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Human Biology C5
Human Structure and Function C5
| Question | Answer |
|---|---|
| Glycolysis | The first stage of ATP synthesis. A series of chemical reactions occurring in the cytosol, which convert glucose into two pyruvic acid molecules, and two ATP molecules. |
| Citric Acid Cycle | A series of chemical reactions occurring inside the mitochondria, which convert pyruvic acid into ATP and electron carrier molecules |
| Oxidative Phosphorylation | The last phase of ATP synthesis. A series of chemical reactions occurring on the inner mitochondrial membrane, which convert electron carrier molecules to ATP |
| Glucose | A simple sugar molecule (monosaccharide). Glucose is used by the body to make ATP or stored as glycogen for future use |
| Adenosine Triphosphate (ATP) | An adenosine molecule with three attached phosphate molecules. When ATP is broken down ‘energy’ is released and used by cells and tissues to function |
| Mitochondria | An organelle located within cells where adenosine triphosphate (ATP) is produced. |
| Lipid bi-layer | The head to tail arrangement of phospholipid molecules in the cell plasma membrane. |
| Selectively permeable membrane | Each specific cell has a plasma membrane which is structured to only let some substances pass through |
| Osmosis | The movement (diffusion) of water across a selectively permeable membrane. Water will move from high concentration to low concentration. |
| Hypertonic | A hypertonic solution has more solutes and less water molecules compared to intracellular fluid. >290 mOsmol/L |
| Hypotonic | A hypotonic solution has less solutes and more water molecules compared to intracellular fluid. <290 mOsmol/L. |
| Isotonic | An isotonic solution has the same total concentration of solutes (osmolarity) as intracellular fluid (fluid inside a cell). Approximately 290 mOsmol/L. |
| Diffusion | The movement of solutes (e.g. salt) from an area of high concentration to an area of low concentration. No ATP is used |
| Facilitated diffusion | The movement of a solute (e.g. glucose) across a plasma membrane via the use of a carrier/channel protein. No ATP is used. |
| Symport | The movement of two different ions or molecules in the same direction across a plasma membrane, via a carrier/channel protein. |
| Antiport | The movement of two different ions or molecules in the opposite direction across a plasma membrane, via a carrier/channel protein |
| Table on Diffusion | Movement of solute. Moves down concentration gradient. Doesn't require energy. Used by oxygen and carbon dioxide. Example O2, CO2, urea, hormones |
| Table on Osmosis | Movement of solvent (water), moves down concentration gradient. Doesn't require energy. Used by water to enter and leave cell. Example, water |
| Table on Active Transport | Movement of solute, Substances move up concentration gradient. Sodium potassium pump is an example. Examples, ions. |
| Explain why a change was observed in the volume? Hypertonic | (>290 mOmol/L) higher in solutes and lower in water molecules compared to the dialysis bag Concentration gradient exists, water moved into the cylinder from the bag down its concentration gradient. |
| Solution B, no change. Why? | The osmolarity in both the cylinder and the bag were equal (approx 290mOmol/L) therefore a concentration gradient did not exist and equilibrium was present = no net movement |
| Solution C, hypotonic? | (<290 mOmol/L) lower in solutes and higher in water molecules compared to the dialysis bag. Concentration gradient exists, water movement from cylinder into bag, down its concentration gradient, high to low causing the volume within cylinder decreases |
| What substances need to move into and out of a typical cell? | Ions, water, proteins, nutrients, waste products, macromolecules , gases such as oxygen and carbon dioxide |
| Describe the arrangement of the phospholipid molecules in the plasma membrane. | The phospholipid molecules are arranged in a double layer with their polar heads (hydrophilic) facing the intracellular fluid and extracellular fluid, and their non-polar fatty acid tails (hydrophobic) facing the interior of the membrane |
| What does hydrophobic mean? How does this relate to the arrangement of the plasma membrane? | Hydrophobic means "not water liking" The long phospholipid nonpolar tails, which are hydrophobic, are confined to the interior of the membrane away from the water molecules. |
| What does hydrophilic mean? How does this relate to the arrangement of the plasma membrane? | hydrophilic means "liking water". The polar heads of the phospholipid molecules are hydrophilic. They face the polar extra- and intracellular fluids, which are predominantly composed of water, a polar fluid. |
| What are the roles of proteins in the membrane? | Help cell "communicate" with environment. Some are enzymes, some line ion channels, allow certain ions to move through cell membrane. Some -carrier molecules for transport of molecules across the cell membrane. Some essential for cell-to-cell recognition |
| What does the fluid mosaic model of cell membranes mean? | Theory that cell membrane is not rigid structure but fluid (constantly moving) in nature, changing shape and composition over time. Nature of phospholipid molecules influenced by diet. Membrane proteins come and go depending on metabolic state of cell |
| The cell membrane can be described as the gate keeper of the cell. What does this mean? | The cell membrane is a highly selective membrane. It controls what can pass across in, either into or out of the cell. The cell membrane determines what substances pass, in what amounts and at what time |
