Cellular processes, control (2) + (5) Flashcards

Question

what are the 7 stages of translation

Answer 1

1. After *leaving the nucleus*, the **START codon** of the **mRNA binds** to a specific site on a **ribosome**, which holds the mRNA in position. 2. *transfer (t)RNA is a strand of RNA folded so that the anticodon is at one end of the molecule. It carries amino acids corresponding to the anticodon.* 3. a **complementary anticodon** of **tRNA** from the *cytosol* binds to the START codon, and brings the first **amino acid** in the sequence. 4. tRNA molecules continue to bring complementary anticodons and amino acids to the mRNA molecule until the **STOP codon**. 5. At the same time, **peptidyl transferase** catalyses the bonding of the **amino acids** by **peptide** bond to form a **polypeptide chain**. 6. As amino acids bond, they fold into *secondary and tertiary structure*, which is determined by the *sequence of amino acids*. 7. The protein may then be *released* to the Golgi Apparatus for modification/packaging.

Answer 2

Muscle contaction, memory formation, cell division, transmission of nerve impulses 1. synthesis 2. transport eg. pumping ions across cell ms by active transport 3. movement eg. protein fibres in muscle cells for muscle contraction

Answer 3

a *nitrogenous base, adenine*, a pentose sugar, **ribose**, and three phosphate groups Adenine is on the **1st carbon** and phosphates on the **5th carbon** *_(it is a nucleotide)_*

Answer 4

approx. 30.6kJmol-1 energy is released when ATP is hydrolysed to ADP and Pi (inorganic phosphate) a little energy is required to form the bond between Pi and ADP again, releasing water. Net release of energy.

Answer 5

The **instability of bonds between phosphates in ATP.** Fats and carbohydrates are better suited- the energy released in breakdown of these molecules (in cellular respiration) is used to create ATP by phosphorylating ADP. This *constant interconversion means ATP is a good immediate energy store*. *It is a single-step process to hydrolyse ATP. Small quantites of energy are released, preventing large losses of heat energy. Suitable for the metabolic reactions within the cell.*

Answer 6

* **Small**- *therefore it can _move easily_ in and out of cells* * **Water soluble**- *energy-requiring processes occur in _aqueous_ environments* eg. cytosol * *Contains _bonds between phosphates with intermediate_ energy, large enough to be useful for cellular reactions but not so large that energy is wasted as lost heat energy* * **Small quantities of energy are released-** *suitable to cellular needs, energy not lost as heat energy* * **Easily regenerated**, *can be 'recharged' with energy- phosphorylated and dephosphorylated*

Answer 7

a body cell i.e. any cell in a multicellular organism that is not a gamete/sex cell

Answer 8

from the formation of the cell to eventual division into two daughter cells

Answer 9

**I** *interphase: growth and synthesis: **G1, S, G2*** **II** *mitosis: nuclear division: **P, M, A, T*** **III** *cytokinesis: cell division*

Answer 10

G1 = growth phase S = synthesis phase (DNA is replicated) G2 = second growth phase G1 can enter G0, which is programmed cell death (apoptosis) there are check points during the cell cycle: *G1 checkpoint checks for cell size, nutrients, DNA damage* *G2 checkpoint checks for cell size and DNA and organelle replication*

Answer 11

1. a _resting phase_- a period of inactivity or dormancy before entering G1 again 2. _apoptosis_ - programmed cell death 3. _specialised cells_ 4. _senescence_ - cell ageing

Answer 12

The four stages: Prophase, Anaphase, Metaphase, Telophase Within these phases: Appearance of chromosomes Distribution of chromosomes to daughter cells Nuclear division

Answer 13

in animals, **cytoplasm divides** in plants, cytokinesis does not occur; the **cell wall** is laid between two daughter cells

Answer 14

the DNA of the cell **condenses** to change from **chromatin to form chromosomes**

Answer 15

DNA supercoiled around histone proteins a nucleosome is 8 histone molecules with DNA wrapped around them

Answer 16

a continuous stretch of *DNA* containing segments; *genes*; that code for *proteins*

