Module 2 - Cellular Physiology Flashcards
What are the principles of cell theory?
- Cells are the smallest structural and functional unit capable of life
- Functionality depends on anatomy of specific cells
- Cells are living building blocks of all organisms
- An organism’s anatomy and physiology depend on the individual and collective characteristics of its cell’s anatomy and physiology
- All new cells and new life arise only from pre-existing cells
- Cells of all organisms fundamentally similar in anatomy and physiology
How many specialized cell types exist in the human body?
About 200
What are 3 major parts of all cells, regardless of specialization?
o Plasma membrane
o Nucleus
o Cytoplasm
What is the structure and function of the plasma membrane?
- Lipid occurs in 2 layers, called a bilayer with a sandwich-like structure
- Composed primarily of proteins and lipids, especially phospholipids
- Substantial amounts of cholesterol (also a lipid) that helps stabilize the membrane
- Acts as a selective barrier between cellular contents and extracellular fluid
- Controls traffic in and out of the cell
What is the structure and function of the nucleus?
- Contained in every human cell except red blood cells
- Composed primarily of histone protein and DNA enclosed in a double-layered membrane
- Acts as a control center of the cell, providing storage of genetic information
- Nuclear DNA provides codes for synthesis of structural and enzymatic proteins and serves as blueprint for cell replication
What is the structure and function of the endoplasmic reticulum?
• Extensive, continuous membranous network of fluid-filled tubules and flattened sacs
• Forms new cell membrane and other cell components and manufactures products for secretion
May be smooth or rough
What is rough endoplasmic reticulum?
- Endoplasmic reticulum studded with ribosomes
* The ribosomes are where the amino acids are chemically linked to form proteins
What is smooth endoplasmic reticulum?
- No ribosomes present
- Site of lipid and membrane synthesis
- Site of calcium storage
What is the structure and function of the Golgi complex?
- Series of flattened sacs usually curled at the edges
- Proteins and lipids are modified, packaged, and distributed from here
- The sacs pinch off bits of themselves to form vesicles that contain the products as they move to their final destination
What is the structure and function of the lysosomes?
- Derived from sacs of the Golgi body
- Contains hydrolytic enzymes break down particles of food taken into the cell and make the products available to the cell
- Destroy foreign substances and cellular debris
What is the structure and function of the centriole?
• Usually paired, small barrel-shaped organelles that consist of nine short triplet microtubules
• Site of growth of new microtubules including
o Cytoplasmic transport microtubules
o Microtubules that form the mitotic spindle
What is the structure and function of the peroxisomes?
- Membranous sacs containing oxidative enzymes
* Perform detoxification activities
What is the structure and function of the mitochondria?
• Often called powerhouses of the cell
• Rod or oval shaped bodies enclosed by 2 membranes
o Inner membrane folded into cristae that project into an interior matrix
• Carbohydrates, lipids, and proteins broken down here to form ATP (adenosine triphosphate)
• Contains enzymes for citric acid cycle and electron transport chain
• The site where oxygen you breathe used in “cellular respiration”
What is the structure and function of the vaults?
- Shaped like hollow octagonal barrels
* Serve as cellular trucks for transport from nucleus to cytoplasm
What is the structure and function of the intermediary metabolism enzymes?
- Dispersed within the cytosol
* Facilitate intracellular reactions involving the degradation, synthesis, and transformation of small organic molecules
What is the structure and function of the ribosomes?
- Granules of RNA and proteins
- Some attached to rough endoplasmic reticulum, some free in the cytoplasm
- Serve as workbenches for protein synthesis
What is the structure and function of the transport, secretory, and endocytotic vesicles?
- Transiently formed, membrane-enclosed products synthesized within or engulfed by the cell
- Transport and/or store products being moved within, out of, or into the cell, respectively
What is the structure and function of the inclusions within the cytosol?
- Glycogen granules, fat droplets
* Store excess nutrients
What is the structure and function of the microtubules?
• Long, slender, hollow tubes composed of secretory vesicles
• Maintain asymmetric cell shapes and tubulin molecules
• Coordinate complex cell movements, specifically
o Facilitating transport of secretory vesicles within cells
o Serving as main structural and functional component of cilia and flagella
o Forming mitotic spindle during cell division
What is the structure and function of the microfilaments?
• Intertwined helical chains of actin molecules
• Composed of myosin molecules (also present in muscle cells)
• Play a vital role in various cellular contractile systems including
o Muscle contraction
o Ameboid movement
• Serve as mechanical stiffener for microvilli
What is the structure and function of the intermediate filaments?
