Cells and Tissues

Cell theory

The structural and functional unit of life

Cell

The basic unit of life — all living things are made of it (50-100 trillion cells)

Cell

Life continues because it divide and make new ones

Plasma membrane

(Semipermeable membrane that encloses the cytoplasm) Membrane made of a double layer of lipids (phospholipids and cholesterol) with proteins embedded within. Most externally facing proteins

Membrane

is a phospholipid bilayer containing proteins, sugars, and cholesterol

Membrane

Can act as enzymes, transport proteins, channel proteins; serve as receptors for hormones and other cell-to-cell communication molecules

Hydrophilic

(water loving") and are attracted to water, the main component of both the intracellular and extracellular fluids, and so they lie on both the inner and outer surfaces of the membrane

Hydrophobic

(water fearing"), avoid water and line up in the center (interior) of the membrane

Tight junctions

are impermeable junctions that encircle the cells and bind them together into leakproof sheets

Desmosomes

anchoring junctions scattered like rivets along the sides of adjacent cells

Gap junctions

function mainly to allow communication

Nucleus

control center of a cell; necessary for reproduction

DNA

found in nucleus; contains instructions for protein synthesis

Cytoplasm

contains cytosol, inclusions, stored or inactive materials

Nuclear envelope

nuclear boundary is a double membrane barrier called

Nuclear envelope

Double-membrane structure pierced by large pores. Outer membrane continuous with the endoplasmic reticulum. Nuclear boundary is a double membrane barrier called

Chromatin

when a cell is not dividing its DNA is carefully wound around proteins called histones to form a loose, network of "beads on a string" called

Chromosomes

when a cell is dividing to form two daughter cells, the chromatin threads coil and condense to form dense, rodlike bodies called

Cytoplasm

the cellular material outside the nucleus and inside the plasma membrane. It is the site of most cellular activities, so you might think of it as the "factory floor" of the cell

Cytosol

semitransparent fluid that suspends the other elements

Organelles

("little organs") are specialized cellular compartments that are the metabolic machinery of the cell

Mitochondria

Rodlike, double-membrane structures; inner membrane folded into projections called cristae. they lengthen and change shape almost continuously (ATP syntesis)

Ribosomes

Dense particles consisting of two subunits, each composed of ribosomal RNA and protein. Free or attached to rough endoplasmic reticulum. (protein syntesis)

Endoplasmic reticulum

("network within the cytoplasm"), or ER, is a system of fluid-filled tunnels (or canals) that coil and twist through the cytoplasm (tunnel system involved in fat and protein synthesis)

Rough endoplasmic reticulum

It is studded with ribosomes, because essentially all of the building materials of cellular membranes are formed either in it or on it, you can think of the rough ER as the cell's membrane factory

Golgi apparatus

(modifies and packages proteins for export) A stack of flattened membranes and associated vesicles close to the ER.

Lysosomes

("breakdown bodies"), Membranous sacs containing acid hydrolases (powerful digestive enzymes). (intracellular digestion)

Peroxisomes

Membranous sacs of oxidase and catalase enzymes. (detoxify free radicals)

Centrioles

collectively called the centrosome, lie close to the nucleus. Paired cylindrical bodies, each composed of nine triplets of microtubules. (cell division and form the bases of cilia and flagella)

Microfilaments

are most involved in cell motility and in producing changes in cell shape, Fine filaments composed of the protein actin. (form the blue batlike network)

Intermediate filaments

Protein fibers; composition varies. They help form desmosomes and provide internal guy wires to resist pulling forces on the cell (form the purple network surrounding the pink nucleus)

Microtubules

Cylindrical structures made of tubulin protein. They determine the overall shape of a cell and the distribution of organelles (appear as gold networks surrounding the cells' pink nuclei)

Nucleus

Largest organelle. Surrounded by the nuclear envelope; contains fluid nucleoplasm, nucleoli, and chromatin

Nucleolus

Dense spherical (non-membrane-bounded) bodies, composed of ribosomal RNA and proteins.

Chromatin

Granular, threadlike material composed of DNA and histone proteins. "Beads on a string."