| What is diffusion? | This is when solute molecules move passively from one region to another down their concentration gradient i.e. there is net movement of molecules from a region of high solute concentration to a region of low solute concentration |
| How do gases such as oxygen and carbon dioxide cross the cell membrane? | Small non-charged particles such as oxygen and carbon dioxide gases diffuse across the cell membrane by moving between the phospholipid molecules of the cell membrane lipid bilayer. Move down their concentration gradient |
| What is meant by facilitated diffusion? Is it an active process (i.e. uses cellular energy?) or passive process (i.e. does not use cellular energy)? | Passive process, doesn't use cellular energy, molecule "helped" across cell membrane by carrier/channel protein. Movement down concentration gradient. Necessary because molecules are too big or too polar to cross the lipid bilayer independently. |
| Give an example of a substance that crosses the membrane via facilitated diffusion with the help of a carrier protein. | Glucose |
| What is the name for the process by which water crosses the membrane? | Osmosis |
| Water will move in the direction of a higher solute concentration, true or false? | True. A solution with a higher solute concentration has a lower concentration of water molecules, so water moves towards the lower concentration of water molecules to try and even things up) |
| What are aquaporins? | These are water channels lined by proteins through which water uses to move across cell membranes |
| What is meant when we say a solution is isotonic? | Has the same tonicity (solute concentration) as the cell cytoplasm, such that if placed in such a solution there is no NET movement of water into or out of the cell and as a consequence the cell neither shrinks nor swells. An isotonic solution is 290 mOsm |
| Which direction will water move when cells are placed in a hypertonic solution? | If the hypertonic solution is outside the cell (extracellular), water will move from the intracellular fluid to the extracellular fluid i.e. water will move to where the solute concentration is higher. The cell will lose water and shrink (crenate) |
| Which direction will water move when cells are placed in a hypotonic solution? | If hypotonic solution outside the cell (extracellular), water will move from the extracellular fluid to the intracellular fluid. The cell will gain water and swell (and eventually burst or lyse) |
| When is the process of active transport required? Does it use cellular energy? | This is required when a solute moves "up" its concentration gradient (from low solute concentration to high solute concentration). It requires a carrier and requires energy, ATP, to drive the process |
| Give an example of two substances that are moved across the membrane in this way. For each substance describe the concentration on either side of the membrane and which direction the active transport would move them. | The Na+/K+ pump in the cell membrane is an example here where Na+ is constantly pumped out of cells and K+ pumped into cells. Both ions are moved against their concentration gradients. |
| Cellular respiration consists of 3 stages: | Glycolysis Citric acid cycle Oxidative phosphorylation. |
| Main role of glycolysis and the citric acid cycle is... | break down glucose and store the energy obtained from breaking these chemical bonds in molecules (e.g. NADH, FADH2) that can be used in the last stage, oxidative phosphorylation, to produce large amounts of energy in the form of ATP. |
| Glycolysis- occurs in | Occurs in the cytoplasm Breaks down 1 glucose molecule (6 carbon sugar) into 2 pyruvate molecules (3 carbons) Uses 2 ATPs in the early stages, but produces 4 ATP by the end = net production of 2 ATP |
| Glycolysis - produces | Is ANAEROBIC – i.e. does not require O2 If no oxygen is available, pyruvate converted to lactic acid. Produces 2 NADH molecules that are used in oxidative phosphorylation to produce more ATP |
| Glycolysis - occurs in | Occurs in the matrix of the mitochondria Before the cycle begins, pyruvate is converted to acetyl CoA, producing 1 NADH and 1 CO2 (remember for each glucose we started with there are two pyruvates) |
| Glycolysis - acetyl CoA... | Acetyl CoA enters citric acid cycle, transferred to 4 C molecule, makes 6 carbon molecule (citrate) Citrate goes through series of chemical transformations, loses two C groups as 2 C02, end up back as a 4 C molecule ready to go through another cycle |
| Glycolysis - purpose | The purpose of this is to produce energy from the chemical bonds that are broken The energy produced for every turn of the cycle = 1 ATP + 3 NADH + 1 FADH2 |
| Glycolysis - citric acid cycle | The cycle twice for every 6 C glucose entering glycolysis, 1 glucose produces 2 pyruvates Overall energy production (Citric acid cycle) is 2 ATP, 6 NADH and 2 FADH2; plus the 2 NADH produced converting 2 x pyruvate to 2 x acetyl CoA at the start. |
| Oxidation phosphorylation (electron transport chain) | Most of the energy produced by cellular respiration is by oxidative phosphorylation NADH and FADH2 produced by glycolysis and the citric acid cycle pass through the electron transport chain (the ETC) in the inner membrane of the mitochondria |
