Howard University Biology Senior Comprehensive Exam!!!

Which of the following is the definition of "Atomic Weight"?

a. atomic weight is the weight of two substances that have been measured in a lab

b. atomic weight is the weight of a single atom

c. atomic weight is the average of the mass numbers of all naturally occurring isotopes of the element.

d. none of the above

C

True or false: Isotopes have the same number of protons and a different number of neutrons.

True

Light-dependent rxn

light from photons being used and converted into chemical energy, what is the chemical energy: ATP, NADPH. photosystem II, photosystem I. light energy excites chlorophyll and electron transport produces ATP, noncyclic electron transport, ATP being produced. NADPH is the electron carrier. Go into calvin cycle

light independent rxn

glucose being formed. Goes through 6 cycles of calvin cycle to make one molecule of CO2. byproduct of this process is .. CO2 is important. RuBisco an important enzyme in the production of glucose.

electron transport chain

majority of ATP produced in ETC. high concentration of hydrogen ions(flow high to low) makes ATP. facilitated diffusion through ATP synthase causes it to spin, creating ATP

kreb's cycle(citric acid cycle)

breaks down glucose. Acetal CoA broken to make citric acid which is then oxidized and rxn releases. Purpose of NADH are to fxn as electron carriers. Happens twice to make two acetyl CoA. produces 10 NADH. produces 6 carbons. Glucose completely broken down into 6 molecules of carbon dioxide. 4 ATP

glycolysis

the breakdown of glucose by enzymes, releasing energy and pyruvic acid.

cellular respiration

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

Define an "ion" and a "cation".

Ions form when an atom gains or loses one or more electrons whereas a cation has more protons that electrons.

What best defines organic molecules?

a. carbon-hydrogen bonds

b. presence of electronegativity

c. molecules that have not been yet discovered

d. the bonded molecule must have a metal present

A

List the monomers group

(Think of it as a family as opposed to a group or FAM'N.)

Fatty Acids and glycerol

Amino Acids

Monosaccharides

Nucleotides: guanine, adenine, cytosine, thymine

List the polymers group

(Think of polymers as people, or PPL(N) instead of a group)

Proteins

Polysaccharides/Carbohydrates

Lipids

Nucleic acids

On the pH scale of 1-14, what numbers indicate the most acidic, the most neutral and the most basic respectively?

a. 14, 7 and 1

b. 2, 4, and 6

c. 14, 1 and 7

d. 1, 7 and 14

D

Why is water (H2O) considered polar?

Water is polar due to partial negative charge on the oxygen atom and partial positive charges on the two hydrogen atoms. This is why water is able to form hydrogen bonds.

Which bonds are considered strong bonds?

a. Covalent Bonds

b. Hydrogen Bonds

c. Van deer Waals interactions

d. both covalent bonds and Van der Waals interactions

A

True or False: hydrogen bonds, hydrophobic bonds (or interactions), ionic bonds, and Van der Waals interactions are all considered relatively weak reactions?

True

What are the 4 properties of water?

High specific heat

High heat of vaporization

Cohesion

Surface tension

Match these bonds with their chemical behaviors

a. Covalent bonds

b. Hydrogen bonds

c. Hydrophobic interactions

d. Ionic bonds

e. Van der Waals interactions

1. interactions between nonpolar molecules.

2. occurs when atoms of two molecules are in close proximity

3. attraction between an electronegative atom and a hydrogen atom

4. sharing one or more pairs of electrons

5. one interacting atom is much more electronegative

a4, c1, e2, d5, b3

What 3 roles are nucleic acids responsible for?

Storage, transmission and use of genetic information

Through what process is DNA replication done?

Polymerization reaction

Experiments conducted by Meselson and Stahl demonstrated what about DNA replication?

DNA replication is semiconservative

What are the two types of nucleic aids?

DNA (GCAT) and RNA (GCAU)

What is the difference between nucleotides and nucleosides?

Nucleotides have a nitrogenous base, sugar, and a phosphate group whereas nucleosides have no phosphate group.

True or false: There are two "basic" steps of DNA replication: DNA double helix is unwound to separate the two template strands and make them available for new base pairing and old, identical nucleotides form complementary base pairs with template DNA.

False, the nucleotides that are formed after the strands are unwound are new nucleotides (not old or identical).

For DNA replication, what is the last missing component of this list?

Origin of replication

Primer

DNA Polymerases

DNA helicases

Single-stranded binding proteins

Leading strand synthesis

Lagging strand synthesis

DNA ligase

Okazaki fragments

Why are Okazaki fragments important?

The problem of replication on the lagging strand is solved by DNA through the use of Okazaki fragments.

Explain the Central Dogma

The Central Dogma is also known as the Information Flow Theory and mentions that (after replication) DNA (is transcribed to) -> RNA (and is then translated to) -> Protein

Who established the Central Dogma?

