P site, and the amino acid carried by the tRNA at the A site.
5) After peptide bond formation, the tRNA at the P site detaches, from the ribosome, and the ribosome shifts the mRNA strand by one codon. The tRNA in the A site bearing the two-peptide protein shits in the the P site, allowing another tRNA with its amino acid to bind to a newly exposed codon at the A site. Steps 3 through 6 occur repeatedly, and the protein lengthens progressives.
6) Protein sythesis ends when the ribosome reaches a stop codon, which causes the completed protein to detach from the final tRNA. When the tRNA vacates the ribosome, the ribosome splits into its large and small subunits.
Define the term: transcription
Using DNA to make RNA. Transcription is catalyzed by the enzyme RNA polymerase.
A segment of DNA where transcription begins is located at the beginning of a gene (the promotor)
Instruction to end occurs as a result of a terminator sequence
Define the term: messengerRNA
mRNA - directs the sythesis of a protein
Define the term: transferRNA
tRNA - binds to an amino acid and holds it in place until it is incorporated into a protein
Define the term: ribosomalRNA
rRNA - joins with proteins to make ribsomes
Define the term: translation
in translation, RNA binds to a ribosome. the mRNA nucleotide sequence specifies the amino acid sequence of the protein.
Define the term: recombinant DNA
genes from one organism can be inserted into another host organism enabling the host to synthesize a protein that it would not normally synthesize.
Define the term:alternative splicing
genes can be cup up (spliced) in different ways to translate into different proteins
How is the process of transcription turned on and off?
Turned on by the promotor, a segment of DNA at the beginning of the portion to be transcripted. Truned off by a sequence at the end called the terminator sequence.
Define Mitosis:
The process of cell division
Describe what is happening in interphase:
period between cell divisions; chromosomes not visible under light microscope
Describe what is happening in G1 phase
metabolically active cell duplicates most of its organelles and cytosolic componentsl replication of chromosomes beings.
Describe what is happening in G2 phase
cell growth, enzyme and protein synthesis continue, replication of centrosomes complete
Describe what is happening in S phase
Replication of DNA and centrosomes
Describe what is happening in prophase
chromatin fibers condense into paired chromatids; nucleolus and nuclear envelope disappear; each centrosome moves to an opposite pole of cell
Describe what is happening in metaphase
centromeres of chromatid pairs line up at metaphas plate
Describe what is happening in anaphase
centromeres split; indentical sets of chromosomes move to opposite poles of cell
Describe what is happening in telophase
nuclear envelopes and nucleoli reappear; chromosomes resume chromatin form; mitotic spindle disappears
Describe what is happening in cytokinesis
cytoplasmic divisionl contractile ring forms cleavage furrow around center of cell, dividing cytoplasm into separate and equal portions.