- Irregular, threadlike proteins
* Help resist mechanical stress
What is intermediary metabolism and where does it occur?
- Chemical reactions inside the cell that involve degradation, synthesis, and transformation of small organic molecules
- Captures energy and provides raw materials for cell functions
- All occur in cytosol
What are anabolic reactions and what does it require?
- Synthesis of molecules that build up organs
* Requires building blocks and energy to be present
What are catabolic reactions?
• Breakdown complex molecules into simpler ones
What ATP pathway is used for immediate ATP production that is required at times such as the onset of intense exercise?
Substrate level phosphorylation
Where does substrate level phosphorylation occur?
Cytosol of skeletal muscle and brain cells
What is creatine phosphate (CP) and how is it used?
• Also called phosphocreatine
• Stored in the cytosol and is stored energy for skeletal muscle
• Creatine kinase is enzyme involved in this creation
• Energy released when the bond between phosphate and creatine is broken
o This energy and the phosphate can be donated to ADP to form ATP
• Reaction is reversable, energy and phosphate from ATP can combine with creatine to form CP again
o Created once there is enough ATP available
• ATP levels remain relatively stable, CP levels vary greatly
What is McArdle disease, what are the signs and symptoms, and what is the treatment?
Lack of phosphorylase enzyme needed for first step of glycolysis resulting in lack of glycogen needed for muscle contractions. Symptoms include muscle fatigue, pain, and cramps. Treatment aimed at correcting enzyme deficiency and may involve gene-therapy
What is glycolysis and what does it produce?
• 10 separate sequential reactions that break down simple sugars into pyruvic acid molecules
• Not very efficient ATP production and cannot meet body needs alone
• Energy released produces
o 2 molecules of ATP
o 2 molecules of NADH
o 2 pyruvic acid molecules
Describe the process of pyruvate decarboxylation
• Pyruvic acid moves into mitochondrial matrix via monocarboxylate transporter protein
• Enzyme pyruvate dehydrogenase metabolizes pyruvic acid
o This results in decarboxylation
Removal of carbon and forms CO2 and is eliminated
Transfers H to NAD+ to form NADH
o Pyruvate is converted to acetyl coenzyme A (acetyl CoA)
What are other names for the tricarboxylic acid cycle?
TCA cycle or Krebs cycle
How many TCA cycles are made per 1 molecule of glucose?
2
How many molecules of ATP is made from each TCA cycle?
1
What is the most important function of the TCA cycle?
• Prepares hydrogen carrier molecules for next step that produces most energy
Where does the TCA cycle take place?
Mitochondrial matrix
What is GDP and how does it relate to the TCA cycle?
guanosine diphosphate which picks up a phosphate group released from the TCA cycle forming DTP which can be used to form ATP from ADP
What is the original acid that Acetyl CoA combines with to begin the TCA cycle?
oxaloacetic acid
What happens to the carbon atoms released in the TCA cycle?
Expelled from the body as CO2 via the respiratory system
What are the 2 hydrogen carrying molecules released at the end of the TCA cycle?
NADH and FADH2
Where does the electron transport chain occur?
In the inner lining of the mitochondrial membrane lining the cristae
Which stage of ATP production uses a chemiosmotic mechanism?
Electron transport chain
What are the 4 steps taken to aerobically break down sugar into ATP?
Glycolysis
Pyruvate decarboxylation
Tricarboxylic acid cycle
Electron transport chain
What inputs the energy into the electron transport chain?
NADH and FADH2
How does the electron transport chain?
• Steps include electron carrier molecules I to IV, the quinone pool (Q), and cytochrome c (C)
• Some energy used to pump H+ ions into the intermembrane space
o ATP synthase enzyme activated by flow of H+ back into matrix
o Energy of flowing H+ used to take ADP and Pi and create ATP
What is oxidative phosphorylation?
• Entire sequence of mitochondrial biochemical reactions using oxygen to extract energy from nutrients in food and transforms it into ATP, producing carbon dioxide and water in the process
How many ATP molecules is made from each NADH and FADH2 molecule?
- Each NADH leads to 3 ATP molecules
* Each FADH2 leads to 2 ATP molecules
How many molecules of ATP can be created from 1 molecule of glucose?
• Theoretically, 38 molecules of ATP per molecule of glucose
o The system is not 100% efficient however, so realistically its about 30-32 ATP
What is the main dietary source of energy for the body and what can be used as back ups?