Francis Crick from Watson and Crick

Why do retroviruses carry out reverse transcription?

Their genetic material is not DNA but RNA

What is the basis of Griffith's Experiment?

DNA from one type of bacteria genetically transforms another type.

What were Avery, McLeod, and McCarty able to identify with their experiment?

They identified the substance causing bacterial transformation by eliminating other possibilities and conducting a positive experiment.

What did the Hershey-Chase Experiment confirm?

Their viral infection experiments confirmed that DNA is the genetic material.

Which part of the tRNA base-pairs with the codon in the mRNA?

a. the ribosomes

b. the anticodons

c. RNA polymerase

d. phosphate groups

B

Which of these statements is correct about the major differences between plant and animal cells.

a. neither have a mitochondrion, chloroplasts, a cytoplasm, or cell walls

b. Plant cells have a cell wall and chloroplasts whereas the animal cell has no cell wall and no (or a very small) vacuole. Also, there is flagella only in gametes for plants. Animal cells have flagella.

c. The Golgi apparatus is only present in animal cells.

d. none of the above.

B

True or False: All of these are found in both animal and plant cells.

Mitochondrion

Golgi apparatus

Rough and smooth endoplasmic reticulum

Nucleus

Cytoplasm

Ribosomes

True

Fill in the Blank: Ribosomes are a collection of ____ that are needed for _____.

proteins and RNAs; translation

What serves an energy currency in cells?

ATP

What is the final electron acceptor of the electron transport chain that functions in oxidative phosphorylation?

Oxygen (O2)

What does this reaction represent?

6 CO2 + 6 H2O --> C6H12O6 + 6 O2

Photosynthesis, an anabolic process by which the energy of sunlight is captured and used to convert carbon dioxide into more complex carbon-containing compounds.

How does an enzyme accelerate metabolic reaction?

Lowering the activation energy

In mitosis, how many somatic cells arise from a single nucleus?

a. 3 haploid

b. 6 diploid

c. 2 diploid

d. 12 haploid

C

Fill in the Blank(s): An organism with a chromosome number of _____ has a diploid chromosome number of ____ and a haploid chromosome number of 8.

2n=16, 16

If a sexually reproducing species has a chromosome number of 2n=16 then how many chromosomes are there and how many pairs does this make?

32 chromosomes and 16 chromosome pairs

During meiosis, when are the homologous pairs of chromosomes separated?

Meiosis 1

Consider a diploid with 2n=24. Assume that the amount of DNA in cell at G1 interface is represented by the quantity X. Give the number of chromatids and then the quantity of DNA for the cell in prophase of meiosis 1.

The amount of chromatids are 48 and the quantity of DNA is 2X

How do the phases of meiosis I and meiosis II differ?

Meiosis I has 3 stages of prophase (early, mid and late) whereas meiosis II has one prophase (prophase II).

Consider Mendelian Genetics, DNA and Heredity

Which of these statements is incorrect and how should it be corrected?

a. Griffith's experiments in the 1920s demonstrated that some substance in cells can cause heritable changes in other cells.

b. The location and quantity of DNA in the cell suggested that DNA might be the genetic material. Avery and his colleagues isolated the transforming principle from bacteria and identified it as DNA.

c. The Hershey-Chase experiments established conclusively that DNA (and not protein) is the genetic material, by tracing the DNA of radioactively labeled viruses, with which they infected bacterial cells.

d. Genetic transformation of eukaryotic cells is often called transduction. Transformation and transduction can be studied with the aid of a genetic marker gene that confers a known and observable phenotype.

D, genetic transformation for eukaryotic cells is called transfection not transduction.

What is the purpose of a test cross?

To determine whether an individual showing a dominant trait is homozygous or heterozygous

True or False: Bacteriophages and bacteria are diploid

False, bacteriophages and bacteria are haploid (having a single copy of each gene)

A microbiologist found that some bacteria infected by phages had developed the capacity to make a particular amino acid that they did not make before. What does this new capacity probably reflect?

Transduction

Which of the following techniques would you use to produce a great number of copies of DNA?

a. polymerase chain reaction

b. synthesis of recombinant molecules

c. phage cloning vectors

d. GTF

A

Define "Population Bottlenecks"

When only a few individuals survive a random event, a drastic shift in allele frequencies within the population and the loss of genetic variation occurs.

How does the Hardy-Weinberg equilibrium define the theoretical conditions of a non-evolving population?

1. There is no mutation

2. There is no selection among genotypes

3. There is no gene flow

4. Population size is infinite

5. Mating is random

What is the earliest stage of development for a multicellular organism?

a. a newborn baby

b. a fetus

c. a toddler

d. an embryo

D

What is the term for programmed cell death that occurs normally in the development of the nervous and immune systems?

