Bio

4 Postulates of Cell Theory

1. all living things are composed of cells

2. The cell is the basic functional unit of life

3. cells arise only from preexisting cells

4. Cell carry genetic info in the form of DNA, which is passed down generations

Nucleolus

a subsection of the nucleus in which ribosomal RNA (rRNA) is synthesized

Nucleoid

What prokaryotes have instead of a true nucleus

Rough ER (RER)

Studdeed with ribosomes, which permit translation of proteins destined for secretion

Smooth ER (SER)

Used for lipid synthesis and detoxification

Golgi Apparatus

consists of stacked membrane-bound sacs in which cellular products can be modified, packaged, and directed to specific cellular locations.

Actin microfilaments

composed of actin. They provide structural protection for the cell and can cause muscle contraction through interactions with myosin. They also help form the cleavage furrow during cytokinesis in mitosis.

Intermediate Filaments

are involved in cell-cell adhesion and maintenance of the integrity of the cytoskeleton; they help anchor organelles. Common examples include keratin and desmin.

Microtubules

composed of tubulin. They create pathways for motor proteins like kinesin and dynein to carry vesicles. They also contribute to the structure of cilia and flagella, where they are organized into nine pairs of microtubules in a ring with two microtubules at the center (9 + 2 structure). Centrioles are found in centrosomes and are involved in microtubule organization in the mitotic spindle.

Parenchyma

the functional parts of the organ

Connective Tissue types

bone, cartilage, tendons, ligaments, adipose tissue, and blood

Prokaryotes

• no membrane-bound organelles

• have a nucleoid

• perform the ETC using their cell membrane

• have small ribosomes (30S and 50S)

• multiply thru binary fission

Plasmids

extrachromosomal material, which can be incorporated into prokaryote DNA (if so, becomes an episome). Can increase bacterial genetic recombination.

Archaea

extremophiles, divide by binary fission

Bacteria

can be mutualistic or parasitic to humans. They can have one or multiple flagella, and use chemotaxis to find stuff.

Obligate aerobes vs. obligate anaerobes

aerobes need oxygen, while anaerobes die in the presence of oxygen

Facultative anaerobes vs. aerotolerant anaerobes

Facultative don’t care at all about oxygen, while aerotolerant can surive in oxygen, but cannot use it for metabolism

What controls the movement of solutes into and out of bacteria?

The cell wall and cell membrane, which form the envelope

Gram-positive bacteria

bacteria have a thick cell wall composed of peptidoglycan and lipoteichoic acid. The purple ones

Gram-negative bacteria

have a thin cell wall composed of peptidoglycan and an outer membrane containing phospholipids and lipopolysaccharides. The pink ones.

Transformation

Outside materials comes into cell and incorporates

Conjugation

transfer between bacteria, almost like sex, but using a conjugation bridge

Transduction

a virus infects the cell and adds DNA

Transposons

can go anywhere on the genome, move around, and delete themselves

The Bacterial Growth Pattern

1.       The bacteria adapt to new local conditions during the lag phase.

2.        Growth then increases exponentially during the exponential (log) phase.

3.       As resources are reduced, growth levels off during the stationary phase.

4.       As resources are depleted, bacteria undergo a death phase.

What do bacteriophages use their tail sheath and fibers for?

tail fiber to attach to bacteria, and sheath to inject their genetic material

Retroviruses

contain a single-stranded RNA genome, from which a complementary DNA strand is made using reverse transcriptase. The DNA strand can then be integrated into the genome.

*are the chronic infections viruses*

Positive vs. negative sense

Single-stranded RNA viruses may be positive sense (that can be translated by the host cell) or negative sense (which requires a complementary strand to be synthesized by RNA replicase before translation).  

