NCEA EXAM QUESTIONS Flashcards
Cell Transport - NCEA QUESTION - Photosynthesis
Describe osmosis and explain how it occurs in root cells of a plant
Osmosis is the process of when water is diffused from a high concentration to a low concentration of water though a semi permeable membrane. It occurs down a concentration gradient and will cease if the distribution of water becomes equal.
It is passive & requires NO energy
In plants, osmosis is used to transport water from in the ground into the root cells of the plant. At the end of the roots, when they become very thin, water diffuses through osmosis into the cells which have a lower concentration of water than the soil around them.
The accumulation of water through osmosis in the roots of plants is necessary as it is one of the key reactants in the photosynthesis reaction plants use to gain energy and synthesis in order to complete life processes - such as growth.
Cell Transport - NCEA QUESTION:
The hog-choker lives in estuaries, where salt water concentration changes regularly. However, the hog-choker actively adjusts the salt water concentration of its body when in high salt concentration water. As salt concentration increases, oxygen consumption also increases.
Explain how salt water moves across the the membrane in the Hog-choker by active transport
Active transport does require ATP/energy. The movement of salt water across the hog-choker cell membrane is via active transport. Salt moves against the concentration gradient from an area of low concentration (inside the cell) to an area of high concentration (seawater) through protein pumps in the cell membrane. This requires ATP/energy.
Cell Transport - NCEA QUESTION:
In the small intestine, it is the function of the brush border cells to absorb nutrients. When nutrients first enter the intestines, the nutrients can move into the brush border cells by diffusion. The brush border cells can absorb these nutrients using active transport.
a) Describe the process of diffusion
MY ANSWER: In diffusion, particles spread randomly spread out from a high concentration to a low concentration. This sets up a concentration gradient. Small uncharged molecules like O2, CO2, glucose, etc can pass through the cell membrane and go down the concentration gradient.
CORRECT ANSWER: The random movement of particles down a concentration gradient, from an area of high concentration to an area of low concentration.
Photosynthesis - EXAM QUESTION
Discuss how photosynthesis occurs, and the factors that affect it. In your answer:
- Explain light-dependent & Light independent reactions
- Discuss how water AND one other factor can affect the rate of photosynthesis
Photosynthesis is the process by which plants synthesis (make) food using sunlight. Sunlight is used twice in the process of photosynthesis. This is where light dependent and light independent process comes into the frame. Light dependent reactions in the plant are reactions which require sunlight to function, unlike the light independent reaction which does not require sunlight.
Water can affect the rate of photosynthesis because it is a reactant in the reaction. Plant’s require H2O molecules from the ground in order to split and bind hydrogen with carbon dioxide, and release O2 to form the glucose (food) and energy they require. If there is abundant sunlight and carbon dioxide but no water, the reaction cannot take place. Water is often the most limiting factor in photosynthesis reaction. Therefore, limiting the rate of ATP energy production & the energy for life processes. Water abundance can heavily influence the photosynthesis reaction as it is necessary. Without water, the plant cannot perform the reaction & it will die.
Another factor influencing the rate of photosynthesis is temperature. Enzyme is necessary in carrying out the reaction. One key aspect is temperature and light intensity will raise the temperature. As the temperature rises, the number of collisions between enzymes and substrate will also rise which increases the rate of photosynthesis. In colder temperatures, the collision rate and photosynthesis rate will fall. There will be an optimum temperature for the enzymes in the plant to function, optimising the rate of photosynthesis. Past this point, the enzyme will denature, unraveling the the proteins and disfiguring the active site rendering the enzyme unable to bond to substrate and react. If this occurs, the rate of photosynthesis will slow, and likely come to a stop altogether.
Cell Respiration - NCEA EXAM
intertidal animals such as the blue mussel, rely on seawater to get dissolved oxygen for aerobic respiration. At low tide, the mussels are exposed to the air and tightly close their shells to prevent drying out. During low tide they rely on anaerobic respiration to maintain essential life processes.
Compare & Contrast Anaerobic & Aerobic respiration in mussels. In your answer:
- An explanation of anaerobic respiration that includes where it takes place in the cell, and the products formed.
- An explanation of aerobic respiration that includes where it takes place in the cell, and the products formed.
- A discussion of one advantage and one disadvantage for BOTH anaerobic AND aerobic respiration in blue mussels
Cellular respiration is the process by which cells release energy from food to maintain their cellular processes such as growth&repair.
