Biology and Life Sciences - GED Science

Fungal cell walls can be differentiated from plant and bacterial cell walls in that they are made of the polysaccharide chitin. Plant cell walls use cellulose, and bacteria use peptidoglycan. Amylose is a component of starch.

The plant is only able to use absorbed light during photosynthesis; reflected light cannot be used as energy, as it is simply returned back into the surroundings. Red light will make a plant grow the fastest because it is absorbed. Since green light is reflected, growing a plant in green light will result in very slow growth. The light will effectively bounce off the plant, rather than being absorbed.

Glycolysis is the first step in cell metabolism. It is responsible for converting glucose (a 6-carbon sugar) into two molecules of pyruvate (a 3-carbon sugar). Glycolysis occurs in the cytoplasm, where the sugar molecules interact directly with enzymes. After pyruvate is created, it is transported to the mitochondria for the remainder of cellular respiration (the citric acid cycle and electron transport chain).

Though plants undergo photosynthesis, they also use cellular respiration. Glycolysis takes place in both animal and plant cells.

Photosynthesis is the process by which plants use the sun's energy to convert water and carbon dioxide into glucose and oxygen .

The equation is the equation for cellular respiration. Cellular respiration happens inside the mitochondria and chloroplast for those cells containing chloroplasts.

The plasma membrane of the cell acts as a semi-permeable barrier, regulating what can enter and exit the cell. Only small, nonpolar molecules are able to cross the membrane via diffusion, without the assistance of protein channels. Larger molecules will be blocked, as will molecules that are charged or polar.

This principle is true for both prokaryotic and eukaryotic cells, and is not affected by the presence of a cell wall. Virtually all organic molecules contain carbon and hydrogen; the presence of these atoms will not affect the molecule's ability to cross the membrane.

A hypertonic solution will have a higher solute concentration than the cell. To reach equilibrium, water must flow so that the concentration fo the solution is equal to the concentration of the cell. In order for this to happen, water must enter the solution, diluting it and reducing the concentration. Water will flow out of the cell and into the solution.

Note that the membrane of the cell will prevent ions from crossing.

Crossing over is an event that recombines DNA between homologous, non-identical chromosomes. The result is an increase in genetic variation because the resulting daughter cells have slightly different genetic combinations than the original parent cell. Crossing over only occurs during meiosis. This is because homologous chromosomes are only in adjacent positions during prophase I. Crossing over cannot occur during mitosis because this alignment is never present; daughter cells of mitosis are always genetically identical to the parent cell.

Sister chromatids separate during anaphase of mitosis and anaphase II of meiosis. Chromosomes condense and the nuclear membrane dissolves during prophase of mitosis and prophase I of meiosis.

Homeostasis describes the resistance of the body to change and serves to reinforce equilibrium. Concentration of ions and water in the blood and regulation of body temperature are examples of homeostatic regulation. These processes must be tightly regulated and maintained in order for the body to operate.

Negative feedback reinforces equilibrium and plays a key role in homeostasis. In a negative feedback system, deviations from equilibrium trigger processes that serve to return the body back to equilibrium. In contrast, a positive feedback system will respond to deviations from equilibrium by enhancing the changes, deviating farther and farther from the equilibrium state.

Hormones can play a key role in maintaining homeostasis, but many other molecules also help return the body to equilibrium.

The plasma membrane of the living cell is made up of a phospholipid bilayer, meaning two opposed sheets of phospholipids with their hydrophilic heads facing outwards, and their hydrophobic tails facing one another. This structure allows the cell to remain fluid in shape while also staying "water tight".

Active transport is the movement of individual small molecules across the plasma membrane against their concentration gradient (from lower concentration to higher concentration). This is usually accomplished by proteins embedded in the membrane which use ATP energy to act as "pumps".

In contrast, osmosis, simple diffusion and facilitated diffusion are all forms of passive transport and do not require additional energy from the cell. These transport methods move with the concentration gradient, rather than against.

Osmosis is the movement of water across a selectively permeable membrane, like the plasma membrane. It flows with its concentration gradient (from high concentration of water to low concentration of water).

A hypotonic solution is a solution that has a lower solute concentration than the fluid in the interior of the cell (the cytoplasm). When the cell is placed in this solution water will flow into the cell via osmosis, causing it to expand and potentially burst.

A hypertonic solution is a solution that has a higher solute concentration than the fluid in the interior of the cell (the cytoplasm). When the cell is placed in this solution water will flow out of the cell via osmosis, causing it to contract.

Exocytosis is the transport of waste materials or secretions from the cells. These molecules are packaged in membrane bound vesicles and are released across the membrane to the outside of the cell.

One of the primary differences between plant cells and animal cells is that plant cells must be able to undergo photosynthesis. Photosynthesis takes place in the chloroplasts, which contain the pigment chlorophyll. Chloroplasts are not found in animal cells, but are found in plant cells.

Both animal and plant cells contain Golgi bodies, smooth endoplasmic reticulum, and mitochondria.

Meiosis allows for increased genetic variation through crossing over and independent assortment. These processes result in daughter cells that are non-identical to the original parent cell. Crossing over describes the exchange of portions of DNA between homologous chromosomes, generating unique allelic combinations. Independent assortment means that the daughter cells of meiosis will have a mixture of genetic material from each set of the organism's alleles, representing DNA from both the mother and father sets of genes. The product of meiosis is four daughter cells that are genetically unique.

Each daughter cell of meiosis has only one copy of each gene, meaning that they are haploid. Only gametes (sex cells) undergo meiosis, allowing for sexual reproduction. The fusion of two haploid gametes results in a diploid cell.

Meiosis is the process that creates gametes (eggs and sperm). The cell divides twice, creating 4 unique daughter cells that contain half (haploid) of the genetic information of the parent cell. Somatic cells are body cells and they are produced via mitosis.

Mitosis is composed of four primary phases: prophase, metaphase, anaphase, and telophase.

During prophase the chromosomes condense, the nuclear membrane dissolves, and spindle fibers begin to form. Metaphase marks the time when the chromosomes align at the center of the cell and the spindle fibers attach to the centers of the chromosomes. During anaphase, the spindle fibers contract, separating the sister chromatids and pulling them toward opposite poles of the cell. Telophase marks the beginning of cytokinesis, when the cell fully divides, and the nuclear membrane reappears.

The correct answer is anaphase.