MCAT BIO

facts about cells ?

• make up living things

• arise from pre-existing cells

• carry DNA that gets passed to daughter cells (not RNA cause it eventually destroys itself)

prokaryotes vs eukaryotes ?

pro:

• single cell

• no nucleus or membrane-bound organelles (processes in membrane)

euk:

• single (yeast) or multi (us) cell

• has nucleus and membrane-bound organelles so can compartmentalize (everything working together at the same time)

eukaryote cell organelles (+ functions) ?

• nucleus:

  • double membrane

  • linear DNA wrapped around histone proteins → chrom.

    • DNA: when loose = euchromatin; wrapped/compressed = heterochromatin

• nucleolus (center)

• lysosome (recyle)

  • work w/ endosomes (package and transport)

• golgi: series of membrane-bound sacs

  • modifies and packages newly synthesized proteins into vesicles (merge w/ cell membrane)

• cytoplasm

• ribosomes (protein synthesis)

• rough ER (has ribosomes so ^)

• smooth ER (lipids and detox of drugs and materials)

• mitochondria:

  • double membrane: inner (has cristae to increase SA/efficency) and outer

  • have their own genes so can replicate (moms pass down mT and other women before her)

    • mT diseases (mom has it so so do you)

  • do apoptosis

what is the endomembrane system ?

DNA → mRNA → proteins → packed into vesicles in Golgi → fuse into membrane → leave cell via exocytosis

what is a peroxisome ?

single membrane and not part of endomembrane system

• ion (O2,2-) produces hydrogen peroxide → splits into 2 hydroxide radicals

  • these radicals are SUPER reactive/dangerous so that’s why they’re not part of system

what is the cytoskeleton ? what is it made out of ?

structure for cell

• microfilaments: actin interacts w/ myosin for muscle contraction

  • cytokinesis

• microtubules:

  • tubulin (cilia and flagella)

  • form kinesin (out of cell body) and dyenin (motor proteins; “dive” into cell body)

• intermediate filaments: anchor organelles

simple diffusion vs facilitated diffusion vs active transport vs osmosis ?

• no ATP used; goes from high conc. to low

• no ATP used; goes from high conc. to low

• uses ATP (primary uses direct; secondary stored); low to high

• no ATP used; water movement to high solvent conc.

  • hypotonic: water moves in; cell swells

  • hypertonic: water out shrivels

  • isotonic: no change

  • *refers to outside solute conc.

what are the types of tissues ?

• nervous

• muscle

• connective: framework and produces extracellular matrix

• epithelial: covers cavities and skin

  • make up the parenchyma (active/functional portion of organ)

  • shapes:

    • squamous: horizontally long

      • simple (one layer) and stratified (more layers)

    • cuboidal: cubed shaped

      • simple and stratified

    • columnar: vertically long

      • simple, stratified, and pseudostratified (1 layer of opp. triangles)

prokaryiotic cell organelles ?

• flagella (propellor)

• cell wall

  • thick peptidoglycan layer (Gram +)

  • thin (Gram -)

    • causes harsher infections cause of LPS

• nucleoid (holds genetic material)

prok. reproduction ?

• binary fission: copy copy copy (asexual)

• genetic recombination: steal genetic info

  • transformation: steal DNA from dead cells

  • conjugation: come together to make bridge to pass DNA

  • transduction: sits on cell to inject DNA

    • bacteria is the victim here

what are the different types of bacteria ? how do they grow ?

• cocci (round), bacilli (rod), spirilli (spiral)

• aerobic (need O2) vs anaerobic (don’t; it kills them)

  • facultative anerobe can switch to an. pathway when beneficial

• rate grow = rate death

  

  • very limited resources (die if they can’t get through

viruses structure ?

• lipid envelope around for protection

• capsid: long hexagon (protein coat)

  • genetic material inside

*NOT prok.

what are bacteriophages ?

viruses that target bacteria and perform transduction since viruses can’t reproduce on their own:

• inject viral material → DNA turns into RNA → proteins → viral capsule and materials

  • all of this together = virus

what are retroviruses ?

take RNA and use reverse transcriptase to produce DNA → hijack our cell → inject DNA → trick our cells to make more

*HIV

what are super infections ?

sickness over another (body busy fighting 1 thing so another steps in)

what are prions ?

misfolded protein that causes misfold in others → leads to blockage

*CJD

what are viroids?

tiny viruses that infect plants

what is cellular reproduction ?

using somatic cells (body) to make diploid (2 sets of chromosomes; 2n)

• 2 × 23 chrom. = 46 total (enough to sustain life !)

cell cycle ?

