Week 1 Flashcards
(42 cards)
Which statement about spontaneous generation is false?
- Pasteur demonstrated that it does not occur…
- it apparently occurred at least once - when like on Earth began
- it occurs every time a new species evolves from a preexisting species
- it addresses the formation of living cells from previously nonliving material
It occurs every time a new species evolves from a preexisting species.
Suppose a researcher announced the discovery of a fossil that is 4.5 billion years old. Why would you be skeptical of this claim?
According to current models and data, the planet was probably molten at the time.
What do the nodes and branch points on a phylogenetic tree represent?
Ancestral groups that split into two descendant groups.
Why is water such a good solvent?
It is small and has a bent shape, it is highly polar, it can participate in hydrogen bonds.
How many electrons are involved in a single covalent bond?
Two
You’ve just sequenced a new protein found in corn and discovered that it contains a long run of hydrophobic residues (amino acids). What is the significance of this finding?
In solution, they are likely to move towards the interior of the protein and thus contribute to tertiary structure.
Why are protein structure and functioning correlated?
Denatured (unfolded) proteins do not function normally
What is the difference between an uncatalysed reaction to the same reaction with a catalyst?
The catalysed reaction will be faster. The catalysed reaction will have lower activated energy. The catalysed reaction will not consume any of the catalyst.
What interaction is directly responsible for the formation of protein secondary structure?
Hydrogen bonds between sections of the polypeptide backbone.
What does the presence of hydrogen atoms in carbohydrates indicate when comparing the molecular formula or a carbohydrate with that of carbon dioxide?
Carbohydrates are more reduced than carbon dioxide.
When an insect is crushed, it creates a crunching sound. What carbohydrate is the most likely source of this sound?
Chitin
If you were going to develop a new antibiotic, you would probably need to become an expert on what carbohydrate?
Peptidoglycan
What is the major structural difference between starch and glycogen?
The amount of branching that occurs in the molecule.
What best explains why fats, instead of carbohydrates, are used for long-term energy storage in animals?
Carbohydrates contain less energy than fats do, because they have oxygens that oxidise some of the carbons.
What structure features do cellulose, chitin and peptidoglycan have in common?
They can all form bonds between molecules that create parallel strands.
How can the term phospholipid best be described?
A nonpolar lipid molecule that is made amphipathic by the addition of a phosphate.
What substance would most likely require a protein to facilitate its diffusion across a cell membrane?
Fatty acid
What is the best explanation for why cholesterol decreases the permeability of biological membranes?
Because cholesterol is amphipathic, it fits in between the phospholipids and blocks diffusion through the membrane. It fills gaps in membranes and increases hydrophobic interactions.
Why do lipid bilayers form spontaneously?
The process is exergonic.
What will happen to a red blood cell, which has an internal ion concentration of about 0.9 percent, if it is placed into a beaker of pure water?
The cell would swell because the water in the beaker is hypotonic.
Is osmosis an energy-demanding or “active” process?
No
Suppose you put some of your blood cells into an isotonic solution. What will happen to them?
They will remain the same size.
What is the same of the current accepted model of membrane structure, and where does it place membrane proteins?
Fluid-mosaic, embedded within the membrane and on the surfaces of the membrane.
What is the significance of the phosphate group in a phospholipid?
It is highly hydrophilic.
