Biology 100 Test 1

A hypothesis must be testable in order to be scientifically valid. This means that it must be possible to design and conduct experiments or gather evidence that can either support or refute the hypothesis. Without the ability to test a hypothesis, it cannot be proven or disproven, and therefore cannot be considered scientifically valid.

Based on the presence of mitochondria, chloroplasts, and cell walls, it can be concluded that the cells are plant cells. Mitochondria are found in both plant and animal cells, but chloroplasts, which are responsible for photosynthesis, are only present in plant cells. Additionally, cell walls are a characteristic feature of plant cells, providing them with structural support. Therefore, the combination of these three organelles suggests that the cells observed are plant cells.

Eukaryotic cells are more complex than prokaryotic cells because they contain membrane-bound organelles, such as mitochondria, endoplasmic reticulum, and Golgi apparatus. These organelles perform specific functions within the cell, allowing for greater specialization and efficiency. In contrast, prokaryotic cells lack membrane-bound organelles and their functions are carried out by different structures within the cell. This fundamental difference in cellular organization is one of the key distinctions between prokaryotic and eukaryotic cells.

Cellular respiration produces the most ATP per molecule of glucose compared to the other processes mentioned. This is because cellular respiration involves the complete breakdown of glucose in the presence of oxygen, which results in the production of a large amount of ATP through the process of oxidative phosphorylation. Alcoholic fermentation and lactic acid fermentation, on the other hand, are anaerobic processes that produce a smaller amount of ATP per glucose molecule. Therefore, cellular respiration is the most efficient process for ATP production.

The prediction in this scenario is "If hummingbirds prefer red flowers, then they will choose to visit a red flower over a white flower or a yellow flower." This prediction is based on the observation that hummingbirds often visit red flowers and the hypothesis that they prefer red flowers over flowers of other colors. The experiment is designed to test this prediction by giving hummingbirds a choice between red, white, and yellow flowers and observing their preference.

The statement "Hummingbirds often visit red flowers" represents an observation because it describes a behavior that can be directly observed and measured. It does not make any assumptions or predictions, but rather states a fact about the behavior of hummingbirds.

Photosynthesis is the correct answer because it is the process by which plants, algae, and some bacteria convert sunlight, carbon dioxide, and water into glucose and oxygen. This glucose is then used as a source of chemical energy by all living organisms on Earth through cellular respiration. Without photosynthesis, there would be no source of chemical energy for life on Earth, making it the ultimate process that sustains all life.

Exocytosis is the process by which large molecules are transported out of the cell. It involves the fusion of vesicles containing these molecules with the cell membrane, resulting in their release into the extracellular space. This mechanism is essential for various cellular functions such as secretion of hormones, neurotransmitters, and digestive enzymes. Therefore, the correct answer is "the movement of large molecules out of the cell."

Chlorophyll is the pigment that absorbs solar energy during the light reactions. The light reactions are the first stage of photosynthesis, where light energy is converted into chemical energy in the form of ATP and NADPH. Chlorophyll molecules in the chloroplasts of plant cells capture photons of light and use their energy to excite electrons, which then participate in a series of reactions that generate ATP and NADPH. These energy-rich molecules are essential for the subsequent Calvin cycle, where carbon dioxide is fixed and converted into glucose. Therefore, chlorophyll's role in absorbing solar energy is crucial during the light reactions.

All cells contain DNA, which is the genetic material that carries the instructions for the cell's functions. Ribosomes are also present in all cells and are responsible for protein synthesis. Additionally, all cells have plasma (cell) membranes that surround and protect the cell, regulating the movement of substances in and out of the cell. Chloroplasts and mitochondria are not found in all cells, as they are specific to certain types of cells.

The statement "The appearance of organelles was a huge evolutionary advancement" is false because organelles themselves did not appear as a result of evolutionary advancement. Organelles, such as mitochondria and chloroplasts, are believed to have originated through a process called endosymbiosis. This theory suggests that certain organelles were once free-living prokaryotic organisms that were engulfed by ancestral eukaryotic cells. Over time, a symbiotic relationship developed, and these engulfed organisms became organelles within the host cell.

The correct answer is thylakoid membranes of a chloroplast. This is because the light reactions of photosynthesis, which involve the conversion of light energy into chemical energy, occur in the thylakoid membranes of chloroplasts. The thylakoid membranes contain pigments like chlorophyll that capture light energy, and the reactions that take place in these membranes generate ATP and NADPH, which are used in the subsequent dark reactions of photosynthesis. The stroma of the chloroplast, on the other hand, is where the dark reactions occur. The other options (cristae of a mitochondria, endoplasmic reticulum of a skin cell, and cytoplasm) are not involved in the light reactions of photosynthesis.

The 15% sucrose solution outside the circle has a lower concentration of solutes compared to the 25% sucrose solution inside the circle. Since the selectively permeable membrane is permeable only to water, water molecules will move from an area of lower solute concentration (outside the circle) to an area of higher solute concentration (inside the circle) through the process of osmosis. Therefore, a net movement of water into the circle would be expected.