1. G1 (pre-synthetic gap): transcription (DNA → RNA) and translation (RNA → proteins)

   1. allows for mT, ER, and ribosomes to grow; increases cell size

*check-point/restriction point: to make sure G1 did its job

2. S (synthesis): DNA replication so that e/a daughter cell has identical DNA

*2nd restriction point: harder to get through cause we in more deep

3. G2 (growth): transcription and translation continue

4. M (mitosis): cell actually divides

   1. Prophase:

      1. condensation of genetic material

      2. nuclear envelope dissolves (to allow for mitosis)

      3. chromosomes visible

   2. Metaphase:

      1. chrom. line up in center of cell

   3. Anaphase:

      1. sister chromatids separate (pulled by the mitotic spindles- made up of microtubules/tubulin)

   4. Telophase:

      1. nuc. membrane reforms

      2. spindle apparatus disappears

      3. chrom. uncoil

      4. cleavage

   5. Cytokinesis: splits into 2 2ns

* cells that don’t divide go to G0 (retirement

chrom. structure ?

2 sister chromatids joined together by centromere

what is sexual reproduction ? steps ?

meiosis: make haploid cells (1n); 23 (enough to make genome !)

• combine 2 haploids to get diploid (and now can do mitosis)

1. 2 homologous chrom. (mom and dad)

2. synapsis (pair up)

3. crossing over (swap pieces of DNA)

   1. where problems occur

   2. if not, you’re 100% your mom/dad and their problems

4. meiosis 1 (separate pairs)

   1. same step name as mitosis but pulling chrom. instead of chromatid (+ crossing over during prophase 1)

   2. get spermatocyte and oocyte

5. meiosis 2 (separate copies like mitosis)

   1. 4 1n cells (spermatid and ovum)

what is the sex chrom. ?

23rd pair:

• non-disjunction errors: chrom. don’t properly separate during meiosis 1

  • most common in females: when female developing, all the ova/eggs they will ever have start meiosis but stop midway and continue w/ some when ovulating

    • this freeze (prophase 1) then restart (metaphase 2) again and again makes errors more likely in mom’s gametes

  • cell left w/ 2 chrom. → XXY / Klinefelter’s syndrome (man w/ increased feminine qualities)

  • cell w/ none (missing 23rd) → XO / Turner’s syndrome (short women w/ flat chests and webbed necks)

male reproductive anatomy ?

• S: seminiforus tubules produce sperm (spermatogenesis: sertoli cells that nurse and Leydig cells that produce testosterone)

  • sperm does NOT = semen (semen carries sperm)

• E: epididymis: sperm motility and where stored

  • travels through…

• V: Vas deferens *enters…

• E: ejaculatory duct

• N: DONT WORRY

• U: urethra

• P: penis

*SEVEN UP

*seminal vesicles, prostate gland, and bulbourethtral make pre-cum

female reproductive anatomy ?

• ovary: has many follicles that nourish and protect ova

• fimbriae: hands that grab ovary; end of …

• fallopian tube

• uterus

• cervix (narrow passage b/w uterus and vagina)

• vagina

*before puberty, hypothalamus restricts synthesis of GnRH → doesn’t allow production of:

• FSH: stimulate ovary and secrete estrogen → thickens endometrium (uterine lining protected by thick layer of mucus = decidua)

  • estrogen secretion has negative feedback on GnRH: we got enough, go chill

• LH: secretes progesterone to protect endometrium (w/ the help of corpus luteum)

  • what Leydig is in males

menstrual cycle ? menopause ?

