Cells and Life - GED Science

The mitochondria are organelles that are often referred to as the "power plant" of the cell. Mitochondria are responsible for extracting energy from food molecules and binding it in the high energy bonds of the ATP molecule.

Ribosomes are composed of a unique type of RNA, rRNA, and are located within the cytoplasm of the cell and on the surface of the rough endoplasmic reticulum. Here, proteins are assembled from amino acids piece by piece using instructions copied from DNA.

The "water-loving" hydrophilic heads of phospholipids orient themselves outwards towards the watery cytoplasm inside the cell and interstitial fluid outside the cell. Meanwhile, the "water-fearing" hydrophobic tails of phospholipids orient themselves inwards toward one another.

Interstitial fluid is the substance surrounding living tissue cells, its solute concentration is critical to the maintenance of homeostasis for the cells. Cells may have to spend valuable energy to keep unwanted materials from passing through their semi-permeable membranes in some conditions.

Diffusion, facilitated diffusion, and osmosis are all examples of passive transport because no energy is required to move molecules across the cell membrane. The driving force is the concentration gradient of the substance.

Water can pass through the cell membrane without using energy. We call this passive transport. Diffusion is a type of passive transport and osmosis is specifically the diffusion of water molecules. So all of the answers are correct.

The Golgi apparatus can be thought of as the "shipping center" of the cell. Here, proteins and other materials are packaged in vesicles which are transported to other sites in the cell or outside the cell membrane for "export".

The chloroplast is unique to plant cells (and some bacteria and protists), and is the site of photosynthesis. Almost all energy used by life is captured by this organelle. All other answers listed can be found in both plant and animal cells.

Active transport always requires energy since molecules are being pumped against their concentration gradients by being transported from areas of low concentration to areas of high concentration. Osmosis and diffusion are examples of passive transport and do not require energy.

The mitochondria is the "powerhouse" of the cell and converts chemical energy (sugars) into ATP during cellular respiration.

In a hypertonic solution, the cell has a greater concentration of water molecules inside it than the solution does. Because of this, the water will move out of the cell in an effort to balance the concentration of water molecules both inside and outside of the cell.

Cellular respiration is composed of many steps used to break down glucose and convert the chemical energy into ATP. Of the four steps described in the answer choices, oxidative phosphorylation via the electron transport chain is the most effective step for producing ATP. The electron transport chain can produce between 32 and 38 ATP from a single glucose molecule.

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.