This sequence correctly illustrates the hierarchy of life from smallest and simplest to largest and most complex. It starts with macromolecules, which are the building blocks of cells. Cells then form tissues, which make up organs. Organs work together to form organ systems, which make up an organism. Populations consist of multiple organisms of the same species, and communities consist of multiple populations of different species. Ecosystems are made up of multiple communities interacting with their environment, and the biosphere is the highest level of organization, encompassing all living organisms and their environments.

Water freezing at 0°C is not biologically important because many organisms have evolved mechanisms to survive in freezing temperatures. The ability of water to freeze and form ice is actually beneficial for some organisms, as it provides insulation and allows for the formation of habitats such as ice caps and glaciers. On the other hand, the other properties listed (high specific heat capacity, high heat of vaporization, excellent solvent, unique density behavior) are all biologically important. Water's high specific heat capacity helps regulate temperature in organisms, its high heat of vaporization aids in evaporative cooling, its solvent properties are crucial for biochemical reactions, and its unique density behavior allows for the formation of ice on top of bodies of water, insulating and protecting the organisms below.

Enzymes are biological catalysts that increase the rate of chemical reactions by lowering the energy of activation. This means that they make it easier for a reaction to occur by reducing the amount of energy required to start the reaction. The second statement, "Their shape determines their function," is also true. Enzymes have specific shapes that allow them to bind to specific substrates and catalyze specific reactions. The third statement, "Once they have been used, they are unchanged and can be reused," is not true. Enzymes can be denatured or altered during a reaction and may require certain conditions or cofactors to function properly. Therefore, the correct answer is "B and C are true, but not A."

Active transport is not the most common type of transport mechanism in eukaryotic cells. Passive transport, such as diffusion and facilitated diffusion, is actually more common. Active transport requires the cell to use ATP to transport molecules across a membrane, and it also requires a transport protein to move molecules across a membrane. Additionally, active transport involves the movement of molecules against a concentration gradient, not up a concentration gradient.

Diffusion is a continuous process that occurs until equilibrium is reached. Once equilibrium is reached, the concentration of molecules becomes equal throughout the system, and there is no net movement of molecules. Therefore, the statement that diffusion stops after equilibrium is reached is false.

The given statement is false because the fluid filled space inside the inner membrane of chloroplasts is called the stroma, not the cytoplasm. The cytoplasm is the fluid found inside a cell, which is present in all types of cells. Glycolysis, a metabolic process, indeed occurs in the cytoplasm of a cell.

Lysosomes are only found in eukaryotic cells. Prokaryotic cells do not have membrane-bound organelles like lysosomes. Lysosomes are responsible for the breakdown of cellular waste and foreign substances through the action of their digestive enzymes. They are considered part of the endomembrane system, which also includes the endoplasmic reticulum, Golgi apparatus, and plasma membrane. Therefore, the statement "Lysosomes are found in both prokaryotic and eukaryotic cells" is false.

The statement "Two (2) molecules of ATP are formed during chemiosmosis" is false. During chemiosmosis, ATP is produced through the flow of protons across the inner mitochondrial membrane, but the exact number of ATP molecules formed can vary. The actual number of ATP molecules produced depends on the specific conditions and the efficiency of the process.

The stroma is where chemical energy is stored in molecules of glucose. The stroma is a part of the chloroplast, which is involved in photosynthesis. During photosynthesis, glucose is synthesized in the stroma using light energy, and this glucose serves as a source of chemical energy for the cell. Therefore, the statement that the stroma is where chemical energy is stored in molecules of glucose is true.

Insulin is produced in the rough ER (endoplasmic reticulum) where it is synthesized. After synthesis, it is transported in transport vesicles to the Golgi apparatus for further processing and packaging. From the Golgi apparatus, it is then transported in transport vesicles to the cell membrane where it is released into the bloodstream. Lysosomes are not involved in the production or transportation of insulin, so the correct answer is rough ER, transport vesicles, Golgi apparatus, transport vesicles, cell membrane.

During fermentation, only glycolysis occurs. This is because fermentation is an anaerobic process that occurs in the absence of oxygen. In this process, glucose is partially broken down through glycolysis to produce a small amount of ATP and other byproducts such as lactic acid or ethanol. Unlike aerobic cellular respiration, fermentation does not involve the complete breakdown of glucose and does not produce oxygen as a byproduct.

This statement is incorrect because membranes are present in both eukaryotic and prokaryotic cells. Prokaryotic cells, such as bacteria, have a plasma membrane that separates the interior of the cell from the external environment. While it is true that eukaryotic cells have additional membrane-bound organelles, such as mitochondria and chloroplasts, both cell types possess membranes that serve important functions like regulating the transport of molecules and maintaining cellular integrity.