Positive: infect right away
Negative: requires a viral enzyme to make an RNA strand that the host ribosome can read and create viral proteins

Lytic vs. Lysogenic Cycle

Lytic: virus produces massive numbers of new virions, until the cell lyses (virulent)

Lysogenic: the provirus can remain in the genome indefinetly or may leave the genome in response to a stimulus

Prions vs. Viroids

Prions: infectious proteins that trigger misfolding of other proteins (typically convert α-helix into ß-pleated sheets)
Viroids: a plant pathogen that inactivates their genes.

Peroxisomes

contain hydrogen peroxide and can break down very long chain fatty acids via ß-oxidation. They also participate in phospholipid synthesis and the pentose phosphate pathway.

What produces the Myelin on neurons in the CNS and PNS

CNS: oligodendrocytes

PNS: Schwann Cells

Astrocytes

take part in the blood-brain barrier

Ependymal Cells

line the ventricles and produce cerebrospinal fluid

Absolute Refractory Period

no amount of stimulation will trigger another AP

Relative Refractory Period

a really greater than normal amount of stimulation could cause an AP

Sensory Neurons

afferent (ascend towards the brain)

Motor Neurons

efferent (exit the spinal cord towards the body)

Monosynaptic Reflex

a sensory (afferent, presynaptic) neuron fired directly onto a motor (efferent, postsynaptic neuron) … (knee-jerk)

Polysynaptic Reflex

a sensory neuron may fire directly onto a motor neuron, but interneurons are used as well … (stepping on a nail)

Fertilization (5 terms)

occurs in the ampulla of the fallopian tube, where the sperm penetrates the corona radiata and zona pellucida by secreting acrosomal enzymes. Once it passes through and injects its nucleus, it causes the cell to have a cortical reaction, in where a release of calcium occurs which depolarizes the cell, this prevents fertilization by other sperms and increases metabolic rate for the zygote

Zygote

the fertilized egg before dividing

Embryo

the zygote after dividing

Blastocyst

the clump of cells that implants in the endometrium

Embryonic Development Sequence

Fertilization → cleavage (division) → morula → blastulation → gastrulation

Blastulation

Going form a solid clump of cells (morula) into a blastula. The embryo now has a fluid-filled space which creates space for cell movement and separates self from support cells.

Blastocoel

The fluid-filled space of a blastula

Trophoblast

The layer of cells in the blastula that will form the plancetal structures

Chorion

Contains chorionic villi, which penetrates the endometrium and creates the interface between maternal and fetal blood

Allantois

involved in early fluid exchange between the embryo and the yolk sac

Amnion

lies just inside the chorion and produces amniotic fluid (really the most inner layer of the placenta)

What is Grastulation

happens after blastulation, and is the process of making 3 layers of cells (the ectoderm, mesoderm, and endoderm) … It also establishes the cranial and caudal ends, as well as left to right

Ectoderm

becomes epidermis, hair, nails, and the epithelia of the nouse, mouth, and anal canal, as well as the nervous system (including adrenal medulla) and lens of the eye

Mesoderm

becomes much of the musculoskeletal, circulatory, and excretory systems.  It also gives rise to the gonads and the muscular and connective tissue layers of the digestive and respiratory systems, as well as the adrenal cortex

Endoderm

becomes much of the epithelial linings of the respiratory digestive tracts and parts of the pancreas, thyroid, bladder, and distal urinary tracts

Neurulation

Formation of the neural tube (by giving rise to 3 germ layers)

Notochord

induces a group of overlying ectodermal cells to form neural folds surrounding a neural groove

Nueral Folds

fuse to form the neural tubes, which becomes the central nervous system … the tip of each neural fold contains neural crest cells

Neural Crest Cells

become the peripheral nervous system (sensory ganglia, autonomic ganglia, adrenal medulla, and Schwann cells), as well as specific cell types in other tissues (calcitonin-producing cells of the thyroid, melanocytes in the skin, and others)

Teratogens

substances that interfere with fetal development

Specification

the process is still reversible

Determination

complete commitment

Differentiation

process of becoming the next cell

specification → determination → differentiation

Totipotency

(can become ANY cell) Any cell type in the developing embryo or in extraembryonic tissues (amnion, chorion, placenta)

