Cellular level of organization

cytology

the study of cells

cell fun facts

-there are 200 different types of cells in the human body

-one cells (the parent cell) divides into 2 cells (daughter cells) in a process called cell division or mitosis

parts of a cell

-plasma membrane (cell membrane)

-cytoplasm (cytosol and organelles)

-nucleus (control center and DNA)

plasma membranes; 2 major functions

1) regulates the passage of materials into and out of the cell

2) helps communication between and amoung cells and their outside environment

plasma membrane; structure

the fluid mosaic model best describes this flexible, yet sturdy barrier: continually moving sea of lipids that contains a mosaic of many different proteins and carbohydrates

the lipid bilayer

2 back to back layers made up of 3 different lipid molecules (phospholipids, cholesterol, glycolipids)

phospholipids

about 75% of the lipid membrance

-amphipathic: polar and nopolar

cholesterol

about 20% of the lipid membrane

-strengthen membrane and maintains fluidity

glycolipids

about 5% of the lipid membrane

-membrane stability and cell recognition

membrane proteins: types (2)

integral and peripheral

integral proteins

firmly attached to the lipid bilayers

-integrated into the membrane

transmembrane proteins

extend across the lipid bilayer

glycoproteins

carbohydrate portion is unique to each cell

-allows cells to recognize one another and attach to form tissues

-also allows WBCs to detect “foreign” carbs

peripheral proteins

loosely attached to the inner and outer surfaces of the lipid bilayer

-stay on the perimeter of the membrane

functions of membrane proteins

ion channels, carriers, receptors, enzymes, linkers, cell identity markers

ion channels

pores that specific ions can flow through

carriers

selectively moves a polar substance or ion from one side of the cell to the other

receptors

recognize and binds a specific type of molecule, like a hormone

enzymes

catalyze specific chemical reactions at the inside or outside surface of the cell

linkers

anchor cells to one another or to protein filaments inside or outside of the cell

cell identity markers

glycoproteins and glycolipids that enable cells to recognize cells of the same kind and recognize and resopond to potentially dangerous foreign cells

transport across the plasma membrane

-substances in solution are in constant motion

-they move in straight lines in all directions until they run into other substances or into the walls of their container

-because of this, some methods of transport require energy and some do not

-depends on particle size, polarity, and concentration inside and outside the cell

2 classifications of transport

passive and active

passive transport

the movement of substances through plasma membrane that does not require energy

-substances more down their concentration or electrical gradient using their own kinetic energy (high to low)

active transport

movement of substances through the plasma membrane that does require energy

-substances move against their concentration gradient or require a vesicle to get into or out of cells (low to high)

examples of passive transport

diffusion, facilitated diffusion, osmosis

diffusion

movement of a substance down its concentration gradient through the lipid bilayer of the plasma membrane (high to low)

facilitated diffusion

allows specific polar molecules and ions to diffuse through openings formed by protein channels or carriers

types of protein channels or carriers

aquaporins, GLUTs

aquaporins

protein channels that allow the diffusion of water, this is the plumbing system for cells

GLUTs

protein carries that allow diffusion of glucose

osmosis

the diffusion of water

-water diffuses from an area with low solute concentration to and area of high solute concentration

cells require very specific conditions in order to function properly

-the concentration of water (solvent) and nutrients (solutes) must all be just right in the cytoplasm and in the extracellular fluid in order for a cell to be healthy

-these optimal conditions vary depending on the organism

cells can be exposed to three different kinds of extracellular solutions:

isotonic, hypotonic, hypertonic

isotonic solutions

the concentration of solute is the same both inside and outside the cell

-the cell and the extracellular fluid are in equilibrium

-the cytoplasm will stay the same

hypotonic solutions

the concentration of solute is greater inside the cell than outside the cell

-water will diffuse into the cell

-the cytoplasm will swell (get bigger)

hypertonic solutions

the concentration of solute is greater outside the cell than inside the cell

-water will diffuse out the cell

-the cytoplasm will shrivel (get smaller)

examples of active transport

protein pumps, endocytosis, exocytosis

protein pumps

carrier proteins open and close using ATP

-this allows substances to move from a region of low to a region of high concentration

endocytosis

transport of substances into a cell by engulfing them in a small membrane (vesicle), this requires energy (ATP) from the cell to occur

phagocytosis

“cell eating”

-key role in immune system (WBCs)

pinocytosis

“cell drinking”

-allows cells to take in large amounts of solute at once

exocytosis

transport of materials out of a cell by releasing them from a small membrane, fuses, and then releases contents out of the cell

-release of neurotransmitters during nerve impulse

-release of proteins made by a cell

cytoplasm

consists of cytosol and organelles

cytosol

fluid portion of the cytoplasm

-75-90% water, then dissolved nutrients and ATP

organelles

specialized structures with in cells that perform specific functions

nucleus

contains DNA

mitochondria

cellular respiration (generates ATP)

ribosomes

protein synthesis

cell destiny… cells will:

-remain alive and functioning without dividing

-grow and divide

-or die

apoptosis

an orderly, genetically programmed cell death

-needed to shape and remodel developing tissues, replace old or damaged cells, and kill pro-cancerous and infected cells