This respiration can either be anaerobic or aerobic. Anaerobic respiration is respiration that does not require oxygen to complete. This process occurs in the cytoplasm of the cell where in glycolysis glucose is broken down into pyruvate and a small amount of ATP is produced. From this point on, the
DNA Replication - EXAM QUESTION
Explain the purpose of DNA Replication
DNA replication is the process that uses the two strands of the parent DNA as templates to produce two identical daughter copies so new cells can carry out some function as original cell.
Enzyme - EXAM QUESTION:
Enzymes are needed for DNA replication. Discuss the functions of enzymes in DNA replication and the factors that affect them. In your answer:
- A description of the structure of an enzyme
- An explanation of how enzymes function in DNA replication
- A discussion of at least three factors that affect enzymes during DNA replication
An enzyme is a globular protein which is a biological catalyst. it can either break molecules (catalyst) or build molecules. All enzyme contains an active site to where substrate(s) - one for breaking or two for building - bind to. Each enzymes active site only fits with it’s specific substrate. The substrate is then released
Inhibitors are substances that prevent enzymes from catalysing a reaction. They are poisons and can include heavy metals such as lead, mercury, and cadmium. There are two types of Inhibitors.
- Competitive Site Inhibitors - The site competitive Inhibitors bind to the enzyme’s active site. They block out the active site so that the substrate cannot bind to the enzyme’s active site. If the substrate does not bind, the reaction cannot proceed. This may be reversible or irreversible.
- Non Competitive site Inhibitors - The non competitive site Inhibitor binds a location away from the enzyme’s active site. This causes a change in the shape of the enzyme’s active site so that the substrate does not bind, or binding is impaired. If the substrate can’t bind securely, the reaction cannot proceed
Enzymes play a huge role in DNA replication.
Osmosis & Facilitated diffusion - NCEA QUESTION:
The lugworm lives on sandy shores where the salt water concentration can fluctuate slightly. To survive in this habitat, the lugworm passively adjusts the salt water concentration of its body to match the surrounding seawater. Oxygen consumptions remain constant during this process.
Explain how sea water moves across the cell membrane in a lugworm via osmosis and facilitated diffusion.
Osmosis is a type of passive transport. Passive transport does not require ATP (energy) and moves on from an area of high concentration to an area of low concentration.
- Water moves across the area of lugworms membrane by osmosis, and salt moves by facilitated diffusion. Salt is moving from an area of high concentration (seawater) to low concentration (inside the worm) down the concentration gradient through protein channels in the cell membrane. Water moves from an area of higher water concentration (inside the worm) to an area of lower water concentration (seawater) by diffusing through the membrane. This process requires no energy (passive transport)
- Both processes work together to ensure that the lugworm always has the same salt water concentration.
Respiration & Enzymes - EXAM QUESTION
Describe the purpose of cellular respiration, and WHERE it occurs in the cell.
The purpose of cellular respiration is to release energy from food.
The process occurs in the mitochondria of the cell.
Photosynthesis - EXAM QUESTION
Photosynthesis occurs in the leaves of plants. Describe the process of photosynthesis (REMEMBER equations)
Photosynthesis is the process by which plants synthesis (make) food using sunlight. They use sunlight, carbon dioxide, and water to produce glucose and oxygen.
Photosynthesis Word Equation: carbon dioxide + water = glucose + oxygen
Photosynthesis Chemical Equation: 6CO2 + 6H2O = C6H12O6 + 6O2
Photosynthesis - EXAM QUESTION
Water is an important requirement for the process of photosynthesis.
Explain how water enters a plant AND how it is used in the light-dependent reaction.
Water is an important requirement for the process of photosynthesis because water is a reactant of the reaction. If there is abundant sunlight and carbon dioxide but no water, the reaction cannot proceed.
Water in the soil enters through the root of a plant. Water enters via osmosis. Osmosis is the process of when water is diffused from a high concentration of water to a low concentration of water through a semi-permeable membrane. Osmosis is passive and requires no ATP/energy.
Water in the soil enters (capillary action) through tiny root hairs. The soil must have high concentration of water to move into the root cell semi-permeable membrane and into the root cell, which will have a low water concentration.
Water is then transported to a chloroplast within a leaf cell. In the chloroplasts, thylakoid membrane light energy is absorbed by the pigment chlorophyll. This light energy splits the water molecule into oxygen and hydrogen. Hydrogen ‘goes to the’ light independent (next phase) process, while oxygen is excreted as a waste product (via stomata on leaves). The hydrogen from the water molecule is used to help (combines with carbon) make the glucose molecule.
