Organelles Flashcards

Question

Endomembrane System: Microbodies photo

Answer 1

cis face - adjacent to ER, vesicles arrive from the ER trans face - points toward plasma membrane ➢ transport vesicles pinch off & fuse with cisternae ➢ carry proteins being modified by the addition of sugar groups ➢ correlation of enzyme location (e.g. which cisterna) & what step it catalyses in sugar-modification pathway

Answer 2

Peroxisomes ▪ single-membrane bound ▪ contain oxidative enzymes In animals ➢ sites of detoxification (e.g. lots in liver) In plants ➢ sites of detoxification ➢ photorespiration (carbon recycling) ➢ conversion of stored fats into sucrose during germination of some seeds (= glyoxysomes)

Answer 3

Membrane growth, secretion ➢ Outward = exocytic pathway ➢ Proteins synthesised on rough ER & glycosylated ➢ Vesicles containing glycoproteins bud off ER & fuse with cis Golgi cisternae ➢ Glycoproteins are further glycosylated as they travel through Golgi cisternae by vesicle budding & fusion ➢ At the trans face of the Golgi, vesicles are directed to plasma membrane or lysosome/vacuole

Answer 4

➢ Inward = endocytic pathway ➢ Ingestion & degradation or recycling) of extracellular molecules ▪ Regions of the plasma membrane containing molecules to be degraded bud inward to form vesicles ▪ Vesicles fuse with early endosomes ▪ Ultimately molecules are degraded in the lysosome /vacuole ▪ Some degradation products can be reused by the cell

Answer 5

➢ Vacuoles of plant cells are sites of degradation ➢ They also act as: ▪ storage organs (e.g. seed proteins) ▪ detoxification sites (e.g. tannins) ▪ pigment deposition (e.g. anthocyanins)

Answer 6

o nucleus – double membrane o Mitochondria – double membrane o chloroplasts – double membrane

Answer 7

➢ Surrounded by a double membrane * continuous with ER * interrupted by pores ▪ allow passage of selected molecules between cytosol & nucleus ➢ Contains most cellular DNA * heterochromatin ▪ DNA + proteins - highly condensed, even at interphase * euchromatin ▪ DNA + proteins - not condensed until mitosis ➢ Typically contains a nucleolus * site of ribosomal RNA (rRNA) synthesis & ribosomal subunit assembly

Answer 8

➢ sites of cellular respiration & major energy (ATP) production in a process called oxidative phosphorylation ➢ surrounded by a double membrane ▪ smooth outer membrane ❖ permeable to ions & small molecules ▪ inner membrane ❖ highly folded (into cristae) ❖ impermeable ❖ transport proteins control substrate movement across the inner membrane ❖ contains an electron transport chain & ATP synthase

Answer 9

Thylakoids ▪ formed by a folded internal membrane system ▪ folded into stacks – grana ➢ light-harvesting pigments ➢ electron transport chain ➢ ATP synthase Lumen ➢ space between thylakoids

Answer 10

➢ Region not taken up by membranes ➢ Contains: ▪ DNA ➔ mitochondrial genome ❖ codes for o mitochondrial tRNA o mitochondrial rRNA o mitochondrial mRNA * proteins for DNA synthesis & oxidative reactions ▪ Mitochondrial ribosomes (70S) ▪ Enzymes for the tricarboxylic acid (citric acid, Krebs) cycle

Answer 11

➢ sites of photosynthesis ❖ two sets of reactions: ▪ light harvesting ▪ carbohydrate production ➢ surrounded by a double membrane: ❖ outer membrane ▪ permeable to ions & small molecules ❖ inner membrane ▪ impermeable ▪ transport proteins control movement of substrates across internal membrane system

Answer 12

➢ region not taken up by thylakoid membranes ➢ contains ❖ DNA codes for ▪ tRNA ▪ rRNA ▪ mRNA ➔ proteins for DNA synthesis & photosynthesis ❖ ribosomes (70S) ❖ enzymes for carbohydrate production

Answer 13

* An ancestral eukaryotic cell ingested, but did not digest an aerobic bacterium, which over time evolved into a mitochondrion. ➔ eukaryotic cells * Eukaryotic cells later ingested a photosynthetic bacterium without digesting it. Over time, this ingested bacterial cell evolved into a chloroplast ➔ plant cells

Answer 14

➢ Digestive enzymes breakdown: * proteins to amino acids * polysaccharides to simple sugars * fats to fatty acids & glycerol ➢ Breakdown products enter cell cytosol for gradual oxidation & production of some energy (ATP) and reducing molecules (NADH) ➢ The final stages and the majority of energy production takes place in the mitochondria.