Answer 17

46, made of 23 pairs, of which half have been inherited from one parent and half from the other (mother and father)

Answer 18

the **same length** **centromeres** in the same **position** the same genes at the **same locus** *genes may have alternative alleles, DNA inbetween the genes will be different* after DNA replication, each chromosome is made of **two identical 'sister' chromatids**

Answer 19

any two chromatids in a pair of homologous chromosomes that are not sister chromatids i.e. two molecules of condensed DNA joined by a centromere, with alleles of the same gene at the same locus, and of the same length

Answer 20

**autosomal genes** on the first 22 pairs **sex-linked genes** on the 23rd pair (the sex chromosomes)

Answer 21

1. **intact nuclear envelope** 2. **chromatin** (replicating towards the end of S phase) **nucleolus** present 3. pair of **centrioles** present

Answer 22

1. **centrioles** move to **opposite poles** 2. **spindle fibres** starts to form at opposite poles from **centrioles**, made of **microtubules** 3. **nuclear envelope degrades** 4. pair of **identical chromatids** on each chromosome 5. **centromere present**, joining sister chromatids

Answer 23

1. homologous chromosomes line up at the **metaphase plate/equator** 2. **spindle fibres,** formed from **microtubules,** at both poles 3. they **attach** to the **centromeres** of the sister chromatids

Answer 24

1. **sister chromatids separate** and are pulled to opposite **poles** by **contracting spindle fibres** attached to the centromeres

Answer 25

1. **centrioles replicate** 2. **chromatin reforms/** nucleolus reappears 3. **nuclear envelope** reforms 4. cytoplasm **divides**

Answer 26

ANIMALS equator region invaginates, cytoplasm is split, two daughter cells formed PLANTS cell wall laid between separated nuclei at the equator, cannot invaginate due to rigid cellulose cell wall however, division does occur in meristematic tissue in the cambium of roots, shoots, buds

Answer 27

\>mitotic division chromosomes ensures that 1. **equal quantity of DNA** to both daughter cells 2. the DNA is **genetically identical** for both daughter cells (i.e. genetic variation is only caused by *mutation)* \>**growth** of multicellular organisms \>tissue **repair** \>**asexual reproduction** 1. **binary fission** in unicellular organisms 2. vegetative propagation: **cloned/new plants** grow from parts of **parent plants** (when there is meristematic tissue) eg. runners, tubers, strawberries

Answer 28

the formation of gametes

Answer 29

\< **sexual reproduction** a diploid organism (two sets of homologous chromosomes, one from each parent) produces haploid gametes (a single set of unpaired chromosomes) which contain half the DNA in a somatic cell \< **genetic variation** in the daughter cells, important for survival of a species, such as against disease \< **number of chromosomes is halved** there are two divisions resulting in four daughter cells with half the number of chromosomes

Answer 30

DNA replicates in S phase centrosomes replicate organelles replicate

Answer 31

chromatin condenses to form bivalents i.e. pairs of homologous chromosomes nuclear envelope degrades centrosomes move to opposite poles, spindle fibres start to form, made of microtubules genetic recombination occurs; at chiasmata, sections of chromatids crossover with the same length of non-sister chromatid i.e. the chiasmata is at the same locus of the chromatids

Answer 32

spindle fibres attach to centrosomes on the bivalents, which are lined up on the equator independent assortment; there are 2 possible orientations for each bivalent, leading to 2(22) possible assortments, as each bivalent lines up independent of the other 22.

Answer 33

reduction division pair of homologous chromosomes is split up by contracting spindle fibres and sister chromatids remain attached to their centromere the resulting cells are haploid

Answer 34

two haploid cells form, centrosomes replicate, nucelar envelope reforms, there are 23 homologous chromosomes (46 chromatids), cell membrane invaginates to form cleavage furrow, cytoplasm divides etc.

