H2 Biology 6 - Cell structure

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

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

selective barrier b/w aq interior & exterior of cell, restricts movement of polar molecules/charged ions across membrane >

separates cytoplasm from extracellular fluid

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

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

folded membranes form network of tubules >

ribosomes absent from membrane

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

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

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

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

site of AeR; energy in form of ATP synthesised during [O] of substrates >

heat production; 55% of energy of respiration given off as heat

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

site of polypeptide synthesis; translation of mRNA into protein 1^o structure >

LRS contains peptidyl transferase, catalyses formation of peptide bonds b/w adjacent a.a

single membrane bound vesicle, contains hydrolytic enzymes w/ low optimum pH 1-5

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

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

site of photosynthesis; 2 stages, LDR on thylakoids, LIR in stroma >

involved in biosynthetic processes; e.g. synthesis of biomolecules such as a.a

composed of 2 membranes(double membrane) >

outer membrane continuous w/ ER, perforated w/ nuclear pores

separates DNA in nucleus from cytoplasm >

regulate entrance, exit of small polar molecules/macromolecules(mRNA, proteins) b/w nucleus & cytoplasm via nuclear pores

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

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

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

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

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

plays role in nuclear division; act as MTOC >

centrioles produce spindle fibres growing towards metaphase plate during mitosis

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