Chapter 3 - Cells Flashcards
What is a Cell?
cell is the basic unit of structure and function in the
body.
* Cells are measured in micrometers
* Cells that have developed specialized characteristics are
said to be differentiated.
* Cells vary in size and shape; structure and function are
inter-related.
what is a composite cell
there is no typical cell, but a composite cell shows components found in most cells
3 Major Parts of a Cell
Nucleus, Cytoplasm, Cell Membrane
Nucleus
Contains genetic material, directs cell’s activities
Cytoplasm
Consists of organelles, with specific functions, suspended in a
liquid called cytosol
Cell membrane
Outer boundary of the cell
* Maintains integrity of cell
* Separates intracellular fluid (cytosol) from extracellular
fluid
* Selectively permeable: Regulates entry and exit of
substances
* Signal transduction: permits cell to receive and respond to
messages
* Consists mainly of lipids and proteins, with some
carbohydrates
Phospholipid bilayer: Cell membrane framework
Water-soluble (hydrophilic) heads form surfaces
* Water-insoluble (hydrophobic) tails form interior
* Bilayer is permeable to lipid-soluble substances, but not to
water-soluble substances
Cholesterol
Stabilizes membrane, helps keep it
impermeable to water-soluble substances
Membrane proteins have many functions. What are they?
Think pcrecic
Pores, channels,
receptors, enzymes, cell contact and identification, CAMs
(Cell Adhesion Molecules)
Carbohydrates
Think c, I, s
Cell recognition and interaction, self markers
Cytoplasm is…?
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, a supporting framework of
protein rods and tubules
Cytoskeleton
supporting framework of
protein rods and tubules
Cytospl
fluid portion of the cytoplasm
Organelles
tiny solid structures with specific functions in the cell
Ribosomes are?
Composed of protein and RNA
* Free in cytoplasm or on RER
* Provide structural support and enzyme activity to link amino
acids in protein synthesis
Endoplasmic Reticulum (ER
Membrane-bound sacs, canals, vesicles
* Tubular transport system
* Rough ER contains ribosomes, conducts protein synthesis
* Smooth ER does not have ribosomes; conducts lipid synthesis
Vesicles
Membranous sacs
store or transport substances
Golgi Apparatus
**Think of UPS system
sacs of flattened, membranous sacs
refines, packages, and delivers proteins made of the RER
Example of organelle interaction
Milk secretion is an example of interaction among rough
and smooth ER, Golgi apparatus, and transport vesicles
Mitochondria
Membrane-bound, fluid-filled sacs
* House chemical reactions that extract energy from nutrients
(cellular respiration, which produces ATP)
* Called the “powerhouse of the cell
Lysosomes
Small membranous sacs
* Contain enzymes that digest proteins, carbohydrates, nucleic
acids, bacteria, debris, worn out cell parts
* “Garbage disposals” of cell
Peroxisomes
Membranous sacs similar to lysosomes
* Contain enzymes that digest lipids, alcohol, hydrogen peroxide
Microfilaments, Microtubules, and Intermediate Filaments
Thread-like structures in cytoplasm that create the cytoskeleton
Microfilaments
tiny rods of actin
* Provide cellular movement, such as muscle contraction
Intermediate filaments:
Composed of several proteins
* A cytoskeletal structure
* Support nuclear envelope
Microtubules
Larger tubes of tubulin
* Rigidity maintains cell shape
* Make up cilia, flagella, and centrioles
* Help move organelles
Centrosome
“Central body” ; consists of 2 centrioles
* In cytoplasm, near nucleus
* Centrioles are cylindrical, composed of microtubules
* Centrioles produce spindle fibers during cell division,
which distribute chromosomes to forming daughter cells
Cilia
Motile extensions of cell membrane
* Consist of microtubules in cylindrical pattern
* Form a “fringe” on surface of certain epithelial cells
* Shorter than flagella, but very abundant when present
* Beat back and forth in coordinated manner
* 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
* Flagellum causes the entire cell to move
* Tail of a sperm cell is the only flagellum in a human cell
* Each cell has only 1 flagellum
Cell nucleus contains?
genetic material and controls cell activities
Nuclear envelope:
Double-layered membrane surrounding nucleus
* Separates nucleoplasm from cytoplasm
* Nuclear pores allow 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
Physical (Passive) Mechanisms:
Do not require cellular energy (ATP)
* Diffusion, osmosis, facilitated diffusion, filtration
Diffusion
Movement of atoms, molecules, or ions, from region of higher
concentration to region of lower concentration
* Occurs due to constant motion of atoms, molecules, ions
* Occurs only with substances that the cell membrane is permeable to:
oxygen, carbon dioxide, and other lipid-soluble substances
Example of Diffusion?
