Biology ALL

Nucleus: Structure & Function


1. what are relevant structures
2. what is its purpose

Nucleus stores the cell’s genetic information in the form of chromosomes.

It is surrounded by the **nuclear envelope**, which is actually connected to the endoplasmic reticulum.

Within the nucleus is the **nucleolus,** where rRNA is synthesized.

It is the site of DNA and RNA synthesis.

Mitochondria: Structure & Function

Mitochondria is responsible for energy generation within the cell, in the form of oxidative phosphorylation, calvin cycle, and beta-oxidation of fatty acids.

Has a double-membrane, therefore an intermembrane space and inner matrix. The aforementioned processes occur in the matrix, where ox/phos is located on the inner-membrane.

Lysosome: Structure & Function

Functions as the cell’s garbage disposal; breaks down unneeded materials, and works with **endosomes** to move them around.

Endoplasmic reticulum: Structure & Function

Smooth: lipid synthesis, poison/drug detoxification

Rough: protein synthesis.

Golgi Apparatus: Structure & Function

UPS of the cell. Receives, modifies, then ships out cellular materials via vesicles.

What are the components of the cytoskeleton, from smallest to largest?

Microfilaments, intermediate filaments, microtubules.

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Microfilaments: Made of actin fibers, may use ATP to interact with myosin, generating movement.

Intermediate filaments: Made of many different proteins, responsible for structural integrity of the cell.

Microtubules: Made of tubulin strands which project through the cell, acting as “roads” that transport proteins can move across. (such as kynesin and dynein)

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What type of structure allows for the motility of cilia and flagella?

Microtubules, composed in a 9-2 structure, where 9 tubule pairs form an exterior ring around 2 tubules in the center.

what are the four types of tissues

epithelial

connective

muscle

nervous

Key characteristics of epithelial cells:

Primarily function to line the body and its cavities.

Are **polarized:** differing surfaces have varying function

Make up the **parenchyma (functional component)** of an organ.

Exist as simple, stratified, and pseudostratified (1, 2+, 1 layers)

Can be shaped as cuboid, columnar, and squamous.

Key characteristics of connective cells:

Primarily function to support the cell and allow epithelial cells to function.

These make up the stroma of organs.

Secrete materials like collagen and elastin to form an ECM.

What are the methods of bacterial gene transfer? Describe them.

Transformation: foreign gene uptake from environment

Conjugation: sex pili bridging +male and -female bacteria, the +male donates genes to the -female. allows for proliferation and spread of antibiotic resistance.

Transduction: requires viral vectors; bacteriophage transfer of genes.

What are viruses composed of?

nucleic acids and proteins

the proteins make up the capsid

sometimes they have envelopes containing lipids.

What type of gene language do viruses contain? (ssDNA, ssRNA, dsDNA, dsRNA, etc)

single or doublestranded

DNA or RNA

Positive-sense vs. negative sense in viruses

Positive-sense: ssRNA viruses are able to utilize host machinery to directly translate their genome into proteins

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Negative-sense: ssRNA viruses must utilize RNA replicase to synthesize a complimentary strand that then utilizes host machinery to translate their genome into proteins

What is a retrovirus?

A retrovirus containing identical ssRNA strands.

requires RNA reverse transcriptase to synthesize DNA from RNA.

allows for integration of viral genome into bacteria’s.

what are lytic vs lysogenic cycles?

In viruses, they can exist within a host as one of the two stages.

Lytic: virulent form of the virus, it maximizes its usage of its host’s machinery without regard to its survivability-- the virus replicates as much as possible, ultimately killing its host.

Lysogenic: less active form of the virus, it integrates into the host’s genome and becomes very prolific within the organism. It can revert to lytic cycle at any time.

What molecules regulate the transition from one phase of the cell cycle to another?

p53, cyclins, cyclin dependent kinases

Describe the process of mitosis/meosis (or draw it out)

\-What is a kinetochore, spindle fiber, centrosome?

**Mitosis:**

Prophase: dissolution of nuclear envelope, formation of mitotic spindle

Metaphase: homologous chromosomes will line up at the equatorial plate, guided by connected kinetochores by spindle.

Anaphase: hom. chromosomes are separated to opposite ends of the cell.

