CHAPTER 3 A & P: CELLS

what is the basic unit of structure and function in the body?

cell

what are the three main parts of a cell?

plasma membrane, nucleus, and cytopalsm

plasma membrane

surrounds the cell, keeps it intact, and regulates passage into and out of the cell

nucleus

control center

cytoplasm

-gelatinous, semi-fluid of water and suspended and dissolved substances

-organelles and cytoskeleton

what is the function of the plasma membrane?

-separates the inside of the cell (cytoplasm) from the outside

-contains the fluid mosaic model and the phospholipid bilayer

fluid mosaic model

-working description of cell membrane structure

-the molecules of the cell membrane form a continuous “sheet” that is “fluid-like” in nature

phospholipid bilayer

-hydrophilic heads point outwards and hydrophobic tails point inward

-attached proteins serves as receptors, channels, and carriers

-cholesterol molecules stabilize the membrane

-glycoproteins and glycolipids attached to outer surface of some protein and lipid molecules. mark cells as belonging to a particular individual

what organelles occupy the cytoplasm?

-consists of networks of membranes and organelles suspended in cytosol

-cytoplasm= cytosol+organelles

-cytosol: fluid portion of the cytoplasm

-organelles: tiny solid structures with specific functions in the cell

-contains the cytoskeleton, which is a supporting framework of protein rods and tubules

endomembrane system

-works to produce and secrete products for cell

-contains the nuclear envelope and the endoplasmic reticulum (ER); attached to outer membrane of nuclear envelope; system of membranous channels and saccules

what is the function of the nucleus?

-contains genetic material and controls cell activities

-consists of the nuclear envelope, nucleolus, and chromatin

nuclear envelope

-double-layered membrane surrounding nucleus

-separates nucleoplasm from cytoplasm

-nuclear pores allows passage of certain substances

nucleolus

-dense body of RNA and protein

-site of ribosome production

chromatin

-consists of cell’s chromosomes, each containing DNA wound around proteins

-stores information for protein synthesis

endoplasmic reticulum (ER)

-rough ER: has attached ribosomes & ribosomes synthesize proteins, which move toward the golgi apparatus and eventually leave the cells

-smooth ER: has no attached ribosomes & synthesizes phospholipids, detoxifies drugs, and has other functions depending on the type of cell. removes and stores calcium ions from the cells interior

golgi apparatus

-processes, packages, and secretes various substances and enzymes

-receives protein and/or lipid-filled vesicles from ER and modifies them.

-lysosomes (digestive enzymes) and vesicles leave and move to other parts of the cell or to plasma membrane for secretions

peroxisomes

vesicles contain enzymes that detoxify toxins and break fats into fatty acids

vacuoles

isolate substances capture inside the cell, storage

mitochondria

• rod-shaped organelle bound by a double membrane

• each has its own DNA molecule (mitochondrial DNA)

• inner membrane folds into cristae→ increases surface area

• site of ATP production through cellular respiration→ “cell powerhouse”

the cytoskeleton

• microtubules: help maintain the cell’s shape and anchors or assists the movement of organelles

• help detect changes inside and outside the cell

• intermediate fibers: involved in cell-to-cell junction

• action filaments: involved in cell movement

• assembly regulated by the centrosome

centrioles

• found near the nucleus of every cell in the area called the centrosome

• form the mitotic spindle in cell division

• forms the basal body (anchor point) for each cilium or flagella

cilia

• motile extension of cell membrane; consist of microtubules in cylindrical pattern that beat back and forth in coordinated manner

• forms a “fringe” on surface of certain epithelial cells

• shorter than flagella, but very abundant when present

• propel mucus in respiratory tract, propel egg toward uterus

flagella

• another type of motile extension from cell membrane

• similar in structure to cilia, but much longer

• causes the entire cells to move

• tail of sperm cell is the only flagellum in a human cell

• each cell has only 1 flagellum

the semipermeable membrane only allows what?

only certain ions and molecules can cross through

passive process

does NOT require cellular energy; transport based on concentration gradient (movement from greater to lesser concentration)

active processes

DOES require cellular energy (ATP); transport against concentration gradient (movement from lesser to greater concentration)

simple diffusion

• transportation of a solute from an area of higher concentration to lower concentration

