Chapter 3 The cell Flashcards
Modern Cell Theory
- All organisms composed of cells and cell products
- Cell is the unit of life
- An organism’s structure and functions are due to the activities of its cells.
- Cells come only from preexisting cells, not from nonliving matter.
- Cells of all species have many fundamental similarities in their chemical composition and metabolic mechanisms.
Cell Shapes
• Squamous - thin and flat with nucleus creating bulge
• Polygonal - irregularly angular shapes with 4 or more
sides
• Stellate – starlike shape
• Cuboidal – squarish and about as tall as they are wide
• Columnar - Like a column
• Spheroid to Ovoid – round to oval
• Discoid - disc-shaped
• Fusiform - thick in middle, tapered toward the ends
• Fibrous – threadlike shape
Cytoplasm
• fluid between the nucleus and surface
membrane
contains: organelles, cytoskeleton and cytosol
Resolution
• ability to reveal detail
Plasma membrane form
- surrounds cell
* made of proteins and lipids
Extracellular Fluid
• fluid outside of cell
Plasma membrane function
- defines cell boundaries
- governs interactions with other cells
- controls passage of materials in and out of cell
- intracellular face – side that faces cytoplasm
- extracellular face – side that faces outward
Membrane Lipids
98% of plasma membrane are lipids
• Phospholipids
• Cholesterol
• Glycolipids
Phospholipids
- Most of the membrane lipids are phospholipids
- drift laterally from place to place
- movement keeps membrane fluid
hydrophilic Phospholipids
•heads face water on each side of membrane
hydrophobic tails
• directed toward the center, avoiding water
Cholesterol
– holds phospholipids still and can stiffen membrane
Glycolipids
– phospholipids with short carbohydrate chains on extracellular face
– contributes to glycocalyx – carbohydrate coating on the cells surface
Membrane Proteins Form
- Transmembrane proteins
* Peripheral proteins
Transmembrane proteins
- pass through membrane
- have hydrophilic regions in contact with cytoplasm and extracellular fluid
- have hydrophobic regions that pass back and forth through the lipid of the membrane
- most are glycoproteins
- can drift about freely in phospholipid film
- some anchored to cytoskeleton
Peripheral proteins
- adhere to one face of the membrane
* usually tethered to the cytoskeleton
Membrane Proteins Function
• receptors, second-messenger systems,
enzymes, ion channels, carriers, cell-identity
markers, cell-adhesion molecules
Membrane Receptors
• Bind to chemical signal
(hormones such as insulin) neurotransmitter
Membrane Enzymes
• enzymes in plasma membrane carry out
final stages of starch and protein digestion
in small intestine
Ion Channels (Gated Channels)
– some constantly open
– some are gated-channels that open and close in
response to stimuli
• ligand (chemically)-regulated gates
• voltage-regulated gates
• mechanically regulated gates (stretch and pressure)
Membrane Carriers or Pumps
• Transmembrane proteins bind to glucose,
electrolytes, and other solutes
(consumes ATP)
Cell-Identity Markers
• Enables our bodies to identify which cells
belong to it and which are foreign invaders
• Glycoproteins contribute to the glycocalyx
(acts as an id tag)
Glycocalyx
• Unique fuzzy coat external to the plasma membrane • Functions - cell identification - fertilization - embryonic development – transplant compatibility
Microvilli
• Extensions of membrane
increase surface area needed for absorption
Cilia
- nonmotile primary cilium
* Motile cilia
Motile cilia
• sweep substances across surface in same direction
Flagella
- tail of the sperm - only functional flagellum
- allows the sperm to fertilize the egg
- movement is more undulating, snakelike movement is snakelike
Membrane Transport
- plasma membrane
- passive transport mechanisms
- active transport mechanisms
- carrier-mediated mechanisms
plasma membrane
• a barrier and a gateway between the
cytoplasm and ECF
passive transport mechanisms
- requires no ATP
* filtration, diffusion, osmosis
active transport mechanisms
- consumes ATP
* active transport and vesicular transport
carrier-mediated mechanisms
- can move substances from one side to another in use of a protein
- sometimes uses atp sometimes no atp is needed
Filtration
• process in which particles are driven through a selectively permeable membrane by hydrostatic pressure (force exerted on a membrane by water)
Simple Diffusion