Answer 35

(short INTERPHASE II, no DNA replication occurs) homologous chromosomes appear due to condensed chromatin, joined by centromeres, nuclear envelope degrades, centrioles move to opposite poles, spindle starts to form

Answer 36

homologous chromosomes line up along equator, spindle attaches to centromere, sister chromatids are no longer identical independent assortment; 2(22) possible assortments as chromosomes line up independent of each other

Answer 37

*autotrophic nutrition* carried out by *plants, algae and cyanobacteria.* The basis for through energy flow food chains.

Answer 38

R: **organic molecules, O₂, CO₂, H₂O, ATP** N R: **light, heat** energy flows into and out of an ecosystem, while the chemical elements essential to life are recycled

Answer 39

the chlorophyll molecules in chloroplasts **absorb violet-blue and red light**, the colours most effective in driving photosynthesis, and **reflect or transmit green light**

Answer 40

on the **thylakoid membranes**, involving two **membrane-bound** photosystems: **photosystem II** and **photosystem I**

Answer 41

*photosystems are the protein complexes where light energy is absorbed* Each photosystem is comprised of a **primary pigment reaction centre** containing the primary pigment **chlorophyll a** and an antenna containing **accessory pigments**, which **pass the light energy** they absorb onto chlorophyll a these are **photosynthetic pigments**, of which there are many types *photosystems are found between the lipid and protein layers of the membranes*

Answer 42

*chlorophyll has a **porphyrin ring** containing **magnesium** and a **hydrocarbon tail** known as **phytol*** chlorophyll a has a **blue-green colour** and **absorbs red and violet light** TWO TYPES: P₆₈₀in photosystem II P₇₀₀ in photosystem I chlorophyll b is an accessory pigment that has a **yellow-green colour** the same structure as chlorophyll a apart from one functional group

Answer 43

680nm in P₆₈₀ in chlorophyll a in photosystem II 700nm in P₇₀₀in chlorophyll a in photosystem I chlorophyll a also absorbs wavelengths of light around 440nm (violet-blue light) chlorophyll b absorbs light of wavelengths 400-500nm and 640 nm the other accessory pigments have 3 peaks- they absorb in the blue-green range

Answer 44

yellow, orange, red or brown photosynthetic pigments that pass the light energy absorbed onto chlorophyll a also known as CAROTENOIDS two groups: **carotenes eg. B carotene** and **xanthophylls**

Answer 45

to *maximise the absorption* of light that can be utilised for photosynthesis

Answer 46

*PHOTOLYSIS is the splitting of a water molecule using light* H₂O → 2e^-+ 2H⁺ + ½O₂ ELECTRONS- replace the electrons excited by light energy and removed by ETC (electron carriers) PROTONS- used for generating energy for photophosphorylation and source of H to reduce NADP OXYGEN- byproduct and can be used in respiration

Answer 47

*the movement of **protons** (hydrogen ions) **down** their **electrochemical/proton concentration gradient** across a selectively permeable membrane, through a **transmembrane protein enzyme complex; ATP synthase**; where the energy is used to **generate ATP from ADP and Pi** (inorganic phosphate group)*

Answer 48

the electron passed down the ETC releases energy, which is used to **pump H+ protons against their concentration gradient** from the **stroma into the thylakoid space.** This creates a **proton concentration gradient** across the thylakoid membrane. Protons move down their **electrochemical/proton** concentration gradient through a **transmembrane protein enzyme complex, ATP synthase.** The energy gained from the movement of the protns down the conc. grad. is used to add a **phosphate to ADP to form ATP.** This drives photophosphorylation. (in resp. used to drive ox. phos.)

