Study Guide Flashcards
What does a Nucleotide molecule consist of:
nitrogenous base
5-carbon sugar
1+ phosphate groups
4 different Nucleotides
ATP (Adenine)
GTP (Guanine)
TTP (Thymine)
CTP (Cytosine)
Hydrogen Bonds role in Nucleic Acid
- allows ALL nucleotides to form secondary structures between nitrogenous bases
- hydrogen bonds formed by Complementary Base Pairing
- holds together 2 complimentary chains to form a double helix
Covalent Bonds role in Nucleic Acid
- hold atoms in molecules together in each amino acid chains
- Phosphate of 1 nucleotide is covalently bound to the sugar of the next nucleotide
DNA
- Sugar deoxyribose (H)
- Double-stranded molecule
- Stable under alkaline conditions
- Stores & transfers genetic info
- A,T,G,C
RNA
- Sugar ribose (extra 0H group)
- Single-stranded molecule
- Not stable
- -Directly codes for amino acids
- Act as a messenger between DNA and ribosomes to make protein
- A, U, G, C
- Uracil lack metyl group in its ring
Explain “5 prime”, “3 prime”?
The distinct ends of the molecule I referred to as the 5’end and the 3’ end reflecting the number of the carbon in the sugar
Explain complementary base pairing
requires that the bases be oriented in a way that the facilitates the formation of the hydrogen bonds
-This can only happen if the two strands of nucleic acid are anti-parallel
Explain what is anti-parallel
when two strands run parallel to each other but with opposite alignment
Apply the idea of complementary base pairing to folding of DNA
DNA is well known as a double helix.
Two individual strands of DNA are held together by complementary base pairing.
Define “semi-conservative replication”
DNA replication were each of the 2 daughter DNA molecules contains 1 intact strand of the parental DNA molecule in 1 continuous newly synthesized strand of DNA.
Describe the role of the various proteins involved in DNA replication
- DNA helicase helps to unwind the DNA making it possible for the other proteins to gain access to the sequence
- Topoisomerase helps relieve the torsional stress (twist) that form because of the unwinding
- The Single Stranded Binding proteins help stabilize the DNA while it is unfolded and unattached
- DNA polymerase III catalyzes the formation of the new DNA strand using the original strand as it’s template
Outline the steps of DNA replication
- DNA ‘unzips’
- DNA unwinds
- The original DNA strands function as templates for the addition of new, complementary nucleotides
- Covalent bonds link the nucleotides together
- The process repeats until the entire molecule of DNA is copied
Leading Strand Synthesis
synthesized in the same direction as the movement of the replication fork, and is synthesized continuously.
Lagging Strand Synthesis
synthesized in the opposite direction and is synthesized in short fragments that are ultimately stitched together (okazaki fragments.)
Describe how DNA is packaged and organized in a eukaryotic cell
• In most eukaryotes, chromosomes are linear, and multiple replication bubbles at different stages in the replication process are located along the chromosomes.
• The linear nature of eukaryotic DNA presents a challenge not typically found in bacterial DNA replication
o DNA polymerase III cannot add the final sequence of DNA to the 5′ end of the lagging daughter strand.
Euchromatin
- the parts of the DNA that are actively transcribed
- a loosely packed form, contains areas of DNA that are undergoing active gene transcription
Heterochromatin
- DNA that is NOT actively transcribed
- mostly made up of highly condensed DNA
Histone
One of several families of proteins around which DNA is wrapped during compaction
Chromatin
The combination of DNA and proteins that makes up the chromosomes
Nucleosome
- The complex of DNA coiled around the eight core histone subunits: two subunits each of the histones H2A, H2B, H3, and H4; forms bead-like, repeated units in the chromosomes of eukaryotic cells.
- A nucleosome is made up of eight histone proteins. There are two Histone 2A’s (H2A), two Histone 2B, two H3s’ and H4. Histone H1 hold it all together from outside the nucleosome.
Centrosome
Organizes the microtubules of the spindle during mitosis in animals.
Describe the levels of DNA packaging within the cell (levels of organization of a chromosome)
- The nucleosome is the start of DNA folding and packaging inside the cell
- The next level of packaging is the 30nm fiber. Ultimately, the DNA can be fully condensed
- Condensed chromosomes are only found in cells that are going through cell division.
Explain why lipids do not dissolve in water, but sugars do
- Water molecules are polar, which means the oxygen side of the molecule is more negative, and the hydrogen side is more positive.
- Lipids are non polar, which means that one side is not more negative than the other.
- no nonpolar substances dissolve in polar liquids
- Sugars are polar
Describe/draw the structure of a biological membrane
- Biological membranes contain both a lipid and a protein component.
- While there is a diversity of proteins present in the bilayer – many of the proteins function as transport proteins
Describe the various uses of carbohydrates by cells
Energy Storage
Structural Support
Cell-to-Cell Communication
Energy Storage
- starch used in plant cells
- glycogen used in animal cells
Structural Support
- cellulose used in cell walls of plants and algae
- peptidoglycan used in cell walls of bacteria
Cell to Cell Communication
Attached to proteins and lipids in plasma membrane of cells
Memorize examples of molecules that can easily cross a membrane and those that cannot
CAN
• small
• nonpolar
• hydrophobic
CANNOT • charged ions • large • proteins • sugars
Fluid mosaic
- Being made of many separate and distinct components not bonded to each other so as to retain fluid properties; the currently accepted model of cell membrane structure.
- Biological membranes have been described as Fluid Mosaics
Intergral Membrane Protein
• A protein that is permanently attached to a membrane
Peripheral membrane protein
• A membrane protein associated with either the inside or the outside of the membrane; it is anchored to the surface of the membrane but is not embedded within the membrane
Glycoprotein
• A protein with carbohydrate modifications; can be secreted from the cell or embedded in the membrane; interactions between glycoproteins on adjacent cells permit cell-cell communication.
Diffusion
- Movement of materials from areas of generally higher concentrations to areas of generally lower concentrations; requires no input of energy.
- The story of membrane transport is the story of how molecules (solutes) that are suspended in water (the solvent) move across phospholipid bilayers.
- Net movement by diffusion is always from high to low.
Concentration gradient
- A difference in the concentration of a substance between two different areas, such as the two sides of a selectively permeable membrane.
- The state of having different amounts of a solute molecule on one side of a membrane compared to the other
Osmosis
• The diffusion of water through a selectively permeable membrane.
Solvent
• The solution that is doing the dissolving.
Solute
• The “stuff” (molecules) dissolved in a solution
Pump protein
- A kind of protein that is capable of pumping out compounds that could pose a threat to the cell
- Use ATP energy to change conformation - carrying solute molecules across the bilayer
- Moves molecules UP a concentration gradient (against entropy).
Channel protein
• Tunnel-like protein structures in cell membranes through which molecules or ions can move; present on both the cell membrane and intracellular organelles such as mitochondria and the endoplasmic reticulum.
Carrier protein
- Bind to their solute molecule – like a substrate – and undergo a conformation change that results in the transport of the solute across the membrane.
- Work like enzymes
- Binding to a specific substrate molecule
- Undergoes a conformational change
• Moves the molecule DOWN the
concentration gradient
Connect the idea of energy with concentration gradients
- A concentration gradient is a representative of energy storage.
- ATP the energy currency of the cell will require this concentration gradient for its formation.
- Higher the concentration gradient the higher will be the stored energy