Telophase: a new nuclear envelope forms, and the cell prepares to split

Cytokinesis: cell splits into two genetically identical ones

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**Meiosis:**

Meiosis 1: separation of homologous chromosomes, parallels mitosis

Meiosis 2: separation of sister chromatids. results in haploid cells.

Males are considered *what* for the X chromosome?

hemizygous.

What is the path sperm will take from formation to ejaculation?

Seminiferous tubules: production of sperm

Epididymus: sperm gain motility, storage until ejaculation

Vas deferens: pathing to

Ejaculatory duct: mixes with seminal fluid

N(othing)

Urethra

Ppenis

What produces fluid necessary for ejaculation?

Prostate, seminal ~~glands~~ vesicles, and bulbourethral glands

Describe the process of spermatogenesis

Primary spermatocyte: S phase has been completed

Secondary spermatocyte: meiosis I has been completed

Spermatid: meiosis II has been completed

Spermatozoa: maturation of cell

Describe the anatomy of a sperm.

Head: contains genetic information. surrounded by acrosome, containing enzymes necessary to penetrate ovum

midpiece: has mitochondria, provides energy for motility

tail: movement

endpiece: movement

both tail and endpiece make up the flagella.

What is a primary oocyte?

Present in all females by birth. These are sex cells arrested in Prophase I of meiosis. They will remain primary until menstruation.

What is a secondary oocyte? How is it formed, what is the byproduct?

Once menarche is reached (first period), an egg will be ovulated, turning into a secondary oocyte, in which it progresses to metaphase II of meiosis until fertilization or dissolution. Cytokinesis at the end of meiosis I is **unequal,** resulting in a polar body with no cytosol.

Describe the anatomy of an oocyte.

Large cell of genetic information surrounded by two layers: zona pellucida and corona radiata.

What hormone triggers the release of two main sex hormones? What are those hormones?

Gonadotropin-releasing hormone (GRH) triggers the anterior pituitary gland to release follicule-stimulating hormone (FSH) and luteinizing hormone (LH)

What is the function of FSH in males?

In females?

FSH in males stimulates the initiation of sperm production at puberty, by stimulation of sertoli cells.

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In females, FSH triggers the release of estrogens, which will cause development of ovarian follicles.

What is the function of LH in males?

In females?

LH in males stimulates the release of testosterone, and the development of secondary sexual characteristics like deepening of the voice and facial hair growth.

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In females, LH causes ovulation.

What are the phases of the menstrual cycle?

Menstruation: Low estrogen, low progesterone

\-shedding of the uterine lining.

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Follicular phase: High estrogen, low progesterone

\-release of FSH and LH, promoting fertility

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Ovulation: Surge of LH, caused by high estrogen

\-release of ovum into fallopian tubes via peritoneal sac

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Luteal phase: Estrogen dropping (but still high), high progesterone

\-preparation to slough menstral endometrium

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Pregnancy and menopause occur outside of these cycles.

What occurs during fertilization?

Sperm interacts with ovum in the fallopian tubes; utilizes enzymes within the acrosome to penetrate the outer layers of the ovum.

Once a bridge is established, sperm’s genetic info goes into ovum, along with the “cortical reaction"

What is the cortical reaction?

Occurs during fertilization in which the sperm that fertilizes the ovum will cause a release of Ca2+ to prevent fertilization by any other sperm, and to support faster metabolism by the zygote.

What happens directly after fertilization?

The zygote will mitotically cleave; that is, differentiate either determinately (develop) or indeterminately (twins). Upon doing so, it is now known as an embryo. It begins its journey from the Fallopian tubes towards the uterus.

What happens directly after formation of an embryo?

Blastulation. The embryo will form a clump of cells known as a **morula** which will hollow out, forming a blastula. It has two different layers, the trophoblastic outer layer, and inner cell mass (future fetus).

It will make it to the uterus, where it will implant itself.

What happens after blastulation, once the blastula makes it to the uterus?

Implantation. Formation of chorion and chorionic villi from trophoblastic cells, the villi penetrating into the endometrial wall and chorion eventually forming the placenta.

Name three early embryonic membranes essential to its development.

Yolk sac: nourishes and develops blood for the embryo

Allantois: fluid exchange between yolk and embryo

Amnion: acts as a shock absorber from movement.