-complicated process that can be triggered by many internal and external factors

necrosis

pathological cell death due to tissue damage

aging

the normal process that produces observable changes in structure and function and increases the vulnerability to stress and diseases

geriatrics

the branch of medicine that deals with aging

physiological changes due to:

1) cellular senescene (cells stop dividing)

2) genetic mutations and toxic chemicals accumulate in the body over accumulation of free radicals and glucose, causing tissue damage such as wrinkled skin, stiff joints, or hardening of arteries

telomeres

noncoding pieces of DNA on the tips of chromosomes

-protect chromosomes from erosion and sticking to one another

-each time a cell divides, the telomeres get shorter

anatomical changes

-graying of loss of hair

-loss of teeth

-wrinkling skin

-decreased muscle mass

disorders-homeostatic imbalances

cancer

cancer

cells divide without control, uncontrolled mitosis

tumor, growth, or neoplasm

(neo- = new) the excess of tisse that develops due to uncontrolled cell growth

oncology

(onco- = swelling or mass) the study of tumors

oncologist

physician who specializes in tumors

malignant tumor (malignancy)

a cancerous tumor that usually spreads

metastasis

a property of malignant tumors to spread cancerous cells to other parts of the body

benign tumor

a non-cancerous tumor that does not metastasize

benign tumor facts

-noncancerous

-capsulated

-noninvasive

-slow growing

-does not metastasize

-cells are normal

malignant tumor facts

-cancerous

-noncapsulated

-fast growing

-metastasize

-cells have larger, dark nclei; abnormal shape

types of cancers

cancers are classified by their microscopic appearance and the body site from which they arise

-the name is derived from the type of tissue in which the cancer develops

carcinoma

any cancer arising from epithelial tissue

-most human cancers are carcinomas

(ex. skin cancer and most cancers of the organs and glands)

melanomas

cancerous growth of melanocytes, which are skin cells that produce the pigment melanin

sarcoma

any cancer arising from muscle cells or connective tissue

osteogenic sarcoma

cancer destroys normal bone tissue

leukemia

cancer of blood forming organs (bone marrow)

lymphoma

cancer of the lymphatic tissue, lymph nodes

myeloma

cancer of plasma cells (WBCs that make antibodies, b-cells)

blastoma

cancer of precursor cells (stem cells)

growth and spread of cancer

malignant cells divide exponentially during the early stages as malignant cells invade surrounding tissues, they often trigger angiogenisis; compete with normal tissues for space and nutrients; cause pain due to pressing on nerves and blocking passageways; cause surrounding normal tissue to die

angiogenesis

the growth of new networks vessels to feed the malignat cells (pathway for metastasis)

causes of cancer

carcinogens, oncogenes, tumor suppressor genes, viruses, chronic inflammation

carcinogens

a chemical or environmental agent that produces cancer

-induce mutations, which are permanent changes in DNA

-associated with 60-90% of all human cancers

9ex. cigarette tars, radon gas (earth), UV radiation (sun), industrial chemicals)

oncogenes

genes that cause normal cells to become cancerous cells

-oncogenes are mutated versions of genes known as proto-oncogenes

proto-oncogenes

code for proteins that stimulate cell division, inhibit cell differentiation, and stop cell deth

-all normal for development and maintenence of healthy tissue

-oncogenes increase production of these proteins in excess or at the wrong time

tumor suppressor genes

produce proteins that slow down cell division, repair DNA mistakes, or induce apoptosis (also known as anti-oncogenes)

-mutations to a tumor suppressor genes known as the “P53 gene” located on chromosome 17 has been found in more than half of human cancers

viruses

packages RNNA of DNA that use cell machinery to replicate and infect other cells

-chronic viral infections are associated with up to one-fifth of all cancers

human papillomavirus (HPV)

the main cause of cervical cancer

human immunodeficiency virus (HIV)

associated with kaposis sarcoma- cancer of the blood vessels

Epstein-Barr virus

virus that causes mononucleosis (mono)

chronic inflammation

a constant immune response to injury even where there isnt injury

-chronic inflammaton can lead to DNA damage that can cause cancer

(ex. inflammatory bowel diseases such as crohns disease and ulcerative colitis, have and increased risk or colon cancer;chronic acid reflux can lead to esophageal cancer)

treatment of cancers: difficult because…

1) cancer is not a single disease, each cancer is different

2) some cancers metastasize and some do not

3) some cells in a single tumor behave differently than the other cells in the same tumor

4) some cancer cells respond to drugs and others a resistance to drugs

treatment of cancers: used alone or in combinations

surgery, radiation, chemotherapy, immunotherapy

surgery

remove the tumor/malignant tissue surgically

-usually the first step

radiation

uses high-energy particles (x-rays, gamma rays, electron beams, or protons) to damage DNA in cancer cells to stop them from dividing

-targeted at the site of the tumor to reduce damage to nearby healthy cells

-can experience pain and blistering on the surface of skin where radiation is administered

chemotherapy

drugs that target and destroy rapidly cells

-systemically kills cancer cells but also kills other rapidly dividing cells like skin cells, blood cells, and gastrointestinal cells

• this is why chemo symptoms include hair loss, reduced ability to fight infection, anemia, and nausea

immunotherapy

using a persons own immune system (WBCs) to attach the cancer cells

-stimulate the patients own white blood cells to make antibodies against their won cancerous cells

-cancer vaccines: not a major type of cancer treatment but is currently being researched