The Anatomy and Physiology of The Cell - AnaPhy Lecture Flashcards
- Acts as a boundary
- Controls what enters and leaves cell
- Regulates chemical composition
- Maintains homeostasis
Plasma Membrane
What is the structure of a Plasma Membrane?
Fluid Mosaic Model
Plasma membrane has a
Phospholipid bilayer with proteins partially or fully
imbedded
- Acts as a boundary
- Controls what enters and leaves cell
- Regulates chemical composition
- Maintains homeostasis
Plasma membrane
the plasma membrane has the consistency of olive oil at body temperature, due to unsaturated phospholipids.
Fluid
membrane proteins form a collage that differs on either side of the membrane and from cell to cell (greater than 50 types of proteins), proteins span the membrane with hydrophilic portions facing out and hydrophobic portions facing in.
Mosaic
Substance Permeability Across Membrane
Few molecules move freely:
Water, Carbon dioxide, Ammonia, Oxygen
embedded in lipid bilayer
Transport Proteins
channel for lipid insoluble molecules and ions to pass freely through
Channel Proteins
bind to a substance and carry it across membrane, change shape in process
Carrier Proteins
Types of Passive Transport
- Diffusion
- Osmosis
- Facilitated diffusion
- molecules move to equalize concentration
Diffusion
- Special form of diffusion
- Fluid flows from lower solute concentration to higher solute concentration
- Often involves movement of water: Into cell/Out of cell
Osmosis
solvent + solute =
solution
– Solutes in cell more than outside
– Outside solvent will flow into cell
Hypotonic
– Solutes equal inside & out of cell
Isotonic
– Solutes greater outside cell
– Fluid will flow out of cell
Hypertonic
- Channels (are specific) help molecule or ions enter or leave the cell
- Channels usually are transport proteins (Aquaporins facilitate the movement of water)
- No energy is used
Facilitated Diffusion
How does facilitated diffusion work?
- Protein binds with molecule
- Shape of protein changes
- Molecule moves across membrane
- movement of water and solute molecules across the cell membrane due to hydrostatic pressure generated by the cardiovascular system.
- Depending on the size of the membrane pores, only solutes of a certain size may pass through it.
Filtration
- Molecular movement
- Requires energy (against gradient)
Active transport
example of active transport
sodium-potassium pump
Movement: To the ICF
Vesicles: Large membrane bound vesicle
Mechanism: phagosome pinches off from the cell membrane
phagocytosis
engulfs a bacterium or other particles
phagocytosis
To move large molecules or particles into cells
endocytosis
Movement: To the ICF
Vesicles: Smaller vesicles
Mechanism: membrane surface indents, could be nonselective or receptor mediated
endocytosis
export large lipophobic molecules, (proteins), get rid of wastes left in lysosomes, insert proteins into the cell membrane
exocytosis
Movement: To the ECF
Vesicles: Intracellular vesicles
Mechanism: Rabs, help vesicles dock onto the membrane, & SNAREs, which facilitate membrane fusion
exocytosis
Movement of large material
– Particles
– Organisms
– Large molecules
Movement is into cells
endocytosis
Types of endocytosis
- bulk-phase (nonspecific)
- receptor-mediated (specific)
Process of Endocytosis
- Plasma membrane surrounds material
- Edges of membrane meet
- Membranes fuse to form vesicle
- Reverse of endocytosis
- Cell discharges material
exocytosis
Process of Exocytosis
- Vesicle moves to cell surface
- Membrane of vesicle fuses
- Materials expelled
Components of Cytoplasm
– Interconnected filaments & fibers
– Fluid = cytosol
– Organelles (not nucleus)
– Storage substances
Cytoskeleton are made of 3 fiber types
microfilaments, microtubules, intermediate filaments
strands made of spherical protein subunits called actins
microfilaments
hollow tubes of spherical protein subunits called tubulins
microtubules
tough, insoluble protein fibers constructed like woven ropes composed of tetrameter (4) fibrils
intermediate filaments
– mechanical support
– anchor organelles
– help move substances
Cytoskeleton
– Short
– Used to move substances outside human cells
cilia
– Whip-like extensions
– Found on sperm cells
Flagella
- Increase surface area in small intestine for absorption of nutrients
- made up of actin filaments
Microvilli
- a microtubule organizing center made up of pairs of centrioles
centrosome
- small, barrel-shaped organelles
centrioles
- Control center of cell
- Double membrane
nucleus
- Separates nucleus from rest of cell
- Double membrane
- Has pores
nuclear membrane
- Hereditary material
DNA
- Most cells have 2 or more
- Directs synthesis of rRNA
- Forms ribosomes
Nucleolus
- Dense particles consisting of two subunits, each
- composed of ribosomal RNA and protein.
- Free or attached to rough endoplasmic reticulum.
- the sites of protein of synthesis.
Ribosomes
- Helps move substances within cells
- Network of interconnected membranes
Endoplasmic Reticulum
Two types of ER
– Rough endoplasmic reticulum
– Smooth endoplasmic reticulum
- With ribosomes attached to surface
- Manufacture proteins
Rough Endoplasmic Reticulum
- No attached ribosomes
- Has enzymes that help build molecules: Carbohydrates and Lipids
– Smooth endoplasmic reticulum
- A stack of flattened membranes and associated vesicles close to the nucleus.
- Packages, modifies, and segregates proteins for secretion from the cell, inclusion in lysosomes, and incorporation into the plasma membrane
Golgi Apparatus
- Contain digestive enzymes
- Aid in cell renewal
- Break down old cell parts
- Digests invaders
- Contains acid hydrolases
Lysosomes
release energy
mitochondria
store energy
chloroplasts
- Have their own DNA
- Rodlike, double-membrane structures; inner membrane folded into projections called cristae.
- Break down fuel molecules
mitochondria
- cells in various regions of the embryo are exposed to different chemical signals that channel them into specific pathways of development
Cell Differentiation
- attributes aging to little chemical insults and formation of free radicals, both of which have cumulative effects.
wear-and-tear theory
- Most free radicals are produced in the mitochondria.
mitochondrial theory of aging
According to this theory, cell damage results from (1) autoimmune responses, which means the immune system turns against one’s own tissues, and (2) a progressive weakening of the immune response, so that the body is less able to get rid of cell-damaging pathogens.
cell aging due to progressive disorders in the immune system
which means the immune system turns against one’s own tissues
autoimmune responses
so that the body is less able to get rid of cell-damaging pathogens.
a progressive weakening of the immune response
Cessation of mitosis and cell aging are “programmed into our genes.”
One interesting notion here is that a telomere clock determines the number of times a cell can divide.
genetic theory
an enzyme that lengthens the previously shortened telomeres
telomerase
telomerase is pegged as the
immortality enzyme
is found in germ line cells (cells that give rise to sperm and ova), but it is absent or barely detectable in other adult cell types.
telomerase
- programmed cell death
- particularly common in the developing nervous system.
- “Carving out” fingers and toes from their embryonic webbed precursors
- eliminates cells that are stressed, no longer needed, injured, or aged
apoptosis