After implantation, what occurs to the blastula?

Gastrulation: the formation of the 3 primary germ layers

What are the three primary germ layers, and what will they develop into?

**Ectoderm:** Nervous system and integument; eye lens, hair, skin, nails.

**Mesoderm:** Musculoskeletal and cirulatory system, gonads, connective tissue.

**Endoderm:** Digestive/respiratory lining, pancreas, thyroid.

Describe the process of neurulation.

1. formation of a notochord by mesodermal cells
2. formation of neural folds; ectodermal cells will overlap
3. formation of neural tube; becomes the CNS

Describe the facets of nutrient exchange between a fetus and its mother.

There are two arteries and one vein that supply the fetus with nutrients from the placenta.

There is no direct blood intermingling.

Gas exchange occurs at the placenta; thus,

The arteries carry **deoxygenated** blood to the placenta.

The vein carries oxygenated blood to the fetus.

Name the three fetal circulation bypasses, and what they bypass

Foramen ovale: bypass lungs

Ductus arteriosis: bypass lungs

Ductus venosus: bypass liver

What is the function of astrocytes?

Nourish neurons, comprise the blood brain barrier.

What is the function of ependymal cells?

Produce cerebrospinal fluid, act as cranial shock absorbers.

What is the function of microglia?

Phagocytotic brain waste removal.

What is the function of oligodendrocytes/schwann cells?

Create myelin sheaths around axons in the CNS/PNS, respectively.

What are three classifications of hormone types?

**Peptide hormones**: amino acids formed by larger proteins that were posttranslationally modified. Peptide hormones act on G-protein coupled receptors, initiates signal cascades. Effects are fast but short lived. Are blood-soluble.

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**Steroid hormones:** derivatives of cholesterol. Transported through the blood via albumin. Act by crossing cell membrane and binding directly to DNA; work via regulation of gene expression. Effects are slow but longer lived.

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**Amino-acid derived hormones**: Epinephrine, norepinephrine (catecholamines), and triiodothyronine, thrydoxin (thyroid hormones)

What are the endocrine organs?

Hypothalamus, pituitary gland, adrenal glands, thyroid, testes, ovaries, pineal gland. (all the glands)

Hypothalamus’s role in the endocrine system

Is the Boss, specifically over the pituitary gland. Is connected via a portal system to the anterior pituitary and regulates it via tropic hormones. Is regulated itself by negative feedback.

Anterior pituitary releases which hormones?

LH, FSH, TSH, ACTH, etc.

Luteinizing hormone

Follicule-stimulating hormone

Thyroid-stimulating hormone

Adrenocorticotropic hormone

Endorphins

Prolactin

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Functions of thyroid-stimulating hormone

Released by anterior pituitary, causes release of T3 (triiodothyrodonine) and T4 (thyrodoxin) (3, 4 iodine respectively)

These regulate basal metabolic rate directly.

Release of calcitonin by thyroid causes decreased blood Ca2+ levels

Functions of adrenal cortex → what hormones does it release? what do those hormones do

Releases adrenal corticosteroids: glucocorticoids, mineralocorticoids, sex cortical hormones (sugar, salt, sex regulating hormones)

Functions of adrenal medulla → what hormones does it release? what do those hormones do

Part of the nervous system, releases epinephrine and norepinephrine. part of the fight/flight response.

Pancreas hormones → what are they and their functions?

Produced by cells called islets of langerhaus

alpha: glucagon (raises blood sugar, increases gluconeogenesis, inhibits glycolysis, increases glycogen breakdown, decreases glycogen synthesis)

beta: insulin (lowers blood sugar, decreases gluconeogenesis, increases glycolysis, increases glycogen synthesis, decreases glycgen breakdown)

gamma: somatostatin (inhibits insulin/glucagon)

Pineal gland hormones → and what do they do?

melatonin, sleep cycle regulation

What is the function of calcitonin? What is the function of T3, T4? What is the function of PTH?

Calcitonin: lowers blood calcium, produced by thyroid

T3, T4: regulate basal metabolism rate

PTH (parathyroid hormone) antagonist to calcitonin, raises blood calcium.