- no ATP required
* the net movement of particles from area of high concentration to area of low concentration
Diffusion Rates
– temperature - ⬆ temp ⬆ motion of particles
– molecular weight - larger molecules move slower
– steepness of concentrated gradient - ⬆ difference, rate⬆
– membrane surface area - ⬆ area,⬆ rate
– membrane permeability - ⬆ permeability, ⬆rate
Membrane Permeability
- Diffusion through lipid bilayer (small substances)
- Diffusion through channel proteins (water)
- Cells control permeability
Osmosis
• movement of water from one side of a selectively permeable membrane to the other
Aquaporins
• channel proteins specialized for passage of water
effects tonicicty
Tonicity
- Tonicity - ability of a solution to affect fluid volume and pressure in a cell
- Hypotonic solution- has a lower concentration of non permeating solutes than intracellular fluid
- Hypertonic solution- has a higher concentration of nonpermeating solutes
- Isotonic solution – no changes in cell volume or cell shape cause the concentration is the same
Carrier-Mediated Transport
• Transport proteins in the plasma membrane that carry
solutes from one side of the membrane to the other
• solute binds to a specific receptor site on carrier protein
facilitated diffusion
• move high to low
• carrier-mediated transport (carries protein) of solute through a membrane down the concentration gradient
no atp
active transport
• sodium-potassium pump keeps K+ concentration
higher inside the cell
• requires ATP
• from low to high
Uniport
• carries only one solute at a time
Symport
• carries 2 or more solutes simultaneously in same direction
Antiport
- carries 2 or more solutes in opposite directions
* (e.x) sodium-potassium pump brings in K+ and removes Na+ from cell
Sodium-Potassium Pump
- each pump cycle consumes one ATP and exchanges three Na+ for two K+
- keeps the K+ concentration higher and the Na+ concentration lower with in the cell than in ECF
- necessary because Na+ and K+ constantly leak through membrane
Vesicular Transport
•processes that move large particles, fluid droplets, or numerous molecules at once through the membrane in
vesicles – bubblelike enclosures of membrane
• motor proteins consumes ATP
Endocytosis
- vesicular processes that bring material into the cell
- phagocytosis-– “cell eating” - engulfing large particles
- pinocytosis – “cell drinking” taking in droplets of ECF containing molecules useful in the cell
- receptor-mediated endocytosis – particles bind to receptors on plasma membrane (surface)
Exocytosis
• discharging material from the cell
Cytoskeleton
- collection of protein filaments
* microfilaments, intermediate filaments, and microtubules
Inclusions
• stored cellular components and fat droplets
Nucleus
- anuclear - RBC no nucleus
* multinucleate- more than one nucleus
nuclear envelope
• phospholipid bilayer that surrounds the nucleus
nuclear pores
• formed by rings of protein
nucleoplasm
• material in nucleus
• chromatin- (thread-like matter) composed of DNA and protein
• nucleoli-one or more dark masses where ribosomes are
produced
Endoplasmic Reticulum
• Produce phospholipds
• detoxification of alcohol other drugs
(in liver)
Rough endoplasmic reticulum
• Produce protein
Ribosomes
• made up of protein and RNA
Function
• read messenger RNA and make proteins from it
Golgi complex
- modification of protein
* carbohydrates synthesis
Lysosomes
- vesicles that have enzymes
* digest protein (destroy things)
autophagy (self eating)
• digest and dispose of worn out organelles
autolysis (self suicide)
• some cells are meant to do a
certain job and then destroy themselves
• webbing of the fingers
Peroxisomes
- main function to detoxify all compounds
* breakdown fatty acids
Mitochondrion
• to produce ATP
Centrioles
• are envoled in the process of cell division (mitosis)
microfilaments (small)
- made of protein actin
- keeps the shape
- envovled in transport of orgenelle
- plays a role in cell division
intermediate fibers (medium)
- thicker and stiffer than microfilaments
- keeps the shape
- envovled in transport of orgenelle
- plays a role in cell division
microtubules (large)
• cylinders made of 13 parallel strands called protofilaments • keeps the shape • envovled in transport of orgenelle • plays a role in cell division
Inclusions
- Stored material no membrane (fat droplets) (pollen)
- Foreign bodies (viruses)
- non essential
