BIOLOGY MIDTERM
Draw a labelled diagram to show the fluid mosaic structure of a plasma membrane, indicating the hydrophilic and hydrophobic regions.
( lol do it)
Which describes these molecules correctly?
(shows a diagram. One molecule is hexagon shaped and the other is in a line with a little branch thing coming off of it). Molecule I is glucose. Molecule II is fatty acid.
Which of the following chemical elements are part of biochemical molecules in living organisms?
nitrogen, sulfur, phosphate, and iron
State two characteristics of stem cells that can be used to distinguish them from other body cells
-Continuous division-can keep dividing and never stops -Are undifferentiated (blank slates)
Deduce two processes that occur in human cells during this part of the cell cycle, but not during the other part.
-S-DNA Replication -G2-produces organelles, membranes, proteins
A red blood cell is 8 micrometers in diameter. If drawn 100 times larger than its actual size, what diameter will the drawing be in mm?
0.8 mm
List two processes that involve mitosis
1)Multicellular organisms -> growth 2) eukaryotes -> asexual reproduction
Outline the process of DNA Replication.
1. Helicase unzips DNA helix. 2. SSB proteins keep the strands stabilized. 3. Primase lays down RNA primer at the end of the 3' strand. 4. DNA Polymerase III moves in and adds complementary bases to create the daughter strand. 5. DNA Polymerase I moves in and proofreads and edits, and also removes the RNA primer. 6. Ligase glues together okasaki fragments.
Describe the events of mitosis.
1. INTERPHASE -G1: cell grows (RNA and proteins) -S: DNA replicates -G2: organelles appear. 2. PROPHASE -Chromosomes condense -Nuclear membrane disappears -Centrioles move to opposite poles -Spindle fibers appear 3. METAPHASE -Chromosomes line up at equator -Spindle fibers attach to centromeres 4. ANAPHASE -Spindle fibers retract -Pull chromatids to opposite poles 5. TELOPHASE -Chromosomes uncoil -Spindle fibers disappear -cell begins division 6. CYTOKINESIS -cell divides (cytoplasm)
The length of a sample of tiger canines were measured. 68% of the lengths fell within a range between 15 mm and 45 mm. The mean was 30 mm. What is the standard deviation of this sample?
15 mm
the levels of iron in liver tissue from 12 rats fed on beef and 11 rats fed on plant oils were compared using the t-test to see if there was a significant difference at the 5% level. Part of the table showing the critical values for the t-test is shown below. What is the critical value above which the two samples can be considered significantly different?
2.080
All cells has cytoplasm, a cell wall, naked DNA and ribosomes. Based on this information, what type of cell could this be?
A bacterium
Explain the significance of polar and non-polar amino acids
A polar amino acid is hydrophilic and on the outer edge of the cell membrane. A non-polar amino acid is hydrophobic and is centered in the cell membrane. The active enzyme sites for the amino acids depend on the polarity.
What does facilitated diffusion across a cell membrane require?
A pore protein? YES! ATP? NO! A concentration gradient? YES!
Define active site:
A region on an enzyme that binds to a protein or other substance during a reaction.
Which pair of features is correct for both a human liver and an Escherchia coli cell?
A) Human liver cell: Contains DNA associated with protein Escherchia coli cell: Contains naked DNA
When do chiasmata form in meiosis?
A. During prophase I
What happens in crossing over?
A. Exchange of genetic material between homologous chromosomes
Distinguish between active and passive movements of materials across plasma membranes, using named examples.
ACTIVE: -Requires ATP -Protein pump is used -moves from low to high conc. PASSIVE: -does not require ATP -Does not require the use of a protein -Moves from high to low concentration -Includes osmosis the diffusion of water through the aquaporin protein
The following sequence of pictures, made using an electronic imaging technique, shows a cell undergoing division. State the stages of mitosis typified by image II.
Anaphase
Which of the following terms correctly describe the molecule below? I. Monosaccharide II. Ribose III. Carbohydrate
B. I and III only
What happens in the G2 stage of interphase?
B. Synthesis of proteins
What is a difference between a cell in the G1 phase and a cell in the G2 phase of the cell cycle?
B.) A cell in the G2 phase would have more mitochondria than a cell in the G1 phase ****it has more ATP to go through the cell cycle****
What route is used to export proteins from the cell?
B.Rough Endoplasmic-reticulum ---> Golgi apparatus ---> Plasma membrane
How many autosomes are there in a human sperm?
B. 22
Compare prokaryotic and eukaryotic cells
BOTH HAVE RIBOSOMES Prokaryotic: no membrane bound organelles no nucleus naked DNA came first (3.5 billion years ago) Eukaryotic: DNA has histones nucleus has membrane bound organelles came later (1.5 billion years ago
The graph below represents the amount of DNA during the cell cycle. Which part of the graph represents metaphase? (FLAT PART OF GRAPH)
C on the graph
What is the correct order of increasing size (small to large) for the following biological structures? I. The width of a virus II. The width of a bacterium III. The thickness of a cell surface membrane IV. The diameter of a eukaryotic cell
C) III ---> I ----> II ---> IV
A cell in the testis of a male chimpanzee contains 48 chromosomes. It is about to undergo meiosis. How many molecules of DNA will be present in the nucleus of the sperm cells just after meiosis?
