Errors & Explanations

What type of images do diverging lenses produce?

Virtual, upright

What does parathyroid hormone do?

• Promotes osteoclast activity → raises blood calcium levels

• Activates Vitamin D (calcitriol), which also raises blood calcium levels (but Vitamin D does so in order to replace the broken-down bone with newer, stronger bone)

What does calcitonin do?

Lowers osteoclast activity → decreases blood calcium levels

What is gamma decay?

When a high-energy photon is released from a nucleus but no particles are lost, so the mass of the atom is unchanged

Where are chief cells located and what do they do?

Gastric glands of the stomach; they secrete pepsinogen

Where are parietal cells located and what do they do?

Gastric glands of the stomach; they secrete HCl and intrinsic factor (which helps in absorbing Vitamin B12)

Where are mucous cells located and what do they do?

Gastric glands of the stomach; they secrete mucus (which has bicarbonate that protects the stomach lining)

Where are G-cells located and what do they do?

Pyloric glands of the stomach; they secrete gastrin, a peptide hormone that increases HCl secretion by parietal cells and signals stomach to contract + mix its contents

What is the formula for elastic potential energy?

U = (1/2)kx²

Where is rRNA (ribosomal RNA) synthesized?

The nucleolus

What are the two names for transmission of genetic material without a nucleus?

Cytoplasmic or extranuclear inheritance

What do lysosomes do?

They hydrolize (break down) substances from endocytosis and cellular waste products using hydrolytic enzymes

What do endosomes do?

Transport, package and sort cell material traveling to and from the membrane

Describe the rough endoplasmic reticulum

Studded with ribosomes which allows for protein translation

Describe the smooth endoplasmic reticulum

• No ribosomes, mainly site of lipid synthesis

• Detoxifies some drugs

• Transports proteins from rough ER to Golgi apparatus

What is autolysis

When lysosome releases its hydrolytic enzymes into the cell, resulting in cell death

Describe the Golgi apparatus

Stack of membrane-bound sacs; receives materials from ER and can modify them in various ways (adding carbohydrates, phosphates or sulfates); directs materials where they need to go and secretes them via exocytosis

What are three roles of peroxisomes?

1) Break down very long fatty acid chains
2) Help form phospholipids
3) Use some of its enzymes in the pentose phosphate pathway

What are the three components of the cytoskeleton?

Microfilaments, microtubules, and intermediate filaments

What are three roles for microfilaments?

1) Physically protect the cytoskeleton (they’re made of polymerized rods of actin which makes them resistant to compression)

2) Interact w/ myosin and use ATP to generate movement

3) Play a key role in cytokinesis by forming cleavage furrow, then contracting into a small ring to split cell into two daughter cells

What are the 4 types of tissue?

1) Epithelial
2) Muscle
3) Connective
4) Nervous

What is the parenchyma?

The functional part of the organ, usually formed by epithelial cells

What is the basement membrane?

A layer of connective tissue under epithelial cells that holds them together as one unit

What are 3 types of epithelial cells?

1) Cuboidal (cube-shaped)
2) Columnar (tall/thin)
3) Squamous (flat, scale-like)

What is the stroma?

The support structure of an organism, usually formed by connective tissue (e.g. bone, cartilage, blood, ligaments)

How and where is prokaryotic DNA stored?

In a single circular molecule of DNA in the nucleoid region (there is no nucleus)

What are 3 similarities between eukaryotes and archaea?

1) They start translation with methionine
2) They associate DNA w/ histones
3) They share some RNA polymerases

How many pascals in 1 atm?

101,325 Pa

Bacilli

Rod-shaped bacteria

Spirilli

Spiral-shaped bacteria

Cocci

Spherical bacteria

Obligate aerobes

Bacteria that need oxygen for metabolism

Facultative anaerobes

Bacteria that can switch between aerobic and anaerobic metabolism

Obligate Anaerobe

Bacteria that cannot use oxygen for metabolism and ARE harmed by its presence

Aerotolerant Anaerobe

Bacteria that can’t use oxygen for metabolism but are NOT harmed by its presence

What are the two parts of the envelope in a prokaryotic cell?

1) Cell wall
2) Cell membrane

Describe gram-positive cell walls in bacteria

1) Contain thick layer of peptidoglycan: a polymer consisting of sugars and Amino acids, provides structure and may protect against immune system of host organism
2) Contains lipoteichoic acid - unclear role, may activate human immune system

Describe gram-negative cell walls in bacteria

1) Have very thin walls, some peptidoglycan but much less than gram-positive
2) Between the cell wall and cell membrane is the periplasmic space
3) There’s also an outer membrane w/ phospholipids and lipopolysaccharides (which trigger human immune response way more than lipoteichoic acid in gram-positive)

What are three parts of the flagellum in bacteria, and how do they relate to each other?

The filament (hollow tubule, composed of flagellin) is connected to the basal body (complex, generates torque that allows for motion) via the hook

What’s the difference between eukaryotic and prokaryotic ribosomes?