• movement follows the concentration gradient

• passive→ no ATP required

osmosis

movement of water from higher to lower concentration (passive)

tonicity

concentration of solute vs. concentration of water

isotonic

equal concentration of solutes (dissolves substances) and solvent (water) inside and outside cell; cell is maintained

hypotonic

higher concentration of water (lower concentration of solutes) outside the cell; water moves into the cell causing it to swell and eventually lyse

hypertonic

lower concentration of water (higher concentration of solutes) outside the cell; water moves out of the cell causing it to shrink or crenate

facilitated diffusion

• solutes are transported by means of a protein carrier

• movement from area of higher concentration to lower concentration

• passive

filtration

• movement of liquid from high pressure to low pressure

• passive

• blood pressure creates the hydrostatic pressure in capillaries where filtration occurs

active mechanisms

• require cellular energy in the form of ATP to move substances across the memebrane

• active transport, endocytosis, exocytosis, and transcytosis

active transport

• solutes move against the concentration gradient (low concentration to higher)

• requires a protein carrier (often called pumps) and cellular energy (ATP)

• the sodium/potassium pump is an important pump that all cells have

endocytosis

• bring into cell

• the plasma membrane envelopes a substance and forms an intracellular vesicle

• Phagocytosis: (cell eating); cell ingests solid particles

• Pinocytosis: (cell drinking); cell consumes solutions

• need ATP

exocytosis

• send out of cell

• a vesicle fuses with the plasma membrane as secretion occurs

• need ATP

what is the importance of growth and reproduction of cells?

-it is the most fundamental of all living functions

-constitute the cell life cycle

-cell growth depends on the use of genetic information in DNA to make the structural and functional proteins needed for cell survival

-cell reproduction ensures that genetic information is passed from one generation to the next

the cell cycle

• set of stages that takes place in between the time a cell divides and the time the daughter cell divides

• controlled by external and internal signals

• interphase, mitosis, and cytokinesis

• some specialized cells don’t go through the cell cycle, muscle and nerve cells

interphase

• cell is not dividing, but it is growing and preparing to divide; carries on regular activities

• G1 Phase: cell doubles number of organelles and accumulates material used for DNA synthesis (end serves as “check point” for continuation of cell on to S Phase- Apoptosis)

• S Phase: “synthesis” phase; DNA replication occurs

• G2 Phase: cell synthesizes proteins that will assist cell division and completes replication of centrioles

mitosis

• the M stage

• the process of organizing and distributing nuclear DNA during cell division

• 4 phases: prophase, metaphase, anaphase, and telophase

cytokinesis

• division of cytoplasm and organelles

• begins in anaphase and completes in telophase

• actin filament form a ring around the equator that contracts, pinching the cell in half

DNA replication

• when replication is complete, two identical doubles helix molecules have been formed

• each strand of this double helix is equivalent to a chromatid; held together by the centromere

protein synthesis

• DNA also serves as a template for RNA formation→ protein construction

• transcription: formation of mRNA

• translation: involves mRNA, tRNA, and rRNA; specifies the order of amino acids in a polypeptide

prophase

• the centrioles begin moving towards opposite ends of nucleus and spindle fibers appear between the

• nuclear envelope begins to fragment, and nucleolus disappears

• chromosomes appear randomly and attached to spindle fibers by their centromere

metaphase

• literally means “position-changing phase” or “in the middle phase”

• chromosomes are moved by the cytoskeleton into an orderly pattern

• aligned along a plane at the “equator” of the cell; between the centriole pairs at the opposite poles of the cell

• each chromatid attaches to a spindle fiber

anaphase

• means “apart phase”

• the centromere of each chromosome splits to form two chromosomes, each consisting of a single DNA molecule

• each chromosome is pulled toward the nearest pole to form two separate but identical pools of genetic information

• move towards opposite poles of the cell; toward centrioles

telophase

• means “end phase”; marks end of mitosis of the cell cycle

• DNA returns to its original state and location within the cell

• after completion of telophase, each daughter cell begins to develop into a mature cell

• chromosomes become chromatin as spindle disappears and nucleoli appear

• nuclear envelop reassembles and two daughter nuclei can be observed

what is the importance of mitosis?

• maintains chromosome number

• each cell in out body is genetically identical

• each cell type has certain gens turned “on” and others turned “off” to give the different types of body cells

• important to the growth and repair of multicellular organism

apoptosis

• programmed cell death

• normal part of development

• a continuous, stepwise process

• removes webbing between fetal fingers and toes

• protective, peels away damaged skin cells after sunburn

necrosis

cell death from damage

not a normal process