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MCAT Biology 2


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What is a phospholipid made of?
phosphate group
2 fatty acid chains
proteins containing a carbohydrate portion
Spherical structure formed when amphipathic molecules spontaneously aggregate in aqueous solution, turning polar ends toward the solution and nonpolar ends toward each other
Difference between Prokaryote and Eukaryote Plasma Membrane
E-contains steroids like cholesterol
P-contains only steroid like hopanoids
Membrane model
Fluid Mosaic model in which parts can only move laterally.

The membrane is asymmetrical.

Fluidity moderated by cholesterol.
Types of prokaryotes
Archaea--like bacteria and eukaryotes, extreme environments

Bacteria--peptidoglycan cell walls
What do organisms require in order to grow and what are the types?
1. Carbon: autotrophs ( fix CO2) or heterotrophs (organic molecules)

2. Energy: chemotrophs (organic/inorganic matter) or phototrophs (light)

3. Electrons from H+ usually:
What can acquire energy from an inorganic source other than light?
Prokaryotes: lithotrophs (electrons acquired from inorganic matter) or organotrophs (electrons acquired from organic matter)
Bacteria fix nitrogen

requires 2 genera of chemoautotroph prokaryotes
Characteristics of the Structure of Prokaryotes
No nucleus, only a single double stranded molecule of DNA twisted around histones in supercoils forming a nucleoid

Two major shapes: cocci (round) and bacilli (rod shaped). Also spirilla (rigid) and spirochete (gave rise to flagella).

no complex, membrane bound organelles

contain both RNA and DNA, so have ribosomes
Electrical Gradient
points in the direction a + charge would move
Semipermeability depends upon...
size and polarity

larger size and more polar = less permeable

ex. natural membrane more permeable to water than sodium--charge difference outweighs size difference
Integral/intrinsic membrane proteins
transverse the membrane and create holes that facilitate leakage or passive diffusion of water.
Transport or carrier membrane proteins
designed to facilitate diffusion of specific molecules across the membrane
facilitated diffusion
Occurs down the electrochemical gradient.

Makes the membrane selectively permeable b/c it's able to distinguish b/w size and permeability depends on lipid solubility and size

Requires carrier proteins.
Active transport
Against gradient...requires energy (ATP)
type of bacteria that has a tail, base plate, tail fiber, capsid, and DNA or RNA and infects bacteria
mature virus outside host
capsid protein coat and contains DNA or RNA, require hosts’ machinery to reproduce
Bacterial Envelope
Includes the cell wall (preventing bursting), periplasmic, and capsule
cytosol more aqueous than environment

most bacteria are hypertonic
cytosol contains the same amount of particles as the environment
cytosol contains less particles
Makes up the bacterial cell wall

Polymer disaccharide chains connected by amino acides.

Elastic and porous, and antibiotics weaken it.
Gram Staining
Staining technique used to ID bacteria.
Gram-positive Staining
thick peptidoglycan cell wall prevents gram stain from leaking out = purple

cell wall 4 times thicker than PM
Gram negative staining
Thin cell wall doesn't retain stain.

Phospholipid bilayer outside cell wall that is more permeable.
long, hollow, rigid, helical cylinders made from the globular protein flagellin.

Rotate counterclockwise to propel bacterium in a single direction...tumbling

Propelled by a hydrogen gradient (not ATP).
Bacterial Reproduction & Recombination
No sexual reproduction and do not undergo meiosis or mitosis.

Genetic Recombination by conjugation, transformation, and transduction.

Reproduce also by binary fission (no recombination).
Binary fission
Bacterial Reproduction:
circular DNA is replicated (DNA polymerase) and cell divides

genetically identical daughter cells
On Bacteria with the F plasmid with the gene coding for the sex pilus (allowing connection for DNA passage)
R plasmid
donates resistance to certain antibiotics.

can be transferred in conjugation.
Proces by which bacteria may incorporate DNA from their external environment into their genome (S & R bacteria)
host DNA incorporated into a virion, so it injects foreign DNA into a new host instead of virulent DNA
Bacterium divides within its cell wall and then one side engulfs the other..forming an ultra-resistant spore...occurs in conditions of lack of nutrients

Germination triggered by nutrients.
Characteristics of Fungi
Eukaryotic heterotrophs that obtain energy by absorption not ingestion (external digestion)

Saprohpytic--feed on decayed matter
Also eat living matter

Septa-cell wall made of chitin

1n dominant

Mitosis takes place in the nucleus

multicellular (except yeast)

Consist of a tangled mass of mycelium or branched hyphae
Sexual Reproduction in Fungi
Occurs between hyphaie from two mycelia of different mating types.