- Glucose is the main dietary source of energy
- Fats (fatty acids) can be used when necessary
- Proteins (amino acids) are usually used for protein synthesis but can be used as a last resort for fuel
How does anaerobic ATP synthesis work?
• The only process that can occur during anaerobic conditions is glycolysis forming:
o 2 molecules of ATP
o 2 molecules of NADH
o 2 pyruvic acid molecules
• The pyruvate is converted to lactic acid consuming NADH produced during glycolysis
What main activities require the input for ATP?
Synthesis of new chemical compounds (anabolic reactions)
Membrane transport
Mechanical work such as contraction of muscle
What form of ATP production does red blood cells use and why?
Glycolysis. They have low energy requirements as they do not contract and as they have no nucleus they do not have protein synthesis
What does trilaminar mean in reference to the plasma membrane?
- Appearance of 3 layers when viewed by an electron microscope
- Two dark layers separated by a light middle layer
What is the phospholipid layer and what is it called in the plasma membrane?
• Lipid occurs in 2 layers, called a bilayer with a sandwich-like structure
What is the phospholipid bilayer composed of?
- Composed primarily of proteins and lipids, especially phospholipids
- Substantial amounts of cholesterol (also a lipid) that helps stabilize the membrane
What is the function of the plasma membrane?
- Acts as a selective barrier between cellular contents and extracellular fluid
- Controls traffic in and out of the cell
What are the two ends of a phospholipid?
Head - Phosphate group
Tail - 2 fatty acid tails
What is the polar end and what is it’s importance to the phospholipid layer?
- Negative charge of the phosphate group
- React with water and are referred to as hydrophilic (water loving)
- Are exposed to the water on the outside and inside of the cell
What is the non-polar end and what is it’s importance to the phospholipid layer?
- Two neutral fatty acid tails per phospholipid
- Avoid water and are referred to as hydrophobic (water fearing)
- Face each other on the inside portion of the membrane
- Serve as a barrier for water soluble substances across the membrane
What is a fluid mosaic model and why is the plasma membrane named that?
• Fluid in nature
o Phospholipids are not held in place and are free to move and rearrange themselves
• Name comes from changing pattern of proteins within the bilayer
What are glycolipids and what is their importance to the plasma membrane?
- Molecules of the external lipid layer that have a carbohydrate molecule attached
- Allow cells to recognize each other
Are proteins fixed in place in the plasma membrane?
• No, they are free to move within the membrane
o Some anchored by cytoskeleton
What are integral proteins and what purpose do they serve the plasma membrane?
• Span the entire width of the membrane, protruding on both sides
What are peripheral proteins and what are their importance to the cell membrane?
- Attach to the membrane surface
- Usually temporary
- Are anchored by integral proteins or by attachment to the lipid bilayer
What are glycoproteins and how are they important to the plasma membrane?
- Carbohydrate molecule attached to a protein on the outside of the cell
- Allow cells to recognize one another
What are channel proteins?
- Water filled channels for membrane transport
- Serve as carriers of small water-soluble substances
- Specific shape of inside of channel can make it selective to the ions that can pass through
- May close as a result of a change in the channel shape
What are carrier molecules?
- Specific to a particular molecule or closely related molecules
- Different cell types have different carriers depending on cell needs
What are docking-marker acceptors?
- Located on the inner surface of the membrane
* Have a lock and key mechanism with secretory vesicles allowing exocytosis
What are membrane-bound enzymes?
- May be located on inner or outer surface
- Control specific chemical reactions
- Different cell types have different enzymes depending on cell needs
What are the receptors in the plasma membranes?
- Located on the outer surface
- Respond to specific molecules such as hormones in the cellular environment that alter the activity of the cell
- Different cell types have different receptors depending on cell functions
What are glycoproteins?
- Carbohydrate molecule attached to a protein on the outside of the cell
- Allow cells to recognize one another
What are cell adhesion molecules (CAMs)?
• Proteins that connect to other cells and connective tissue fibers
What are cadherins?
- Located on the surface of adjacent cells
* Form zipper-like adhesions between adjacent cells
What are integrins?
• Span entire membrane
• Connect to the cytoskeleton as well as the extracellular environment to lock them in place
• Some may act as signalling molecules
o Signal for growth or for immune system cells
What is the extracellular matrix and how does it play a roll in cell adhesions?
- Meshwork of fibrous proteins embedded in watery interstitial fluid
- Acts as a biological glue for cells
What are collagen fibers and what do they provide?
- Cable-like fibers or sheets
* Provide tensile strength
What are elastin fibers and what do they provide?
