cell biology Flashcards
what are the three main components of a cell
plasma membrane
cytoplasm
nucleus
what is the plasma membrane?
the flexible outer surface of a cell separating the internal and external environments
list the passive proccesses by which movement occurs through the membrane
Diffusion: molecules moving from regions of high to low concentration
o Simple diffusion: moves through the lipid bilayer unassisted
o Facilitated diffusion: diffusion with help (carrier mediated or channel mediated)
list the active proccesses by which movement occurs through the membrane
Active transport: uses ATP to push substances through the membrane against the gradient (low to high)
Vesicular transport: (involves a vesicle)
o Endocytosis: movement of substances into a cell in vesicles
1. Pinocytosis: membrane engulfs small droplets of fluid from extracellular
2. Phagocytosis: membranes engulf solid particles from the extracellular environment
o Exocytosis: moves substances out (exits) of a cell in secretory vesicle, fuses with plasma membrane and releases contents into ECF
what is endocytosis
endocytosis: movement of substances into a cell in vesicles
what is pinocytosis
- Pinocytosis: membrane engulfs small droplets of fluid from extracellular
what is phagocytosis
- Phagocytosis: membranes engulf solid particles from the extracellular environment
what is exocytosis
o Exocytosis: moves substances out (exits) of a cell in secretory vesicle, fuses with plasma membrane and releases contents into ECF
what is diffusion
Diffusion: molecules moving from regions of high to low concentration
explain the structure of the plasma membrane
- Lipid bilayer = made of lipid + protein
Lipid = phospholipid, cholesterol, glycolipids
Proteins = integral and peripheral proteins
what is the nucleolus and what does it do
Nucleolus: a spherical structure within the nucleus; produces components of the ribosomes, which are important in protein synthesis.
what is the function of the nucleus
- Controls cellular structure
- Directs cellular activity
- Contains nucleoproteins and DNA, which encodes the instructions for making cells, tissues, organs, and eventually, the whole organism
what is the cytoplasm
• The part of the cell outside the nucleus; bounded by the plasma membrane
what is the cytosol
- The viscous fluid portion of the cell
what is the role of the cytosol?
- Maintain cell structure and cellular growth
whatis the role of the cytoskeleton
- Maintains structural integrity of cell that are dynamic in nature. Movement of cells, organelles and muscle fibre contraction
what are the 3 structural elements of the cytoskeleton
- Microfilaments
- Microtubules
- Intermediate filaments
why may organelles be folded?
to increase SA for absorption
what is the rough ER responsible for?
ribosomes -protein synthesis
what is the smooth ER responsible for?
- Detoxifies drugs/harmful substances
- Store/release Ca2+ fpr muscle contraction in form of sER called sarcoplasmic reticulum
what are ribosomes
- Small, granular organelles found within the cytosol (free) or bound to rER
what do bound ribosomes do?
Bound ribosomes: synthesise proteins destined for secretion
what do free ribosomes do?
Free ribosomes: synthesise proteins to be used in cytosol
what is the function of the golgi apparatus
modify and package proteins
what is the mitochondria matrix
- Mitochondrial matrix – fluid filled cavity between inner membrane and cristae.
what does the mitochondria perform?
- “cell powerhouse” – perform aerobic respiration, converting carbohydrates and oxygen into carbon dioxide and water, thus generating energy (in form of ATP
what produces lysosomes?
golgi complex
what are the three specialisations of the cell surface?
microvilli
stereocilia
cilia
what is microvilli
- Small, close together protrusions (brush border)
where is microvilli found?
small intestine
proximal renal tubules
what is stereocilila?
elongated microvilli
where is stereocilia found?
- found in the inner ear, epididymis, vas deferens
what is cilia
- short hair; like projections from cell surface
elongated motile structures
what benefits does cilia provide
- Moves fluid and particles over cells surface
where is cilia located
respiratory tract
what is flagella
- similar in structure to cilia but longer
- moves the entire cell
e.g. of flagella
sperm cell tail
what are cell junctions
Cell junctions are intercellular connections between the plasma membranes of adjacent cells
what are the five cell junctions
tight junction adherens junction desmosomes hemidesmosomes gap junctions
explain tight junctions
- Web-like strands of transmembrane proteins that fuse together adjacent plasma membrane
- prevents leakage
e.g. of tight junctions
uriniary bladder
what does the adherens junction do?
- Adheres several cells together so that they function as one unit
what is the adherens junction made of?
- Made of plaques (dense layer of proteins attached to microfilaments and membrane proteins) joined by cadherins (transmembrane glycoproteins) e. g. cardiac muscle cells
e.g of a adherens junction
cardiac muscle cells
what does desmosomes cell junction do
- Specialised for strong adhesion
- Link intracellularly to intermediate filaments in cytoskeleton
What are desmosomes specialised for?
- Specialised for strong adhesion
e.g. of desmosomes
- e.g. epidermis, myocardium
describe hemidesmosomes cell junctions
- Anchor epithelial cells to basement membrane
e.g. of Hemidesmosomes
- e.g. skin, cornea, GI and respiratory tract
what do gap junctions do?
- Connect cytoplasm of 2 cells, allows molecules and ions to pass through
- Transmembrane channels/tunnels connecting cells
e.g. gap junctions
- e.g. neurons and cardiac cells (cell types involved in direct electrical activity)
what is the principle function of epithelial tissues
Covering, lining and protecting surfaces (e.g. skin and gut), secretion (glands), absorption (intestine), sensation (neuroepithelium), contractility (myoepithelial cells)
main two types of epithelial tissues
- Covering: the cells are organised in layers that cover the external surface or line the cavities of the body
- Glandular: the cells specialised to produce secretions
what are some basic features of epithelial tissues?
- consists of an uniterrupted layer of tightly packed cells
- polarised: has a free surface (the aprocal surface) exposed ot the outside and the basal surface (opposite) which may be attached to the underlying connective tissue
- constantly regenerates and renews
- epithelium is avascular – receives nutritents by diffsion from lamina propia
what is the basement memnbrane formed by?
- Basement membrane is formed by secretion of both, epithelial cells and cells in connective tissue
what does THE basement membrane seperate?
- It separates epithelium from the underlying connective tissue
what are the two layers that compose a basement membrane?
basal lamina
reticular lamina
what is the basal lamina
- basal lamina : the layer closely attached to the basal surface of the epithelium – consists of protein filaments (collagen.. etc.)
what is does the reticular lamina consist of?
- reticular lamin: consists of reitcular fibres embedded in hround substance – synthesised by cells of the connective tissue underlying the epithemium.
what are the two types of epithelia
simple
stratified