Eukaryotic ribosomes: 40S and 60S subunits
Prokaryotic ribosomes: 30S and 50S subunits

Plasmid

Small, circular DNA molecule that isn’t part of organism’s genome and can replicate independently, but may confer an advantage

Episomes

A type of virulence factor (trait that increases pathogenicity) that integrates into the bacteria’s genome

Describe the 3 types of genetic bacterial recombination

1) Transformation

• Bacterium integrates foreign genetic material - usually material that’s spilled over from another bacterium that was lysed

• Many gram-negative rods are capable of transformation

2) Conjugation

• Bacterial equivalent of sexual reproduction

• One bacterium needs the necessary sex factor (a plasmid) to generate a pilus, which creates a conjugation bridge that it uses to donate the sex factor to another bacterium, and so on…

• The best studied example is the fertility factor (F) in E. coli…sometimes the F plasmid becomes integrated into the genome of a bacterium, in which case it tries to donate its entire genome to another bacterium (but the bridge usually breaks before that happens)

  • These bacteria are labeled Hfr (high frequency of recombination

3) Transduction

• A bacteriophage (virus that infects bacteria) reproduces inside a bacterium, stealing some of that bacterium’s DNA during reproduction. The virus then infects another bacterium and incorporates that DNA into the second bacterium’s genome.

Transposon

Genetic element capable of inserting and removing itself from the genome

Capsid

Protein coat for a virus

Positive sense RNA virus

Has a strand of RNA that can be directly translated into proteins

Negative sense RNA virus

Has an RNA template strand that’s used to produce a complementary strand, which is then used for protein synthesis (they require RNA replicase to ensure complementary strand is synthesized)

Retrovirus

Contains two identical strands of RNA and an enzyme called reverse transcriptase, which uses this RNA to synthesize DNA that then gets integrated into the host cell’s genome

Extrusion

Method by which viral progeny spread: a virion fuses with the cell membrane, thus keeping the cell alive and allowing the virus to continue its life cycle

Prion

Subviral protein particle that causes disease by triggering the misfolding of other proteins (usually changing alpha-helix to beta-pleated sheet)

Viroid

Small pathogen that infects plants, has very short single-stranded RNA (there are a few that affect humans too)

Lytic cycle

One of two possible cycles for a bacteriophage, in which the virions reproduce and fully take over the host cell, causing it to lyse and the virions to spill out and infect other bacteria. Bacteriophages in this cycle are considered virulent.

Lysogenic cycle

One of two possible cycles for a bacteriophage, in which the bacteriophage turns into a prophage: integrates into the genome of the host bacterium and gets replicated as the host reproduces

What are the phases of the cell cycle?

Interphase: G1, S, G2; Mitosis: M

G1 stage

First phase of cell cycle: cells create organelles (mitochondria, ER, ribosomes) and grow in size. There’s also a restriction point which ensures that certain criteria are met before entering S phase (e.g. cell must contain proper complement of DNA). The main protein that controls this checkpoint is p53.

S Phase

Second phase of cell cycle: cell replicates its genetic material so that two identical daughter cells can be formed. Each chromosome is replicated to form two identical sister chromatids bound together at a centromere

G2 Stage

Third phase of cell cycle: checkpoint during which cell checks that DNA has been replicated properly and there are enough organelles and cytoplasm for two daughter cells (p53 protein plays a role in this).

What are the molecules responsible for the cell cycle?

Cyclins and cyclin-dependent kinases (CDKs). Cyclins bind to CDKs, which then phosphorylate transcription factors that promote transcription of genes needed to reach next stage in cell cycle.

Describe microtubules

Hollow, made of protein called tubulin, run throughout the cell and act as main pathways for motor proteins dynein and kinesin to carry vesicles

What is the structure of eukaryotic flagella and cilia?

9+2 structure: 9 pairs of microtubules surrounding a central pair

Centrosome

Region in animal cell outside the nucleus that contains two centrioles

Hydroxyurea

DNA replication inhibitor used to arrest cells in same stage of cell cycle so they can be studied together

What’s the very end of the small intestine called?

The ileocecal valve (because it connects the ileum with the cecum)

Describe the cecum

• The first part of the large intestine

• An outpocketing that accepts fluid from the ileocecal valve

• Attachment site of the appendix

Describe the colon

• Second part of the large intestine

• Consists of four parts: ascending, transverse, descending, sigmoid

• Main function is to absorb water and salts from leftover undigested food - it then concentrates the remaining material into feces

• Small intestine absorbs more water than colon

Which two fatty acids are crucial to maintaining membrane fluidity?

Linoleic acid and linolenic acid (polyunsaturated)

Centriole

Paired structure made of microtubules, responsible for correct division of DNA - the pair splits up during prophase of mitosis

Spindle fibers

Made of microtubules, radiate out from separated centrioles during prophase

Asters

Fibers formed by the centriole that anchor it to the cell membrane during prophase

Kinetochores

Protein structures located on the centromeres of chromatids that serve as attachment points for the spindle fiber apparatus during prophase

What happens during prophase?