Answer 49

it occurs when there is a **lack of water available to the plant; not enough water is taken up by the roots to replace water lost in transpiration at the leaves** - *leaf tissue becomes flaccid* * -the cells become plasmolysed* * -guard cells close the stomata* * -rate of photosynthesis is reduced*

Answer 50

**water is a substrate for photosynthesis** **water keeps plant cells turgid, and in particular the guard cells, which keep stomata open, allowing CO₂ to enter** **it has a cooling effect on the plant as it leaves the leaves during transpiration, due to the high latent heat of vaporisation**

Answer 51

from the MITOCHONDRIAL MATRIX into the **intermembrane space** via the INNER MITOCHONDRIAL MEMBRANE (phospholipid bilayer imbedded with proteins eg. the electron acceptor protein complexes in the ETC)

Answer 52

THE FINAL ELECTRON ACCEPTOR IN THE ETC ON THE INNER MITOCHONDRIAL MEMBRANE it forms **water** when it **accepts** the **electrons** from the e.t.c. and **protons** **O₂ + 4e¯ + 4H⁺ → 2H₂O**

Answer 53

Electron transport chain; electron transport and pumping of protons (H⁺) which create an H⁺ gradient across the membrane **+** chemiosmosis; ATP synthesis powered by the flow of H+ back across the membrane

Answer 54

If rate of photosynthesis is greater than the rate of respiration, biomass will increase, i.e. CO₂ is being converted to organic compounds such as starch and cellulose (something farmers would want to maximise).

Answer 55

An **Mg ion** in the middle of a **porphyrin** ring with a **long** **hydrocarbon (hydrophobic) chain**- therefore **organic solvents** are used to extract the pigments for chromatography.

Answer 56

by accepting the electrons at the end of the chain, it **oxidises the last protein complex** so that it can **receive more electrons** from the chain of carriers

Answer 57

1. *more reduced hydrogen carriers* can be used as *substrates* at the beginning of the chain 2. *more H⁺can be pumped* 3. *more ADP can be phosphorylated to make ATP*

Answer 58

1. **electrons** are **not removed**/accepted from the end of the e.t.c. 2. **NADH + FADH₂ are not oxidised** to NAD + FAD and are **not regenerated** to be used as **substrates** in the Krebs cycle 3. **no more NADH + FADH₂** can be used at the start of the chain 4. Krebs cycle, Link reaction and e.t.c. cannot proceed due to a lack of oxidised NAD and FAD 5. **only** the **glycolysis** pathway continues to form **pyruvate**

Answer 59

1. **ADENINE;** a nucleotide 2. **RIBOSE;** a pentose (5C) monosaccharide 3. **3x** **PHOSPHATE GROUP** joined by high energy bonds

Answer 60

* the conversation of energy from consumed/stored products into ATP* * sugars, amino acids, fatty acids + glycerol undergo the respiration pathway to produce ATP from ADP + Pi*

Answer 61

CARBOHYDRATES; PROTEINS; LIPIDS undergo digestion by hydrolysis SACCHARIDES; AMINO ACIDS; FATTY ACIDS + GLYCEROL

Answer 62

- the reaction creating the bond (phosphorylation) requires energy (obtained through respiration) - the reaction breaking the bond (dephosphorylation) releases energy (which is used to carry out work in the cell) ATP is used in **Active transport** **Muscle contraction** **Exo/endocytosis** **Nervous transmission** **Anabolism**

Answer 63

1. **substrate-level phosphorylation** where an *intermediate* of the respiration pathway *donates a phosphate group* to ADP to make ATP Pi + ADP → i + ATP 2. **oxidative phosphorylation** * requires oxygen* as the final electron acceptor and *hydrogen carriers/acceptors*, which are the *co-enzymes* of the *dehydrogenase enzymes* of respiration- NAD and FAD

Answer 64

ATP + H₂O (dephosphorylation, hydrolysis) ---------\> ADP + Pi + H (phosphorylation, condensation reaction) ----------\> ATP

Answer 65

the process of respiration takes **hydrogens** away from the **intermediates** of the pathway, using the **dehydrogenase enzymes and donates them** to the **co-enzymes** or **hydrogen carriers** The REDUCED NAD or FAD CARRY THE HYDROGENS to the ETC in the INNER MITOCHONDRIAL MEMBRANE, where ther ENERGY is RELEASED to PHOSPHORYLATE ADP to ATP, through a series of REDOX (ox/red) reactions and the process of CHEMIOSMOSIS.