Cilia

project from the cell surface and aid in moving substances (for example, mucus) across the cell surface; composed of microtubules

Flagella

are longer projections made of microtubules that propel the cell

Microvilli

structures to increase surface area, are composed of actin filaments ("little shaggy hairs") are tiny, fingerlike extensions of the plasma membrane

Cell diversity

Cells differ in their sizes, shapes, and number of organelles; structure determines function

Cells physiology

All cells respond to stimuli (irritable), digest foods, excrete wastes, and are able to grow, move, and metabolize; most can reproduce by mitosis

Fibroblast

This cell has an elongated shape, like the cable-like fibers that it secretes. It has an abundant rough ER and a large Golgi apparatus to make and secrete the protein building blocks of these fibers.

Cells that connect body parts

Contains Fibroblast and Erythrocyte (red blood cell)

Erythrocyte

(red blood cell). This cell carries oxygen in the blood. Its biconcave disc shape provides extra surface area for the uptake of oxygen and streamlines the cell so it flows easily through the bloodstream.

Cells that cover and line body organs

Epithelial cell. The hexagonal shape of this
"cell is exactly like a "cell" in a honeycomb of a beehive. This shape allows epithelial cells to pack together in sheets. An epithelial cell has abundant intermediate filaments and desmosomes that résist tearing when the epithelium is rubbed or pulled.

Cells that move organs and body parts

Skeletal, cardiac, and smooth muscle cells.
These cells 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

Cell that stores nutrients

Fat cell. The huge spherical shape of a fat cell is produced by a large lipid droplet in its cytoplasm

Cell that fights disease

White blood cells such as the macrophage (a phagocytic cell). This cell extends long pseudopods ("false feet") to crawl through tissue to reach infection sites. The many lysosomes within the cell digest the infectious microorganisms (such as bacteria) that it "eats."

Cell that gathers information and controls body functions

Nerve cell (neuron). This cell has long processes (extensions) 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

Cells of reproduction

• Oocyte (female). The largest cell in the body, this egg cell (not shown) contains several copies of all organelles, for distribution to the daughter cells that arise when the fertilized egg divides to become an embryo.

• Sperm (male). This cell is long and stream-lined, built for swimming to the egg for fertilization. Its flagellum acts as a motile whip to propel the sperm.

Selective permeability

means that a barrier allows some substances to pass through it while excluding others. Thus, it allows nutrients to enter the cell but keeps many undesirable or unnecessary substances out. At the same time, valuable cell pro. teins and other substances are kept within the cell, and wastes are allowed to pass out of it

Diffusion

is the movement of a substance from higher concentration to an area of lower concentration due to the kinetic energy of the molecules themselves

Simple diffusion

Diffusion of dissolved solutes through the plasma membrane

Osmosis

Diffusion of water across the plasma membrane

Facilitated diffusion

Diffusion that requires a protein channel or carrier

Filtration

Passive transport that requires a pressure gradient across a membrane

Active processes

When a cell uses ATP to move substances across the membrane, the process is ___z

Active transport

requires both ATP and a carrier protein and can move items against their gradient

Solute pumps

move specific solutes

Vesicular transport

includes endocytosis and exocytosis, the movement of bulk substances into or out of the cell, respectively

Exocytosis

(“Out of the cell”) the mechanism that cells use to actively secrete hormones, mucus, and other cell products to be released is first “packaged” (typically by the Golgi apparatus) into a secretory vesicle.

Endocytosis

("into the cell") includes those ATP-requiring processes that take up, or engulf, extracellular substances by enclosing them in a vesicle

Phagocytosis

a term that means "cell eating" Certain white blood cells, 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

Pinocytosis

("cell drinking"), during which the cell "gulps" droplets of extracellular fluid

Cell division

two phases: mitosis (division of the nucleus) and cytokinesis (division of the cytoplasm); provides cells for growth and repair

Cell life cycle

is the series of changes a cell goes through from the time it is formed until it divides

Interphase

period of normal cell function between divisions; DNA replication occurs

Mitosis

four phases: prophase, metaphase, anaphase, and telophase; results in two daughter nuclei that are identical to the mother nucleus

