CHAPTER 3: CELLS AND TISSUES

Cells

• are the structural units of all living things

• human body contains 50 to 100 trillion of these

Robert Hooke

In 1600s, he was looking through a crude microscope at some plant tissue—cork. He saw crucible structures which reminded him of the long rows of monk’s rooms (or cells) at the monastery, so he named these "cells”

1. A cell is the basic structural and functional unit of all organisms.

2. The activity of an organism depends on the collective activities of its cells

3. According to the principle of complementarity, the activities of cells are dictated by their structure (anatomy), which determines function (physiology)

4. Continuity of life has a cellular basis. In other words, cells come from cells.

What are the cell theories?

60%

living cells are about ___ percent of water

plasma membrane, nucleus, and cytoplasm

three main regions or parts of all cells

plasma membrane (dont use cell membrane nor cytoplasmic membrane)

• a fragile, transparent barrier that contains the cell contents and separates them from the surrounding environment

• passive envelope of “baggie

The Fluid Mosaic Model

• structure of plasma membrane: two phospholipid (fat) layers arranged “tail to tail” with cholesterol and floating proteins scattered among them.

bilayer contents

glycoprotein - carbs attached to protein; determine your blood type; cell-to-cell interactions; receptors that certain bacteria, toxins, etc. can bind to. changes in this occur in cells that are being transformed into cancer cells.

channel

proteins (some r enzymes)

cholesterol

helps stabilize the plasma membrane and keep it flexible

glycocalyx

makes the surface of the bilayer fuzzy and sticky due to the glycoproteins

glycolipid

carbs attached to the head of phospholipid

microvilli

increase surface area of the cell for more absorption and secretion

phagocytic cells

cells that ingest bacteria and debris

• glycoproteins in the glycocalyx act as an adhesive or cellular glue

• wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion

• special cell membrane junctions are formed. These junctions vary structurally depending on their roles.

cells are bound together in three ways?

• tight junctions

• desmosomes

• gap junctions

3 main types of junctions?

tight junctions

• impermeable junctions that encircle the cells and bind them together into leak-proof sheets.

• adjacent plasma membranes fuse together tightly like a zipper and prevent substances from passing through the extra-cellular space between cells.

• ex. in small intestine, this juction prevent digestive enzyme from seeping into the bloodstream

desmosomes

• are anchorinng junctions scattered like rivets along sides of adjacent cells.

• prevent cells subjected to mechanical stress (heart muscle cells from being pulled apart)

• are buttonlike thickenings of adjacent plasma membranes (plaques) that are connected by fine protein filaments.

gap junctions

transmembrane proteins

• allow communication

• found in the heart and between embryonic cells neighboring cells are connected by hollow cylinders composed of proteins (connexons) that span the entire width of the abutting membranes, much like adjoining hotel rooms are directly connected by a door inside the rooms.

• Because they span both membranes, these connexons are called _____________.

• Chemical molecules, such as nutrients or ions, can pass directly through the water-filled connexon channels from one cell to another.

nucle = kernel

nucleus comes from the word?

elongated as well (conforms)

if the cell is elongated, the shape of the cell will be

nuclear envelope, nucleolus, and chromatin

the nucleus has three recognizable regions or structure?

nuclear envelope

• a double membrane barrier

• between the two is a fluid-filled “moat” or space.

• when these fuse, they form nuclear pores

• selective like plasma mem, but more freely

nucleoplasm

the nuclear envelope encloses a jellylike fluid called _________ in which other elements are suspended.

Nucleolus

• nucleus contains one or more small, dark-sustaining, round bodies called _______

• sites where ribosomes are embedded

• then ribo integrate into the cytoplasm

ribosomes

where does protein synthesis occur

chromatin

chromosomes

• when a cell is not dividing, its DNA is carefully wound around proteins called histones to form a lose network of “beads on a string” called ______.