1) Chromatin condenses into chromosomes
2) Spindle forms from centrioles
3) Nuclear membrane dissolves and nucleolus disappears

What happens during metaphase?

Chromosomes align at the metaphase plate as a result of interactions between the kinetochore fibers and the spindle

What happens during anaphase?

Sister chromatids separate (pulled to opposite ends of cell due to shortening of kinetochore fibers)

What happens during telophase?

1) Spindle apparatus disappears
2) Nuclear membrane and nucleolus reappear
3) Chromosomes uncoil and divide between two daughter cells

What happens during cytokinesis?

Separation of cytoplasm and organelles between daughter cells

What are 3 types of beta decay?

1) B(-)
2) B(+)
3) Electron capture

What are the 3 types of magnetism found in different materials?

1) Diamagnetic: Substance has no unpaired electrons, weakly repelled by magnetic field (not magnetic)
2) Paramagnetic: Substance has unpaired electrons, weakly attracted to magnetic field but not magnetic when field is removed (bc then the dipoles randomly reorient)
3) Ferromagnetic: Substance has unpaired electrons, strongly attracted to magnetic field

Fluorescence

Absorption of a photon (in UV or visible region) by a fluorophore, enabled in a conjugated compound

How do antibodies bind to their antigens?

Via noncovalent interactions (e.g. hydrogen bonding)

Epitope

Region on an antigen which an antibody binds to (usually a poypeptide sequence)

Western Blot

1) Protein of interest is separated via electrophoresis
2) Antibody binds to target protein, causing a band to appear
* Sometimes, a blocker is used to prevent the antibody from binding non-specifically

Which two amino acids are rarely found in alpha-helices, and why?

1) Glycine bc it’s too flexible
2) Proline bc it’s too rigid (introduces kinks in the chain)

What are three general types of carrier proteins?

1) Uniport: Transports one type of molecule
2) Antiport: Transports two types of molecules in opposite directions
3) Symport: Transports two types of molecules in the same direction

Describe ion-exchange chromatography

The beads in the column are coated with cations or anions, and charged particles bond to the beads. The compound left on the beads is then eluted using a salt gradient.

Describe differences in how polar vs. nonpolar compounds behave in chromatography

Polar compounds have a longer retention time (more interaction w/ the stationary phase) while nonpolar compounds have a shorter retention time (more interaction with the mobile phase)

Describe the sarcomere

Z Lines: Vertical lines defining the left and right boundaries
M Line: Vertical line down middle
I Band: Only thin filaments
H Zone: Only thick filaments
A Band: All of thick filaments (including overlap with thin)

Describe enzyme-linked receptors

• Proteins consisting of three domains: catalytic, membrane-spanning, and ligand-binding

• Binding to the ligand-binding domain activates the catalytic domain and sometimes induces a second messenger cascade

Describe receptor tyrosine kinases (RTKs)

• Type of enzyme-linked receptor protein

• They have a monomer that dimerizes upon binding to a ligand, which then induces autophosphorylation and also causes it to phosphorylate other enzymes

Formula for hydrostatic pressure

P = (Density of fluid)(g)(Height/depth)

Formula for buoyant force

F = (Density of fluid)(g)(Volume of fluid displaced)

Formula for osmotic pressure

P (denoted by pi symbol) = iMRT

• i = van ‘t Hoff factor

• M = molarity

• R = ideal gas constant (0.0821)

• T = temp (K)

How is meiosis different from mitosis?

1) Meiosis has two rounds of division while mitosis only has one
2) In prophase I of meiosis, homologous chromosomes pair up and intermingle (synapsis) which doesn’t happen in mitosis
3) In metaphase I of meiosis, homologous chromosomes line up on the metaphase plate across from each other, held by one spindle fiber. But in mitosis, each homologous chromosome is lined up on the metaphase plate by two spindle fibers

Describe meiosis I

• Unlike mitosis, generates two haploid (not diploid) daughter cells (reductional division)

Describe meiosis II

• Results in four haploid daughter cells

• Similar to mitosis, ploidy of cells is maintained (equational division)

Describe the difference between homologous pairs and sister chromatids

• A homologous pair consists of two separate chromosomes, one from each parent

• Sister chromatids are two identical DNA strands organized at the centromere

• 92 chromatids = 46 chromosomes = 23 homologous pairs

What are the main structural proteins found in the body?

Collagen, elastin, keratin, tubulin, and actin

Describe collagen

• Most abundant protein in the body (30% of total protein mass)

• Found throughout body, key part of connective tissue

• Triple helix structure

• Important for strength and flexibility

Describe elastin

Important connective protein, primarily acts like a spring to help tissue maintain shape

Describe keratin

• Intermediate filament protein found in epithelial cells

• Plays roles in cell structure and regulation

• Main component of hair and nails

Describe actin

• Makes up microfilaments and the thin filaments of myofibrils

• Most abundant protein in eukaryotic cells

• Has a positively and negatively charged end, which allows motor proteins to travel along it in one direction