Cell and Molecular Test 1

Why is it that D-amino acids are toxic?

D-amino acids are toxic because they are incorporated into a protein they mix up the hydrogen-bonding pattern in alpha helices and beta sheets

Which organelle acc eats proteins and lipids from the endoplasmic reticulum, modifies them, and redistributes them to other destinations of the cell?

Golgi apparatus

Which of the statements about binding and active sites are true?

a binding site recognizes the substrate and the active site catalyzes the reaction

What configures a transmembrane domain?

a stretch of amino acids intercalated by non-polar and polar amino acids where all non-polar amino acids face the membrane and polar amino acids produce a hydrophilic lumen.

What type of bond is formed when atoms share electrons?

covalent

Proteins that lack a sorting signal peptide are retained in the?

cytosol

All enzymes

decrease the activation energy of a reaction

Which characteristic of a phospholipid contributes to the fluidity of the membrane?

double bonds in the fatty acid tails

Which subatomic particle is displaced when two or more atoms combine make a molecule?

electrons

In anabolism which of the following are precursor molecules used to synthesize amino acids.

oxaloacetate pyruvate 3-phosphoglycerate alfa-ketoglutarate and phosphoenolpyruvate/erythrose -4P.

Light reactions in photosynthesis are equivalent in reverse to?

oxidative phosphorylation

Which of the following generates the largest amounts of ATP?

oxidative phosphorylation

In oxidative phosphorylation, which of the following accepts the electron?

oxygen

Which of the following is NOT required for glycolysis to occur?

oxygen

In water, hydrogen binds form between:

oxygen and hydrogen atoms

Which of the following bonds are non-polar?

oxygen and oxygen (O-O)

The covalent linkage between two amino acids is a?

peptide bond

Even though peroxisomes, chloroplasts and mitochondria import proteins via a translocon complex they do it differently. Which of the following is NOT TRUE about protein import into specialized organelles?

peroxisome importer proteins (POC/PIC) denature cargo proteins while importing proteins across a double layer membrane structure

Cells ingest large particles (e.g. invader bacterium) by:

phagocytosis

Which transport mechanism can bring whole cells into a cell?

phagocytosis

What group is found in a nucleotide but not a nucleoside?

phosphate

Phospholipids make a fluid liquid, meaning molecules move within the membrane structure without the input of energy. Which of the following phospholipid movements require the input of energy?

phospholipid flipping (movement from one layer to another)

The movement of electrons in oxidative phosphorylation:

pumps protons across the inner mitochondrial membrane.

How is polarity established in a protein?

the amino- and carboxy-group of an amino acid establishes the polarity on the backbone.

Which amino acid groups are involved in making a peptide bond?

the carboxyl group of one amino acid and the amino group of the other

What determines the number of covalent bonds an atom can create?

the excess or shortage of electrons in its outermost electron shell

What makes alpha helices and beta sheets universal protein folds?

the hydrogen bonds that establish alpha helices and beta sheets happen between atoms that are part of the backbone structures.

Protein kinases phosphorylate target enzymes and as a result enzymes become activated or inactivated. Which of the following statements is not true?

the presence of a phosphate group tags the enzyme allowing interactions with other enzymes.

If a signal sequence is removed by genetic engineering from an ER protein:

the protein is retained in the cytosol

In photosynthesis, what drives generation of ATP by ATP-synthase?

the proton gradient across the thylakoid membrane

Which group provides an amino acid with its unique chemical properties?

the side chain

Two molecules are similar but not identical in structure and affect enzyme activity differently. Identify the statements that are NOT TRUE?

the substrate that has sa higher Vmax must have a lower Km

Phospholipids form lipid bilayers spontaneously because?

they are amphipathic (polar and non-polar)

Are there chemical differences between galactose, glucose, and mannose? Identify the statement that is NOT TRUE?

they are sugars that have a sweet taste

Which statement is NOT TRUE?. Exocytosis and endocytosis are regulated secretion and importing processes because?

vesicles transit randomly and fuse randomly with target organelles

When sugars combine via a covalent bond usually it happens between a -OH group from one donor sugar molecule with another -OH group from the acceptor. What type of molecule is released in this type of condensation reaction?

water

When an electron is removed from the reaction center of photosystem II, how is the lost electron replaced?

with an electron from water splitting

What makes an unfolded protein to become folded in an aqueous environment?

- the amino acid sequence - amino acid side chains interact by forming hydrogen bonds electrostatic and van der Waals attractions. - backbone interactions help with 3-D folding

Which of the statements are TRUE about oxidative phosphorylation? (Select two answers)

-Electrons start out at very high free energy and lose energy at each transfer step. -Electrons start at very low redox potentials that increases at each transfer step.

