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Ribosomes (~ 22 nm) Small organelles often attached to the RER but also found free in the cytoplasm Site of protein synthesis Not membrane bound A large protein subunit and a small ribosomal RNA (rRNA) subunit form the functional ribosome Subunits bind with mRNA (copy of gene) in the cytoplasm This starts translation of mRNA for protein synthesis (assembly of amino acids into proteins) 80S in eukaryotes Larger (22 nm) Composed of 60S + 40S subunits Links amino acids to make polypeptide (protein) 70S in prokaryotes Smaller (18 nm) Composed of 50S + 30S subunits Free ribosomes make proteins used in the cytoplasm. Responsible for proteins that go into solution in cytoplasm or form important cytoplasmic structural elements S = Svedberg unit - sedimentation coefficient (rate of sedimentation under centrifugal force in a sucrose gradient) Ribosomal ribonucleic acid (rRNA) is made using the DNA in the nucleolus Two types of ribosomes exist 1S = 10-13 s Larger units sediment faster 1 Mitochondria (1µm in diameter and 2- 7µm in length) Double membrane structure – inner membrane is folded - folds are termed cristae; can divide to make more mitochondria in more active cells Power house of the cell – site of production of ATP – the universal energy carrier; free energy from energy rich molecules (e.g. glucose) is stored in the form of ATP Cristae provide a large surface area for attachment of proteins and enzymes required for the later stages of aerobic cell respiration (electron transport and oxidative phosphorylation) Matrix – contains enzymes involved with the Krebs cycle; synthesis of lipid and phospholipids; contains DNA and RNA ; contains ribosomes – able to manufacture some of their own proteins (enzymes) Cells with a high metabolic activity (e.g. heart muscle cell; plant root cell) have many well developed mitochondria – i.e. with more cristae and enzymes, to provide large amounts of ATP Stalked particle in inner membrane – site of ATP production Cross section 2 Chloroplast (4-6 µm in diameter and 4-10 µm in length) Only in photosynthesizing cells (plants) and some protoctists Double membrane envelope with a third internal membrane system (thylakoid membrane system) in the stroma Thylakoids – site of light dependent reactions - are membrane bound structures containing the light absorbing pigment chlorophyll, and arranged in the form of stacked flattened discs (grana), joined by connecting membranes (lamellae) and surrounded by fluid (stroma) – large surface area Stroma – fluid containing enzymes for making organic compounds (e.g. glucose ) by light independent reactions; contains DNA, ribosomes, and lipid droplets Using light energy, the inorganic reactants, CO2 and H2O are converted to organic chemical energy (glucose) and O2 – light energy is transformed into chemical energy in glucose Photosynthesis 6CO2 + 6H2O C6H12O6 + 6O2 Intergranal lamella Starch grain Chloroplasts are moved around plant cells by the cytoskeleton– to maximise light absorption 3 Flagella (Undilipodia) and Cilia Flagella (longer) and cilia (shorter) are cylindrical hair like extensions that stick out from the surface of cells. They are made of protein microtubules, covered with an extension of the plasma membrane Flagella (one or few) move organisms through a liquid medium– e.g. bacteria, spermatozoa, protozoa Cilia (large numbers on a cell) – move cells through a fluid medium (e.g. paramecium), or, Paramecium – a ciliate move fluid past the cell - e.g. ciliated cells in trachea to move mucus, with trapped material (e.g. bacteria, dust) towards the throat Each flagellum (or cilium) is made up of a cylinder that contains 9 microtubules arranged In a circle, with 2 microtubules in a central bundle – a 9+ 2 arrangement. Microtubule function requires energy (ATP) Trypanosome (a flagellate) – a protozoan 4 - causes sleeping sickness 9 + 2 arrangement The motor protein dynein has “arms” that can push one doublet ahead of the other 5 Plant Cell Walls Covers outside of cell surface membrane of plant cells Made of cross-linked chains of cellulose (polymer of beta-glucose) molecules, crosslinked by hydrogen bonds Forms sieve like network of