bio test 2 Flashcards
cell
- fundamental structural and functional unit of an organism/living thing - capable of performing all the necessary functions of life
- very small; many are only as small as 1/1000 mm (1 micrometer)
surface area to volume ratio
- the smaller the cell is, the larger its SA2VR is
- makes cell more efficient in absorption and excretion at the cell’s surface
- many cells increase their SA2VR by having finger-like projections (brush border)
3 examples of finger-like projections
- villi in small intestine have many tiny projections called microvilli which increase efficiency of absorption of nutrients
- PCT (proximal convoluted tubule) of a nephron in the kidney has microvilli for efficient absorption
- alveoli in lungs are very small to increase SA2VR for efficient diffusion of oxygen into carbon dioxide out of blood/lungs
organelles
- almost all human cells have these in common
- perform specific tasks/functions
nucleus
- controls all cell activities through genes on DNA such as protein synthesis, cell division and all other metabolic functions
chromatin and chromosomes
- made up of DNA and proteins such as histones
- chromatin is seen as a network of fibrils when cell is not dividing. during cell division, distinctly shaped chromosomes are seen
- human cells normally have 23 pairs of chromosomes
nucleoplasm
- semifluid. liquid found in nucleus, rich in enzymes and many monomers like nucleotides
- nucleoplasm has slightly different pH and composition than cytoplasm
nuclear envelope/membrane
- double membrane which separates nucleus from cytoplasm
- similar to cell membrane but lacks recognition chains found on surface of cell membrane
nuclear pores/holes
- nuclear membrane has tiny pores through which info and materials pass between nucleus and cytoplasm
- ex/ RNA synthesized in nucleus passes through pores for cytoplasm and some proteins produced in cytoplasm are imported
nucleolus
- 1 or more dark area inside nucleus
- produces rRNA (ribosomal RNA). rRNA is the major component of ribosomes (ribosome = rRNA + proteins)
rough endoplasmic reticulum (RER) location
- typically RER are attached to nuclear envelope
- abundance of RER found where proteins/enzymes are synthesized such as liver and pancreas cells
translation in RER
- individual amino acids are brought to ribosomes attached to ER and joined together by peptide bonds. result is linear structure of protein which enters lumen/ cavity of RER.
final protein shape given in RER
- hydrogen bonds between amino acids form resulting in secondary structure. ionic bonding between R-groups of amino acids/disulphide bonding gives the protein its tertiary structure. for some proteins such as myosin, the 3D shape is final. other proteins like oxygen carrying protein in red blood cell, Hb, moves on to 4th stage where several proteins join together to work as team
carb chain/metals/ minerals and other specific components attached in RER
- functional proteins are rarely 100% amino acids. they have carb chains attached to them. these proteins are known as glycol (sugar) proteins like the ones present on surface of plasma membrane
- metals such as iron are present in Hb. attachment of iron in Hb is done in RER.
rigorous quality control of freshly prepared proteins maintained in RER
- incorrectly formed or folded, or proteins with errors during synthesis are rejected by RER. rejected polypeptides are stored in lumen or sent out for recycling.
emphysema
this lung disease occurs when a faulty gene makes wrong folding of protein. protein is assembled as usual but due to wrong folding, RER quality control rejects it and it never reaches its destination
cystic fibrosis and RER quality control
- occurs when a single amino acid, phenylalanine, is missed at a particular position during translation/putting amino acids together by a faulty gene. RER finds error and rejects the required protein causing complications like irregularities in chloride ion transport and accumulation of mucus
smooth endoplasmic reticulum (SER)
- not studded with ribosomes; smooth in texture
- abundance found in liver where detox of drugs happens (liver is known as gate keeper. everything that enters blood /body will pass through liver), in testis and ovaries where steroid hormones are made, and in cells which make lipids and phospholipids.
main functions of SER
- transport products of RER to Golgi bodies (packaged into transport vesicles)
- synthesis of oils such as skin oils and skin glands
- synthesis of phospholipids for plasma membrane
- synthesis of steroids and cholesterol
- detoxification of drugs and alcohol (their byproducts are poisonous for cells)
ribosomes
- made up of 2 subunits and consist of rRNA + proteins
- proteins are assembled here from amino acids
- only known organelles in cells which lack plasma membrane
smaller subunit of ribosome, larger
- s: binding site for mRNA (messenger RNA)
- l: completes the ribosome
3 types of ribosomes
- free ribosome
- polysomes/polyribosomes
- ribosomes attached to ER/ on RER
Golgi bodies/apparatus
- continues function of processing, modification, and attaching destination tags. after products leave the ERs, Golgi gives finishing touches and packages them into secretory vesicles
- Golgi and RER attach destination tags so that they would go where they are meant for
lysosomes
- one of the many types of products which are given final touches by the Golgi for cell’s internal use
- “garbage disposal units” “suicide sacs”
- tiny vesicles which contain hydrolytic enzymes for cell’s internal use. enzymes break apart unwanted polymers by the process of hydrolysis
where may products of ERs be used?
- for internal use or to export to other cells. if for export, they are sent to cell membrane and exported to other cells by a process called exocytotis
functions of lysosomes
- auto digestion (old/nonfunctional cell parts are broken down and recycled)
- breaking down bacteria and viruses which invade cells
- destroying cells which could become cancerous
- when cell itself becomes “too old” and not as useful, cell commits suicide using hydrolytic enzymes
abundance of lysosomes and Golgi are found in…
- Golgi is abundant in cell’s synthesizing products (liver, pancreas)
- lysosomes abundant in cells which fight infections (white blood cells or WBCs)
mitochondrion is bound by a ___
double membrane. inner membrane invaginates (folds inwards) finger- like projections known as cristae