- Rubber-like fiber
* Allows for stretching and recoil (elasticity)
How does the fibronectin protein fiber play a roll in cell adhesions?
• Promotes cell adhesion and holds cells in position
What is a cell junction?
• Cell junctions are contact points between the plasma membranes of cells
How do cell adhesion molecules help with cell junctions?
- Plasma membrane proteins that work like Velcro between cells
- Have special loop and hook shaped surface
What are tight junctions, where are they usually located, and how do they help/hinder permeability?
- Found in epithelial cells
- Cell membranes fuse to the cell membranes of adjacent cells with interlocking membrane lipoproteins
- Minimal intercellular space
- Inhibit passage of substances between cells and prevent contents of organs from leaking into the blood or surrounding tissues
What are adhering junctions, where are they usually located, and how do they help/hinder permeability?
- Contain plaque, a dense layer of proteins on the inside of the plasma membrane that attaches both membrane proteins and to microfilaments of the cytoskeleton
- Cadherins are transmembrane glycoproteins that join the cells
- Each cadherin inserts into the plaque, partially crosses the intercellular space, and connects to a cadherin of an adjacent cell
- Often called adhesion belts because they encircle the cell
- Help epithelial cells resist separation during various contractile activities
What are desmosomes, where are they usually located, and how do they help/hinder permeability?
• Act like rivets between 2 close cells that do not touch
• Prevent epidermal cells from separating under tension and cardiac muscle fibres from pulling apart during contractions
• Dense plaque formed by cytoplasmic thickenings located on the inside of both cells
o Spanning the distance is a glycoprotein filament containing cadherins (a CAM)
• In some tissues, cytoskeleton will attach to plaques on both sides of the cell
o Forms continuous network of fibers from cell to cell like people holding hands in a line
o Allows for lots of tensile strength to prevent tissue from being torn when stretched
What are hemidesmosomes, where are they usually located, and how do they help/hinder permeability?
- Similar to a desmosome but do not link to other cells, but rather to the basement membrane
- Transmembrane glycoprotein used here is integrins
- Inside the plasma membrane, the integrins attach to intermediate filaments made of keratin
- Outside the membrane, the integrins attach to the protein laminin, present in basement membranes
What are gap junctions, where are they usually located, and how do they help/hinder permeability?
• Connexons
o Channels formed by membrane proteins called connexins
o Made of 6 protein subunits arranged in a hollow tube-like structure
• Connexons extend from each plasma membrane and join in the middle to form the tunnel
• Cells are separated by a narrow intracellular gap
• Small molecules and ions can pass through, but larger molecules cannot
• Allow tissues to communicate with each other
• Enable nerve or muscle impulses to spread rapidly among cells, crucial for normal operation of some parts of nervous system and heart contraction
What does selectively permeable mean?
- Membrane permits some particles through while preventing others
- Permeable to a substance means it will allow that substance across
- Impermeable to a substance will prevent that substance from crossing
What are the 2 properties of permeability?
Lipid solubility and molecule size
How does high lipid solubility affect a particles ability to pass through the cell membrane?
Can pass easily through the membrane
What are properties of highly lipid soluble particles?
Uncharged or nonpolar
Give examples of molecules that have high lipid solubility.
o Include O2, CO2, and fatty acids
How does low lipid solubility affect a particles ability to pass through the cell membrane?
Cannot pass through the membrane and must use a protein to get access to the cell
What are properties of highly lipid soluble particles?
Charged or polar
Give examples of molecules that have high lipid solubility.
Ions, glucose, proteins
How does molecule size affect permeability?
• Large particles with low lipid solubility need assisted transport including glucose, proteins, and amino acids
What molecules does diffusion work for?
Those permeable to the membrane
What is the concentration gradient and how it effects diffusion
• The pathway the molecules take
o Molecules are said to move down the concentration gradient
o The movement of molecules from an area of high concentration to an area of low concentration
What is net diffusion?
o Difference between molecules moving from area A to area B and those moving from area B to area A (movement is random so never only in one direction)
What is a steady state as it relates to membrane transport?
o Molecules evenly spaced
What affects the speed at which diffusion occurs?
Temperature and molecule size
What is an electrical gradient and how does it work in relation to diffusion of ions?
o Difference in charge between two adjacent areas
o Promotes movement of ions towards area of opposite charge
What is an electrochemical gradient?
Both an electrical and concentration (chemical) gradient act simultaneously on a specific ion
What is osmosis?