strands – confers strength and shape Held rigid by internal pressure (in vacuole) – gives turgidity - gives support to plant and prevents cell from bursting (due to high internal osmotic pressure) Plant cell “ghosts” (cell contents removed – cellulose cell walls remain) 6 Cooperation between organelles – illustrated by protein synthesis and secretion 1 DNA contains the gene for insulin – DNA is located in the nucleus 2 DNA unwinds (using the enzyme helicase); a mRNA copy of the gene (e.g. for insulin) is made by transcription 3 mRNA leaves the nucleus through a nuclear pore and attaches to a ribosome on the rough endoplasmic reticulum (or with free ribosomes) 4 Ribosome translates mRNA into protein; protein enters lumen of RER; insulin assumes a tertiary (3D) shape (conformation) 5 Vesicles containing insulin are pinched off from RER – vesicles transport insulin to Golgi apparatus. 6 Vesicles fuse with the Golgi apparatus (cis face) and release insulin into the lumen 7 Golgi apparatus processes and packages insulin into secretory vesicles for secretion 8 Secretory vesicles (formed from the trans face) move to the plasma membrane 9 Secretory vesicles fuse with the plasma membrane and release (secrete) insulin by exocytosis Organelles involved – nucleus, ribosomes, RER, vesicles, and, plasma membrane 7 Nucleus 4 3 Protein is secreted (expelled) by exocytosis 2 9 1 Plasma membrane 6 5 8 7 Ribosomes on RER generally synthesize proteins destined for secretion (export) – e.g. the hormone insulin in pancreatic endocrine cells. Free ribosomes make proteins required for intracellular function 8 Destination proteins (“address proteins”) are present in membranes of vesicles “Address proteins” are embedded in membranes of vesicle in order to direct vesicles to their particular destinations . • Destinations (target organelles) have complementary receptors to address proteins • Shape of receptor and address protein are complementary COPI proteins coat vesicles that transport materials from the Golgi to the rough endoplasmic reticulum COPII proteins coat vesicles that transport materials from the RER to the Golgi 9 Cytoskeleton Interconnected system of fibrous proteins (fibers) in the cytoplasm - between organelles – not a rigid structure - assembled or dismantled in seconds Enables cell movement – e.g. white blood cells, amoeba; enables intracellular movement of organelles (e.g. chloroplasts, vesicles, centrioles),proteins, translocation of mRNA from nucleus to ribosomes in cytoplasm in protein synthesis Provides mechanical strength to cells and shape; holds organelles in place; maintains cell shape (e.g. red blood cells) Forms the spindle during cell division to move chromosomes / chromatids – termed microtubules – composed of tubulin – require ATP to drive movement 10 Prokaryotic Cells (Bacteria & Blue-green Algae) Kingdom – Prokaryotae (“before nucleus”) • Small (0.5 - 5µm); unicellular - simple; little internal organisation; reproduce by binary fission • No membrane bound organelles present (e.g. nucleus, mitochondria, etc) • Single circular chromosome (“nucleoid”) – suspended freely in cytoplasm – not membrane bound; “naked” - no proteins (histones) associated with DNA. May contain plasmids – small, extra chromosomal pieces of circular DNA • Mesosome (one or more) – infolding of cell membrane; increases surface area for location of vital enzymes (e.g. respiratory enzymes for energy production; photosynthetic membrane – containing photosynthetic enzymes) • Ribosomes - 18 nm (22 nm in eukaryotes) • Cell wall present – composed of mucopeptide (murein) • Flagella – sometimes present - for movement; • Pili – extensions of cell membrane – for attachment (to other cells or surfaces), involved in “sexual” reproduction • Slime layer (polysaccharide or polypepide) – for attachment to surfaces ; protection against desiccation • Capsule – for additional protection Forms colonies containing individual cells – never tissues or multicellular organisms 11 A generalised bacterial cell (a prokaryotic cell) plasma membrane Size ~ 18 nm 12 Differences between Prokaryotic and Eukaryotic Cells Feature Prokaryotic (bacteria) Eukaryotic (plant/animal/fungi) Size Small cells – 0.5 - 5µm