Apoptosis

Define Phylogeny

The evolutionary history of a particular group of organisms or their genes. A phylogenetic tree is a graphic representation of these lines of evolutionary descent.

Fill in the Blank: A _______ cell lacks a membrane-enclosed nucleus.

Prokaryotic

What categories (hint: 1 word/group) of organisms have the characteristics of the different groups below?

Group 1 --> some contain a cell wall while some don't, are either autotrophs-heterotrophs-parasite-saprotrophs, asexual reproduction occurs via binary fission and sexual reproduction occurs via production of gametes, no septa are found, examples are algae-slime molds-euglena and amoeba

Group 2 -- contain a cell wall made up of chitin, heterotrophs, asexual reproduction occurs via spores and sexual reproduction occurs via mating, septa are found, examples yeast-pichia-basidiomycota-eomycota

Group 1 is protists and group 2 is fungi

Mammals are distinguished from other vertebrates by the presence of what features?

Hair and mammary glands

What groups are the major endothermic vertebrates?

Birds and mammals

A mycelium consists of what mass of individual tubular filaments?

Hyphae

What is the hydrogen concentration of a lake for which acid rain has lowered its pH to 3.0?

10 ^-3 M

Name some important roles of nucleotides

Energy production and utilization, nucleic acid organization, transmission of hereditary information.

What is the unique sequence of amino acids in a polypeptide chain?

Primary structure of protein

True or False: The primary energy source for most plant and animal cells differ

True, the mitochondria produces the majority of the cells energy from food. It does not have the same function in plant cells. Plant cells use sunlight as their energy source.

A biochemist isolated and purified molecules needed for replication. When DNA was added, replication occurred but the DNA molecules were defective. Each consisted of a normal DNA strand paired with many DNA segments a few hundred nucleotides long. What did the biochemist leave out of the mixture?

Primer

Fill in the Blank: the cells of the liver are distinct from cells of the spleen because they have _____ ribosomes?

Unique (different, specific)

the cells of the liver are distinct from cells of the spleen because they

express different genes

3 multiple choice options

Which of the following would never contribute to genetic variation within a bacterial population?

a. meiosis

b. transformation

c. conjugation

d. transduction.

A

a microbiologist found that some bacteria infected by phages had developed the capacity to make a particular amino acid that they did not make before. the new capacity probably reflects

transduction

3 multiple choice options

During human gestation, when does organogenesis occur?

The first trimester

The region of DNA in prokaryotes to which RNA polymerase binds most tightly is the

promoter

3 multiple choice options

Where does the development of organogenesis begin?

The neural tube

all of the following compounds are required at some stage of photosynthesis except

oxygen

3 multiple choice options

As human diverged from other primates, which of the following most likely appeared first?

a. expansion of the gills

b. the depletion of mammary glands

c. an erect stance

d. all of the above

C

the final electron acceptor of the mitochondrial electron transport chain that functions in chemiosmotic ATP synthesis is

oxygen

3 multiple choice options

What enzyme acts first during digestion?

Amylase

Which blood vessels would you expect to find the most nutrients?

The intestinal artery

In what part of the cardiovascular system does various metabolic exchanges occur?

The capillaries

What is the pulse a direct measure of?

Heart rate

What is humoral immunity mediated by?

B lymphocytes

HIV compromises the immune system primarily by infecting what?

Helper T cells

Where does the fertilization of human eggs most often take place?

Oviduct (fallopian tube)

Through what process(es) is nitrogenous waste excreted by animals?

Protein and nucleic acid metabolism

True or False: Reabsorption, ultrafiltration, secretion is used by the kidneys to control blood composition?

True

Coordination of movement is meditated by which part of the brain?

a. cerebral cortex

b. cerebellum

c. hypothalamus

d. gray matter

B

What is the largest and most complex part of the human brain?

The cerebral cortex

Which of the following components of the nervous system is the most inclusive?

a. cerebral cortex

b. cerebellum

c. hypothalamus

d. gray matter

D

What are nucleosides are composed of?

Ribose sugars and phosphates

What is the notation that designates a normal human male sex chromosome?

XY

What is the form of RNA that carries the code from the DNA to the site where the protein is assembled?

Messenger RNA

What is Char Gaff's rule for double helical DNA?

A+T/G+C always approximates 1.0

What process occurs in the cytoplasm of a eukaryotic cell?

Translation

What process are gametes in the human body produced by?

Meiosis

During replication in e. coli, DNA is maintained as single stranded molecules at a replication fork by what component?

SSB proteins

What are the two strands of a double helical DNA held together by?

Hydrogen bonds

In which direction does DNA polymerase I synthesizes new molecules of DNA?

5' to 3'

What is the genotypic ratio in a cross between a homozygous recessive and a heterozygous (aa x Aa)?

1:1

What are snRNPs involved in?

Splicing

What does processing Primary Transcripts result in?

mRNA precursors