• Water moves from an area of low solute concentration to an area of high solute concentration (high water concentration to low water concentration)
o Simply diffusion of water down its concentration gradient
• Water able to readily permeate plasma membrane
What are aquaporins?
o Channels for water
What happens if a concentration gradient occurs and the membrane is permeable to both the molecule and water?
diffusion and osmosis will occur in opposite directions until steady state is reached
What is osmotic pressure?
- Measure of tendency for water to move into a solution because of its relative concentration of nonpenetrating solutes and water
- Major force of net movement of water in and out of cells
What is tonicity?
- The effect a solution has on cell volume
- Determined by nonpenetrating solutes
- Creates the osmotic pressure
What is an isotonic solution and how does it affect osmosis?
- Solute concentrations are the same on the inside and outside of the cell
- No net movement of water so cell size remains unchanged
- Normally ECF is carefully regulated to be isotonic so that osmotic pressure in ECF is the same as ICF
What is an hypotonic solution and how does it affect osmosis?
- Below-normal concentration of nonpenetrating solutes of ECF
- Water moves into the cytoplasm
- Causes the cells to swell or lyse (burst)
What is an hypertonic solution and how does it affect osmosis?
- Higher than normal concentration of nonpenetrating solutes of ECF
- Water moves out of the cytoplasm
- Causes the cells to shrink (crenation)
What is carrier mediated transport?
• Carrier proteins span the plasma membrane
o Binding causes protein to change shape to change if it is open to ICF or ECF, releasing the molecule to the other side of the membrane
o Shape allows specific molecule (or similar related molecules) to attach
o Different cell types have different types and amounts of different carrier proteins
What is the transport maximum of carrier mediated transport and what can change this value?
o Limit of transport possible by the number of proteins present on membrane
o Until this is reached, amount transferred is directly related to molecule concentration
o Hormones can increase carriers in plasma membrane to increase transport
Ex insulin affecting increase in glucose carriers
What happens if a binding site can attach to a few similar molecules for carrier mediated transport?
Transport for each is less if both are present
What is facilitated diffusion?
• No ATP required
• Diffusion down the gradient is assisted by proteins
o Can move them in or out of the cell, just depends on concentration gradient
• Most notable example is glucose transport
o Levels in blood are always higher than in the cells so continuously flows in
o Glucose metabolized nearly immediately upon entry into the cell
• Rate limited by transport maximum (saturation of proteins)
What is active transport and what are some notable examples?
• Commonly called pumps
• Requires the input of energy (ATP)
• Proteins carry molecules across the membrane against the concentration gradient
o Binding site has higher affinity on low concentration side
• Notable example is sodium-potassium pump and movement of iodine by thyroid
• Uses a phosphorylation/dephosphorylation cycle
What is the phosphorylation/dephosphorylation cycle?
• Phosphorylation
o ATP binds to the protein
o Molecule binds to protein on low concentration side
• Dephosphorylation
o Phosphate group detaches from ATP creating ADP and the energy needed for the transport
o Changes protein to expose molecule to high concentration side
• Once molecule and ADP detaches, protein goes back to facing low concentration side and cycle repeats
What is the sodium potassium pump and how does it work?
• Transports sodium out and potassium into the cell against the gradient
• Phosphorylation
o Increases Na+ affinity inside the cell
o 3 Na+ molecule bind, causing protein to change shape, releasing Na+ to outside the cell
• Dephosphorylation
o Increases K+ affinity on the outside of the cell and 2 K+ attach
o Protein shape is restored, releasing K+ to inside the cell
What are 3 important functions of the sodium-potassium pump?
o Establishes concentration gradient and electrical gradient, critical for nerve and muscle cell function
o Controls concentration of solutes minimizing osmotic effects
o Energy used indirectly serves as energy for secondary active transport
What is secondary active transport?
• Energy required in the entire process, but not directly to run the pump
o Uses second-hand energy from stored energy of concentration gradient
What cells use secondary active transport and what is being transported?
• Intestinal and kidney cells actively transport glucose and amino acids against the gradient
What are the cotransport carriers used in secondary active transport and what do they move?
o Proteins different from regular carrier proteins
o Exist on the lumen side of the membrane
o Have 2 binding sites
1 for Na+
1 for nutrient molecule
What is the protein used in secondary active transport?
• Cotransport carriers
How does secondary active transport work and what does the cell do with the products?
• Na+ concentration is low due to sodium-potassium pump so Na+ binds to the cotransport carrier
o This increases affinity for nutrient molecule
o Binding of nutrient molecule causes change in shape and both are brought to ICF
• Na+ will be pumped back out using the sodium-potassium pump
• Nutrient molecules use facilitated diffusion (down the concentration gradient) at the basal surface to enter blood stream
What are the 2 types of vesicular transport?