Large cells – 20 – 40 µm and larger Capsule (protection) Present Absent Cell wall Present (peptidoglycan / murein) In fungi (chitin); in plants (cellulose); NOT in animals Plasma (cell) membrane Present (cell surface membrane only) Present (cell surface membrane + membrane bound organelles) Vacuole Absent Present (plant cells only) Temporary in animal cells Absent Absent Absent Absent Absent Small ribosomes (70S), always free in the cytoplasm (size 18 nm) Only in plant cells (has DNA) Present Present Present (+ ribosomes) Present (+ DNA) Larger ribosomes (80S) - size 22 nm; free in cytoplasm and attached to rough ER Cytoplasm - Chloroplast - Lysosomes - Golgi Apparatus - E Reticulum - Mitochondria - Ribosomes 13 Nucleus - Nuclear envelope - Nucleoli - Chromosomes (DNA) Absent Absent Absent Single and circular (+ Plasmid) No histones (DNA is “naked”) Present (true nucleus) Present Present Many and linear (No plasmids) DNA is associated with histones Lipid droplets / glycogen granules Present Present Centrioles (organise spindle fibres for cell division) Absent Only in animal cells Some plant cells? Flagella (undulipodia) (if present) Sometimes present Sometimes present (None in plant cells) Single microtubule Microtubules in 9 + 2 arrangement Present Absent Pili 14 Bacterial flagella Bacterial flagella are structurally different to eukaryotic flagella. They are composed of a spiral of protein (flagellin) The flagellum is anchored into the plasma membrane by a basal body – allowing it to rotate Energy (ATP) is used to rotate the disc which spins the flagellum, thus creating movement 15 √=Present x = Not present S=Sometimes present Eukaryotic and Prokaryotic cells - Summary Cell wall Chloroplasts Nuclear membrane Cell surface membrane Ribosomes (not membrane bound) Plant Cell (Eukaryotic) √ √ √ √ √ (22 nm) Animal Cell (Eukaryotic) x x √ √ √ (22 nm) Bacterial Cell (Prokaryotic) √ x x √ √ (18 nm) Centrioles Mesosome Pili Flagella (undulipodia) Mitochondria Golgi body Endoplasmic reticulum Vacuole Glycogen granules Starch granules Lipid droplets Plasmids Plasmodesmata Capsule x x x x √ √ √ √ x √ √ x √ x √ x x S √ √ √ S √ x √ x x x x S S S x x x x √ x √ √ x S 16 A* Examination Questions & Answers 17 Qs 1 The figure shows an organelle from a ciliated cell as seen with an electron microscope a) Name the organelle b) State the function of this organelle c) State why ciliated cells contain relatively large numbers of these organelles d) Calculate the actual length of the organelle as shown by the line AB in the figure Express your answer to the nearest micrometre (µm). Show your working An image drawn to the same magnification as the figure could be produced using a light microscope. e) Explain why such an image would be of little use when studying cells 18 Ans 1 a) Mitochondrion b) Site of aerobic respiration; release energy (produce ATP by aerobic respiration); provide energy (ATP) for movement of cilia c) Require large amount of energy for movement of cilia d) Use formula: M=I/A A = I /M Actual size = Image size / 20 000 Image size (I) - measure the image size (line AB) in mm and convert to micrometres Line AB = 100 mm = 100 000 micrometres Substitute in formula: A = 100 000 / 20 000 = 5 µm 19 Qs 2 State one function of each of the following. a) b) c) d) Mitochondrion. Centriole. Lysosome. Chloroplast. Ans 2 a) aerobic respiration / respiration using oxygen provides / produces , ATP ; releases / provides , energy AVP ; e.g. Krebs cycle, protein synthesis , ornithine cycle, regenerate NAD, lipid cycle, oxidative phosphorylation, oxidation of fats (beta oxidation) b) ref spindle / microtubules / cytoskeleton ; synthesis urea Ignore mitosis c) contains / has / provides , digestive / hydrolytic / named , enzymes; digestion / destruction / breakdown , of , cell / organelle / foreign body / pathogen / bacteria / unwanted material / unwanted structure ; DO NOT CREDIT engulfs / removes d) photosynthesis / light absorption / ATP production / NADPH production / carbohydrate production / named carbohydrate production ; ALLOW traps light lipid / protein , synthesis ; 20 Qs 3 The hormone insulin is a protein. It is produced in the human pancreas. Once insulin molecules have