Unit 1 Practice Problems

What are the different variables in an experiment? What are controls?

-Ind Variable: what your manipulating to cause effects

-Dep Variable: what your measuring, outcome

-Standardized Variable: what you’re keeping the same to isolate cause and effect

-Negative Control:iv will not effect dv, baseline

-Positive Control: iv will affect dv, already shown results

You are planning an experiment to test if a new drug is able to act as a ligand for the estrogen receptor. What would be a good negative control for this experiment? What would be a good positive control?

A good negative control would be to test the drug with a ligand that we know doesn’t interact with the estrogen receptor, and a good positive control would be to test the drug with a ligand that has already been known to work with the estrogen receptor

How are ionic and covalent bonds different from each other?

Ionic bonds form when atoms gain or lose electrons they are electrons transferred from one atom to another, attraction between oppositely charged ions (electronegativity has big difference)

Covalent bonds are two atoms that share electrons (electronegativity is about the same)

Describe at least two ways in which polar and non-polar bonds are different from each other.

Polar bonds have partial charges from electrons spending more time around one atom than the other, while non-polar bonds are uncharged since electrons are shared equally. Polar bonds are hydrophilic and non-polar bonds are hydrophobic.

What are hydrogen bonds? Where do you expect them to form and why?

Hydrogen bonds are the attraction between partially charged atoms created by polar covalent bonds, electrons give hydrogen a slightly positive charge and oxygen or nitrogen a slightly negative charge, they are found when hydrogen is bound to oxygen or nitrogen since they both have higher electronegativity than hydrogen

What does pH measure and how does the pH scale work?

pH measures the concentration of H+ ions in a solution, measured on a log10 scale from 0-14, acidic is 0-6 with high h+ concentration, neutral is 7, basic is 8-14 with low h+ concentration

Define the terms hydrophilic and hydrophobic. What causes a molecule to be hydrophobic or hydrophilic?

Hydrophilic is water-loving, it dissolves in water. While hydrophobic is water-hating, and remains separate from water. A molecule is hydrophilic or hydrophobic based on its polarity.

What are the parts of a phospholipid and what chemical qualities do they have? How are they arranged to make a membrane? What other molecules are found in membranes?

Phospholipids have a hydrophilic phosphate head and a hydrophobic fatty acid tail. They form two sheets with the hydrophilic heads facing the aqueous environment of the cell and the hydrophobic fatty acid tails on the inside. Proteins and carbohydrates (glycolipids and glycoproteins) are also found within the membrane.

What are the differences between cell membranes and cell walls?

Cell membranes (made up of phospholipid bilayer) are in all cells and are flexible barriers that control what goes in and out of the cell while cell walls (made of cellulose) are seen in plant cells for structure to allow water pressure to build up and to keep plants stiff (turgid) and upright

What are the similarities and differences between saturated and unsaturated fats?

They are both lipids with hydrophobic non-polar properties. Saturated fats are animal fats with single bonds and solid at room temp, unsaturated fats are plant fats with double bonds that cause bent tails and are liquid at room temp

What are the similarities and differences between starch, glycogen, and cellulose (fiber)?

They are all complex carbohydrates (polysaccharides) made of repeating glucose units. Animals store glucose for energy in glycogen, while plants store glucose for energy in starch. Plants chain glucose into cellulose (fiber) for structural support (humans can’t digest).

Why are proteins/polypeptides capable of carrying out so many different types of tasks?

Because they are built with amino acids and amino acids have a side chain “r” that can be different for all and change the function of them

What are the levels of protein structure? What defines them? What bonds are involved in each?

-Primary: Linear chains of amino acids (peptide bonds), covalent bonds, connect carboxyl group of one atom to the amino group of its neighbor, gives sequence of amino acids that are parts that are same for all

-Secondary: Interaction with backbone of chain, alpha helixes, beta pleated sheets, hydrogen bonds between parts of the amino acid that are same for all

-Tertiary: bonds between the side chains (individual polypeptides), all bonds

-Quaternary: bonds between side chains (different polypeptides), all bonds

How do the qualities of individual amino acids affect where they end up in folded protein structures? How is this different for free-floating vs transmembrane proteins?

The side chain “r” determines it’s chemical properties, including if its hydrophilic or hydrophobic, free floating proteins would have hydrophobic amino acids in the center to avoid the water, while transmembrane proteins would have hydrophobic amino acids within the fatty acid tails and hydrophilic amino acids if they are facing the outside of the cell

What does it mean to denature a protein? What are some things that can denature a protein?

A protein loses its 3D shape and functional structure by breaking the weak chemical bonds that hold it together without altering its primary amino acid sequence. pH or temperature could denature a protein

Give two reasons why a protein with the correct amino acid sequence might not be functional.

The protein could not have folded correctly beyond the primary structure of the amino acid sequence, or it could be in an environment that doesn’t allow it to work properly, or from missing necessary co-factors.

What are chaperones?

proteins that assist in the folding of other proteins

What types of molecules can cross a membrane without help? What kinds need help? Why? What provides that help?

small, non-polar, uncharged, hydrophobic molecules can cross a membrane without help. While charged, polar, hydrophilic, proteins need help. Transport proteins such as carriers and channels help.

What type(s) of membrane transport require energy? Why?

If the molecule is going against its concentration gradient, from low to high, it needs energy to move across the membrane. This is Active Transport.