Endocytosis and exocytosis
What are the 3 forms of endocytosis?
Pinocytosis, receptor-mediated endocytosis, and phagocytosis
What is vesicular transport and does it require energy?
- Wrapping large molecules in a membrane enclosed vesicle
* Requires ATP
What is endocytosis?
- Small patch of plasma membrane folds in and encloses particles at the cell surface
- A vesicle is formed when the membrane pinches off into the cytoplasm
- Lysosomes fuse with the vesicle to degrade and release contents into ICF
- In some cases, it may be moved across the cell and released out the other side via exocytosis (such as at capillaries to move particles across)
What is pinocytosis?
• Performed by most body cells
• Endocytosis involving droplets of fluid
o Brings in ECF when needed
o Retrieve extra plasma membrane that has been added by exocytosis for recycling
• Vesicle created when membrane-deforming coat proteins attach to inner surface of membrane and link together
• Protein dynamin pinches off vesicle from membrane surface
What is receptor-mediated endocytosis?
• Performed by many body cells
• Imports specific large molecules it needs from the environment including
o Cholesterol
o Vitamin B12
o Insulin etc.
• Can be exploited by viruses such as influenza and HIV
• Molecule binds to a receptor on surface to start process
What is phagocytosis?
• Performed by a few specialized cell called phagocytes
• Endocytosis of large, multimolecular particles
• Pseudopods
o Surface projections that completely surround or engulf the particle trapping it within a vesicle
• Lysosomes break down particles into raw ingredients the cell can use
What is exocytosis?
• The opposite of endocytosis
• Membranous sacs move to and then fuse with the cell membrane spiling the contents into the external environment
• Packaged by endoplasmic reticulum or Golgi complex
• Used for
o Releasing hormones and enzymes unable to cross the membrane
Highly specific and only released when signaled
o Adding components to membranes such as carriers, channels, receptors etc.
Contents may be regular ICF as it’s the membrane components needed
How does the Golgi complex produce secretory vesicles?
• Vesicles have different surface proteins that serves as a specific docking marker so that they go to the correct place
• Products created and then stored as dilated edges of Golgi complex until stimulated for release
• Recognition markers
o Proteins facing inwards towards Golgi lumen
o Trap desired molecules for release
Have sorting signals that uniquely fits with the recognition markers
• Coat-protein acceptors
o Bind with coatomer (coat protein that causes membrane to curve) forming a bud
o Eventually surface membrane closes and pinches off the vesicle
o Shed after vesicle buds off
• Docking markers
o Also called v-SNAREs are exposed after coat protein shed
o Binds with t-SNARE found in target membrane
In cell membrane for secretory vesicles
Once fused, membrane opens and contents released
What are the 3 parts to the nucleotide?
- Phosphate group
- Sugar deoxyribose
- Nitrogenous base
What are the double ringed bases?
adenine (A) and guanine (G)
What are the single ringed bases?
cytosine (C) and thymine (T)
What is the basic structure of DNA?
- Double helix with a right hand twist
- Sugar phosphate backbone, or handrail
- The rungs of the ladder are made of the bases
Which bases pair with which and what types of bonds connect them?
o A and T has a double hydrogen bond
o C and G form a triple hydrogen bond
What are histones and what do they do?
- A group of 8 proteins which DNA wrap around
* Acts as structural support when packaging and storing DNA in the nucleus
What is a nucleosome?
Length of DNA wrapped around a histone protein
What are the sections of DNA between histone groups?
Linker DNA
What is the purpose of the non histone proteins in DNA storage?
• Important in gene regulation
What is chromatin and what is its purpose?
- An indistinguishable mass of chromosomal material and its associated proteins contained within the nucleus
- How DNA is normally found within the cells
- Allows DNA to be exposed during interphase in order to control cell activities
- Cannot see this under a light microscope, it just looks like a purple mass in the nucleus
- Purple due to the dye they use to make it more visible
What are epigenetics?
- Potential for gene expression to change
- Complicates genetics
- Causes the coiling to become more or less tight, making it more or less difficult to be read
What are chromosomes and when are they seen?
- Condensed chromatin
- Formed from millions of nucleosomes that coil together into linear segments
- Only seen during cell division
What is the diploid number and what is it for humans?
(2n)
• Number of chromosomes found in somatic cells
• Human diploid number 46 made from 23 pairs of homologous chromosomes
What is the haploid number?