Describe the path air takes during inhalation

Nares (nasal cavity), passes through mucous membranes and hairs to filter out solids.

Pharynx, the back of the mouth

Larynx, guarded by the epiglottis

Trachea, cartilaginous tube lined with protective cilia

Bronchi, same as trachea, just further down

Bronchioles, divided bronchi; increased surface area, turns into

Alveoli, high surface area sites of gas exchange

What protects the high surface area of brionchioles and alveoli from high surface tension?

Surfactants with lower surface tension

What is the membrane surrounding the lungs called?

Pleurae.

Inner side facing the lungs is visceral

Outer side is parietal

Describe the muscles involved with inhalation and exhalation

Inhalation: external intercostal muscles

Diaphragm contracts. increases lung volume, decreasing pressure, forcing air in

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Exhalation: internal intercostal muscles

Diaphragm relaxes. decreases lung volume, increases pressure, expelling air out.

The right atrium and right ventricle are separated by

the tricuspid valve

The left atrium and left ventricle are separated by

the bicuspid valve

(oxygenated/deoxygenated) blood travels through the right side of the heart, heading from ___ to ___.

Deoxygenated blood travels through the right side of the heart, heading from the vena cava to the pulmonary artery.

(oxygenated/deoxygenated) blood travels through the left side of the heart, heading from ___ to ___.

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Oxygenated blood travels through the left side of the heart, heading from the lungs to the aorta (and the rest of the body)

Explain systole and diastole.

Systole: The ventricles empty their contents; the AV valves are closed, semilunar valves are open (atria fill)

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Diastole: The ventricles fill with blood from the aorta; semilunar valves close.

Name the components of the vasculature and their relative sizes.

Arteries carry oxygenated blood away from the heart and towards bodily tissues. They will branch into arterioles and then into capillaries with high surface area for gas exchange into tissues. Arteries are thick and are able to recoil to pump blood out.

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Veins return deoxygenated blood back to the heart from bodily tissues. Venules are the capillary equivalent that turn into veins. Veins are thin walled, but can stretch to accomodate lots of blood. Most of the body’s blood is present in the venous system. They prevent backflow through their valve structures.

Name the components of blood.

Plasma, cells, and platelets.

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Cells: Erythrocytes (RBCs), Leukocytes (WBC), platelets

Function of erythrocytes vs. leukocytes

Carry oxygen vs. immune response

Name granular leukocytes. what are their functions?

basophils, eosinophils, neutrophils. Involved with attacking foreign invaders.

Name agranular leukocytes. what are their functions?

lymphocytes: specific immune response.

monocytes: phagocytotic killer cells.

What are the two types of immunity?

adaptive

innate

What are features of the innate immune system?

Skin: a physical barrier against pathogenic infiltration

GI tract: has acid inhospitable to most pathogens

\-also has gut flora that will outcompete most bacteria

Complement system: proteins that will destroy bacteria, either activated by antibody binding or something else binding.

Interferons: proteins that prevent viral replication & proliferation within cells

What are specific cell types of the innate immune system?

Macrophages: destroy antigens via phagocytosis, delivers a piece of it to MHC cells (I from inside the cell, II from outside the cell) and the MHC will remember it for later.

Describe the functions of neutrophils, basophils, and eosinophils

Neutrophils: destroy bacterial cell walls, when they die they become pus

Eosinophils: release histamine, involved with allergic rxns and parastitic infections. promote inflammation

Basophils: also involved with allergic rxns, release histamine

What are cell types of the adaptive immune system?

B-cells

T-cells: Killer T, helper T, suppressor T, memory T

What is the function and some features of the lymphatic system?

It is a secondary circulatory system that functions to expose immune cells to pathogens in the body. It is where B-cells mature. Nodes get bigger the closer to the center of the body.

What is the path that food will take through the alimentary canal?

Oral cavity

Pharynx

Esophagus

Stomach

Small intestine

Large intestine

Rectum

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Notable mentions: liver, pancreas, gallbladder, salivary glands

What types of glands does the stomach have? In which region? What cell types do those glands have, and what are their functions?

**Body/Fundus: Gastric glands**

Chief cells: produce pepsinogen (zymogen form of pepsin)

Parietal cells: produce H+ ions in the form of HCl

Mucous cells: produce mucous lining

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**Antrum/Pylorus: Pyloric glands**

G-cells: produce gastrin

What are the functions of the excretory system?

