cell structure, membrane transport + ionic homeostasis Flashcards
What are prokaryotic cells?
1) simple cells without nucleus
2) mostly unicellular bacteria
What are eukaryotic cells?
complex cells with nucleus + organelles
What is the plasma membrane?
outer, limiting membrane that separates cell’s internal parts from extracellular fluid/external environment
What is the function of the plasma membrane?
1) regulates flow of materials into/out of cell
2) identifies cell to other cells
3) participates in intercellular signalling
What is the lipid bilayer?
arrangement of molecules in two parallel sheets in cellular membrane that acts as barrier to polar substances
What are transmembrane proteins?
gatekeepers that allow passage to specific molecules/ions
Give some example of plasma membrane proteins.
1) ion channel (integral)
2) carrier (integral)
3) receptor (integral)
4) enzyme (integral + peripheral)
5) linker (integral + peripheral)
6) glycoproteins
What is the function of ion channel proteins?
allows specific ions to move through water-filled pores
What is the function of carrier proteins?
carries specific substances across membrane by changing shape
What is the function of receptor proteins?
recognises specific ligands + alters cell’s function in some way
What is the function of enzymes?
catalyses reaction inside/outside cell
What is the function of linker proteins?
1) anchors filaments inside + outside plasma membrane
2) provides structural stability + shape for cell
3) may participate in movement of cell/link 2 cells together
What is the function of glycoproteins?
distinguishes your cell’s from anyone else’s
How do substances move across cellular membranes?
via passive/active transport processes
What happens in passive processes?
substance moves down concentration/electrical gradient using only its kinetic energy
What happens in active processes?
cellular energy used to drive substance “uphill” against concentration/electrical gradient
What is the cellular energy used in active processes?
adenosine triphosphate (ATP)
What is cytoplasm?
cytosol + all organelles except nucleus
What are chromosomes?
small, threadlike structure in nucleus of cell that bears genetic material; composed of DNA + proteins
What is cholesterol?
lipid that is the most abundant steroid in animal tissues; located in cell membranes + used for synthesis of steroid hormones + bile salts
What is cytosol (intracellular fluid)?
semifluid portion of cytoplasm in which organelles + inclusions are suspended + solutes are dissolved
What factors influence the rate of diffusion across plasma membranes?
1) steepness of concentration gradient
2) temperature
3) mass of diffusing substance
4) surface area
5) diffusion distance
How does steepness of the concentration gradient influence the rate of diffusion?
the greater the difference in concentration between the two sides of the membrane, the higher the rate of diffusion
How does temperature influence the rate of diffusion?
the higher the temperature, the faster the rate of diffusion
How does mass of the diffusing substance influence the rate of diffusion?
the larger the mass, the slower the diffusion rate
How does surface area influence the rate of diffusion?
the larger the membrane surface area available for diffusion, the faster the diffusion rate
How does diffusion distance influence the rate of diffusion?
the greater the distance over which diffusion must occur, the longer it takes
What is simple diffusion?
passive process in which substances move freely through lipid bilayer of plasma membranes of cells without help of membrane transport proteins
What moves across the lipid bilayer through simple diffusion?
1) nonpolar, hydrophobic molecules
2) small, uncharged polar molecules
Give some examples of nonpolar, hydrophobic molecules.
1) oxygen
2) carbon dioxide
3) nitrogen gases
4) fatty acids
5) steroids
6) fat-soluble vitamins
Give some examples of small, uncharged polar molecules.
1) water
2) urea
3) small alcohols
What is facilitated diffusion?
passive process in which an integral membrane protein assists a specific substance across the membrane
What is channel-mediated facilitated diffusion?
process in which a solute moves down concentration gradient through membrane channel
What are channels?
integral membrane proteins that allow specific, small, inorganic ions to pass across the membrane by facilitated diffusion
What are carriers?
integral membrane proteins that undergo changes in shape in order to move substances across the membrane by facilitated diffusion
What do the mechanisms of gating (opening/closing) depend on?