(n)
• Number of chromosomes found in gametes (eggs and sperm)
• Human haploid number is 23 chromosomes without pairing
What is a centromere?
• The area that joins identical chromosomes
What are genes?
- Functional segments of chromosomes
* There are an estimated 50 000 genes in human cells
What type of process is DNA replication and what does this mean?
o DNA unzips, separating the two strands
o Each strand acts as a template for the base paring
o The two double helices produced will have one original strand and one new strand
• Once replicated, the DNA coils back up
• Entire process has specific enzymes that each have a different task
• Original strand may be called the template strand or parent strand
What are the main differences between DNA and RNA?
• RNA is single stranded while DNA is double stranded
• RNA has uracil instead of thymine
• RNA has ribose instead of deoxyribose
o Only difference is that ribose has a single oxygen atom that deoxyribose does not
• Much shorter strands than DNA
• Does not self replicate
How many amino acids are made from human DNA?
20
What are the 3 phases of RNA translation?
Initiation, Elongation, and termination
How much ATP is required for translation?
• 4 ATP required
o 2 to charge tRNA with its amino acid
o 1 to bind tRNA to mRNA complex
o 1 to move the ribosome forward 1 codon
What is the process of mRNA creation?
Transcription
How is mRNA transcripted?
- mRNA is messenger RNA
- DNA is used to create mRNA within the nucleus
- Uses the enzyme RNA polymerase to add the nucleotides
- Only one DNA strand is transcribed in the gene
- The whole DNA strand is not transcribed, just the part that is needed
- Finished mRNA leaves nucleus through nuclear pores and heads to a ribosome for translation
What is the template or anti-sense strand?
- Strand being used to create the mRNA
- mRNA will be the opposite of this template strand
- Read from 3 to 5 just like DNA
What is the coding or sense strand?
- Also called a complementary strand
- The strand that is not being used to create the mRNA
- The mRNA strand that is created mirrors this strand, hence the name
What is the promoter during transcription?
- Where transcription begins
* Special sequence of DNA to which RNA polymerase binds
Where does translation occur?
Ribosomes
How many subunits of ribosomes are there and what are they made of?
o The 2 sub units of ribosomes are made of ribosomal RNA (rRNA)
How are amino acids brought to the ribosomes?
• mRNA is held by the ribosomes as transfer RNA (tRNA) brings amino acids based on the codons
o tRNA shape is unique to the amino acid it carries
o tRNA has an anti-codon, which is what pairs to the codon on the mRNA
What are the steps to initiation of RNA translation?
• The small ribosomal subunit binds to the mRNA
• Leader sequence
o Also called a start codon
o Point where translation begins
o Since AUG is always the start codon, methionine is always the first amino acid
• Once the first tRNA is bound to the mRNA, the large ribosomal subunit also attaches
o This piece holds the amino acids in place so they can be bound together
What are the steps to elongation of RNA translation?
• A second tRNA molecule carrying the second amino acid joins the ribosome complex
• A peptide bond forms between the methionine and the second amino acid (this is the reason proteins are sometimes called polypeptides)
• The tRNA carrying the methionine is then released and the mRNA moves one codon down
• A third tRNA carrying the third amino acid joins, a peptide bond is formed, and the second tRNA is released
o This process repeats until the stop codon is reached
What are the steps of termination of RNA translation?
• Stop codon binds to a protein called a release factor, which attaches a water
o This releases the last amino acid from the tRNA molecule
• After the stop codon, the protein (polypeptide chain) is released from the ribosome
What are polyribosomes?
- Multiple ribosomes attaches to the same strand of mRNA in a chain before the mRNA degrades
- Produces multiple copies of the same protein
What are the options for protein destinations after they are created at the ribsomes?
• Most proteins released directly into cytosol
• Some will go back into nucleus via nuclear pores
• Ribosomes on rough endoplasmic reticulum feed chains directly into the ER lumen
o Resulting proteins are packed for export out of the cell
What is body’s universal energy carrier?
ATP
What is the end product of glycolysis?
Pyruvate
Which of the following plasma membrane components has a head and two tails?
Phospholipids
Which type of connective tissue forms sheets that provide tensile strength?
Collagen
The Na+/K+ ATPase pump is an example of what type of membrane transport?
Active transporter
List the 4 stages of the pathways for production of ATP
Glycolysis
Pyruvate decarboxylation
Kreb’s cycle or citric acid cycle or tricarboxylic acid cycle
Electron transport chain
List the types of cell junctions
Gap junctions
Tight junctions
Desmosomes
Describe the primary function of gap junctions
Form connecting junctions between cells to allow communication between cells by allowing the passage of small, water soluble molecules
What are aquaporins?