• follicular phase: start bleeding (shedding of endometrium layer)

  • response to loss of hormones (estrogen and progesterone)

  • ^ brain: “oh shit, let’s get more LH and FSH”

  • late follicular phase: estrogen levels peak and negative feedback becomes +

  • causes LH spike …

• … release of mature ova (ovulation)

• luteal phase:

  • LH stimulates corpus luteum → releases progesterone (negative feedback)

  • *estrogen continues doing its thing getting ready for pregnancy

*menopause: ovaries decrease sensitivity to FSH and LH (drop in progesterone and estrogen)

why does the menstrual cycle repeat ? what happens ?

waiting for fertilization:

• no fertilization: corpus desensitizes to LH → progesterone drops → endometrium sheds → start again

• fertilized:

  • zygote burrows into endometrium → produces BhCG (molecule you use to test for pregnancy) → stimulates corpus HELLA

  • placenta forms and maintains progesterone levels

what is the point of the cardiovascular system ?

heart transfers blood (and O2) to body and keeps adequate perfusion pressure (pressure that pushes O2-rich blood into brain, arteries, etc)

heart anatomy ?

1. deoxygenated blood enters through vena cava (vein that carries all venous blood body to heart) into right atrium

2. passes through tricuspid valve into right ventricle

3. exits through pulmonary valve to pulmonary artery and goes to lungs where it picks up O2

4. oxygenated blood enters through pulmonary vein into left atrium

5. passes through bicuspid/mitral valve into left ventricle

6. exits through aortic valve to aorta and goes to the rest of the body

7. *body → arteries → arterioles (main source of systemic vascular resistance/SVR) → capillaries (so small, RBCs travel through them in single file to improve O2 transfer) → venules → veins → back to vena cava …

*ventricles more muscular than atria

*valves prevent back-flow and open when it’s time

• relax/repolarize = valve leaving closes

• contract/depolarize = valve leaving opens

what can the heart be compared to and why ?

a battery ! (has action potentials)

1. signal by: sinoatrial node (SA): heart’s internal pace-maker (normal heart rate/ 60-100 bpm)

   1. by vena cava

2. signal wraps around atrial ventricular node (AV): 0.1 sec delay (pause after e/a “lub-dub”

   1. delay gives ventricles enough time to fill up w/ blood

   2. “lub: heart contracts (systole) / S1: tricuspid and bicuspid valve closing

   3. dub”: heart relaxes (diastole) / S2: pulmonary and aortic valve closing

   4. middle of heart

3. travels down bundle of His (middle of right and left ventricle) → wraps around ventricular walls of heart (purkinje system)

*everything the action potential touches, contracts

what do arteries do ?

resist change by creating pressure (pushes so heart needs to contract to also push)

• need enough blood volume inside and outside the heart

• Blood pressure / MAP (mean arterial pressure) = systolic / diastolic => (heart rate) (stroke volume) (SVR)

  • Cardiac output (amount of blood leaving heart) = HR x SV

how do capillaries do O2 transfer ?

1. give cells O2, cells give CO2

2. carries deoxyg. blood to veins → other organ → heart

   1. portal veins / hypophyseal portal system: veins from hypothalamus circulate through pituitary for horm. transfer

      1. hepatic portal system: safety checkpoint for what you eat and drink

what is blood make up of ?

• liquid (plasma)

• cells (produced in bone marrow)

  • erythrocytes (RBC)

    • biconcave to fit more hemoglobin to carry O2 (hemogl. carries around 4 O2 cause Fe binds it)

      • binding increases as partial pressure of O2 decreases (PO2)

      • contrast to normal cells: no mT (cause mT needs O2 so if RBC has mT, O2 would be used up)

  • leukocytes (WBC)

  • platelets (not really cells, instead fragments that aid in clotting)

blood types ?

A, B, O + yes Rh = positive, no Rh = negative

• alleles: I^A, I^B, i

*AB = universal receiver

*O = universal donor

fluid balance ?

b/w capillary and interstitium

• Pc = hydrostatic pressure of capillary (fluid inside capillary pushes fluid out)

• pi c = oncotic pressure of capillary (pulls fluid in)

• P i = hydrostatic pressure of interst. (fluid in)

• pi i = oncotic pressure of interst. (fluid out)

• *in EQ with respective ones (Pc = P i etc) so opp.

