Unit 2 Test Review Answers

Unit 2 Test Review Answers Chapter 2 1. All living things 1. are made up of cells, which are the simplest unit considered to be alive. 2. need to obtain/use energy; either by eating other organisms or from inorganic sources like the sun. 3. grow & develop, which means getting bigger and more complex. 4. reproduce, which means produce offspring, either sexually or asexually. 5. maintain homeostasis, which is keeping internal conditions the same. 6. have a universal genetic code, which is the DNA molecule. 7. adapt to environment, which means they must detect and respond to stiumuli. 8. evolve, which is small changes over a long period of time.

2. Chemical energy is the energy found in molecules typically within their bonds. Free energy is energy that is useable or able to do work. Free energy is released in organisms from removing a phosphate group from an ATP molecule. Chemical energy is obtained either through eating other organisms or using light energy to build sugars (which contain chemical energy).

3. Autotrophs are organisms that use inorganic sources, such as the sun or inorganic compounds, as an energy source. Another word for these organisms is producers. There are 2 types: photosynthesizers (photoautotrophs) use the sun as their energy source – ex: plants and chemosynthesizers (chemoautotrophs) use inorganic compounds such as hydrogen sulfide as their energy source – ex: bacteria. Heterotrophs are organisms that eat living or once living things as their source of energy. Another words for these organisms is consumers. There are 4 groups of consumers: decomposers – break down dead/decaying matter and recycle the nutrients back into the ecosystem, ex = bacteria/fungi; herbivores (primary consumers) are consumers that feed on producers, ex = deer; carnivores (secondary or tertiary consumers) are consumers that feed on animals/meat, ex = hawk/wolf; omnivores are consumers that feed on both producers and animals/meat (can be secondary or tertiary consumers), ex = humans. 4a. producer/autotroph = Eel & Turtle Grass, Phytoplankton consumer/heterotroph = everything else primary consumers = manatee, sea turtle, larval fish mollusks & crabs, zooplankton, krill secondary consumers = jelly fish, arrow worms, baleen whales, penguins, fish tertiary consumers = fish, seals, pelicans, sea turtles, squid, toothed whales carnivore = toothed whale, squid, seal, pelican, penguin, baleen whale, fish, arrow worms, jellyfish herbivore = manatee, krill, larval fish mollusks & crabs omnivore (not included in ?) = sea turtle & zooplankton b. Lots of possible answers; Here are a couple: phytoplankton  krill  penguins phytoplankton  zooplankton  jellyfish  sea turtles eel & turtle grass  manatee c. sea turtles jellyfish zooplankton phytoplankton d. Arrows represent energy flow in a food web. They go from the food to the predator.

5. Abiotic = non-living Biotic = living Examples of abiotic factors would be air, water, minerals in soil, rocks, etc. Examples of biotic would be any organism found in the food web. 7. Solar energy gets converted into chemical energy (in a molecule of glucose) by autotrophs/producers when they perform photosynthesis. Carbon dioxide and water are required for this reaction. The chemical energy is transferred to a heterotroph/consumer when it eats an autotroph. The consumer will perform cellular respiration, which converts the chemical energy in food into ATP molecules. The raw materials needed for this reaction are glucose and oxygen.

8. ATP is a nitrogen base (adenine) connected to a ribose (5 carbon sugar) and three phosphates. ADP is a nitrogen base (adenine) connected to ribose and two phosphates. When an organism needs free

energy, ATP is broken down into ADP and a phosphate group. This is a decomposition reaction that releases free energy that can be used for cellular work, such as transporting materials, building macromolecules, etc. When free energy is no longer needed, ADP can combine with a phosphate group to form ATP again. This is a synthesis reaction, and the energy enters the cycle from the break down of food molecules.

9. The first law of thermodynamics states that energy cannot be created or destroyed. The second law of thermodynamics states that if no energy is added to maintain a system, entropy increases (it becomes more disordered). When a log is burned, much of its chemical energy has been converted into heat/light energy, with a small amount of chemical energy remaining in the ashes left behind. The burning of the log shows an increase in entropy because the molecules of the log are more disordered. So as a log burns, its free energy decreases and entropy increases.

10. Enzymes are proteins that act as biological catalysts. Catalysts are molecules that speed up chemical reactions. They do this by decreasing the activation energy, which is the energy required to start a reaction. They work when the substrate or substrates connect with the active site on the enzyme. The active site has a specific shape because of the tertiary structure of the protein folding in a particular way to match up with the substrate(s). This is why they typically catalyze only one (or maybe a couple) of reactions. When the substrates are combined with the active site, the enzyme-substrate complex is formed. The is brings the materials together so that the product(s) can be formed and then released by the enzyme so that another reaction is performed.