What is the difference between Micelle and liposome. Identify all true statements.

-Liposomes are double layered membranes (made with phospholipids) which separate two aqueous environments -Micelles are single layered lipids (not phospholipids) that form spontaneously in an aqueous environment -Phospholipids are powerful drug delivery systems used by PHARMA -Micelles are powerful bullets that form when we cook pasta at home from scratch

Why is it important to manage glucose availability (Select three answers)

-because glucose has great oxidation potential and is responsible for ATP production. -glucose is the preferred oxidation molecule and the key ATP generator by all cells. -glucose can be converted into almost any other precursor molecule within the cell.

Oxygen with 6 electrons in the outermost electron shell (that needs 8 to be complete) can make how many covalent bonds?

2

Ina typical eukaryotic cell, how much of the intracellular aqueous space is roughly confined into compartments?

50%

What delivers the energy to capture carbon dioxide into sugars (carbon fixation) in chloroplasts?

ATP and NADPH generated in the photosynthesis light reactions

Which of the following is ALL active transport?

ATP and light driven pumps as well as coupled transport

The energy released by oxidizing glucose is saved in the high energy bonds of:

ATP and other activated carrier molecules

Which of the following are true energy carriers in cells?

ATP/GTP and NADH and NADPH and FADH2

Endoglucanases and cellobiohydrolases have the same catalytic center but have a variant configuration of the binding site. Identify, which of the following is TRUE?

Because the catalytic site is identical but the binding site different both enzymes can interact with the substrate in different ways thus producing different catalytic products.

What happens to the membrane of a vesicle after exocytosis?

It fuses with and becomes part of the plasma membrane

Intermediates in glycolysis and the citric acid cycle are precursor compounds to synthesize:

all of the above (amino acids, nucleotides, fatty acids, glucose)

How do proteins, nucleic acids, polysaccharides polymerize?

by condensation reactions

Anabolic and catabolic pathways are opposing but complementary in which ways? (Select two answers)

catabolic pathways degrade energy molecules and anabolic pathways build new molecules

Which of the following describes a breakdown process in which enzymes degrade complex molecules into simpler ones?

catabolism and exergonic reactions

Translation of proteins that initiate in the cytosol but are designated for other organelles must first associate with the:

endoplasmic reticulum

Thinking on the molecules Na+, O2, H2O, K+, and CO2, order them based on their ability to permeate the membrane - from fast to slow.

fast - O2, CO2, H2O, K+, Na+ - slow

In a folded protein, non-polar (hydrophobic) amino acids side chains tend to be:

folded away from the water interface and hidden inside the protein

Under which conditions is gluconeogenesis active?

gluconeogenesis is super active when cells starve (e.g. deprived of a suitable carbon source) they begin to reverse their anabolic pathways degrading amino acids fatty acids nucleic acids and other macromolecules supplying the breakdown products (carbon skeletons that are intermediates of the TCA and glycolysis pathway) to resynthesize glucose

In many ways gluconeogenesis is the reverse of glycolysis. Which of the following IS NOT TRUE?

gluconeogenesis produces pyruvate and glycolysis makes glucose

In amino acid biosynthesis where does the nitrogen come from?

glutamate and glutamine

Sugars (glucose) ingested from food are broken down by:

glycolysis, citric acid cycle, and oxidative phosphorylation

Hemoglobin requires which small non-protein molecule to capture oxygen?

heme

What type of bond links two DNA molecules together in a double helix of DNA?

hydrogen bonds

Why is it that thousands of weak bonds (hydrogen bonds) make such stable and specific structural arrangements? Identify a statement that is not true.

hydrogen bonds are weak individually and do not contribute to an overall equilibrium

the reverse of a condensation reaction is called?

hydrolysis reaction

Which group is not present on ALL amino acids?

hydroxyl group

What is the alpha carbon in an amino acid? Identify the statement that is NOT TRUE?

it is the carbon that has an alpha hydroxyl group attached

Enzymes that add or remove a phosphate group are respectively named?

kinase and phosphatase

Protein structure is dictated by the amino acid sequence. Should a protein in which the order of all amino acids is reversed have the same structure as the original protein?

no, the amino acid sequence is the same but the amino and carboy termini are not (ABC≠CBA).

Photosynthesis enables plants to capture energy from sunlight to produce:

sugars

Gluconeogenesis refers to?

synthesis of glucose from small organic particles such as pyruvate