Answer 15

CYTOSOL: ➢ Glucose & other sugars are converted to pyruvate through glycolysis. ➢ This generates some energy molecules (ATP, NADH) ➢ Some amino acids are converted to pyruvate.

Answer 16

➢ Pyruvate, some amino acids and fatty acids enter the mitochondrion. ➢ Pyruvate, fatty acids and some amino acids are oxidised to acetyl CoA in the mitochondrion.

Answer 17

➢ Acetyl CoA is further oxidised by the citric acid cycle Produces: - CO2 diffuses out of mitochondria via membranes o NADH & FADH2 (FADH2 not shown) o NADH and FADH2 are molecules with strong reducing power Note: some amino acids can enter the citric acid cycle at intermediate steps & be oxidised directly

Answer 18

➢ NADH & FADH2 have strong reducing power = ‘high energy electrons’ ➢ NADH & FADH2 donate electrons to electron transport chain (ETC) in the inner mitochondrial membrane. ➢ The electrons move through the electron transport chain ➔ consist of multiprotein complexes ➢ This results in: ▪ oxidation of NADH & FADH2 ▪ reduction of O2 to H2O ▪ ATP production.

Answer 19

➢ Pumping of electrons leads to a H+ (proton) gradient ▪ higher concentration of protons in the inter membrane space than in the matrix ➢ ATP is synthesised as protons move through the ATP synthase from the inter membrane space into the matrix. ➢ ATP is transported out of the mitochondrion for use by the cell.

Answer 20

➢ Light energy is collected by pigments in the thylakoid membranes ➢ Converted to reducing power (NADPH) and chemical energy (ATP) via a series of oxidation-reduction reactions ➢ H2O being the original electron donor and NADPH the final electron acceptor.

Answer 21

➢ During electron transport, protons move across the thylakoid membranes from the stroma into the thylakoid lumen, generating a proton gradient. ➢ ATP is synthesised as protons move back across the membrane, from the thylakoid lumen into the stroma, through the chloroplastic ATP synthase.

Answer 22

➢ Calvin cycle uses NADPH & ATP produced during the light reactions for the synthesis of carbohydrates from atmospheric CO2 in the stroma. ➢ The enzyme Rubisco = ribulose 1,5-bisphosphate carboxylase/oxygenase catalyses the first reaction in the Calvin cycle ➢ Rubisco is the most abundant enzyme in the world.

Answer 23

➢ complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of eukaryotes, bacteria and archaea. ➢ Functions: support, shape, motility, intracellular transport, chromosome movement, cell division ➢ dynamic - continuously reorganised ➢ three types of components - each formed from protein subunits ▪ actin filaments – microfilaments ▪ intermediate filaments ▪ microtubules

Answer 24

➢ Also known as microfilaments ➢ found in all eukaryotic cells Structure: ▪ composed of linear polymers made up of globular (G-) actin subunits ▪ G-actin monomers combine form a polymer which continues to form the actin filament (7 nm diameter). Two chains intertwine to from an F-actin(Filamentous actin) chain. ▪ cross-linked into bundles & networks ➢ maintenance of eukaryotic cell shape, cell movement, cell division, muscle contraction, intracellular transport and vesicular movement ➢ actin rearrangements within cells is the molecular basis for changes in cell shape & movement

Answer 25

Actin 7nm < intermediate 10nm < microtubules 25nm Found in: ➢ Cytoplasm and nuclear lamin of vertebrates, and many invertebrates Structure: ➢ subunits = heterogeneous family of proteins collectively called intermediate proteins ➢ Two proteins twisted together into an alpha helical dimer. Two dimers form a tetramer. Many tetramers form a rope-like intermediate filament. ➢ Example: keratin filaments Functions: ➢ strengthens the cytoskeleton and nuclear envelope ➢ attachment sites for chromatin ➢ anchoring organelles ➢ protein movement

Answer 26

* … state characteristics of cells and their basic chemistry and life? * … differentiate between archae- and eubacteria, describe features and give examples? * … describe similarities and differences between prokaryotic and eukaryotic cells? * … explain features/structures and roles of ribosomes, membranes and organelles? * … explain a model for the origin of mitochondria and plastids? * … explain key metabolic processes in mitochondria and chloroplasts related to energy production and carbon metabolism? * … describe components of the cytoskeleton and give examples for their roles?

Answer 27

Found in all eukaryotic cells Structure ➢subunits = tubulin - dimers of - & *- tubulin ➢dimers stack into filaments, which form walls of stiff hollow tubes (25 nm in diameter) Function ➢ Maintenance of cell structure ➢ intracellular organisation & transport, mitosis, internal structure of cilia & flagella ➢ Main constituents of mitotic spindles Location ➢ extend from an organising structure, e.g. centrosome, spindle pole, basal body

Organelles Flashcards

(76 cards)