Answer 66

*examples: NAD in respiration, NADP in photosynthesis*

Answer 67

* light energy + CO₂ + H₂O → organic compounds + O₂* 1. the process by which **light energy is converted to chemical energy** (ATP and NADPH₂) on the thylakoid membranes in order to **fix inorganic carbon** (CO₂) into **organic compounds** in the stroma of chloroplasts

Answer 68

In the chloroplast:**THYLAKOID MEMBRANE, INNER MEMBRANE,INTERMEMBRANE SPACE, OUTER MEMBRANE,** H⁺ are pumped **from the** **stroma** **into the thylakoid space**, across the **thylakoid membrane**, and flow down their proton/electromagnetic/concentration gradient into the stroma through **ATP synthase** in light-dependent reaction In the mitochondria: **INNER MITOCHONDRIAL MEMBRANE, INTERMEMBRANE SPACE, OUTER MEMBRANE** H⁺are pumped from

Answer 69

ADENINE: RIBOSE: 3x PHOSPHATE GROUP:

Answer 70

VISIBLE LIGHT- 400nm = shorter wavelength, higher energy 750nm = longer wavelength, lower energy

Answer 71

a graph showing the curves representing the wavelengths of light best absorbed by types of photosynthetic pigment

Answer 72

x axis = wavelength of light (nm) y axis = absorption of light by chloroplast pigments

Answer 73

a graph that plots the rate of photosynthesis against wavelength * the action spectrum resembles the absorption spectrum of chlorophyll a, but not exactly due to the absorption of light by accessory pigments eg. chlorophyll b, xanthophylls etc.* * wherever maximum rate of light absorption = max. rate of photosynthesis*

Answer 74

x axis = wavelength (nm) y axis = rate of photosynthesis (measured by O₂ released)

Answer 75

1. a pencil line is drawn near the bottom of the paper because pen ink contains pigments 2. a solvent front is at the top of the paper to measure the Rf value from. It is placed in silica gel 3. the paper is placed in an organic solvent because the pigments are lipid based and therefore would not dissolve in water (hydrophobic) the solvent is lower than the pencil line 4. Rf value is calculated

Answer 76

^{distance travelled by pigment} R_f = -------------------------- distance

Answer 77

*each **photosystem** contains a light-harvesting complex/antenna complex of 200-300 **photosynthetic pigments*** when a **photon of light** strikes a pigment molecule, the energy is transferred from accessory pigment molecules until it reaches **chlorophyll a at the primary pigment reaction centre**

Answer 78

a photon of light strikes magnesium in the porphyrin ring oh chlorophyll a in photosystem II, exciting two electrons in the outer orbital to a higher energy state, where it is accepted by a primary electron acceptor.

Answer 79

without an electron acceptor or the ETC, the **e^-would fall back down the energy level**, emitting light; **fluorescence**

Answer 80

* the products of non-cyclic photophosphorylation are ATP and reduced NAPH; it utilises PSII and PSI, connected by an electron transport chain* 1. a **photon** of light strikes Mg in **chlorophyll a in PSII** 2. a pair of **electrons** are **excited** to a higher energy level and removed by an electron acceptor to the electron transport chain, where they move down successive energy levels 3. the electron lost is replaced by an electron obtained from the photolysis of water 4. (CHEMIOSMOSIS) the energy released when the excited electron moves down the ETC is used to pump H⁺ protons against their gradient from the stroma to thylakoid space, creating a proton gradient across T.M., causing the protons to then move down their proton gradient into the stroma through ATP synthase. 5. energy gained from the movement of protons down their gradient is used to phosphorylate ADP and Pi to form ATP. 6. low energy electrons continue down the ETC to PSI, where they are further excited to a higher energy level when a photon of light strikes 7. they are added to protons and NADP to form NADPH by the action of the enzyme NADP reductase

Answer 81

the conversion of **light energy** to **phosphorylate** (add a phosphate group to) a molecule of **ADP** to form **ATP** (energy currency of living organisms)

Answer 82

*NADP⁺ + H⁺ + 2e^-→ NADPH (reduced NADP)*

Answer 83

\>produces ATP, NADPH, O₂ \>involves hydrolysis of water into electrons, protons and oxygen \>uses both PSII and PSI