Cell Respiration -NCEA EXAM QUESTION
The short-fin mako shark, Isurus oxyrinchus, is one of the fastest predatory fish in the world.When catching prey, it can swim at speeds up to 74 km h–1 for short periods of time. Discuss where and when anaerobic and aerobic respiration occur in the mako shark.
In your answer:
- explain anaerobic respiration and aerobic
respiration in the mako shark’s cells AND
identify where each type of respiration occurs
in an animal cell - explain why the mako shark can only carry out
anaerobic respiration for short periods of time - discuss the advantages and disadvantages of the mako shark carrying out both anaerobic and aerobic respiration.
Anaerobic occurs in cytoplasm of cell – glucose is broken down into lactic acid and ATP (energy); no oxygen is present, therefore less energy (2 ATP) is produced compared to aerobic. glucose → lactic acid + (2) ATP.
Disadvantage of anaerobic is that it is less efficient and lactic acid build-up causes mako shark cramps and stops muscles from working therefore cannot swim fast. If not removed from cell, it becomes toxic. Advantage is it produces ATP very quickly
because does not require O2. If O2 is temporarily low in the cell, such as during explosive swimming, cells still get the energy they need to continue functioning.
Aerobic respiration occurs in the cytoplasm and the mitochondria. Aerobic respiration is when glucose is broken down in the presence of oxygen to form carbon dioxide, water, and ATP. glucose + oxygen → carbon dioxide + water + (36) ATP Oxygen is present, so more energy (36 ATP) is produced compared to anaerobic, and the mako
shark can swim for longer. Therefore, aerobic is more efficient. Lactic acid / ethanol (which can be toxic) is not produced. However, aerobic requires oxygen, so ATP is produced more slowly. E.g. it would be advantageous for the mako shark to
anaerobically respire because (dissolved) oxygen concentration would become low during fast explosive swimming. Oxygen cannot be transported to all cells quickly enough. The mako shark’s muscles temporarily produce ATP very quickly via anaerobic respiration, so cells would
not shut down. However, the amount of ATP is less than for aerobic respiration swimming.
Protein & Enzyme - EXAM QUESTION:
The eastern oyster’s cellular respiration and enzyme activity are affected by temperature, oxygen, concentration, and cadmium, a heavy metal.
Discuss how these factors can affect cellular respiration AND enzyme activity in the eastern oyster, In your answer:
- Describe the PURPOSE of an enzyme
- Explain how temperature and cadmium affect enzyme activity
- Discuss how environmental temperature, oxygen concentration, and cadmium can affect the rate of cellular respiration in the oyster.
Respiration is a cellular process controlled by enzymes. Enzymes function at an optimum temperature.
If environmental temperature is too low, substrate/enzyme collision will be less frequent, so the rate of respiration will be low. As environmental temperature increases, respiration will also increase.
The optimum temperature for the oyster will be temperature at which peak rate of respiration occurs. Above this temperature, the enzymes may become denatured, which makes them inactive and is irreversible.
They are denatured because of the change i the shape/structure of the active site which can no longer fit in the substrates(s) involved in the process. Once the active site begins to change shape the rate of cell respiration will decrease, or may stop altogether.
Cadmium is a heavy metal that acts as an enzyme inhibitor. it can combine with the active site/enzyme, blocking it or changing it’s shape, and preventing substrates from attaching/binding to the active site and a product being formed. This prevents the enzyme from functioning properly.
PHOTOSYNTHESIS AND MOVEMENT OF MATERIALS - Exam Question 1
Freshwater aquatic plants and animals are able to absorb water and dissolved gases directly from the water into their cells.
Explain how water enters both plant AND animal cells.
Water enters the cell by osmosis, which is the movement of when water is diffused from a high concentration of water to a low concentration of water through a semi-permeable membrane. This is a passive process because no ATP / energy is needed and the water moves along a concentration gradient / from high to low.
- cell wall of plant
cells as preventing bursting / lack
of cell wall in animal cells leads
to bursting.
Photosynthesis and movement of material - EXAM QUESTION 2
Freshwater aquatic plants and animals are able to absorb water and dissolved gases directly from the water into their cells.
Explain why animal cells may burst when placed in fresh water, but plant cells will not.
Plant cells have a cell wall, which provides a pressure, which prevents the cell from bursting due to osmosis.
Animal cells
don’t have a cell wall therefore can burst during osmosis.
Since osmosis is a passive process, it will continue as long as
the water concentration outside the cell is greater than the water concentration inside the cell, thus bursting animal cells.