• scattered throughout the nucleus

• they condense into _______

chromo = colored

soma = body

chromosomes means?

cytoplasm

• it is the cellular material outside the nucleus and inside the plasma membrane

• site of most cellular activities

• “factory floor” of the cell

1. cytosol

2. inclusions

3. organelles

the three major components of the cytoplasm?

cytosol

• is a semitransparent fluid that suspends the other elements.

• dissolved here is largely water, are nutrients and a variety of other solutes

inclusions

• are chemical substances that may or may not be present, depending on the specific cell type.

• most are stored nutrients or cell products floating in the cytosol

• “cellular pantry” , where items are kept on hand until needed

1. liquid droplets common in flat cells

2. glycogen granules abundant in liver and muscle cells

3. pigments such as melanin in skin and hair cells

4. mucus

5. other secretory products

6. various kinds of cyrstals.

what’re some examples of inclusions?

organelles

• “little organs” , specialized cellular components

• metabolic machinery of the cell

• each is specialized to carry out a specific function for the cell as a whole, much like the organs carry out specialized functions for the whole body

• many are bounded by a membrane to maintain an internal environment

mitochondria

• tiny, beanlike or sausage-shaped organelles

• in living cells, they lengthen and change shape almost continuously

• double membrane

• outer membrane is smooth and featureless

Ribosomes

• tiny, bilobed, dark bodies made of proteins and one variety of RNA called ribosomal RNA.

• float freely in the cytoplasm

• some attach to rough er

Endoplasmic reticulum

• “network within the cytoplasm”

• a system of fluid-filled tunnels (or canals) that coil and twist in the cytoplasm

• mini circulatory system for the cell

rough & smooth

two forms of er

rough endoplasmic reticulum

• studded with ribosomes

• has sacs called “transport vesicles”

smooth endoplasmic reticulum

• communicates with the rough variety

• no role in protein synthesis

• functions in lipid metabolism (cholesterol and phospholipid synthesis and breakdown) and detoxification of drugs and pesticides.

golgi apparatus

• appears as a stack of flattened membranous sacs that are associated with swarms of tiny vesicles

• “traffic director”

• modify, package, and ship proteins

• all proteins leaving the golgi accumulate in sacs called Golgi vesicles

secretory vesicles

when the Golgi sacs end, filled with protein, pinch off, and form ______________ which travel to the plasma membrane

Lysosomes

• appear in different sizes

• membranous “bags” containing powerful digestive enzymes

• when these rupture, the cell self-digests

lysoosmes

Golgi vesicle containing digestive enzymes become what?

(see book for pic)

1. Golgi vesicle containing proteins to be secreted becomes a secretory vesicle

2. Golgi vesicle containing membrane components fuses with the plasm a membrane and is incorporated into it

3. Golgi vesicle containing digestive enzymes becomes a lysosome

What are the three pathways of the leaving vesicles of the Golgi apparatus?

Peroxisomes

• are membranous sacs containing powerful oxidase enzymes that use molecular Oxygen (O₂) to detoxify a number if harmful or poisonous substances, including alcohol and formaldehyde

• Convert free radicals to hydrogen peroxide

• has an enzyme called/

• numerous in liver and kidney cells, which are active in detoxification

Free radicals

• These are highly reactive chemicals with unpaired electrons that can damage the structure of proteins and nucleic acids.

• Are normal byproducts of cellular metabolism, but if allowed to accumulate, they can have devastating effects on cells.

catalase

The enzyme ______ then converts excess hydrogen peroxide to water.

pinching

• Unlike lysosomes, peroxisomes replicate themselves by simply _____ in half, like mitochondria, but most peroxisomes appear to bud directly from the ER.

Cytoskeleton

• an elaborate network of proteins structures extends throughout the cytoplasm

• cell’s bones and muscles

• determines cell shape, support other organelles, and provides machinery for intracellular transport and various types of cellular movement.

microfilaments

intermediate filaments

microtubules

cytoskeleton is made up of?

Microfilaments

• actin subunit (7nm)

• most involved in cell motility and in producing changes in cell shape

Intermediate filaments

• strong, rope-like ______ are made up of fibrous subunits (10nm)

• help form desmosomes

• provide internal guy wires to resist pulling forces on the cell

Microtubules

• the tube-like ______ are made up of repeating subunits of the protein tubulin (25nm).