been produced they are secreted through the cell membrane into the blood. Describe the sequence of events involved in the production of an insulin molecule until it passes through the cell membrane. Ans 3 DNA unwinds (enzyme – unwindase / DNA helicase); complementary base pairing occurs – transcription; mRNA formed from DNA template (enzyme RNA polymerase) mRNA is translocated to cytoplasm through nuclear pores; m RNA attaches to ribosomes on RER Specific activated amino acids translocated to ribosomes from cytoplasm by tRNAs as specified by codons on mRNA Amino acids linked via peptide bond (enzyme – transpeptidase) until mRNA is translated into a protein (insulin) Insulin detaches from ribosomes and enters the lumen of the RER - assumes a 3D (tertiary) structure Vesicles containing insulin are formed - vesicle fuse with the Golgi body (cis face); insulin is further modified in Golgi body – e.g. addition of carbohydrate. Insulin is enclosed in vesicles produced by Golgi body – vesicles budded off from Golgi body (trans face) Vesicles fuse with cell membrane and release insulin to the exterior by exocytosis 21 Qs 4 Organisms can be classified based on observable features. Using the information below, label the five bacteria (1 to 5) with the correct letter Bacterium P has a single flagellum to enable it to move whilst bacterium Q has several flagella. Only bacterium R has visible plasmids and bacterium S has a mesosome Bacterium T has a slime capsule 1 2 4 3 5 Ans 4 1-R 2–S 3 -P 4-T 5-Q 22 Qs 5 The drawing shows some bacterial cells. The drawing has been magnified 6000 times. a) Calculate the actual length, in micrometres, of cell A. Show your working A capsule surrounds each of these cells. The main chemical constituent of this capsule is a nitrogenous polysaccharide. b) List the elements present in this compound. c) Give one way in which: i) The genetic material in cell A would differ from that in an animal cell; ii) The distribution of membranes in this bacterial cell would differ from the distribution of membranes in a plant cell. 23 Ans 5 a) Measure length of cell A = 33 mm = 33 000 um (illustrated measurement) Use formula – M = I / A; A=I/M A = 33 000 / 6000 = 5.5 um Answer = 5.5 µm b) Nitrogen, Carbon, Hydrogen and Oxygen c) i) In bacterial cell (cell A) DNA/genetic material is naked and not in a membrane-bound nucleus ii) DNA is not associated with proteins (histones) DNA in loop (circular) DNA in plasmids (extra chromosomal DNA) In bacterial cell No membrane-bound organelles (e.g. mitochondria; endoplasmic reticulum) Bacteria only have a plasma membrane Have mesosomes (infoldings of plasma membrane – location of respiratory enzymes) 24 Qs 6 The cells in the human body and in plants are eukaryotic cells. a) State what is meant by a eukaryotic cell The different organelles within a cell may be seen using an EM The figure is of an electron micrograph of a plant cell showing cell organelles. The organelle labelled D is shown at a higher magnification. b) c) Name the organelles labelled A to C State one function of each of the organelles labelled D to F. The figure is an EM showing a lymphocyte d) Use the scale bar to calculate the actual diameter of the cell along the line X---Y. Show your working and give your answer to the nearest whole number 25 Ans 6 a) A cell that has, membrane bound organelles /nucleus b) i) A B C Nucleus Nucleolus Vacuole ii) D E F Production of ATP / site of aerobic respiration Supports cell Production of glucose /site of photosynthesis c) Measure length of X-----Y - e.g. 10 cm = 100 mm = 100 000 µm Scale bar = 1 cm = 10 mm = 10 000 µm Use formula A=I/M = 100 000 / 10 000 = 10 Answer = 10 µm 26 Qs 7 Leucocytes and palisade mesophyll cells are examples of eukaryotic cells. a) Complete the table below to compare the structure of a leucocyte and a palisade mesophyll cell. Give two structural differences and two structural similarities. Leucocyte Palisade mesophyll cell Structural differences Structural similarities The figure is a diagram of a leucocyte The structures labelled A, B and C are involved in protein synthesis and secretion. b) Outline the roles of these structures in the production of protein. The figure below is an electron micrograph of an erythrocyte. c) Describe how the structure is related to its function. 