Pluripotency

(can become any of the cells derived from the primordial endo, ecto, and mesoderm) Any cell type in the developing embryo

Multipotency

(stem cell that can become a specialized cell type within a specific tissue or organ lineage) Any cell type within a particular lineage (ex. the hematopoietic stem cells)

Fetal Circulation

Fetal blood is not in contact with the mom’s bc of a multitude of risks. It carries fetal hemoglobin (HbF), which has higher affinity for oxygen, making diffusion on capillaries located in the planceta to occur. They also have shunts, which are like blockades so that a lot of blood doesn’t enter and damage tissues that are not “ready” yet.

What are the 3 shunts in fetuses, what vessels/chambers are connected, and what organs are bypassed?

Foramen Ovale: right atrium to left atrium (lungs)
Ductus Arteriosus: pulmonary artery to aorta (lungs)

Ductus Venosus: Umbilical vein to inferior vena cava (liver)

What happens during the first trimester

Organogenesis (development of the major organs)

What happens during the second trimester?

Lots of rapid growth, begins to move, face developsW

What happens during the third trimester?

More growth and transfer of antibodies from mom

What happens in G1 phase of Mitosis

cell creates organelles for energy (more mitochondria), and increases cell size

Chromatin vs. Chromatids vs. sister chromatids vs. chromosome

Chromatin: loose DNA + proteins
Chromatid: one condensed unit of DNA (essentially an L-shaped chromosome
Chromosome: can look like a chromatid (l) or an (x), but it just has to have a centromere to be a chromosome
Sister chromatids: a chromatid and its attached clone from after DNA replication, when it’s x-shaped

Briefly explain mitosis

We start with chromatin, then replicate them during S phase, and condense it into chromosomes (gives us 46 chromosomes, each attached to their identical clone, hence 92 chromatids … the # of chromosomes is always the # of centromeres) ... they then align on the mitotic plate and get separated (PMAT), meaning each cell now has 46 chromosomes and 46 chromatids

Briefly explain Meiosis

We start with chromatin, during S phase we duplicate it, after it condenses and forms chromosomes (46 chromosomes, and 92 chromatids), but during Porphase 1 the maternal and paternal chromosomes form a tetrad (23 tetrads if you will), they cross over and form novel chromosomes. They then align on the mitotic plate and the tetrads get broken up and carried to different cells. We now have 2 cells with each 23 new chromosomes and 46 chromatids. We then align them again in the mitotic plate and separate the sister chromatids. Given rise to 4 cells, each with 23 chromosomes, and 23 chromatids

Sertoli cells vs. Leydig cells

Sertoli cells nourish sperm
Leydig cells secrete testosterone

Describe Spermatogenesis

Remember, we start with our diploid stem cell, spermatogonia (the OG that’ll be used to create the sperms). After they replicate their DNA (S stage), they develop into diploid primary spermatocytes. The first meiotic division occurs, producing haploid secondary spermatocytes. Then they undergo meiosis II to generate haploid spermatids. Once these mature, they become mature spermatozoa

Spermatogonia → primary spermatocytes → secondary spermatocyes → spermatids → spermatozoa

o   -onia: the OG stem cells

o   Primary: still diploid, hasn’t gone or finished meiosis

o   Secondary: haploid

o   -tids: almost ready

o   -ozoa: mature gametes

Define Oogenesis

Here the diploid stems cells are all gone by the time the baby is born, aka no more oogonia once born. Meaning all girls are born with their primary oocytes (they are still diploid but arrested at prophase 1). Later in life, every menstrual period will “select” one primary oocyte, and have it continue to down meiosis to form a secondary oocyte (haploid) which will get arrested at metaphase 2, and it won’t complete the remainder of meiosis 2 until its fertilized.