*pi = i MRT (Van’t Hoffs factor) (molarity)

• covalent compounds (non-metals): i =1

• ionic (metal + non): i = exact # it breaks into (NaCl → 2; NaCl2 → 3)

*more solutes = higher oncotic pressure

• high blood pressure: injest more salt = high pi c = high blood volume = high SV (stroke volume) = high blood pressure

• heart failure (heart can’t pump so pulls in legs): high fluid = high Pc = fluid escapes = legs swell

• liver failure (normally makes albumin which acts as a sponge to pull blood inside vessels): low albumin = low pi c = blood leaves = edema + fluid in belly

fertilization overall ?

• usually in ampulla (widest part of fallopian tube)

• acrosome (tip of sperm) binds to corona radiata and zona palusida of egg

  • creates mini explosion / cortical rxn: Ca2 release

    • stops further fertilization (membrane no longer penetrable)

how do we get twins ?

• 2 separate eggs and sperms = fraternal/dizygotic

• 1 egg divides = identical

embryology mechanism ?

1. zygote (single cell) cleaves into an embryo (>1 cell)

2. cleaves more into morula (ball of cells)

3. blastulation to become blastula (glorified morula; hollow w/ fluid-filled cavity)

   1. implants into uterine wall

4. becomes organism

5. undergoes gastrulation to become gastrula

   1. ectoderm (outside layer): becomes skin*, lens, hair, inner ear canal, nervous system*, and hairs of nose lips and lower anal canal, adrenal medulla*

   2. mesoderm (middle): becomes circulatory system, musculoskeletal system, excretory system, connective tissue, and adrenal cortex

   3. endoderm (inner side): becomes epithelium of digestive and respiratory system, thyroid gland, pancreas, parts of liver, bladder and distal urinary tract

what is aging ?

telomeres (ends of chrom.) shortening

what is neurulation ?

formation of CNS

1. neural plate and notochord connect and fold in

2. now have neural folds; pull up and merge together

3. now have neural tube (→ CNS) and neural crest (→ PNS)

what are development issues due to ?

teratogens

• interfere w/ embryonic dev.

• ex. thalidamide, drugs, viruses, alcoholm vitamin B9 deff (cause NT defects (spina bifida: defect where fetal spine won’t close))

what are stem cells and what do they undergo ?

starting point:

• specification: reversible decision to do something

• determination: not reversible

• differentiation: cell starts looking like a cell

  • morphagens allow for this

  • through cell-cell communication: inducer sends signal to responder

what are the types of cell-cell communication ?

• autocrine: cell signals itself

• paracrine: local

• juxtacrine: “jux-” = next to / touching

• endocrine: far away

types of cell death ?

• apoptosis: breaks into fragments for other cells to eat

  • controlled

• necrosis: murder ! (by environmental factors)

  • releases harmful chem. that can kill other cells

what types of cells can regenerate ?

liver cells, NOT heart

fetal circulation ?

fetal lungs don’t work (cause pulmonary arter and aorta not the same) so gotta find other way through mom: 3 new structures

• foramen ovale: allows blood flow from right atrium to left atrium

  • some blood still escapes to right ventricle …

• ductus arteriosus: connects right ventricle and left ventricle by connecting aorta and pulmonary artery

  • to avoid the blood from going to lungs, we have high pressure

• ductus venosus: connects fetus to placenta and gives baby O2 (oxygen. blood)

*babies have lower pressure in body than lungs so when they’re born, pulmonary pressure drops so that blood can go to the lungs

*O2 carried w/ high affinity (help: 2,3 BPG) so that mom doesn’t take it all

what is gestation ?

pregnancy (around 40 weeks)

• 1st trimester (0-13 weeks): heart beat and get fetus

• 2nd (13-27): increased growth, movement, human face, toes and fingers

• 3rd (28-42): more growth, CNS dev., less space so moves less

how does birth happen ?

uterine contraction → cervical dilation → sends signal to hypothalamus → sends signal to posterior pituitary → releases oxytocin which builds and builds → repeat

neuron anatomy ?

