Outline the cell theory.
cell is fundamental unit of structure & fn in living organisms >
all known cells made up of one or > cells >
all cells arise from pre-existing cells by division >
cells contain DNA, passed from cell to cell during cell division >
energy flow occurs in cells >
all cells same in chemical composition in organism of similar species >
unicellular organisms = 1 cell, multicellular organisms = many cells >
activity of organism depends on total activity of cells
Describe structure of CSM.
phospholipids align w/ one another >
hydrophobic fatty acid tails buried inside 2 layers of hydrophilic phosphate groups >
forms sheet composed of 2 parallel layers = phospholipid bilayer
State functions of CSM.
selective barrier b/w aq interior & exterior of cell, restricts movement of polar molecules/charged ions across membrane >
separates cytoplasm from extracellular fluid
Describe structure of RER.
folded membranes form network of sheets(flattened cisternae) >
ribosomes present on membrane >
ER membrane continuous w/ outer membrane of nuclear envelope >
prominent in protein-secreting cells
State functions of RER.
site of protein synthesis; protein enters ER lumen thru pores >
forms part of intracellular transport system/endomembrane system, transports proteins to GB by transport vesicles budding off from ER membrane, vesicles replenish membrane of GB >
protein modification; enzymes glycosylate proteins
Describe structure of SER.
folded membranes form network of tubules >
ribosomes absent from membrane
State functions of SER.
lipid synthesis; phospholipids & steroids >
carbohydrate metabolism(in liver); glucose phosphorylase catalyses removal of phosphate group from glucose in SER for it to leave cell >
drug/poison detoxification(in liver cells); enzymes add -OH groups to toxins, > soluble & easier to remove from body >
stores calcium ions for muscle contractions
Describe structure of GB.
consists stack of flattened membrane-bound sacs(cisternae) & Golgi vesicles >
2 faces;
cis face receives transport vesicles from ER >
trans face where vesicles bud off; secretory vesicles w/ protein fuses w/ CSM, secretes protein by exocytosis >
lysosomes w/ hydrolytic enzymes remain in cytoplasm for intracellular digestion/autophagy/autolysis
State functions of GB.
further protein modification, sorting, packaging & transportation of proteins; proteins phosphorylated/glycosylated from cis>trans faces, proteins then sorted, packaged into vesicles @ trans face, vesicles transported to other parts of cell/release contents out of cell >
forms lysosomes; lysosomes w/ hydrolytic enzymes fuse w/ food/phagocytic vesicles for digestion >
produce cell wall components
Describe structure of mitochondrion.
surrounded by envelope of 2 membranes(double membrane) >
inner membrane highly folded, form cristae >
↑ SA for proteins to be embedded, ↑ respiration efficiency >
contains matrix(fluid within cristae) w/ 70s ribosomes, DS circular DNA & phosphate granules
State functions of mitochondrion.
site of AeR; energy in form of ATP synthesised during [O] of substrates >
heat production; 55% of energy of respiration given off as heat
Describe structure of ribosomes.
small organelle, consists of LRS & SRS >
made of protein & rRNA >
70s ribosomes found in mitochondria/chloroplasts/prokaryotes; 80s ribosomes found in eukaryotes >
subunits are assembled from rRNA genes in nucleolus & proteins imported from cytoplasm >
subunits exported to cytoplasm via nuclear pores, attach to mRNA form ribosome
State function of ribosomes.
site of polypeptide synthesis; translation of mRNA into protein 1o structure >
LRS contains peptidyl transferase, catalyses formation of peptide bonds b/w adjacent a.a
Describe structure of lysosomes.
single membrane bound vesicle, contains hydrolytic enzymes w/ low optimum pH 1-5
State functions of lysosomes.
intracellular digestion to digest large insoluble material
lysosome fuses w/ phagocytic vacuole, hydrolytic enzymes digest materials within >
products assimilated by cytoplasm, undigested substances remain in vacuole >
vacuole fuses w/ CSM, release contents out of cell by exocytosis >
autophagy to digest worn-out organelles
ER membrane encloses worn-out organelle, forms autophagic vesicle >
autophagic vesicle fuses w/ lysosomes, become autophagic lysosomes >
organelle digested, products assimilated >
autolysis
self-digestion of cell by releasing hydrolytic enzymes of all lysosomes into cytoplasm, occurs after cell death/damage
Describe structure of chloroplasts.
chromoplasts/coloured plastids, contain green pigment chlorophyll >
surrounded by envelope of 2 membranes(double membrane) >
inner membrane encloses fluid-filled space called stroma, contains enzymes, sugars, DS circular DNA, starch grains, lipid droplets & 70s ribosomes >
system of internal membranes instroma consists of interconnected set of flat, disc-like sacs(thylakoids) >
thylakoids arranged in stacks(grana) >
diff grana joint by intergranal lamellae
State functions of chloroplasts.
site of photosynthesis; 2 stages, LDR on thylakoids, LIR in stroma >
involved in biosynthetic processes; e.g. synthesis of biomolecules such as a.a
Describe structure of nuclear envelope.
composed of 2 membranes(double membrane) >
outer membrane continuous w/ ER, perforated w/ nuclear pores
State functions of nuclear envelope.
separates DNA in nucleus from cytoplasm >
regulate entrance, exit of small polar molecules/macromolecules(mRNA, proteins) b/w nucleus & cytoplasm via nuclear pores
Describe structure of nucleus.
largest cell organelle, enclosed by double membrane envelope perforated w/ nuclear pores. contains chromatin which is diffused form of chromosomes during interphase; contains nucleolus.
largest cell organelle, enclosed by double membrane envelope perforated w/ nuclear pores >
contains chromatin, diffused form of chromosomes during interphase >
contains nucleolus
State functions of nucleus.
contains genetic material(DNA), directs cellular activity >
protein synthesis; central dogma of biology states that genetic material flows from DNA>mRNA>polypeptide >
cell division; DNA replication
Describe structure of nucleolus.
largest structure in nucleus >
appears as darkly-stained spherical body >
formed by large loops of DNA from no. of chromosomes containing genes coding for rRNA >
nucleoli ↑ in cells active in protein synthesis
State functions of nucleolus.
site of rRNA synthesis; contains genes coding for rRNA hence site of transcription these genes >
site of RS formation; rRNA combines w/ proteins, form LRS &SRS >
RS leave nucleus via nuclear pores, both combine to form ribosome
Describe structure of centrioles.
exists as pair of rod-like structures made up of 9 triplets of microtubules arranged in ring >
pair of centrioles position themselves perpendicular to EO
State functions of centrioles.
plays role in nuclear division; act as MTOC >
centrioles produce spindle fibres growing towards metaphase plate during mitosis
Describe flow of proteins destined for secretion out of cell.
polypeptide formed by ribosome attached to RER during translation >
enters RER, undergoes PTM(glycosylation) >
released from RER, moves to cis face of GB via transport vesicles >
protein released into cisternal space of GB for further modification, sorting, packaging into secretory vesicles/lysosomes >
protein undergoes modifications(e.g. phosphorylation/glycosylation) >
protein secreted out of cell(exocytosis)/remains in lysosomes as hydrolytic enzymes