IB Bio- Year 1 Summative

Outline the steps of glycolysis

1. Phosphorylation

   1. Glucose + 2ATP → fructose- 1,6-bisphosphate.

   2. ATP is converted into ADP as phosphate group from each ATP attached to the 6C molecule fructose 1,6-bisphosphate (unstable molecule). This makes glucose more unstable (usually very stable) and hence lower activation energy of the reaction.

2. Lysis

   1. The unstable fructose- 1,6- biphosphate (phosphorylated 6C) splits into 2 molecules of 3C (triose phosphate)

3. Oxidation

   1. Hydrogen is removed from each molecule triose phosphate by dehydrogenase enzyme and transferred to coenzyme NAD⁺ (nicotinamide adenine diphosphate) to reduced NAD⁺ (NADP) to form G3P (glycerate-3-phosphate)

4. ATP Formation

   1. Phosphates are transferred from intermediate substrate molecules to form 4 ATP through substrate-link phosphorylation (4 inorganic P + 4 ADP → 4 ATP) 2 molecules of pyruvate = end product (used in next pathway)

   Net gain: 2 ATP, 2 pyruvate, 1 NADP

Outline the steps of anaerobic respiration (alcohol fermentation of yeast)

1. Decarboxylation

   1. Pyruvate from glycolysis removes 1 C to form CO₂

   2. This forms a 2C molecule. (x2 for the other pyruvate molecule) 

2. Oxidation 

   1. NADH from glycolysis is oxidized into NAD which turns the 2C into ethanal = hydrogen acceptor of NADH . This is done by alcohol dehydrogenase 

   2. Ethanal is oxidized again to form ethanol. 

Net gain:

• 2 CO₂

• 2 ethanol 

Outline the steps of anaerobic respiration (lactate) and its function

1. Oxidation Pyruvate from glycolysis is the hydrogen acceptor of NADH (the H⁺). NADH is oxidized into NAD⁺ by lactase dehydrogenase which forms lactate

2. Function. Used in humans when lack of air (exercise). However too much can built up lactate into form of lactic acid which can fatigue muscle.

Outline the steps of the link reaction

Occurs if there is enough oxygen available.

1. Enters to mitochondrial matrix for aerobic respiration.

2. Oxidative carboxylation 2 pyruvate from glycolysis is decarboxylated (removes C) to form 2C compound.

3. 2C compound is oxidized by NAD which reduces it to NADH CoA Coenzyme-A attaches to 2C carbon to form acetyl coenzyme A (acetyl CoA) which enters Krebs Cycle.

Outline the steps of Krebs Cycle

1. Removal of Coenzyme-A

   1. Acetyl CoA’s enzyme is removed. 4C compound from previous Krebs Cycle (oxaloacetate) is joined together to form a 6C compound called citrate

2. Decarboxylation

   1. Citrate is decarboxylated, losing one carbon in the form of CO2. This forms a 5C intermediate. NAD+ is also reduced into NADH by oxidizing the 5C compound.

   2. 5C is converted into a 4C by another decarboxylation (releasing another CO2) and reducing another NAD to NADH 4C undergoes several transformations.

   3. NAD reduced to NADH. FAD reduced to FADH₂ Undergoes substrate-level phosphorylation. (ADP to ATP)

Net products: 1 ATP, 3 NADP, 1 FADH₂, 1 oxaloacetate (redo cycle), 3 CO₂

Outline the steps of electron transport chain in mitochondria

Takes place in inner-membrane of mitochondria

1. Coenzymes

   1. NADH and FADH₂ from Krebs Cycle carries high energy H⁺ ions and electrons 

2. Electron is transported

   1. NADH donates electrons to first protein complex in inner membrane of mitochondria → oxidixed into NAD⁺

   2. FADH₂ donates electrons further down the chain (later carrier) so it produces less ATP

3. Electrochemical gradient

   1. As electrons move along the chain it releases energy that is used to pump protons from NADH and FADH₂ (H⁺ )into the matrix of the innermembrane space

   2. Electrons stay within innermebrane space but H⁺ are pumped out = builds potential energy

4. Chemiosmosis and ATP Production

   1. H⁺  is impermeable to inner membrane and can only go through an enzyme called ATP synthase. 

   2. ATP synthase has ADP and inorganic phosphate attached. H+ goes through the synthase = generates energy to join ADP and inorganic phosphate to form ATP. This process is called chemisomosis.

5. Oxygen as final electron acceptor

   1. At the end of chain electrons are removed to prevent chain from flowing by combining 4H⁺+ and 4 electrons → water.

   2. Without oxygen, ETC can’t pass its electrons so it remains reduced meaning that it prevents carriers from accepting electrons (needs to get rid of spare electrons for new electrons to go through ETC)

   3. As a result NADH and FADH₂ can’t donate electrons and can’t be recylced into NAD⁺ and FAD that are needed for earlier steps of respiration = no glycolysis/Krebs Cycle/ETC = no ATP

Net yield:

Large amounts of ATP per glucose molecule

Outline the steps of cell respiration

1. Glycolysis (cytoplasm)

2. Link Reaction (mitochondrial matrix)

3. Aerobic Respiration OR Krebs Cycle (mitochondrial matrix)

4. Electron Transport Chain (inner membrane of mitochondria)

List the abiotic factors that affect organisms with their habitat

• Salinity

• Temperature

• pH 

• Humidity

• Cloudiness/Turbidity of water  

• Oxygen/CO₂ concentration

• Soil composition

• Light intensity/wavelength

List the adaptaion of leaves for gas exchange in plants

• Waxy cubicle: Prevents water vapor and gas from leaving through the epidermis. Controls gas exchange and water loss.

• Epidermis: Contains stomata for gas exchange. Mostly found in lower epidermis where the temperature is lower which reduces water loss.

• Veins: Xylem vessles transports water necessary for photosyntehsis and transpiration. Photosynthesis requires carbon dioxide to diffuse into the leaf and transpiration involves the loss of water vapor.

• Stomatal guard cells: Controls the opening and closing of stomata which controls gas exchange and water loss

• Air space: Maintain a concentration gradient between

• Spongy mesophyll: Increases SA for gas exchange

List the different tissues in leaves

• Epidermis tissue

  • Formed by single layer of cells (upper and inner that protects inner part of leaf)

  • Lower epidermis has stomata surrounded by 2 guard cells that control gas exchange. Allows diffusion of O₂ and CO₂ gas. 

  • Guard cells becomes turgid when water enters and changes shape = opens stomata. Becomes flaccid when water is lost = water close. 

  • Covered by waxy layer (cuticle) which forms an impermeable barrier 

• Mesophyll tissue

  • Formed by parenchyma cells 

  • Contains chloroplasts where photosynthesis occurs. 

  • Palisade mesophyll

  • Sponge mesophyll= contains large aire space between upper epidermis. 

• Vascular tissue 

  • Arranged in vascular bundles 

    • Forms veins in leaves: xylem transports water + mineral ions from roots to leaves, phloem transports products of photosynthesis from leaves to other parts of plants