cell theory concepts
1. cells are the building blocks of all plants and animals
2. cells are produced by the division of preexisting cells
3. cells are the smallest units that perform all vital functions
two types of cells
sex cells and somatic cells
sex cells
germ cells or reproductive cells; gametes (sperm or oocytes)
somatic cells
include all of the cells in the body other than reproductive cells
light microscopy
uses light to permit magnification and viewing of cellular structure up to 1000 x their natural size
electron microscopy
uses a focused beam of electrons to magnify cell ultrastructure up to 1000 x what is possible by light microscopy
extracellular fluid
thin layer of fluid that surrounds the cell
phospholipid bylayer
the cell membrane containing proteins and cholesterol
integral proteins
are embedded in the phospholipid bylayer of the cell membrane
peripheral proteins
are attached to the cell membrane but can separate from it
(cell) channels
allow water and ions to move across the membrane
gated (cell) channels
cell channels that can open or close
selectively permeable
permit the free passage of some materials
(cell) diffusion
is the net movement of material from an area where its concentration is high to an area where its concentration is lower; diffusion occurs until the concentration gradient is eliminated
osmosis
diffusion of water across a membrane in response to differences in water concentration
facilitated diffusion
a passive transport process that requires the presence of carrier proteins
active (cell) membrane processes
require energy in the form of ATP
ATP
adenosine triphosphate; energy that is required for active membrane processes
active transport mechanisms
consume ATP and are independent of concentration gradients; some ion pumps are exchange pumps
endocytosis
is movement into a cell and is an active transport process that occurs in one of three forms: pinocytosis, phagocytosis, or receptor-mediated endocytosis
pinocytosis
cell drinking
phagocytosis
cell eating
receptor-mediated endocytosis
selective movement
plasmalemma
the cell's outer boundary; also called cell membrane; are selectively permeable; lipid bylayer, containing phospholipids, steroids, proteins, and carbohydrates
plasmalemma functions
isolation; protection; sensitivity; support; control of entrance/exit of materials
cytoplasm
the general term for all of the material inside the cell; contains many more proteins than the extracellular fluid; two subdivisions are cytosol and organelles (nonmembranous and membranous)
cytosol
intracellular fluid that surrounds structures; contains dissolved nutrients, ions, soluble and insoluble proteins, and waste products
cytosol functions
distribute materials by diffusion; stores glycogen, pigments, and other materials
organelles
are intracellular structures that perform specific functions; cellular organelles have two categories: nonmembranous and membranous
nonmembranous organelles
are not enclosed in membranes and are always in contact with the cytosol; include cytoskeleton, centrioles, cilia, flagella, and ribosomes
cytoskeleton
proteins organized in fine filaments or slender tubes
cytoskeleton functions
strength and support; movement of cellular structures and materials
microvilli
are small, fingerlike projections of the plasmalemma that increase the surface area exposed to the extracellular environment; membrane extensions containing microfilaments
microvilli function
increase surface area to facilitate absorption of extracellular materials
centrosome
cytoplasm containing two centrioles, at right angles; each centriole is composed of nine microtubule triplets in a 9 to 0 array
centrosome functions
essential for movement of chromosomes during cell division; organization of microtubules in cytoskeleton
cilia
membrane extensions containing microtubule doublets in a 9 to 2 array
cilia function
movement of materials over cell surface
ribosomes
RNA and proteins; fixed ribosomes bound to rough endoplasmic reticulum, free ribosomes scattered in cytoplasm
ribosomes function
protein synthesis
membranous organelles
are surrounded by lipid membranes that isolate them from the cytosol; they include mitochondria, the nucleus, the endoplasmic reticulum (rough and smooth), the Golgi apparatus, lysosomes, and peroxisomes
mitochondria
double membrane, with inner membrane folds (cristae) enclosing metabolic enzymes
mitochondria function
produce 95% of the ATP required by the cell
nucleus
nucleoplasm containing nucleotides, enzymes, nucleoproteins, and chromatin; surrounded by double membrane (nuclear envelope) containing nuclear pores through which it communicates with the cytosol; contains 23 pairs of chromosomes
nucleus functions
control of metabolism; storage and processing of genetic information; control of protein synthesis
nucleolus
dense region in nucleoplasm containing DNA and RNA
nucleolus function
site of rRNA synthesis and assembly of ribosomal subunits
endoplasmic reticulum (ER)
network of membranous channels extending throughout the cytoplasm
endoplasmic reticulum function
synthesis of secretory products; intracellular storage and transport; detoxification
Rough ER
has ribosomes bound to membranes; function is modification and packaging of newly synthesized proteins
Smooth ER
lacks attached ribosomes; function is lipid, steroid, and carb synthesis and calcium ion storage
Golgi apparatus
stacks of flattened membranes (cisternae) containing chambers
Golgi apparatus functions
packages materials for lysosomes, peroxisomes, secretory vesicles, and membrane segments that are incorporated into the plasmalemma; secretory products are discharged from the cell through exocytosis
Golgi cisternae (flattened membranes)
communicate with the ER and with the cell surface about formation, movement and fusion of vesicles
lysosome
vesicles containing digestive enzymes
lysosome function
intracellular removal of damaged organelles or of pathogens; defend against disease; the endocytic vesicle fuses with a lysosome resulting in the digestion of its contents
peroxisome
vesicles containing degradative enzymes
peroxisome function
catabolism of fats and other organic compounds; neutralize toxins
membrane flow
the continuous movement of membrane among the nuclear envelope, Golgi apparatus, endoplasmic reticulum, vesicles, and the plasmalemma
communicating junction
two cells are held together by interlocked membrane proteins that are channels forming a narrow passageway
occluding junction
an adhering junction, the lipid portions of the two plasmalemmae that are bound together to seal off the intercellular space between cells
anchoring junctions
an adhering junction, provide a mechanical linkage between two adjacent cells at their lateral or basal surfaces
cell division
cellular reproduction
hemidesmosome
attaches a cell to extracellular filaments and fibers
G? period
indefinite period; specialized cell functions
interphase period
a time of growth; most somatic cells spend most of their time in interphase; in a cell preparing for division, interphase is divided into the G?, S and G? phases
G? interphase
8+ hours; normal cell functions plus cell growth, duplication of organelles, protein synthesis
S interphase
6-8 hours; DNA replication, synthesis of histones
G? interphase
2-5 hours; protein synthesis
mitosis
the process of DNA replication and distribution of one copy of the genetic information to each of the two new daughter cells; occurs during the division of somatic (soma, body) cells
4 stages of mitosis
1-3 hours; prophase, metaphase, anaphase, telophase
cytokinesis
physical separation of two daughter cells that begins in late anaphase and completes at the end of telophase; the completion of cytokinesis marks the end of cell division and the beginning of the next interphase period
DNA replication
the original paired strands unwind, and the DNA polymerase begins attaching complimentary DNA nucleotides along each strand. This process produces two identical copies of the original DNA molecule.
DNA polymerase
adenine, guanine, cytosine, thymine
benign tumor
a mass or swelling in which the cells remain within a connective tissue capsule; rarely life-threatening
cancer
an illness characterized by malignant cells
malignant tumor
a mass or swelling in which the cells no longer respond to normal control mechanisms, but divide rapidly
metastasis
the spread of malignant cells into surrounding and distant tissues and organs
tumor (neoplasm)
a mass or swelling produced by abnormal cell growth and division