• help the overall shape of a cell and distribution of organelles.

• very important in cell division

Centrioles

• The paired ______, collectively called centrosome, lie close to the nucleus.

• Rod-shaped bodies that lie at right angles to each other; internally they are made up of pinwheel array of nine triplets of fine microtubules.

• Best known for their role in generating microtubules and also for directing information of the mitotic spindle during cell division

Cilia

Flagella

Microvilli

What are some cell extensions

Cilia

• are whiplike cellular extensions that move substances along the cell surface.

• Ex., mucus is carried up and away from the lungs by “crowd surfing” on the ciliated cells lining the respiratory system.

• When a cell is about to make this, its centrioles multiply and then line up beneath the plasma membrane at the free cell surface. Microtubules then begin to “sprout” from hte centrioles and put pressure on the membrane, forming the projections.

Flagella

• If the centrioles formed above are substantially longer, they are called ____________.

• only example in the human body is the sperm, which is a single impulsive flagellum called its tail.

• Cilia propel other substances across a surface, whereas flagellum propels the cell itself.

Microrovilli

• tiny, fingerlike extensions of the plasma membrane that project from an exposed cell surface

• increase the cell’s surface area

• have a core of actin filaments that extend into the internal cytoskeleton of the cell and stiffen the microvillus

• are “alcoves” projecting off one cell surface and do not involve microtubules

hydrolases

lysosomes are membranous sacs containing acid ___________, a powerful digestive enzyme

200

the trillions of cells in the human body includes over ____ different cell types

1/12000 of an inch

cells also vary in length, how long?

1. Cells that connect body parts

2. Cells that cover and line body organs

3. Cells that move organs and body parts

4. Cell that store nutrients

5. Cell that fight disease

6. Cell that gathers information and controls body functions

7. Cells of reproduction

THE EXAMPLES OF SPECIALIZED CELLS

fibroblast (connect body parts)

• this cell has an elongated shape, like the cable-like fibers that it secretes

• abundant rough er and a large golgi apparatus

Erythrocyte (red blood cell) (connect body parts)

• this cell carries oxygen in the blood

• biconcave disc shape provides extra surface area for the uptake of oxygen and streamlines the cell so it flows easily through the bloodstream

epithelial cell (cover and line body organs)

• the hexagonal shape of this is exactly like a “cell” in ahoneycomb of a beehive

• the shape allows epithelial cells to pack together in sheets

• abundant intermediate filaments and desmosomes that resist tearing when the epithelium is rubbed or pulled.

skeletal, cardiac, and smooth muscle cells (move organs and body parts)

• are elongated and filled with abundant contractile microfilaments, so they can shorten forcefully and move the bones, pump blood, or change the size of internal organs to move substances around the body

fat cell (stores nutrients)

its huge spherical shape is produced by a large lipid droplet in its cytoplasm

white blood cells such as the macrophage (a phagocytic cell) (fights disease)

• extends long “pseudopods” (“false feet”) to crawl through tissue to reach infection sites.

• Its many lysosomes digest the infectious microorganisms

nerve cell (neuron) (gathers information and controls body function)

• has long processes for receiving messages and transmitting them to other structures in the body.

• The processes are covered with an extensive plasma membrane, and a plentiful rough er synthesizes membrane components and signaling molecules called neurotransmitters.

oocyte (female) (for reproduction)

the largest cell in the body

this egg cell contains several copies of all organelles, for distribution to the daughter cells arise when the fertilized egg divides to become an embryo

sperm (male) (for reproduction)

long and stream-lined, built for swimming to the egg for fertilization

Solution

is a homogeneous mixture of two or more components

ex. air, seawater, and rubbing alcohol

solvent

is the largest amount in a solution

solutes

substances in a solution present in smaller amounts

Intracellular fluid

• is collectively the nucleoplasm and cytosol

• solution containing small amounts of gases, nutrients, and salts, discovered in water.