Answer 84

\>only PSI is involved, electrons are excited in its primary pigment reaction centre, they pass down the ETC \>energy from the electrons is used to pump H⁺ across the thylakoid membrane \>only ATP is produced, by ATP synthase phosphorylating ADP to form ATP, by the protons flowing down their concentration gradient \>no photolysis of water

Answer 85

1. N-C: PSII & PSI *C: PSI* 2. N-C: photolysis occurs *C: photolysis does not occur* 3. N-C: electrons leaving PPRC add to NADP and H⁺ to form NADPH *C: electrons leaving PPRC are excited by further light energy to be cycled back through the ETC and PSI* 4. N-C: products are NADPH₂, ATP and ½O₂*C: only ATP is produced*

Answer 86

ATP and NADPH₂ are used to drive the reactions of the light independent stage; they convert G3P to triose phosphate

Answer 87

1. *a cyclical series of enzyme-catalysed reactions used to fix carbon dioxide into organic compounds* 2. carbon dioxide is fixed to ribulose 1,5 bisphosphate (5C) by RuBisCO (ribulose bisphosphate carboxylase oxygenase), known as carbon fixation 3. an unstable 6C compound is formed and immediately breaks down to two molecules of glycerate-3-phosphate 4. G3P is reduced to two molecules of triose phosphate (GALP or glyceraldehyde-3-phosphate) using hydrogens from the NADPH₂ and energy from ATP 5. 5/6 TP is recycled back to ribulose 5 phosphate and 1/6 are converted to organic compounds 6. Ribulose 5 phosphate is phosphorylated using ATP molecules to ribulose 1,5 bisphosphate

Answer 88

**3x CO₂ (1C)** **3x six-carbon intermediate (6C)** **6x glycerate-3-phosphate (3C)** 6x ATP, 6x ADP+P_i, 6x NADPH₂, 6x NADP **6x triose phosphate (3C)** **5x triose phosphate (3C)** **3x ribulose 5 phosphate (5C)** **3x ribulose 1,5 bisphosphate (5C)**

Answer 89

The line will start below 0, i.e. where the rate of respiration is greater than the rate of photosynthesis, i.e. where O₂ uptake/CO₂ evolution is greater than O₂ evolution/CO₂ uptake. The line will increase towards 0 as light intensity increases; when it reaches the line it is the compensation point, i.e. the quantity of O₂ being taken in is compensated for by O₂ evolution. Equally, energy required for one reaction/the reactants are compensated for by the other reaction. Rates of respiration/photosynthesis are equal. Above the compensation point, the rate of photosynthesis is greater than the rate of respiration and more CO₂ uptake/O₂ evolution is occuring.

Answer 90

1. in the light dependent stage, light energy is converted to the chemical energy of ATP and NADPH₂ on the thylakoid membranes 2. H₂O is split and ½O₂ is released into the atmosphere 3. The Calvin cycle then occurs in the stroma, where ATP and NADPH₂ are used to fix carbon and convert Ribulose 1,5 bisphosphate to triose phosphate 4. ADP, inorganic phosphate and NADP are returned to the thylakoid membranes, while 1/6 TP is used to synthesise organic molecules- AAs, saccharides, proteins, lipids

Answer 91

substrate-level phosphorylation: ATP is made by direct enzymatic transfer of a phosphate group from an organic substrate to ADP oxidative phosphorylation: requires a final electron acceptor; oxygen, and hydrogen carriers/acceptors that carry H⁺ to the ETC, where redox reactions and chemiosmosis release energy to phosphorylate ADP to ATP (requires a membrane)

Answer 92

**addition of O₂** **loss of electrons** **loss of H** **LOSS OF ENERGY**

Answer 93

* loss of O₂* * gaining electrons* * gaining H* * GAIN OF ENERGY*

Answer 94

by the addition of electrons, hydrogen or phosphate

Answer 95

* process; glucose (6C) to 2x pyruvate (3C)* * substrates; glucose, ATP, ADP and P_i, NAD* * products; pyruvate, ATP, NADH (ADP and P_i)* * location; cytoplasm (pyruvate enters mitochondrial matrix)*