27 Ans 7 a) Structural differences Structural similarities Leucocyte Palisade mesophyll cell No cell wall Cell wall No chloroplast Chloroplast No large permanent vacuole Large permanent vacuole Centriole No centriole Cytoplasm / cytoskeleton; Vesicles Nucleus /nuclear membrane Cell surface / plasma membrane; SER / RER Ribosomes same size; Mitochondria ; Golgi apparatus b) A B C Packages / modifies proteins (for secretion or use within cell) Contains the genetic code for the protein / produces ribosomes Produces the protein / transports protein / produces vesicles c) Biconcave / large surface area to volume ratio for maximum rate of diffusion / absorption / gas exchange Haemoglobin for transport of oxygen Few organelles / no nucleus, allow it to take on flat / thin / biconcave shape; enable a greater volume for haemoglobin Small size / flexible, to squeeze through capillaries 28 Qs 8 a) State two advantages of using an electron microscope to study cells b) Outline how a sample of tissue may be prepared for the electron microscope The figure shows a mitochondrion, as seen using an electron microscope c) Calculate the actual length of the mitochondrion. Show your working Mitochondria are not found in prokaryotic cells d) State four other ways in which prokaryotic cells differ from eukaryotic cells 29 Ans 8 a) EM provides high magnification EM has high resolution / resolving power b) o o o o o o o c) Specimen dead / killed, as in a vacuum Fix in, glutaraldehyde and osmic acid Dehydrate in alcohol / acetone / propanone; embed in resin / araldite Section, with ultramicrotome / extremely thin / freeze fracture Stain / provide electron scattering capability / electron dense mordant Shadow, with, heavy metal / osmium / uranium / lead / mercury / gold Mount on copper grid – spaces to allow electrons to penetrate Length of image (I) = 60 mm = 60 000 µm; A = I / M = 60 000 / 40 000 = 1.5 µm d) Prokaryotic cell Smaller DNA circular No nucleus / free DNA No associated proteins with DNA Smaller 70S / 18 nm ribosomes No ER No membranous organelles Cell wall (murein) No 9+2 flagella No mitosis / meiosis Eukaryotic cell Larger Nucleus / DNA in nucleus DNA with proteins in chromosome Larger / 80 S / 22 nm, ribosomes Membrane bound organelles (e.g. lysosome) Cell wall not always present (not murein) 9 + 2 flagella Mitosis / meiosis 30 Qs 9 The figure shows an electron micrograph of a cell a) i) State two features of the cell shown that indicates it is eukaryotic ii) The line A-------B represents 20 µm Calculate the magnification of the cell shown. Show your working Microtubules and microfilaments are part of the cytoskeleton b) Suggest two roles of the cytoskeleton in the type of cell shown The cells of a multicellular organism are usually specialised to perform a particular function c) Name the process in which a cell becomes specialised Neutrophils are phagocytic blood cells that can engulf and digest foreign cells found in the blood d) Describe how the ultra structure of a neutrophil is specialised to enable it to perform this function 31 Ans 9 a) i) Nucleus / nuclear envelope / nuclear membrane / nucleolus / Membranebound organelles (e.g. endoplasmic reticulum) ii) Measure scale bar = 90 mm = 90 000 µm Use formula: M=I/A 90 000 / 20 = (x) 4500 b) c) Provides strength / stability / support (cell) Determines shape / changes shape / moves membrane (for endo / exoctytosis Movement of organelles (e.g. lysosomes; chloroplasts) / RNA / protein / chromosomes / chromatids Attach to organelles and hold organelles in place Make up, centrioles / spindle fibres Differentiation d) Many lysosomes / vesicles containing hydrolytic enzymes Many microfilaments / microtubules - intracellular transport; mitosis Many ribosomes / (a lot of) rough endoplasmic reticulum – protein synthesis Many mitochondria – energy from aerobic respiration (lots of) Golgi – modification of proteins and secretion; formation of vesicles (many) receptor sites on cell surface /plasma membrane Multi-lobed nucleus – allows flexibility / diapedisis 32 Qs 10 The Figure is a photomicrograph of cells from a leaf of Canadian