MCAT Study - Biology and Biochemistry

What is the nucleoid region of a cell?

DNA region in prokaryotes

What is the nucleolus and what does it do?

• no membrane

• organelle within the nucleus

• makes ribosomes

What do peroxisomes do?

• break down toxic substances

• metabolize lipids

• neutralize species such as hydrogen peroxide

What does the Rough ER do?

accepts mRNA to make proteins

What does the Smooth ER?

• detoxification

• make lipids

• calcium storage

• carb metabolism

What type of cells have the golgi apparatus?

eukaryotes

What does the golgi apparatus do?

process and package proteins and lipid molecules, especially proteins destined to be exported from the cell

What protein complex for the Golgi handles forward vesicular transport?

COPII

What protein complex for the Golgi handles return vesicular transport?

COPI

What are cisternae?

stacked membrane-bound discs in the Golgi

What are the steps of cisternal maturation?

1. Formation

2. Maturation

3. Completion

4. Dissolution

What happens during the formation period of cisternal maturation?

• Cis-Golgi

• vesicles from ER fuse together to create new cisterna

What happens during the maturation period of cisternal maturation?

• Medial-Golgi

• newly formed cisterna moves forward through stack

• Golgi enzymes delivered into vesicles

• compartment is biochemically changed, alters cargo proteins

What happens during the completion period of cisternal maturation?

• Trans-Golgi and Exit

• by the time cisterna reaches far side, its completely matured

• cargo is sorted and budded off in vesicle

What happens during the dissolution period of cisternal maturation?

• depleted cisterna disassembles

What is the significance of vesicles moving in retrograde for cisternal maturation?

• retrograde = moves from trans (exit) to cis (start) = recycling

• retrograde vesicles (coated in COPI) bud off from more mature cisternae and travel towards younger cisternae

What are centrioles made up of?

9 groups of microtubules

What do centrioles do?

pull chromosomes apart during mitosis

What are lysosomes?

• demo and recycling center of a cell

• single membrane

What makes lysosomes?

Golgi

What type of cells have plasmids?

prokaryotes

What do plasmids do?

carry genetic information that is not essential to survival

• may have virulence factors

What does an obligate aerobe do in a test tube and why?

• accumulates at the top of the tube

• requires O2

What does an obligate anaerobe do in a test tube and why?

• accumulates at the bottom of the tube

• dies in O2

What does an facultative anaerobe do in a test tube and why?

• mostly accumulated at the top with some trickling down, gradient

• toggles between aerobic and anaerobic

What does an aerotolerant anaerobe do in a test tube and why?

• spread out evenly

• does not use O2 but can tolerate it

What color is a Gram positive stain and why?

• PURPLE

• bacteria has a thick peptidoglycan/lipoteichoic acid cell wall

What color is a Gram negative stain and why?

• PINK

• bacteria has a thin peptidoglycan cell wall and an outer membrane

Where does the electron transport chain occur in eukaryotes?

in the mitochondria

Where does the electron transport chain occur in prokaryotes?

in the cell membrane

What is the size of eukaryotic ribosomes?

• large

• 80S = 60S + 40S

What is the size of prokaryotic ribosomes?

• small

• 70S = 50S + 30S

How do eukaryotic cells reproduce?

mitosis

How do prokaryotic cells reproduce?

binary fission

Plasmids that integrate into the genome are ____.

Episomes

What are prions and what effect do they have?

• infectious proteins

• trigger mis-folding of proteins (alpha-helical → beta-pleated sheets)

• decrease solubility

What is a viroid?

plant pathogen

Microfilaments are made up of what?

actin

Microtubules are made up of what?

tubulin

Intermediate filaments are made up of what?

• keratins → epithelial cells

• vimentin and desmin → connective tissues, muscle cells, and some glial cells

• neurofilaments → axon of neurons

• lamins → nuclear lamina under inner membrane of nucleus

What is the parenchyma?

• functional part of an organ

• typically made of epithelial cells

What is simple epithelia?

one layer

What is stratified epithelia?

multi layered

What is pseudostratified epithelia?

one layer that gives the appearance of multi

What is cuboidal epithelia?

cube shaped

What is columnar epithelia?

long and narrow

What is squamous epithelia?

flat and scale like

What is the stroma?

• support, extracellular matrix of an organ

• made up of connective tissue

What are the types of connective tissue?

bone, cartilage, tendons, blood

What are the different forms of genetic recombination?

1. transformation

2. conjugation

3. transduction

4. transposons

What is transformation?

when bacteria takes genetic material from its environment

What is conjugation?