Membrane channels allowing the passage of water
During which stage of cellular metabolism is the most ATP produced under aerobic conditions
Electron transport chain
Which of the following descriptions is best associated with diffusion?
a) a substance moves with its concentration gradient
b) a substance moves against its concentration gradient
c) a substance moves with its electrical gradient
d) a substance moves against its electrical gradient
A
For which type of vesicular transport does the cell extend pseudopods that surround a particle?
Phagocytosis
Identify what happens when water is added to a solution containing a solute
a) Solution becomes more concentrated
b) Solution becomes more dilute
c) Solution becomes isotonic
d) Solution becomes hypertonic
B
Compare and contrast the differences between facilitated diffusion and active transport
Both are carrier-mediated transports; in facilitated diffusion it goes down the concentration gradient and does not require the input of energy; in active transport, it goes against the concentration gradient and requires ATP
Differentiate between tight junctions and gap junctions
Tight junctions prevent molecules from going between the cells. Gap junctions form small, connecting tunnels out of connexons. These communication junctions allow small water-soluble compounds, but prevents large compounds to move between cells
Compare how much ATP is produced by aerobic verses anaerobic metabolism of one glucose molecule
In aerobic conditions, there is about 30 ATP molecules created from each glucose molecule by going through glycolysis, Krebs cycle, and the electron transport chain
In anaerobic conditions, only 2 ATP molecules are created per glucose as it only goes through glycolysis and the pyruvate is converted to lactic acid
What are the differences between pinocytosis and phagocytosis?
Both are forms of endocytosis. Pinocytosis is cell drinking and brings in a small amount of ECF into the ICF. Phagocytosis is the bringing in of large molecules, often damaged cells, bacteria, etc. to be broken down and recycled by the cell
Large, nonpolar molecules would not be able to cross the membrane in which of these plasma membrane components were absent
a) phospholipids
b) cholesterol
c) membrane proteins
d) carbohydrate chains
C
Increasing the efficiency of the electron transport chain would have what effect on ATP synthesis?
Increase
What would happen In the absence of collagen?
Tissues would become more fragile
Increasing the salt concentration in the ECF has what effect on cells?
Water leaves the cells and it shrinks
In the absence of ATP, which one of the following tranport processes would be affected the greatest?
a) passive diffusion
b) active diffusion
c) osmosis
d) active transport
D
What would the cellular consequence be if there was insufficient ATP for the Na+/K+ ATPase pump?
If there is no ATP for the pump, it would be unable to function normally. The resulting imbalance of Na+ and K+ would result in the cell being unable to regulate its internal volume. Processes depending on secondary transport would also be impacted.
Why is a person able to only briefly perform anaerobic exercise but can sustain aerobic exercise for long periods?
Aerobic ATP production is significantly more efficient so it can be sustained for longer periods of time. Oxidative phosphorylation uses less nutrient fuel to generate ATP and can be supported by nutrients delivered to the muscles via the blood stream.
Anaerobic ATP production is inefficient and results in the buildup of lactic acid. It outpaces the ability to deliver supplies to the muscles from the blood and energy stores are depleted quickly
What would happen in a tissue if there was a disruption of desmosomes?
Lead to a loss of tissue integrity; for cells undergoing lots of stretch, such as skin, a lack of desmosomes would lead to the cells beingripped apart.
Why is ATP not stored?
Not an efficient storage. The storage of glucose as glycogen is much more efficient.
Storing large amounts of ATP has an osmotic effect bringing water into teh cell
If osmosis is really only the diffusion of water, why is it important enough to be considered a special type of diffusion?
Because of its significant effects to the size of the cells
When William H was helping victims following a devastating earthquake in a region that was not prepared to swiftly set up adequate temporary shelter, he developed severe diarrhea. He was diagnosed as having cholera, a disease transmitted through unsanitary water supplies that have been contaminated by fecal material from infected individuals. In this condition, the toxin produced by the cholera bacteria leads to opening of the Cl- channels in the luminal membranes of the intestinal cells, thereby increasing the secretion of Cl- from the cells into the intestinal tract lumen. By what mechanisms would Na+ and water be secreted into the lumen in accompaniment with Cl- secretion? How does this secretory response account for the severe diarrhea that is characteristic of cholera?
The sodium will follow the Cl- secretion due to the attraction of opposite charges (electrical gradient). As a result, water will pull via osmosis into the lumen as well. This increase in water would cause the severe diarrhea seen.