C. 24
If the amount of DNA in a haploid gamete is represented by x, what is the net quality of DNA in a cell from the same organism at the start of meiosis?
C. 2x
What do all human males inherit from their mother? I. an X Chromosome II. a Y Chromosome III. Mitochondrial DNA
C. I and III only
What does therapeutic cloning involve?
C. Producing embryonic stem cells for medical use
The DNA of a particular cell is damaged, so that the cell continues to divide uncontrollably. What is the possible result?
C. Tumor formation
What feature do plant cells have but not animal cells?
Cell walls
The diagram below shows a plasma membrane. What is molecule X? (diagram of a cell membrane pointing to little circles (like a grapevine) in the middle of membrane).
Cholestrol
The diagram below shows chromosomes during meiosis (couldn't find pic, but it shows 4 chromosomes with their tips connecting). How many chromosomes and chiasmata are visible?
Chromosomes: 4 Chiasmata: 2
What is the difference between simple diffusion and facilitated diffusion?
D) Simple Diffusion: uses any part of a membrane Facilitated Diffusion: uses channels in the membrane
The diagram below shows a cell during mitosis . What are the structures and stage of mitosis?
D) stage of mitosis= metaphase structure I= centromere structure II=plasma membrane
Which is correct for the non-competitive inhibition of enzymes?
D) Inhibitor resembles substrate? NO! Inhibitor binds to active site? NO!
Consider the metabolic pathway shown below: V →W→X→Y→Z If there is end product inhibition, which product would inhibit which enzyme? (Each arrow represents one enzyme. Number the arrows from left to right starting with 1,2,etc.)
D) Product: Z Enzyme: 1
In the following diagram, which pair represents homologous chromosomes? (shows a bunch of combiniations of chromosomes)
D. 4 and 6
Which of the following take(s) place during either interphase or mitosis in animal cells? I. re-formation of nuclear membranes II. pairing of homologous chromosomes III. DNA replication
D. I and III only
The diagram below shows a bacterium. What structure does the part labeled X identify? (pic shows bacteria and points to all the squiggly stuff in the middle).
Nucleoid.
Explain why DNA must be replicated before mitosis and the role of helicase in DNA replication.
DNA must be replicated so that when the cell splits each cell has the correct amount of DNA and cells are identical. Helicase unwinds or unzips DNA by breaking the hydrogen bonds between complimentary bases.
Outline how Down's Syndrome occurs due to meiosis
During anaphase the chromosomes failed to separate correctly, resulting in an extra chromosome on one of the gametes
What diagram best illustrates the interactions between water molecules?
O H H | O H H
Cells in the adrenal gland produce the hormone epinephrine and store it in vesicles. To release epinephrine these vesicles are carried to the plasma membrane and fuse with it. What process is occuring?
EXOCYTOSIS
Which of the following statements about homologous chromosomes is correct?
Each gene is at the same locus on both chromosomes
Which of these processes require mitosis?
Embryological development
Which of the following is not a function performed by a membrane protein?
Enzyme synthesis
Explain enzyme-substrate specificity
Enzymes and substrates share specificity (a given enzyme will only interact with a small number of specific substrates that complement the active site). This explanation of enzyme-substrate interaction is described as the 'lock and key' model (a lock only opens in response to a specific key)
Which chemical is shown in the diagram below?
Fatty Acid
Using named examples, distinguish between fibrous proteins and globular proteins.
Fibrous proteins occur in the secondary structure. They are insoluble. Keratin (hair) and collagen (skin) are examples. Globular proteins occur in the tertiary (3) and quaternary (4) structures and are soluble. Hemoglobin and insulin are examples.
The electron micrograph below shows an E. coli cell. Identify the structures labeled A and B in the electron micrograph above and state one function of each. (A is the long tail-like things while B is the small little hair all the way around the cell).
Flagella. Function is: controls movement. Pili. Function is: controls what binds to the cell.
Glucose and galactose are examples of monosaccharides. State one other example of a monosaccharide.
Fructose.
What is the sequence of stages during the cell cycle?
G1 S G2 mitosis cytokinesis
Which events occur during the G1 phase and S phase of the cell cycle?
G1 phase= cell grows S phase= DNA replicates
The karyotype below shows the chromosomes from a person with Down's Sydrome. ***X and Y in 23rd chromosome ***3 in 21st chromosome State the evidence provided by the karyotype that shows this person has Down Syndrome.
Has three chromosomes on number 21.
What do error bars on graphs show?
How variable the data is
What does the size of the standard deviation indicate about data?
How widely the data is spread above and below the mean
Which of the following are connected by hydrogen bonds?
Hydrogen to oxygen between two different molecules of water.