• transfer of genetic info via conjugation bridge/sex pilus

• F+ (Hfr bacteria) → F- (recipient bacteria)

What is transduction?

transfer of genetic info from a bacteriophage

What are transposons?

genetic info that can insert and remove itself

What is the capsid of a virus?

protein coat

What is the envelope of a virus?

some viruses have a lipid envelope

What is a virion?

individual virus particles

What is a bacteriophage?

bacteria virus

What is the tail sheath of a bacteriophage?

the part that injects DNA/RNA into host

What can a viral genome look like?

basically any type of DNA/RNA, single or double stranded

What does translation look like for a virus that is single stranded and positive sense?

can be translated by host cell easy peasy

What does translation look like for a virus that is single stranded and negative sense?

RNA replicase is needed to synthesize a complimentary strand for translation

What is a retrovirus?

• single stranded RNA

• reverse transcriptase needed to make DNA in order to replicate

What occurs in a lytic bacteriophage life cycle?

virions made until cell lyses

What occurs in a lysogenic bacteriophage life cycle?

virus integrates into genome as prophage, goes dormant until stress activates it

What happens during the G1 phase of a cell cycle?

makes mRNA and proteins for mitosis

What is the G0 phase of a cell cycle?

cells enter this phase if the cell does not need to divide

What happens during the G1 checkpoint of a cell cycle?

cell decides whether it should divide or not

What happens during the S phase of a cell cycle?

DNA synthesis

What happens during the G2 phase of a cell cycle?

cell growth, makes organelles

What happens during the G2 checkpoint of a cell cycle?

checks the cell size and organelles

What happens during the M phase of a cell cycle?

mitosis and cytokinesis

What is p53?

tumor suppressor protein that either halts division or triggers cell death at the G1 checkpoint

What are the four steps to a positive growth signal of a cell?

1. CDK and Cyclin create complex

2. Phosphorylate Rb → Rb + P

3. Rb changes shape and release E2F

4. Cell division continues

What are the three steps to a negative growth signal of a cell?

1. CDK inhibitors block the phosphorylation of Rb

2. E2F stays attached

3. Cell cycle halts

Sex is determined by which chromosome?

23rd

What are X-linked disorders?

• disorders on the X sex chromosomes

• females can be carriers or express but males always express

What is important to note about the Y chromosome?

• little genetic info

• SRY gene (sex determining region on the chromosome) → sorry you’re a male

What makes up semen?

sperm and seminal fluid

What do the bulbourethral glands do?

make a viscous/thick fluid that clears out the urethra

What do the seminal vesicles and prostate gland do?

make an alkaline fluid to help sperm survive the acidic environment of female reproductive tract

What is the mnemonic to remember the pathway sperm takes?

SEVE(N) UP

Seminiferous tubules → Epididymis → Vas deferens → Ejaculatory duct → Nothing → Urethra → Penis

What do the seminiferous tubules do?

• spermatogenesis

What cell nourishes the sperm created at the spermatogenesis site?

Sertoli cells

What does the epididymis do?

store sperm, allows sperm to gain mobility

What happens during prophase of mitosis?

• DNA condenses

• centrioles migrate to opposite poles and MT form

• nuclear envelope disappears

What happens during metaphase of mitosis?

• chromosomes line up in the middle

What happens during anaphase of mitosis?

• sister chromatids separate and move to opposite poles

What happens during telophase of mitosis?

• chromosomes decondense

• nuclear membrane forms

• cytokinesis

What is aneuploidy and when does it occur?

• the presence of an abnormal number of chromosomes in a cell

• occurs when sister chromatids don’t separate properly during anaphase

What happens during prophase 1 of meiosis?

• chromosomes condense

• nuclear envelope dissolves

• homologous chromosome form bivalents

• crossing over occurs

What happens during prophase 2 of meiosis?

• chromosomes condense

• nuclear envelope dissolves

• centrosomes move to opposite poles, perpendicular to before

What happens during metaphase 1 of meiosis?

• spindle fibers connect to bivalents

• aligns bivalents along the middle

What happens during metaphase 2 of meiosis?

• spindle fibers attach to chromosomes

• aligns them in middle

What happens during anaphase 1 of meiosis?

• homologous pairs move to opposite poles = disjunction

• Law of Segregation

What happens during anaphase 2 of meiosis?

• spindle fibers contract and separate sister chromatids

• chromatids move to opposite ends

What happens during telophase 1 of meiosis?

• chromosomes de-condense

• nuclear membrane might reform

• cytokinesis

• forms two unequal haploid daughter cells

What happens during telophase 2 of meiosis?

• chromosomes de-condense

• nuclear membrane reforms

• cytokinesis

• forms four haploid daughter cells

What do the ovaries do?

• have follicles that produce ova

• controlled by FSH and LH hormones

What is oogenesis?

production of female gametes