Conjugation bridge formed and the tips of the hyphae produce gametes which forms the zygote, aka zygospore.

Zygospore then separates from hyphae and remains dormant till activated by appropriate environmental conditions, where it undergoes meiosis->haploid cells

Occurs when conditions are bad
Eukaryotic Nucleus
Contains DNA, which cannot leave the nucleus.

Double phospholipid bilayer

RNA exits nuclear pores
In the nucleus

where the subunits of ribosomes are assembled
Phagocytosis and pinocytosis and receptor mediated (clathrin coated pit)
Endoplasmic Reticulum
Continuous with the PM. Separates the cytosol from the ER lumen.
Rough ER
Where transcription and tagging of protein occurs..then small transport vesicles bud off and carry proteins across the cytosol to the golgi
series of flattened membrane bound sacs

organizes and concentrates proteins recieved from rER as they are shuttled across the cisterna

Proteins expelled as secretory vesicles or released as lysosomes
secretory vesicles
may contain enzymes or growth factors

release contents through exocytosis
contain acid hydrolases that break down macromolecules within a cell

pH 5
Smooth ER
lacks ribosomes


makes and stores fat

lipid (steroid, cholesterol) synthesis

produces tryglycerides and store them as fat droplets

oxidize foreign substances

cells containing fat droplets
vesicles in the cytosol
Filaments of the Cytoskeleton
microtubules and microfilaments
larger than microfilaments

rigid hollow tubes made from the protein tubulin

involved in flagella and cilia construction and spindle apparatus
Vitamin A
precursor to all the pigments in rods and cones
Lense in the Eye
converging lens

object outside focal length

image on the retina is real and inverted
small point on the retina containing mostly cones

point on the retina where vision is most acute
colored portion of the eye that creates the pupil

circular and radial muscles

when contracted, the pupil dilates (in the dark)
Ciliary Muscles
When relaxed, they flatten the lense making it less powerful, which moves the focal point away from the lens
controls finely coordinated muscular movements
Medulla oblongata
Controls involuntary breathing movements
Knee jerk reflex
governed by the spinal cord

sensory neurons (located dorsally) receive signals from the environment and motor/efferent neurons carry signals to the muscle/gland (synapse ventrally on the spinal cord)
epinephrine and norepinephrine
neurotransmitters in the postsynaptic of the sympathetic nervous system
where pressure waves are converted to neural signals
Peptide Hormones
water soluble, move freely through the blood but hard to diffuse through cell membrane

use second messenger or membrane receptor
manufactured in the rER as preprohormones
Anterior Pituitary Hormones
FSH, LH, ACTH, TSH, Prolactin, hGH

peptide hormones
Posterior Pituitary Hormones
ADH and oxytocin

peptide hormones
Parathyroid Hormones

peptide hormones
Pancreatic Hormones
Glucagon and insulin

peptide hormones
Steroid hormones
derived from or similar to cholesterol

formed in the smooth ER

lipids--require transport through blood

combine with receptor in cytosol (diffuse through membrane)

acts on transcription levels

from adrenal cortex, gonads, or placenta

ex. aldosterone, cortisol, estroge, glucocorticoids, etc.
Hormones of adrenal cortex
glucocorticoids and mineral corticoids
3 types of hormones
steroid, tyrosine, and peptide
Tyrosine derivative hormones
formed by enzymes in the cytosol or rough ER

thyroid hormones (diffuse thru membrane) and catecholamines (bind to membrane)
Adrenal Medulla Hormones
catecholamines: epinephrine and norepinephrine
Thyroid hormones
T3 and T4

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