• nucleus

• axon hillock: where incoming signals are integrated (filters everything to send forward only what’s important)

  • summation of incoming signals can be inhibitory (hyperpolarizes membr.) or excitatory (depol. ; excited enough = gets passed on)

• dendrites: receive signals

• cell body/soma: ER, ribosomes, nucleus

  • collect into ganglia (bundle) in PNS

• axon: long part; in sections to be insoluted

• schwann cells (along axon): make myelin for insulation; produced in PNS

  • myelin prod. by oligodendrocytes in CNS

• nodes of ranvier (non-insoluted gaps b/w schwann): signal jumps b/w these

• axon terminal: signal spat back out in the form of neurotransmitters

how do neurons communicate ?

space b/w 2 neurons = synaptic cleft

*^ + axon terminal + dendrites = synapse

what do glial cells do ?

support and myelination (process of wrapping nerve fibers in myelin)

• astrocytes: nourish and form blood-brain barrier

• ependymal cells: line ventricles of brain and makes CSF (cerebrospinal fluid)

• microglia: phagocytic cells (injest waste and pathogens)

• oligodendrocytes/schwann cells

describe an action potential ?

all or nothing messages that relay electrical impulses

• resting membrane potential: net electrical potential diff. (charge separation) that exists across a cell’s membr.

  • around 70 mV (inside of cell is negative relative to outside)

    • maintained by balance b/w Na+ (more outside → moves in) and K+ (more in → moves out) (diffusion)

      • what makes cell negative

• excitatory signals depolarize membr. (goes toward 0/+) while inhibitary hyerpolarizes it (more negative)

  • if membr. depol. to threshold potential (-55 - -40), we can get an action potenetial

• summation in axon: spatial (# and position) or temporal (multiple signals at a set amount of time)

what happens when the action potential hits the axon terminal ?

Ca2+ influx → exocytosis into synaptic cleft (vesicles that are full of neurotransmitters are released; inhibitory = GABA) → attach onto dendrites

• neurotransm. bind to receptors:

  • ligand-gated ion channels: ligand hits → ions influx into post- synaptic → change (multiple or not action potential)

  • G-protein coupled receptors: have their own everything

how to regulate neurotransmitters ?

• enzymatic breakdown: enzyme blocks neurotransmitter

  • actylcholinesterase blocks acetycholine

• reuptake carriers: takes neurotransmitter back in (recycled)

  • reuptake carries takes seratonin

• diffuse out: leave and get broken down elsewhere

nervous system organization ?

• CNS: brain and spinal cord

• PNS:

  • somatic (can control)

  • autonomic (can’t)

    • signal can’t make trip in 1 go so needs rest stop (autonomic ganglion (cluster of nerve cell bodies outside of CNS): pre (1st neuron: cell body in CNS and axon travels TO ganglion) and post (2nd neuron: FROM ganglion to target organ)

      • sympathetic: fight or flight

        • thorax and lumbar regions

        • short pre-releases acetylcholine

        • long post-releases norepinephrine

      • parasympathetic: rest and digest

        • cranial and sacral regions (lowest part of spinal cord)

        • long pre- acetylcholine

        • short post- acetylcholine

      • enteric: process food

different types of neurons ?

• sensory neurons (dorsal): afferent (“arrive”) / bring info from sensory receptors to CNS

• motor neurons (ventral): efferent / info from CNS to muscles and glands (PNS)

• interneurons: reflexive behavior (take action like taking hand off stove)

  • require no input from brain (only spinal cord cause it’s faster

  • reflex arc: stimulus travels → hits interneuron → signal to spine (first take hand off) then comes back to give response (“ouch”)

what is endocrinology ? importance ?

study of endocrine system (series of glands, hormones, effectors, and pathways that regulate long distance and long term communication within body)

• purpose: get signal out, where it needs to go, and get message to last long enough for response

• how: through glands (send message), circulatory system (carry it), and targets (receive it)

• end goal: homeostasis

what are hormones ? 2 main spots ?

molecule/protein that binds receptor and influence cellular/tissue/organ-level responses

• hypothalamus: headquarters

• pituitary gland: controls almost all horm.