pondweed, Elodea canadensis, which lives in fresh water. a) Use the scale bar to calculate the magnification of the photomicrograph. Show your working. A leaf of Canadian pondweed, which had been kept out of water for a short time, was seen to have wilted (its cells were no longer turgid). b) Explain, in terms of water potential, what would happen to its cells if the leaf were then placed in distilled water with a water potential (Ψ) of 0 33 Qs 10 (continued) A student wanted to find out more about the structures labelled A. Use of an electron microscope revealed that each structure labelled A is surrounded by two membranes. c) Name structure A. d) Suggest a function of these membranes around structure A. Some cells of Canadian pondweed were broken open using a liquidiser and some of the structures labelled A were released intact. e) What would happen to an intact structure A if it were then placed into distilled water with a water potential (Ψ) of 0? 34 Ans 10 a) Measure scale bar = 20 mm = 20 000 um M = I / A = 20 000 / 10 Magnification = 2000 X b) Water will enter by osmosis, down a water potential gradient From high water potential to low water potential Cells / vacuoles, get bigger / swell / expand / increase in volume Cell membrane / cytoplasm / cell contents, presses against cell wall Water potential increases until equilibrium Cell wall, stops it from bursting / resists expansion c) Chloroplast d) separates organelle from cell allows reactions to take place in isolation permits / controls / allows , what can , enter / exit e) (organelle) will take up water (by osmosis) burst - because there is no wall (to restrict expansion) / membrane not strong enough 35 Qs 11 The table below contains statements about four biological molecules. a) Complete the table, using a tick or a cross, to indicate whether the statement does or does not apply to each of the biological molecules. The first one has been done for you. 36 Ans 11 37 Qs 12 The Table compares the structures of prokaryotic and eukaryotic cells. a) Complete the table. As chromosomes / chromatin, OR, associated with proteins / histones (diameter of cell) 20 – 40 µm) Ribosomes about 18 nm in diameter Cell wall always present The cytoskeleton is an important component in the cytoplasm of all eukaryotic cells. b) Name one structure, associated with the cytoskeleton, which can bring about cell movement. c) Suggest two processes inside cells that rely on the cytoskeleton for movement. 38 Ans 12 a) In table b) flagellum / cilium / microtubule / microfilament / undulipodium c) (movement inside cells of) chromosomes / chromatids (in cell division) (cytoplasm in) cytokinesis organelles / named organelle (e.g. chloroplasts) RNA (in protein synthesis) proteins 39 Qs 13 The diagram is of a bacterium as seen using an electron microscope The bacterium contains DNA, as do other eukaryotic cells (a) State two other ways in which the structure of the cell in the figure above is similar to a typical animal cell (b) Describe how bacterial DNA differs from that found in eukaryotic cells Some bacteria similar to that shown in the figure can cause disease. Antibiotics are given to patients who are suffering from diseases caused by bacteria. Examples of the mode of action of two antibiotics are given below (c) Antibiotic 1 binds to the enzyme RNA polymerase in bacteria, preventing transcription Antibiotic 2 prevents the formation of peptide cross links between peptidoglycan chains in the cell wall Explain why the prevention of transcription leads to the death of bacteria (d) Suggest how the action of antibiotic 2 on cell walls leads to the death of bacteria 40 Ans 13 a) Cell membrane Cytoplasm Ribosomes Fat droplets / glycogen granules RNA / tRNA / mRNA No vacuoles b) DNA is Circular/not linear; not associated with protein / no histones A single unit of nuclear material Not membrane bound / not in nucleus Replicated more quickly No formation of mRNA No translation (linking of amino acids) No protein synthesis; no enzyme synthesis No essential proteins made; no new cell structures No reproduction Weak wall formed Antibiotic affects growing bacteria / when wall is forming Cell bursts due to high internal osmotic pressure