Propase

chromatin coil and shorten→ chromosomes visible→ sister chromatids→ centrome → spindle → nuclear envelope breaks down

Metaphase

chromosomes line up → metaphase plate→ center of splinder

Anaphase

centromeres split → chromatids move apart → opposite ends → each daughter cell gets one copy of every chromosome

Telophase

chromosomes uncoil → spindle breaks down → nuclear envelope forms → nucleoli appear

Cytokinesis

the division of the cytoplasm, usually begins during late anaphase and completes during telophase, progressively pinches cytoplasm and cell membrane in half

Protein syntesis

are key substances for all aspects of cell life. Fibrous (structural) proteins are the major building materials for cells (involves both DNA (the genes) and RNA)

Gene

(DNA) carry instructions for building proteins; each three-base sequence (triplet) encodes one amino acid

Messenger RNA (mRNA)

Carries the DNA instructions for building protein synthesis to the ribosome transfer RNA (tRNA) transports amino acids to the ribosome, ribosomal RNA (rRNA) forms part of the ribosomal structure

Transcription

DNA information into mRNA form

Translation

RNA and ribosome build protein

mRNA

three base-pair codons are read by the ribosome; tRNA has anticodons; codons and anticodons temporarily bind to ensure that the correct amino acid is added in the correct position in growing protein

Tissues

Groups of cells that are similar in structure and function are called

Apical surface

The membranes always have one free (unattached) surface or edge. This is exposed to the body’s exterior or to the cavity of an internal organ

Basement membrane

The anchored (basal) surface of epithelium rests, a structureless material secreted by both the epithelial cells and the connective tissue cells deep to the epithelium

Avascular

Epithelial tissues are ____, meaning they have no blood supply of their own and depend on diffusion from the capillaries in the underlying connective tissue for food and oxygen.

Epithelial Tissue

Covers, lines; glandular tissue protects, absorbs, and secretes

Simple epithelium

One layer of cells

Stratified epithelium

More than one cell layer

Simple epithelia

are most concerned with absorption, secretion, and filtration. Because simple epithelia are usually very thin, protection is not one of their specialties

Simple squamous epithelium

a single layer of thin squamous cells resting on a basement membrane. The cells fit closely together, much like floor tiles. This type of epithelium usually forms membranes where filtration or exchange of substances by rapid diffusion occurs.

Simple cuboidal epithelium

one layer of cuboidal cells resting on a basement membrane, is common in glands and their associated small tubes called ducts (for example, the salivary glands and pancreas)

Simple columnar epithelium

made up of a single layer of tall cells that fit closely together and whose nuclei appear to form a straight line

Mucous membranes.

Epithelial membranes that line body cavities open to the body exterior are called ___

Pseudostratified Columnar Epithelium

All of the cells of pseudostratified columnar epithelium rest on a basement membrane

Stratified Epithelia

consist of two or more cell layers. Being considerably more durable than the simple epithelia, these epithelia function primarily in protection

Stratified squamous epithelium

the most common stratified epithelium in the body. It usually consists of many cell layers. The cells at the free edge are squamous cells, whereas those close to the basement membrane are cuboidal or columnar.

Stratified cuboidal epithelium

typically has just two cell layers with (at least) the surface cells being cuboidal in shape

Stratified columnar epithelium

The surface cells of ____ are columnar cells, but its basal cells vary in size and shape.

Transitional Epithelium

is a highly modified, stratified squamous epithelium that forms the lining of only a few organs the urinary bladder, the ureters, and part of the urethra.

Glandular Epithelium

A gland consists of one or more cells that make and secrete a particular product. This product, a secretion, typically contains protein molecules in an aqueous (water-based) fluid

Endocrine glands

lose their ducts; thus they are often called ductless glands. Their secretions (all hormones) diffuse directly into the blood vessels that weave through the glands

Exocrine glands

retain their ducts, and their secretions exit through the ducts to the epithelial surface. Exocrine glands, which include the sweat and oil glands, liver, and pancreas, are both internal and external

Four primary tissue types

epithelial, connective, nervous, and muscle tissues