Excretion of nitrogenous waste, excess nutrients

Regulation of blood pressure, osmolarity, and pH.

What organs are involved in the excretory system?

Kidneys, ureters, bladder, urethra

What is the functional unit of the kidney?

Nephrons

Describe the path of blood flow within the kidneys

Renal artery → afferent arteriole → glomeruli → efferent arteriole (forms vasa recta which surrounds the loop of Henle)

Describe the path/function of a nephron.

**Proximal convoluted tube**: Uptake of nutrients and secretion of waste.

**Loop of Henle (descending)**: Maximizes water reabsorption (regulation of osmolarity, inconjunction w interstitial space) only permeable to water

**Loop of Henle (ascending)**: Maximizes salt reabsorption (regulation of osmolarity, only permeable to salt ions)

**Distal convoluted tube**: secretion of waste, response to aldosterone (raises blood pressure using water) reabsorption of sodium. Concentrates urine

**Collecting duct**: Point of no return for metabolites. Final determiner of urine concentration.

Glomerulus is responsible for:

absorption and filtration of blood

Proximal convoluted tube (PCT) is responsible for:

reabsorption of sugar via ion cotransport

reabsorption of water and ions into blood

Loop of Henle is responsible for:

management of blood osmolarity via permeability to water (descending) and ions (ascending)

Distal convoluted tube (DCT) is responsible for:

reabsorption

impermeable to water

What part of the nephron is responsible for dealing with overhydration and how?

Diluting segment, the midpoint of the loop of Henle, the only part of the kidney able to make urine more dilute than blood.

What is the function of aldosterone and how is it released?

Aldosterone is a hormone that functions in response to low blood pressure that works to raise it.

When blood pressure is low, **juxtaglomerular cells** will release **renin**.

**Renin** will cleave **angiotensin** in the **liver**. In the **lungs,** angiotensin I is cleaved into angiotension II.

**Angiotensin II** is what stimulates the adrenal cortex to release aldosterone.

What hormone responds to high blood osmolarity and how?

Antidiuretic hormone (vasopressin, ADH) is released by the **posterior pituitary** in response to high blood osmolarity. Causes the retention of fluids to lower blood osmolarity. Inhibited by caffeine and alcohol.

What are the three main layers of skin?

Epidermis

Dermis

Hypodermis

What are the different layers of epidermis?

Strata: (from outermost to innermost)

Corneum: protection from outside, many-layered

Lucidum: present only in hairless skin

Granulosum: keratinocytes die

Spinosum: have langerhans cells

Basale: contain stem cells that produce keratinocytes

What are the layers of the dermis?

Papillary (outer): loose connective tissue

Reticular (inner): blood vessels, sweat glands, hair follicles

What constitutes the hypodermis?

Connective tissue, fatty and fibrous.

What are the three types of muscle?

Skeletal muscle

Smooth muscle

Cardiac muscle

Describe notable characteristics of skeletal muscle

Voluntary movement

Innervated by somatic nervous system

Striated due to long, multinucleated sarcomeres.

Slow-twitch: has myoglobin, aerobic energy source, resistant to fatigue, low power output

Fast-twitch: no myoglobin, anaerobic energy source, prone to fatigue, high power output

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Can use creatine shuttle system in situations of low ATP.

Describe notable characteristics of smooth muscle

Involuntary movement

Innervated by autonomic nervous system

Non-striated

Myogenic-activity; doesn’t require nervous system to act.

Describe notable characteristics of cardiac muscle

Involuntary movement

Has characteristics of both skeletal and smooth muscle

Innervated by autonomic nervous system, but also has myogenic activity, and is also striated.

What is the path of depolarization within cardiac muscle?

SA node → AV node → bundle of His → Purkinje fibers

Describe the components of a sarcomere

Thick and thin filaments

Thick: myosin

Thin: actin, troponin, tropomyosin

What are the meanings of M-line, I-line, A-line, and H-line?

M-line: Middle of actin (thick) filaments

I-band: (I is the thinnest) therefore region of only thin filaments

A-line: All of the thick filaments

H-band: thick filament ONLY