| Oxidation phosphorylation (electron transport chain) | The ETC is a series of electron donors and acceptors. NADH and FADH2 donate their electrons to the first acceptor in the chain, who then donates them to the next and so on, until the electrons are passed to oxygen. |
| Oxidation phosphorylation (electron transport chain) | The movement of electrons from molecule to molecule in the membrane releases energy and this is used to generate a proton (H+ ion) gradient across the mitochondrial membrane. |
| Oxidation phosphorylation (electron transport chain) | The protons then flow back across the membrane through a special channel. This flow of H+ is used by ATP synthase to produce ATP. Oxidative phosphorylation produces between 32 – 34 ATP. |
| How do cells derive energy? | Break down (oxidation) of nutrients such as glucose |
| What is the energy currency of the cell? | Adenosine triphosphate (ATP) |
| What happens to the glucose molecule when it enters the cell? | It is phosphorylated (2 phosphate molecules are added) |
| How many molecules of ATP are used during the initial stage of glycolysis? | 2 |
| What is the 6-carbon sugar molecule split into? | 2 x 3 carbon molecules |
| What do the 3-carbon sugar molecules become? | Pyruvate |
| How many NET molecules of ATP are formed during glycolysis? | 2 ATP (4 ATP minus 2 used) |
| What is formed from the 2 pyruvate molecules? | Acetyl-CoA |
| In what organelle in the cell does the citric acid cycle occur? | Mitochondrion |
| What is produced during the conversion of pyruvate to acetyl-CoA? | CO2 and NADH |
| Carbon dioxide is released from the 6-carbon molecule to form a 5-carbon compound. What else is formed during this step? | NADH |
| A second reaction occurs where the 5-carbon molecule becomes a 4-carbon molecule producing NADH AND CO2. What else is produced? | ATP |
| Finally the 4-carbon molecule is further oxidised and the hydrogen removed is used to form what two things? | FADH2 and NADH |
| Where in the cell are the electrons from NADH and FADH2 transferred to electron carrier proteins? | Inner mitochondrion membrane |
| What does this transfer of electrons lead to? | Transport of H+ ions across the mitochondrial wall membrane |
| What is the molecule that finally accepts the electrons? What molecule is then formed | Oxygen, and water is formed |
| Protons that are transferred through the mitochondrion membrane flow back across the membrane through the ATP synthase channel. What does this process produce? | ATP |
| How much ATP is formed during oxidative phosphorylation | 32- 34, depending on the cell type |
| Name the process that occurs in your body cells that converts food into energy? | Cellular respiration |
| Name the carbohydrate that is preferred by the cell to produce cellular energy. | Glucose |
| What is the overall goal for cellular respiration? | To make ATP, the energy currency of the body |
| What does ATP stand for and how is it useful for a cell? | ATP = Adenosine triphosphate - a high-energy phosphate molecule. ATP stores energy in a way that can be used by the body ATP broken down, energy is released, used to drive chemical reactions in body. |
| What does glycolysis mean? | Glycolysis means "breakdown of glucose". Glyco = glucose, lysis = to break |
| What is the first step of cellular respiration and where in the cell does it occur? | The first step of cellular respiration is glycolysis which takes place in the cytoplasm of the cell. Glucose is broken down from a 6 carbon molecule into two 3 carbon molecules. |
| Is ATP used in the beginning of glycolysis and if so how many ATP molecules are used? | Yes, 2 ATP are used in the first stage of glycolysis to activate the glucose molecule |
| At the end of glycolysis, how many ATP, pyruvate and carrier proteins (NADH) are produced? | The end results for 1 molecule of glucose metabolised in glycolysis are: a gain of 2 ATP (4 ATP minus 2 ATP), 2 pyruvate molecules, 2 NADH molecules |
| What happens to the products of glycolysis if oxygen is present? | The pyruvate and NADH molecules are transported into the mitochondria for further processing in the citric acid cycle |
| What happens to pyruvate to prepare it for the citric acid cycle? | Once in the mitochondria, each pyruvate molecule is oxidised to form acetyl coenzyme A (Acetyl CoA) + NADH + CO2 |
| What is the net outcome of the cycle for every glucose molecule? Remember every glucose is broken down into two pyruvate molecules, so the citric acid cycle turns twice for every glucose molecule | Each glucose molecule produces: 2 ATP, 8 NADH, 2 FADH2, 6 CO2 Explanation Every turn of the cycle = 1 ATP + 3 NADH + 1 FADH2 + 2 C02 2 cycles = 2 ATP + 6 NADH + 2 FADH2 + 4 C02 2 NADH and 2 C02 from conversion of 2 pyruvates to acetyl CoA at the start |
| Cellular respiration uses the carrier molecules NADH and FADH2 to carry the hydrogen ions and associated electrons, which have been collected from glycolysis and citric acid cycle to the next step. What is this step called? | The electron transport chain |
| This final step uses oxygen, the hydrogen ions and electrons to form what? | Water (H20) |
| What does the term oxidative phosphorylation mean? | Oxidative phosphorylation refers to the pathway where energy liberated by the movement of electrons thru the electron transport chain in the mitochondria is coupled with the synthesis of ATP |
| How much ATP is produced in this final step of cellular respiration? | 32-34 ATP molecules are produced from glucose in the electron transport chain. |
| Write down the overall formula for glucose oxidation | 1 glucose + 6O2 6 CO2 + 6 H2O + 36 ATP |
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