Answer 96

process; pyruvate → acetyl CoA (CO₂ evolution) substrates; pyruvate, NAD, CoA products; CO₂, NADH, acetyl CoA location; mitochondrial matrix

Answer 97

process; acetyl CoA ⇒ oxaloacetate → NADH + FADH₂ (CO₂ evolution) substrates; acetyl CoA, NAD, FAD, ADP + P_i products; ATP, NADH, FADH₂, CO₂, CoA location; matrix

Answer 98

process; ADP + P_i → ATP substrates; NADH, FADH₂, oxygen, ADP and P_i products; NAD, FAD, ATP, water location; inner mitochondrial matrix

Answer 99

matrix, inner mitochondrial membrane has folds 'cristae' and is the site of electron transport chain, where there are stalked particles (ATP synthase) which is the site of respiratory ATP synthesis, intermembrane space, outer membrane

Answer 100

occurs in **cytoplasm** first three steps require **an input of energy**, to allow the **breaking of the hexose sugar (6C) into 2x triose sugars (3C)** there is a net yield of 2 ATP glycolysis can occur in the absence of oxygen, it is the pathway of anaerobic respiration pyruvate (final product) does not enter the Krebs cycle is there is no oxygen present glucose → (input of 2 ATP) hexose bisphosphate → **triose phosphate → (ADP is phosphorylated- substrate-level, NAD is reduced) glycerate 3 phosphate → (ADP is phosphorylated- substrate-level) pyruvate X2** hexose bisphosphate = fructose 1,6 bisphosphate

Answer 101

pyruvate (product of glycolysis) enters the **mitochondrial matrix** from the cytoplasm (via a transmembrane carrier protein called a _symport_ protein, using energy from flow of H⁺ protons from the chemiosmotic gradient, reducing the actual energy yield from the aerobic respiration of glucose) pyruvate undergoes **decarboxylation** - removal of CO₂ it undergoes **dehydrogenation** - removal of H, reducing NAD to NADH **Co-enzymeA (CoA)** is **added** to the resulting **acetate** to form **acetylCoA** acetylCoA will enter the Krebs cycle for the complete oxidation of glucose

Answer 102

-*purpose = complete oxidation of 2 carbon acetyl to CO₂ and removal of hydrogens by the dehydrogenase enzymes to donate to the hydrogen carriers (co-enzymes) NAD and FAD to reduce them to NADH and FADH₂* the reduced hydrogen carriers/acceptors are the substrates for the electron transport chain. Substrate-level phosphorylation occurs, producing ATP. For each molecule of glucose, 2x LR and 2x Krebs C. KC is also the entry point for other respiratory substrates eg. amino acids **ACETYLCOA (2C) - CoA + OXALOACETATE (4C) = CITRATE (6C) - CO₂ - H (to NAD) = 5C - CO₂- H (to NAD) - P_i (to ADP) = SUCCINATE (4C) - H (to FAD) = 4C + H₂O = 4C - H (to NAD) = oxaloacetate (4C)**

Answer 103

a series of **proteins embedded** in the **inner mitochondrial** membrane, which folds to form **cristae** in order to increase the **surface area**. This allows there to be **many ETCs in each** mitchondria.

Answer 104

**NADH** releases its **hydrogens** to the **first complex** in the ETC; the hydrogens **dissociate into electrons** (1) and **protons** (2) 1. The electrons are **carried along the chain**, **sequentially reducing** the complexes as they reach them and **oxidising** them as they leave. 2. The **protons are pumped** from the **matrix into the intermembrane space**, creating a **proton conc. gradient**. The energy required is **supplied by the energy of the electrons**. **FADH₂ donates its electrons at the second complex** on the chain so **fewer protons** are pumped relative to NADH. NAD and FAD are **oxidised** and return to the **Krebs** cycle.