Effects of LH (luteinizing hormone) in males vs. females

Males: LH causes interstitial cells to produce testosterone

Females: LH causes the corpus luteum (the remains of the previous ovulation), to secrete progesterone

→ helps with hormone secretion ←

Effects of FSH (follicle stimulating hormone) on males vs. females

Males: FSH stimulates Sertoli cells and triggers sperm maturation

Females: FSH allows for estrogen to be secreted, which aids in the development and maintenance of the female reproductive system and female secondary sexual characteristics

Estrogen vs. Progesterone in terms of the menstrual cycle

Estrogen: causes the regrowth of the endometrium
Progesterone: maintains it for implantation

Follicular Phase

During this phase the ovum is maturing and the endometrium is finishing shedding / just began to regrow

Ovulation occurs bc of what?

LH surge

Luteal Phase

LH causes the formation of the corpous lutem, while the endometrium finishes growing

Menstruation

The shedding part. Caused by the decrease in estrogen and progesterone … which had build up bc of LH and FSH but once there’s too much it causes a negative feedback loop.

Purpose of human chorionic gonadotropin (hCG)

Hormone secreted by the developing fetus into the endometrium to ensure progesterone and estrogen keep being made.

Hormonal outcomes of menopause

ovaries become desensitized to LH and FSH, leading to a drop off of estrogen and progesterone, meaning no more menses. No more estrogen/progesterone removes the negative feedback loop on LH and FSH, so levels rise.

Peptide Hormones

They are made up of amino acids. They are packaged into vesicles and later released via exocytosis.

Made of aa, nonpolar, can’t cross membrane, extracellular receptors … fast onset but short acting

Steroid Hormones

Derived from cholesterol, not water-soluble (nonpolar), can cross the membrane, intracellular/nuclear receptors … slow onset but longer acting

Amino Acid-Derivative Hormones

like the name says, they are made of aa, usually one to two, with a few modifications. They are less predictable. For example, epinephrine and norepinephrine bind to GPCR, while thyroid hormones bind intracellularly.

Direct vs. Tropic Hormones

Direct hormones act directly on their target, while tropic hormones bind to some endocrine tissue that will then secrete another hormone

Thyroid and Parathyroid effect on Calcium

So, the thyroid secretes Calcitonin, which causes calcium to be stored in the bones (essentially it removes calcium from the blood), while the parathyroid secretes PTH (parathyroid hormone), which causes the release of calcium from the bone (adds calcium back into the blood).

Corticosteroids

hormones produces by the adrenal gland

Glucocorticoids

as the name suggests, these guys are involved with glucose. They are cortisol and cortisone (popularly known as the stress hormone). So, during stress your body wants to be awake, so we will increase gluconeogenesis, but we will stop protein synthesis. (make sugar, halt protein production)

Mineralocorticoids

Remember, if Vasopressin causes water reabsorption, then aldosterone causes sodium reabsorption. … This is how: low BP causes the juxtaglomerular cells to secrete renin, which cleaves angiotensinogen to its active form, angiotensin I. It then gets converted to angiotensin II by ACE in the lungs

Renin-angiotensin-aldosterone system: increases sodium and water reabsorption in the distal convoluted tubule (DCT) and collecting ducts

Cortical Sex Hormones

the adrenal cortex also releases androgens and estrogens, which help the different sexes physiologically and phenotypically. However, this is more important in females as they rely more heavily on the adrenal cortex for androgens, since males already produce testosterone in the testes

Adrenal Medulla

responsible for releasing epinephrine and norepinephrine

Glucagon

made in alpha cells of pancreas, when you have hypoglycemia, this causes gluconeogenesis and glycogenolysis

Insulin

made in the beta cells of pancreas, when you have hyperglycemia, this causes glycogenesis, and fat and protein synthesis

Somatostatin

made in the delta cells of pancreas; inhibitor of both insulin and glucagon … released when we have high blood glucose and amino acids