MCAT - Bio

What differentiates eukaryotic cells from prokaryotic cells?

• eukaryotic

  • compartmentalization - cell divided into compartments to do diff functions (organelles)

  • organelles - membrane bound

  • nucleus

  • divide by mitosis

  • unique mechanism for processing mRNA - spliceosome-mediated intron splicing

    • in nucleus: pre mRNA with introns and exons → after transcription is RNA splicing where the spliceosome removes introns from pre mRNA → mature mRNA

    • mRNA → out of nucleus into cytoplasm → translated to protein

• prokaryotes

  • no compartmentalization - just one room has to do it all

  • genetic material and everything floating around

  • divide by binary fission

True or false: Eukaryotic organisms are the only ones that can inherit genetic info from other individuals.

False, both eukaryotes and prokaryotes can inherit genetic info.

• eukaryotes: offspring produced sexually via gamete fusion inherit genetic info (alleles) from parents

• prokaryotes: conjugation allows transfer of genetic material from one cell to another

What is binary fission?

process by which unicellular organisms such as bacteria reproduce asexually - exponential growth

1. parental bacterial cell doubles in size

2. divides into 2 identical daughter cells

3. each daughter cell divides into 2 → 4

4. continue dividing

What is the generation/doubling time?

time needed for bacterial pop to double or for single bacterium to divide into 2

How to calculate the number of cells after binary fission?

og # of bacterial cells x 2^n

n = # of generations

What are the stages of a bacterial growth curve?

1. initial lag phase: transplanted bacteria become accustomed to local conditions and synthesize the components required for metabolism

2. log phase: bacterial pop grows exponentially as bacteria effectively metabolize nutrients

3. stationary

4. death

What does assuming unrestricted growth during incubation entail?

only log and lag phase

5 bacterial cells were incubated for 3 hours (180 min); these exhibited a 20 min lag phase and 40 min generation time. Assuming unrestricted growth during incubation, how many cells resulted after incubation?

• unrestricted growth during incubation → lag and log

• log phase:

  • 180 min incubation - 20 min lag pase = 160 min log phase

  • 160 min log phase / 40 min generation time = 4 generations

• og # of bacterial cells x 2^n

  • 5 bacterial cells x 2^4 = 80 cells

What organelles are in a eukaryotic cell?

• nucleus - control center

• mitochondria - power house

• endoplasmic reticulum - folded membrane for protein synthesis factory (mRNA translated here)

• Golgi apparatus - mail room of cell, proteins made in ER → Golgi → send to other parts of cell

• lysosome - recycling center, break down no longer functional cellular components

• peroxisome - reactive oxygen species are reduced to nontoxic cells

nucleus components

• outer membrane + inner membrane - separate nucleus from cytoplasm

• nucleoplasm - fluid inside nucleus

• nuclear pore - integral protein, transport things in and out, very selective (reads signals)

• nucleolus - center of nucleus, site of ribosome assembly, makes up rRNA

• nuclear envelope - inner, outer membranes, nuclear pores

How is the nucleus related to the endoplasmic reticulum?

• outer membrane is continuous with/becomes the ER membrane

What are the components of viruses?

1. genetic material

2. capsid (protein shell)

3. tail sheath

4. tail fiber

What Is an encapsulin?

protein-encoded compartment, does not contain genetic material

What is the difference between a virus and encapsulin?

protein has genetic material, encapsulin does not

What is phagocytosis?

certain immune cells engulf pathogens inside a vesicle

What is a pathogen?

any organism or agent—such as a virus, bacterium, fungus, or parasite—that causes disease in its host (bad)

What are telomeres?

regions of repetitive nucleotide sequences at the ends of eukaryotic chromosomes that shorten with each round of cell division

• present ONLY on linear eukaryotic chromosomes

What kind of chromosomes do archaea and bacteria have?

circular chromosomes

(lacking telomeres)

What is the difference btwn bacteria and archaea?

archaea do not have chemical peptidoglycan in their cell walls

What is loose DNA called?

euchromatin

What is condensed DNA wrapped around histone called?

heterochromatin

What is a small prokaryotic DNA molecule separate from chromosomal DNA?

plasmid

Centrioles contain 9 groups of ___ and they pull ___ apart.

microtubules, chromosomes

What is the pH of the cytosol of the cell?

physiological pH 7.4 —> few H+ outside in cytosol

Which of the following molecules is most likely found within the cell membranes of intestinal epithelial cells?

a. peptidoglycan

b. cholesterol

c. cytoskeletal filaments

d. cellulose

cell membrane = fluid mosaic model

cholesterol helps to regulate the fluidity of the phospholipidbilayer

How many functional eggs are produced per meiosis in females?

1 functional egg + 1 polar body

What are the function of polar bodies?

to discard extra sets of chromosomes

How many functional sperms are produced per meiosis in males?

4 sperms

B

True or false: An secondary oocyte finishes meiosis II.

FALSE. An oocyte finishes meiosis II only after fertilization. Otherwise, a secondary oocyte remains arrested in metaphase II.

What phase is an oocyte in during metaphase II?

ovulation (secondary oocyte)

What part of the reproductive tract is most responsive to estrogen?

endometrium

• incr in estrogen → endometrium lining thickens

Upon ovulation, the oocyte is first released into the:

abdominal cavity → fimbriae of fallopian tube sweep oocyte into site of fertilization

What male reproductive structure produces alkaline fructose containing secretions?

seminal vesicles

• fructose in fluid to nourish sperm

• alkaline neutralizes vaginal acidity

What male reproductive structure is the tube connecting the epididymis to the ejaculatory duct?

vas deferens

What male reproductive structure produces a fluid to clear traces of urine in the urethra?

Cowper’s glands

What male reproductive structure secretes a slightly alkaline fluid to activate sperm and enhance motility?

prostate gland

D

During which phase of the menstrual cycle does progesterone concentration peak?

luteal phase