Transcript
Handout 2 - Answer Key Handout 2
BIO1A Discussion Section
Macromolecules
Proteins
(a) Draw the basic structure of an amino acid. Denote the side chain with an R.
(b) What type of bonds are involved in protein primary structure? In protein secondary structure? In protein tertiary structure? Which would be easiest to disturb?
Primary structure involves covalent bonds. Secondary structure involves hydrogen bonds. Tertiary structures involve covalent bonds, hydrogen bonds, ionic bonds, and hydrophobic forces. Primary structure is the hardest to disturb because covalent bonds are strongest. (Disulfide bonds in tertiary structure are also difficult to disturb).
Carbohydrates
The molecular formula of glyceraldehyde is C3H6O3. What would the molecular formula for a polymer consisting of 8 glyceraldehyde molecules?
C24H48O24
C16H32O16
C17H34O17
C24H34O17
C24H32O16
True or False:
The glycosidic linkage, or the bond that forms when a dehydration reaction joins two monosaccharides, is an ionic bond.
Lipids
4. Explain how phospholipid structure is connected to its function in forming the lipid bilayer. Drawing a diagram may be helpful.
Phospholipids consist of both a phosphate group and fatty acid chains. The phosphate group is negatively charged and polar; the fatty acid chain, on the other hand, is mostly nonpolar. As a consequence, phospholipids form a bilayer in which the phosphate groups point towards aqueous components (i.e. cytoplasm, since hydrophilic) and the fatty acid chains are protected from water (since hydrophobic).
Nucleic Acids
5. Write out the complementary sequence to the one listed below. Label the appropriate ends as 5’ or 3’. Indicate the number of hydrogen bonds in each base pair.
5’ AGCTCATGAAT 3’
3’ TCGAGTACTTA 5’
G and C base pairs have three bonds, A and T base pairs have two bonds.
Different Cell Types
6. For each part of the cell, indicate whether it is present in prokaryotic cells, eukaryotic animal cells, or eukaryotic plant cells. Please check one of the options below.
Cell Component
Prokaryotic
Eukaryotic Animal Cells
Eukaryotic plant cells
Plasma Membrane
x
x
x
Cell Wall
x
x
Flagella
x
x (Sometimes)
Vacuole
x
Ribosomes
x
x
x
Nucleus
x
x
Endomembrane system
7. Many cells have integral receptors in their cell membrane that allow them to detect changes in their environment. Explain how these receptors might get there, starting with the gene encoding the receptor itself.
HINT: Remember the central dogma and the endomembrane system.
The gene will first be transcribed to RNA in the nucleus. This RNA will then be exported from the nucleus through the nuclear pore. The RNA will then be translated by ribosomes on the rough ER, and the protein will be transported via a vesicle to the cis-Golgi complex. The protein will then move to the trans-Golgi complex and be secreted via a vesicle to the cell membrane.
Organelles
8. Why are mitochondria and chloroplasts, but not other membrane-bound compartments, considered organelles?
Mitochondria and chloroplasts contain their own unique DNA. The endosymbiont theory argues that an early ancestor of eukaryotes engulfed a prokaryotic cell. The engulfed cell may have formed a symbiotic relationship with the host cell and evolved to become the mitochondria or chloroplast organelle we know today.
The Cytoskeleton
9. What utilizes microtubule polarity to transport vesicles?
ATP powered motor proteins
Tubulin
Keratin
Centrosomes
Actin
10. Check the corresponding cytoskeletal element next to its cell function:
Microtubules
Actin Filaments
Intermediate Filaments
Flagellar transport
x
Cell Shape
x
x
x
Cytoplasmic Streaming
x
Cell division
x
x
Muscle Contraction
x
Extracellular Matrix
11. True or False: The cell wall grows outwards from the middle lamella in plant cells.
For Additional Practice:
Cell Structure and Organization
Fill in the blank:
Cellular Compartment
Structure
Function
Nucleus
Nuclear Envelope (double phospholipid bilayer) with nuclear pores
Contains genetic material
Ribosome
1 large and 1 small protein subunits
Protein Synthesis
Endoplasmic Reticulum
Network of membrane-bound tubules and sacs with lumen that’s separate from the cytosol
Smooth: metabolic processes (lipid biosyn, carb metabolism, detox)
Rough: protein modification
Golgi Apparatus
Stacks of membranous sacs
Modification, sorting and packaging of proteins
Lysosomes
Small, acidic membrane-bound sacs, full of enzymes
Digestion of macromolecules and cellular components
Vacuoles
Large membrane-bound vesicles (in PLANTS only)
Storage
Cellular Organelle
Structure
Function
Mitochondria and Chloroplasts
Have both outer membrane and inner membrane systems
Contain own DNA, RNA, ribosomes
Energy Production