A sugar cube dissolving in water
Diffusion extra info
Solutes and water can diffuse across a membrane that is permeable
to both of them until they reach equilibrium; at that point, the
concentrations of water and the solute are equal in both compartments
Tonicity
Ability of a solution outside cell to alter water volume inside cell
Isotonic Solution
same osmotic pressure; cells in an isotonic
solution have no net gain or loss of water
Hypertonic Solution
higher osmotic pressure; cells in a hypertonic
solution lose water
Hypotonic Solution
lower osmotic pressure; cells in a hypotonic
solution gain water
Filtration
Process that forces molecules through membranes by
exerting pressure
* Used to separate solids from water, or small particles from
large ones.
* Example: When blood plasma leaves capillaries, water
and small solutes are filtered, but large plasma proteins
are not.
* Passive process; no ATP required
Active Mechanisms
Require ATP to move substances across cell membrane
* Active transport
* Endocytosis
* Exocytosis
* Transcytosis
Active Transport
Movement of substances across a membrane from region of
lower concentration to region of higher concentration (against
concentration gradient)
Uses carrier molecules in cell membrane, which are often called
pumps
Active Process requires…?
ATP Energy
Endocytosis
Movement of a substance into the cell inside a vesicle
* Substances too large to enter by other methods can enter
cell this way
3 types of endocytosis:
Pinocytosis: membrane engulfs droplets of liquid
Phagocytosis: membrane engulfs solid particles
Receptor-mediated endocytosis: membrane engulfs
specific substances, which have bound to receptor
proteins on the membrane
Exocytosis
Release of substances/particles from cell
* Vesicles containing particles fuse with cell membrane and
release contents
* Example: Release of neurotransmitters from nerve cells
Transcytosis
Involves receptor-mediated endocytosis followed by exocytosis
* Quickly transports substance from one end of cell to the other
* Moves substances across barriers formed by tightly connected
cells
* Example: Transport of HIV across lining of anus or vagina
Cell Cycle:
Series of changes a cell undergoes from the time it forms
until the time it divides
Stages of the Cell Cycle:
Interphase
Mitosis
Cytokinesis
Interphase
Growth of cell, maintenance of normal
functions
Mitosis
Somatic cell division produces two daughter cells from an original cell:
Division of nucleus via karyokinesis
Cytokinesis
Division of cytoplasm
What is the Interphase?
A very active period in cell cycle
* Cell grows and maintains normal functions
* Cell replicates genetic material (DNA) to prepare for mitosis
(nuclear division)
* Cell synthesizes organelles, membranes, and biochemicals to
prepare for cytokinesis (division of cytoplasm
Phases of Interphase?
S (synthesis) phase: DNA is replicated during this phase
* G1 and G2 (growth or gap) phases: Structures and other
molecules are duplicated
Phases of Mitosis:
Prophase
Metaphase
Anaphase
Telophase
Prophase
Chromatin condenses to form chromosomes, centrioles
move to opposite sides of cytoplasm, nuclear envelope and nucleolus
disperse
Metaphase
Spindle fibers from centrioles attach to chromosomes
and align them midway between centrioles
Anaphase
Chromosomes separate and move in opposite directions
toward centrioles as the spindle fibers shorten
Telophase
Chromosomes return to chromatin structure, nuclear
envelope forms around each chromosome set, and nucleoli become
visible
Cytokinesis = cytoplasmic division and…?
Begins during anaphase
* Continues through telophase
* Contractile ring of actin filaments pinches cytoplasm in half
* Constriction is called a cleavage furrow
* Newly formed cells will have identical DNA, may have
slightly different size and number of organelles
Characteristics of Cancer Cells
Loss of cell cycle control
Heritability (a cancer cell divides to form more cancer cells)
Transplantability (a cancer cell implanted into another individual will cause
cancer to develop)
Dedifferentiation (loss of specialized characteristics)
Loss of contact inhibition
Ability to induce local blood vessel extension (angiogenesis)
Invasiveness
Ability to metastasize (spread)
Differentiation
process of specialization of cells
Stem Cell
Can divide to form two new stem cells (called self-renewal)
* Can also divide to form a stem cell and a progenitor cell
* Can differentiate as any of many cell types
Progenitor Cell:
Partially specialized stem cell, daughter of stem cell
* Can divide to become any of a restricted number of cells; called a
“committed” cell
Totipotent
Daughter cells that can specialize to become any cell type,
such as fertilized egg, cells of early embryo
Pluripotent
Daughter cells that can become a limited number of cell
types, such as stem cells of later development, progenitor cells
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
