Category 1

Which of the following is NOT true about viruses

• Viruses need a host to reproduce

• Viruses use the lytic/lysogenic cycles to reproduce

• Viruses are made of genetic material (DNA or RNA) and a capsid (protein coat)

• Viruses have a metabolism

Answer explanation

Remember that viruses are considered non-living because they cannot reproduce on their own and use a host's replication mechanism (mitosis) to make more viruses. Another reason they are not considered living is because they cannot metabolize on their own (eat and poop) and they are much smaller than a cell (the smallest living unit)

DNA replication must occur before mitosis because there needs to be 2 copies of the DNA so each new nucleus gets one of those sets. During what phase does DNA replicate?

• M phase of mitosis

• S phase of interphase

• Cytokinesis

• T phase of mitosis

Answer explanation

The cell cycle begins with interphase, which is where the cell spends most of its time. During this phase the cell grows and replicates its DNA during the S (synthesis) phase. After that it goes into mitosis (PMAT) where it splits the nucleus, and then cytokinesis where it splits the cytoplasm into two new cells.

Homeostasis is an organisms way of maintaining a stable internal environment. To do that it uses feedback systems such as positive and negative feedback. Which of the following is an example of positive feedback?

• Sweating when you get too hot

• Insulin levels rising after eating a big meal

• blood clotting when you get a cut

• A plant is in a hot environment so it closes its stoma to conserve water

Answer explanation

Negative feedback brings you right back. Think of it as taking negative steps to bring you back to homeostasis, which is where you want to be.

Positive feedback pushes you away from homeostasis until some action is completed. Then you can go back to homeostasis. Think of the positive sign (+++=more, more, more). This happens less often.

Blood clotting is an example of positive feedback, you bleed, bleed, bleed, until the platelets in your blood close the wound by creating a scab.

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NGSS.HS-LS1-3

Prokaryotes will lack which of the following?

• nucleus and cell membrane

• nucleus and membrane bound organelles

• nucleus and ribosomes

• nucleus and cytoplasm

Answer explanation

Pro rhymes with NO

NO nucleus

NO membrane bound organelles

All cells (both prokaryotes and eukaryotes)

have a cell membrane (lets things in/out of cell), DNA (genetic material), ribosomes (makes

proteins), and cytoplasm (holds and cushions

all other organelles)

Which of the following uses ATP to move particles against the concentration gradient across a cell membrane?

• Endocytosis/Exocytosis

• Facilitated diffusion

• Osmosis

• Simple diffusion

Answer explanation

Passive transport goes with concentration gradient from HIGH concentration to LOW concentration. Passive includes: simple diffusion, facilitated diffusion, and osmosis

Active transport uses ATP to move particles AGAINST the concentration gradient from LOW concentration to HIGH concentration. Active transport includes: protein pumps, endocytosis, and exocytosis.

Which of the following explains why cancerous cells form tumors so fast?

• cancerous cells follow all steps of mitosis

• cancer is uncontrolled cell growth that does not obey cell's checkpoints and apoptosis

• cancerous cells replicate by binary fission

• cancerous cells use meiosis instead of mitosis

Answer explanation

Cancer can be defined as uncontrolled cell growth. Usually a cell that goes through mitosis and has a defect will go through apoptosis to destroy itself. Cancerous cells will not pass the checkpoints and will grow fast to clump together and form tumors.

Tags

NGSS.HS-LS1-4

Which of the following is only found in RNA?

• Thymine

• Guanine

• Cytosine

• Uracil

Answer explanation

RNA is a single stranded nucleic acid that contains the bases: adenine which binds to uracil, and guanine that binds to cytosine.

DNA is double stranded and contains thymine instead of uracil.

Cell differentiation (how cells become different and specialized) happens when -

• genes are turned on and off in the same DNA

• different DNA makes different cells

• proteins are used to make DNA

• differentiation does not happen

Answer explanation

In an organism, all cells will have the same exact DNA. How you get different cells (heart, liver, muscle, nerve, etc.) is all due to the sections of DNA (genes) that get turned on and off during development.

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