1) voltage
2) ligands
3) temperature
4) pH
5) mechanical stress
osmosis
passive net movement of water through a selectively permeable membrane from an area of high water concentration to one of lower water concentration
What is osmosis opposed by?
hydrostatic pressure
How can water pass through plasma membrane?
1) through lipid bilayer by simple diffusion
2) through aquaporins (integral membrane proteins)
tonicity
measure of a solutions ability to change the volume of cells by altering their water content
antiporters
carry two substances across the membrane in opposite directions
symporters
carry two substances across the membrane in the same direction
vesicle
small spherical sac formed by budding off from a membrane
endocytosis
materials moving into a cell in a vesicle
What are the types of endocytosis?
1) receptor-.mediated endocytosis
2) phagocytosis
3) bulk-phase endocytosis
exocytosis
vesicles fusing with the plasma membrane, releasing their contents into the extracellular fluid
transcytosis
combination of endocytosis + exocytosis
phagocytosis
phagocyte engulfs large particles such as viruses/bacteria/dead cells
What are the 2 types of phagocytes?
1) macrophages
2) neutrofils
What is exocytosis important for?
neurotransmitter signalling
exocytosis
release of materials from cells
cytosol
intracellular fluid surrounding the organelles
organelles
specialised structures within a cell
cytoskeleton
network of protein filaments throughout the cytosol
What are the 3 types of cytoskeletons?
1) microfilaments
2) intermediate filaments
3) microtubules
microfilaments
generate movement/mechanical support
intermediate filaments
stabilise organelle positions/attach cells together
microtubules
determine cell shape/movement of organelles + vesicles
cilia
short, hair-like projections from the cell surface that move fluids along a cell surface
flagella
long projections that move an entire cell
ribosomes
site of protein synthesis
Where are ribosomes found?
attached to outer surface of nuclear membrane + endoplasmic reticulum
What do ribosomes contain?
large amounts of ribosomal RNA (rRNA)
endoplasmic reticulum
network of membranes in the shape of flattened sacs/tubules
rough endoplasmic reticulum
connected to the nuclear envelope, a series of flattened sacs whose surface is stuffed with ribosomes
What does the rough endoplasmic reticulum produce?
secretory/membrane/organellar proteins
smooth endoplasmic reticulum
network of membrane tubules without ribosomes that synthesises fatty acids + steroids/detoxifies certain drugs
golgi complex
3-20 flattened, membranous sacs called cisternae
What does the golgi complex do?
modify/sort/package proteins for transport to different destinations
lysosomes
vesicles that form from the golgi complex + contain powerful digestie enzymes
peroxisomes
vesicles that detoxify several toxic substances such as alcohol, using oxidase enzymes
Where are peroxisomes abundant?
liver
proteasomes
vesicles that continuously destroy unneeded, damaged, faulty proteins
Where are proteasomes found?
cytosol + nucleus
What do proteasomes contain?
a multitude of protease enzymes
What is the role of mitochondria?
generates ATP by aerobic respiration
Where are mitochondria prevalent?
active cells (muscles/liver/kidney)
What shape is the nucleus?
spherical/oval
nuclear envelope
double membrane that separates the nucleus from the cytoplasm
nuclear pores
numerous openings in the nuclear envelope that control movement of substances between nucleus + cytoplasm
nucleolous
spherical body that produces ribosomes
What are the 3 main parts of a eukaryotic cell?
1) plasma membrane
2) cytoplasm
3) nucleus
How many chromosomes are there in most cells of the human body?
46
What are the non-polar parts of phospholipids?
fatty acid tail groups
Most intravenous solutions are ? with respect to blood cells.
isotonic
What is the site of synthesis of rRNA and assembly of rRNA + proteins into ribosomal subunits?
rough endoplasmic reticulum??????????
What other organelle besides the nucleus contains DNA?
golgi complex??????????
What organelle engulfs worn-out organelles, digests its chemical components, and recycles them?
lysosomes?????????