Answer 105

For _CHEMIOSMOSIS_: The P C/electrochemical gradient across the inner mitochondrial membrane **drives phosphorylation of ADP to ATP** by the transmembrane complex **ATP synthase**.

Answer 106

The process by which the energy stored in the form of a **proton concentration gradient across a membrane is used to from ATP from ADP and Pi** *i.e. chemiosmosis couples the ETC to ATP synthesis* Aerobic respiration (oxidative phosphorylation), photosynthesis (oxidative phosphorylation), entry of sucrose into the phloem for translocation, symport of pyruvate into mitochondrial matrix

Answer 107

a form of *cellular respiration*, occuring when **oxygen is absent** or under stress, that **generates energy in the form of ATP** by the **oxidation** of nutrients and using an **electron acceptor other than** oxygen ## Footnote * also known as fermentation* * \>reactions of glycolysis to form pyruvate* * \>reduction of pyruvate to another compound (depending on type of cell, ethanol, lactate) in order to recycle NAD so that glycolysis can continue in the absence of oxygen*

Answer 108

glycolysis and Krebs cycle/citric acid cycle a series of redox reactions

Answer 109

electron transport + chemiosmosis

Answer 110

**pyruvate →** *pyruvate decarboxylase* ⇒ CO₂ ⇒ **ethanal →** *ethanol dehydrogenase → NADH --\> NAD ⇒ **ethanol*** *NAD is recycled for use in glycolysis in absence of O₂*

Answer 111

**pyruvate →** *lactate dehydrogenase →* *NADH --\> NAD ⇒* **lactate** * NAD is recycled for use glycolysis in the absence of O₂* * In "oxygen debt" lactate is converted back to pyruvate*

Answer 112

In the **absence of O₂**, cells use fermentation to **produce ATP by substrate-level phoshorylation** in order to continue metabolic/cellular activity. **Pyruvate** acts as an **electron acceptor** in order to **oxidise NADH to NAD**, which can be reused in glycolysis to produce small quantities of ATP. Two common end products are lactate and ethanol.

Answer 113

**theoretical yield = 38 ATP** * +4 -2 in glycolysis* * +2 in Krebs* * +30 from 10NADH₂ in ox phos* * +4 from 2FADH₂ in ox phos*

Answer 114

approx. 32 molecules of ATP for example due to loss of energy as heat and transfer of pyruvate into the mitochondria etc.

Answer 115

**2 molecules of ATP total** * 2 ATP lost in glycolysis* * 4 ATP gained in glycolysis from substrate-level P* * 2NADH₂used up, 2NADH₂ made to regenerate NAD, no ox. phos.*

Answer 116

AEROBIC RESPIRATION IS APPROX. 15x MORE EFFICIENT than anaerobic respiration in converting energy of glucose

Answer 117

approx. -3000 kJ per mole of glucose 30. 5 kJ per mole of ATP

Answer 118

The energy value (KJg^-1) for lipids is twice that for carbohydrates because lipids have more hydrogens in their molecules (Proteins is similar to carbs)

Answer 119

*Carboydrates are hydrolysed to monosaccharides eg. glucose, which enter glycolysis.* _Lipids are hydrolysed to glycerol, which enters glycolysis, and fatty acids, which enter the Link reaction (acetyl CoA)_ **Proteins are hydrolysed to amino acids, which can enter at glycolysis, Link reaction or Krebs cycle. Ammonia (NH₃) is released.**

Answer 120

the creation of protein molecules by amino acid synthesis (producing amino acids from molecules such as glucose or from the molecules in our diet, transcription and translation occurs within cells that produce proteins from the genetic code)

Answer 121

Transcription is the process by which an mRNA template is synthesised using DNA to provide a template , encoding the sequence of the protein in the form of a trinucleotide code, is transcribed from DNA to provide a template for translation.

Answer 122

*Translation is the process in which **amino acids** are coded for by **mRNA** in a specific order according to the codons specified by the genetic code*. ## Footnote They are bonded together by peptide bonds to produce a polypeptide chain. It occurs in the cytoplasm on free ribosomes or those on the RER.