Cannot reproduce c) d) 41 Qs 14 The diagram shows some of the cell structures involved in the secretion of an extracellular enzyme. (a) Identify A, B, C, and D. (b) Outline the role of each of the above structures in this process. Ans 14 a) A = nucleus; B = ribosome/RER; C = (RER) vesicle; D = Golgi body b) (nucleus) contains DNA which codes for the enzyme; DNA code is transcribed to messenger RNA mRNA attaches to ribosomes; code on mRNA translated into the polypeptide polypeptide is transported through cell to Golgi body in vesicle of rough endoplasmic reticulum polypeptides in Golgi body combined / modified to form enzyme; carried in Golgi vesicles to cell surface; for secretion/exocytosis 42 Qs 15 The diagram shows a cell from the proximal (first) convoluted tubule in the nephron of the kidney. (a) Label two features on the diagram that help the cell to take up glucose from the glomerular filtrate. (b) Explain how the two features of the cell help in the uptake of glucose from the glomerular filtrate. 43 Ans 15 a) Labels: mitochondrion microvilli / brush border b) microvilli/brush border increases surface area for uptake of glucose/ enables greater uptake of glucose/ref to larger amount of carrier protein present mitochondria provide ATP (energy); for active transport of glucose (into intercellular fluid) 44 QsQ16 The diagram shows the structure of a chloroplast. a) Name structures labelled A to E on the diagram. b) Describe where in the chloroplast: the light dependent reaction takes place. the light independent reaction takes place. c) Describe three similarities in the structure of chloroplasts and mitochondria. 45 Ans 16 a) A = double membrane B = starch grain C = granum / grana D = stroma E = lipid droplet b) Light dependent reaction – granum / thylakoid membranes/quantosomes Light independent reaction - stroma c) Any three of: both have double outer membrane large internal surface area / many internal membranes contain DNA / ribosomes contains lipid droplets in mitochondria catalyses oxidative phosphorylation; in chloroplasts catalyses (cyclic / non cyclic) photophosphorylation enables both to synthesise proteins/polypeptides; 46 Qs 17 The table below describes the structure and function of organelles in eukaryotic cells. Complete the table by filling in the empty boxes A, B, C, D and E Ans 17 A - ribosome manufacture/synthesis of ribosomal RNA B - mitochondria C - increase surface area for attachment of enzymes/for electron transfer chain/oxidative phosphorylation D - lysosomes E - lipid / steroid synthesis / transport 47 Qs 18 The diagram below shows an electron micrograph of a cell. a) Name the parts labelled A, B, C, D, E and F. b) What evidence can be seen in the diagram that suggests that the cell is: i) metabolically active and involved in secretion of enzymes. ii) involved in production or modification of lipids Ans 18 a) A. Golgi body; B. Centriole; C. Nucleolus; D. double nuclear membrane; E. mitochondrion; F. rough endoplasmic reticulum b) i) Any three of: presence of many mitochondria large rough ER with ribosomes presence of microvilli / Golgi body large nucleus (ii) presence of much smooth endoplasmic reticulum 48 Qs 19 The table below refers to a Bacterial cell, a liver cell and a palisade mesophyll cell and to the structures which may be found inside them. If a feature is present in the cell, place a tick in the appropriate box and if a feature is absent from the cell, place a cross in the Appropriate box. Ans 19 49 Qs 20 The diagram below shows the structure of a mitochondrion a) Name structures A to E. b) State where the following are situated in the mitochondrion. (i) The enzymes involved with oxidative phosphorylation and electron transport. (ii) The enzymes involved with the Krebs cycle. (iii) Why does the mitochondrion contain RNA? c) The magnification of the diagram is 130,000 times. Calculate the actual length of the mitochondrion. Express your answer in um. Make your measurements along the axis XY Ans 20 a) A = outer membrane; B = inner membrane; C = ribosomes; D = crista; E = DNA b) i) Cristae ii) Matrix iii) Synthesises of proteins / polypeptides - e.g. Enzymes c) XY = 112 mm = 112,000 µm; 112,000 / 130,000 = 0.86 µm 50