State the type of chemical reaction that occurs when lactose is digested into glucose and galactose
Hydrolysis
Which of the following will contribute to the cell theory? i. living Organisms are composed of cells ii. All cells come from pre-existing by mitosis iii. Cells are the smallest units of life
I and III only
Which of the following types of information are needed to construct a karotype? I. Size of chromosomes II. Gene Mutation of the chromosomes III. Age of Individual
I only
The diagram below shows one DNA nucleotide and a part of a second nucleotide. State the names of structures I and II.
I. Phosphate Group II. Hydrogen Bond
Determine, giving a reason, the sex of the person in the karyotype
Male, this is because the person has one X and one Y which can be seen on the sex chromosome. The Y is clear because it is much smaller than the X.
The micrograph below shows an adult human stem cell (picture shows a cell with no formed chromosomes). The cell cycle can be divided into two parts: Interphase and mitosis. Identify, with a reason, whether the stem cell in the micrograph is in interphase or mitosis.
Interphase, because there are no chromosomes and you would be able to see chromosomes in mitosis
What is lactase used for?
It improves the digestion of milk by some people
Which processes result in recombination?
Meiosis: YES Crossing over: YES Independent assortment: YES Mutation: NO
What is the difference between galactose and lactose?
Lactose is a disaccharide and galactose is a monosaccharide.
There are several different types of carbohydrate. State which type of carbohydrate lactose is.
Lactose is a disaccharide.
Which variable has the least effect on enzyme activity?
Light Intensity
The table below shows the level of hemoglobin measured in two different groups of athletes. Which of the following statements are correct?
More athletes have their hemoglobin concentration close to the mean in group A than in group B
State TWO functions of proteins, giving a named example of each
One function of proteins is enzymes, with catalase depending on this function. A second function of proteins is movement, which muscles such as actin and myosin rely on.
What is a difference between cohesion and adhesion?
Only adhesion involves the interaction of water with xylem.
What is the difference between the structure of all prokaryotes and eukaryotes?
Prokaryotes: nucleoid Eukaryotes: nuclear envelope
Which of the following structures are found in all cells?
Ribosomes.
Which is chorionic villus sampling (amniocentesis)?
Sampling fetal cells from the amniotic fluid.
Outline one therapeutic use of stem cells.
Stem cells can be pulled from the spongy bone in legs to help repair and replace bone marrow damaged from chemotherapy in the treatment of leukemia. Must have immunocompatibility.
Which of these molecules is a disaccharide?
Sucrose
Which hypothesis can be tested using the t-test?
The difference between the means in two samples is not significant
The graph above shows the effect of substrate concentration on enzyme activity. What conclusion can be drawn about the section the arrow is pointing to-- to the end?
The enzyme is saturated and working at maximum reaction rate
Explain briefly how materials produced in the structure labelled I are transported to the plasma membrane.
The material in the ER is transferred to the golgi apparatus via a vesicle, which forms from the budding of the membrane. The material moves via vesicles from the cis-face of the golgi to the trans face and may be modified along the way (e.g. glycosylated, truncated, etc.)The material is finally transferred via a vesicle to the plasma membrane, whereby it is either immediately released (constitutive secretion) or stored for a delayed release in response to some cellular signal (regulatory secretion = for a more concentrated and more sustained effect)
The graph above shows energy changes during a chemical reaction that occurs without a catalyst. What would change if the reaction was catalysed by an enzyme?
The maximum energy level-- seen at the peak-- would be lower, speeding up the reaction.
Outline the function of the mitochondria in the cell.
The mitochondria performs cellular respiration, which means it takes in nutrients from the cell, breaks it down, and turns it into energy.
Explain the primary structure of proteins and secondary structure of proteins.
The primary structure of proteins relates to the order of the amino acid sequence. The positives in the sequence are held together by peptide bonds. The secondary structure relates to the a-helix (alpha) or b-helix (beta) shapes of the sequence. The b-helix (beta) is shaped by local folding.
What do diffusion and osmosis have in common?
They are passive transport mechanisms
How can cells in a multicellular organisms differentiate?
They express some of their genes but not others
What is the function of the cytoplasmic (plasma) membrane of this bacterium? (shows pic of bacteria)
To control entry and exit of substances
State the process that results in tumor (cancer) formation or development.
Uncontrolled cell division
This question refers to the following micrograph of a liver cell. (it shows a useless, unreadable pic of a cell. But it's unnecessary for the question). Structure X is the Golgi apparatus. What process occurs in this organelle?
Vesicle formation.
Which statement about water is correct?
Water molecules are polar, therefore fatty acids do not dissolve.
What does the karyotype below correspond to? (shows one X and one Y)
a normal male
In viewing an electron micrograph of a cell, ribosomes, pili, and a single circular chromosome are observed. What other structure is likely to be present?
a plasmid
Which of the following does not occur during interphase?
cytokinesis (after telophase)
Which diagram represents the polarity of a water molecule?
diagram shows that the 2 little H's have a negative charge, while the big O has a posiitve charge.
The electron micrograph below shows the ultrastructure of part of an animal cell. Identify the structure labeled I.
endoplasmic reticulum
What does a small standard deviation signify?
the data is clustered closely to the mean value
If a mitochondria has length of 5 micrometers and a student's drawing of the mitochondrion is 10 mm, what is the magnification of the drawing?
x2000
