Биология для вступительных экзаменов на сестринские программы: лист заданий с ответами

Which bonds hold the two strands of a DNA double helix together?

1. APeptide bonds between the sugars
2. BIonic bonds between the phosphates
3. CDisulfide bonds between the bases
4. DHydrogen bonds between the bases

What are cilia?

1. AFolds of the inner mitochondrial membrane that make ATP
2. BSmall round sacs that hold digestive enzymes
3. CShort hair-like projections that beat in waves
4. DOpenings in the nuclear envelope

Какая наименьшая единица считается живой?

1. AМолекула
2. BТкань
3. CАтом
4. DКлетка

Why can small nonpolar molecules cross the cell membrane easily while ions cannot?

1. AThe membrane is made mostly of long carbohydrate chains
2. BIons are larger than most membrane proteins
3. CThe membrane carries a strong positive charge
4. DThe bilayer's core is made of hydrophobic tails

HIV is a retrovirus. What does its enzyme reverse transcriptase do?

1. AIt makes proteins from the virus's DNA
2. BIt makes RNA from the host's DNA
3. CIt makes DNA from the virus's RNA
4. DIt breaks down the host's ribosomes

Why must human gametes be haploid?

1. ASo that the gametes can divide quickly by mitosis
2. BSo that the gametes can make more proteins
3. CSo that the zygote has the normal number of 46 chromosomes
4. DSo that the zygote has twice the normal number of chromosomes

A pesticide that is not broken down is sprayed on crops. Later, hawks at the top of the food chain have much higher levels of it than the insects. Why?

1. AHawks make the pesticide in their own bodies
2. BThe pesticide is broken down faster in insects than in plants
3. CEach predator eats many prey, so the pesticide builds up at each level
4. DHawks eat the crops directly, so they take in the most pesticide of all

PCR starts with one double-stranded DNA molecule, and the number of copies doubles each cycle. How many copies are there after 10 cycles?

1. A100
2. B20
3. C512
4. D1024