E

Extracellular fluid or interstitial fluid

• fluid that continuously bathes the exterior of our cells

selective permeability

it means that a barrier allows some substances to pass through it while excluding others

only applies to healthy cells

passive or active

substances move through the plasma membrane in two ways, what?

diffusion and filtration

what are the passive processes?

Diffusion

• is the process by which molecules (and ions) move away from areas where they are more concentrated to areas where they are less concentrated

• molecules move down their concentration gradient (spread out).

• The greater the difference in concentration between the two areas, the faster diffusion occurs

simple diffusion

• the unassisted diffusion of solutes through the plasma membrane (or any slectively permeable membrane) is called what?

• solutes transported this way are lipid-soluble such as fats, sat-soluble vitamins, oxygen, and carbon dioxide

osmosis

• the diffusion of water through a selectively permeable membrane such as the plasma membrane is specifically called?

• because water is highly polar, it is repelled by the nonpolar lipid core of the plasma membrane, but it can and does pass easily through special cores called aquaporins (“water pores”) created by proteins in the membrane.

facilitated diffusion

• provides passage for certain needed substances (notably glucose) that are both lipid-insoluble and too large to pass through membrane pores, or charged, as in the case of chloride ions passing through a membrane protein channel.

• has a membrane protein that acts as a carrier.

Filtration

water and solutes are forced through a membrane by fluid, or hydrostatic, pressure.

the gradient is a pressure gradient

active processes

• it is called when cells use ATP to move substances across the membrane because it may be too large to pass through,

active transport and vesicular transport.

what are the two important active processes

active transport

solute pumps

• sometimes called solute pumping, it is similar to facilitated diffusion that both processes require protein carriers that interact specifically and reversibly with the substances to be transported across the membrane

• however, it uses ATP to energize its protein carriers, which are called __________

• ex: amino acids, some sugars, and most ions

• moving “uphill”

sodium-potassium (Na⁺ -K⁺) pump

phosphorylation

• it alternately carries sodium ions out of and potassium ions into the cell.

• this process is absolutely necessary for normal transmission of nerve impulses

• ATP splits into inorganic phosphate and ADP, then the phosphate is then attached to the sodium-potassium pump in a process called ______

• more na ions outside the cells

• more k ions inside cells

Vesicular transport

• some substances cannot get through the plasma membrane by active or passive transport.

• it involves help from ATP to fuse or separate membrane vesicles and the cell membrane, moves substances into or out of cells “in bulk” without actually crossing the plasma membrane directly.

exocytosis and endocytosis

two types of vesicular transport

Exocytosis

• “out of the cell”

• is the mechanism that cells use to actively secrete hormones, mucus, and other cell products or to eject certain cellular waste.

• product to be released is first “packaged” by the golgi, into a secretory vesicle. It then fuses with the plasma membrane, ruptures, spilling its contents out of the cell.

Endocytosis

• “into the cell”

• includes those ATP-requiring processes that take up, or engulf, extracellular substances by enclosing them i a vesicle. Once the vesicle is formed, it detaches from the plasma membrane and moves into the cytoplasm , where it typically fuses with a lysosome and its contents are digested.

• Some vesicle travels to the opposite side of the cell and releases its contents by exocytosis there.

phagocytosis, pinocytosis, and receptor-mediated endocytosis

types of endocytosis?

phagocytosis

• if the engulfed susbtances are relatively large particles, such as bacteria or dead body cells, and the cell separates them from the external environment by pseudopods, the endocytosis process is more specifically called?

• a term that means “cell eating”

• wbc such as the macrophage and other “professional” phagocytes of the body act as scavenger cells that police and protect the body by ingesting bacteria and other foreign debris.

• hence, it is a protective mechanism—a way to “clean house” — not a means of getting nutrients

pinocytosis

• the cell gulps droplets of extracellular fluids

• routine activity of most cells, unlike phagocytosis

Receptor-mediated endocytosis

• Highly specific uptake using receptor proteins (e.g., LDL cholesterol uptake).