Enzyme concentration affects a catalyzed reaction because the more enzymes that are available to react with the substrates, the more products that can be made.

If the pH is changed, this can affect the hydrogen bonding of the protein molecule, which would affect the tertiary structure of the molecule, resulting in a differently shaped enzyme that won’t work as well (or at all) because the substrates won’t fit.

If the temperature is warmed up slightly, the enzyme activity increases because the molecules are all moving faster, so there will be more collisions between the enzyme and substrate(s), creating more products. If the temperature is increased drastically, the hydrogen bonds that are responsible for the tertiary structure will be disrupted, changing the shape of the enzyme, making the substrates not fit. If the temperature is decreased, all the molecules move more slowly, so less collisions occur between the enzyme and substrate(s), which means less products will be formed.

11. Reduction reactions are ones in which electrons are gained. Oxidation reactions are ones in which electrons are lost. (Don’t worry about how they cause changes in free energy).

Chapter 3 1. The cell membrane is a phospholipid bilayer. Each phospholipid consists of a polar/hydrophilic head with two non-polar/hydrophobic tails. These arrange themselves in a bilayer, in which the phophate heads are on the outside of both sides of the membrane and the fatty acid tails are in the middle. Throughout the bilayer are proteins that act as channels to help allow certain molecules to move through the membrane. Attached to some of these proteins are carbohydrates, resulting in a structure called a glycoprotein. If the carb directly attaches to a lipid, it’s called a glycolipid. These act as receptors, receiving messages from other cells. Small nonpolar gasses (like O2 or N2) and very small polar (like H2O and CH3OH) molecules are able to pass through the membrane. Ions are repelled by the nonpolar fatty acid tails, and larger molecules usually need to pass through a transport protein. The main property of the cell membrane is that it is selectively permeable – it only allows some materials to pass through it.

2/3. The two major types of transport are active and passive transport. Active transport requires energy, and typically moves materials against a concetration gradient (from low to high). Passive transport does not require energy, and so materials are moved down the concentration gradient (from high to low). Two types of active transport are endocytosis (materials are brought into the cell) and exocytosis (materials are released out of the cell). Three types of passive transport are diffusion (the movement of materials from a high concentration to a low concentration which occurs because of the random movement of the particles eventually causing them to disperse), osmosis (the diffusion of water across a selectively permeable membrane), and facilitated diffusion (the diffusion of materials with the help of transport proteins). Passive transport is important to cells because it is how many simple organisms take in materials that they need such as oxygen.

4. A solution is a homogenous mixture (2 or more substances mixed together but uniform in consistency) and is made up of 2 parts – solvent is the liquid that does the dissolving and solute is the stuff that is getting dissolved. When comparing two solutions, the one that has MORE solute is called hypertonic, the one that has LESS solute is called hypotonic, and if the two concentrations are equal, they are referred to as isotonic. When a cell is placed into a very hypertonic environment, water will leave the cell, causing it to shrivel up. This is called cytolysis. When an animal cell is placed into a very hypotonic environment, the water will enter the cell, eventually causing cytolysis when the cell bursts. In a plant cell, the cell won’t burst because it has a cell wall, so when placed in a hypotonic environment, the cell will experience an increase in turgor pressure pushing against the cell wall. If a cell is placed into a very hypertonic environment, the cell will lose a lot of water and become shriveled up, which is called plasmolysis.

5a. In set up A, the dialysis tubing is placed into a very hypotonic environment (there are no solutes in distilled water) so water will rush into the dialysis tubing causing the mass to increase by a lot. In set up B, the dialysis tubing is put into a hypotonic environment but there is not as much of a concentration gradient, so water will move into the tubing but not as quickly as in A so the mass will increase but not as much. In set up C, the two environments are isotonic so water will be moving in and out equally so there will not be a change in mass. In set up D, the dialysis tubing is placed into a hypertonic environment so the water will move out of the tubing, causing its mass to decrease. The overall process that is occurring is osmosis, the diffusion of water across a membrane. b. Beaker A has the most hypotonic solution because it contains distilled water which has no solutes mixed into it and the tubing is 25% sugar so the difference between the two concentrations is 25%. Beaker D is the most hypertonic (it’s actually the only hypertonic) because it has a 25% sugar solution outside with only a 5% sugar solution inside the tubing.