  • anterior: endocrine (chemical signals)

    • connected to hypothalamus through hypophyseal portal system

  • posterior: neurosecretory (electrical signals)

    • 1 giant neuron that releases oxytocin and ADH (anti-diuretic horm)

      • ADH start signal: high blood osmolarity (salty)

        • increases numbers of aquaporin-2 channels in collecting duct of nephron

      • stops you from peeing and maks you thirsty

structure classifications of anterior pituitary hormones ?

structure:

• steroid horm.: cholesterol derivative; requires carrier proteins to trravel

  • cholesterol is nonpolar so it crosses the membrane and bind intracellular to receptors → forms complex → travels to nucleus and changes transcription of DNA (using a transcription factor)

  • “-oid, -ol, -one”

• amino acid horm.:

  • catecholamines: very polar so can’t pass through membr. → binds instead to receptor w/ secondary messenger pathway → signal transduction

    • adrenaline and non-

  • thyroid: binds intracellular although polar

    • T3 and T4

• peptide horm.: protein derived so MUST be polar (same mech. as catecholamines)

  • + post-translational modification in golgi → released via exocytosis

  • insulin and ghrelin

what do catecholamines and peptide hormones bind to ?

GPCR:

1. horm. ligand binds to GPCR (G-protein coupled receptor) and changes its shape (+ alpha subunit)

2. GDP GTP exchange

3. alpha subunit dissociates

4. alters enzyme activity

5. enzyme converts ATP into an active 2nd messenger (cAMP)

6. cAMP activates PKA (protein kinase A) which gives cellular response

effect classifications of anterior pituitary hormones ?

“FLAT PEG”

• direct (DID the job w/o outside help)

  • P: prolactin: increases milk prod.

    • inhibited by PIF (prolactin inhibiting factor) (dopamine)

  • E ?

  • G: GH (growth hormone) increases linear growth

• tropic (has help from secondary messengers)

  • F L: hypothalamus releases GNRH → anterior pit. releases LH and FSH → hits gonads → releases primary sex hormones (direct) > FSH leads to estrogen in females and spermatogenesis in males and LH leads to progesterone and ovulation in females and testosterone in males

  • A: hypothalamus releases CRF (corticotropen releasing factor) → hits anterior pituitary and releases ACTH (adreno-cortico tropic horm.) → hits adrenal cortex → secretes glucocorticoids (cortisol “stress horm.”) → increases rate of gluconeogenesis and regulates metabolism

  • T: hypothalamus releases TRH → hits anterior pit. and releases TSH → hits thyroid gland and releases T4 (thryoxine) and T3 (triiotothyronine)

    • T3 and 4 increase basilmetabolic rate (how many calories you burn just standing there: (BMR) (cell respiration)

      • increase = weight loss, nervousness; decrease = weight gain, cold intolerance, depression

what is calcitonin ?

tones down serum calcium (Ca in blood)

• comes from parafollicular cells

what is the parathyroid gland ?

releases horm. which increases serum Ca

what is the adrenal gland ?

3 layers: outer to inner: G (glomerulosa- releases aldosterone/salt) - F (fasciculata- releases cortisol/sugar) - R (reticularis- releases androgen/sex)

what is the endocrine tissue of the pancreas ?

islets of langerhans:

• alpha cells secrete glucagon: opp. (released when decrease) ; stimulates glycogenolasis (breakdown of glycogen)

• beta cells secrete insulin:

  • released after meal when blood-glucose conc. is high —> glucose uptake by cells

  • regulates anabolic processes (fat and protein)

• delta cells secrete somatostatin (stops everything)

*sugar regulation

melatonin vs cortisol ?

• melatonin: sleep; from pineal gland

• cortisol: awake

what is the thymus gland ?

by sternum- allows for maturation of T cells

respiratory system overview ?

air in (N) → oxygenate blood → CO2 out

respiratory system anatomy ?

• nasal cavity

• pharynx (air and food)

• larynx (only air)

• trachea

  • flap b/w = epiglottis

  • esophagus is posterior

• lungs

  • resting state is collapsed !

  • 2 layers: visceral plura (inner/ON lung) vs parietal plura (attached to chest wall)

    • space b/w = intraplural space (IPS) which has negative pressure that keeps the layers together

• bronchus → bronchioles → alveoli

  • alveoli is where blood picks up O2 since PO2 here is higher than in artery so O2 diffused into artery (CO2 moves into alveoli since it’s opposite)

    • this is called countercurrent exchange

• diaphragm

how do we breathe ?

lungs