The Ultimate Biology Gauntlet: Are You a True Biologist?

The reactants in the process of photosynthesis are carbon dioxide and water. Sunlight is needed for the reactions to occur. The products of photosynthesis are oxygen and glucose, a simple carbohydrate. ATP is used in photosynthesis but is neither a reactant nor a product. ATP is produced in a different process called cellular respiration.

A cell membrane is a thin layer of molecules that surrounds the cell. Its function is to allow certain materials to enter the cell, yet, keep harmful materials out. In order to do this, the cell controls which substances can enter the cell through the membrane. The cell membrane is selectively permeable (or semipermeable), which means that certain molecules, such as oxygen and water, are permitted to enter the cell. Molecules that are not recognized as helpful are not able to pass through the membrane.

Enzymes are catalysts, chemicals that speed up chemical reactions. The conditions inside mostcells do not allow reactions to proceed quickly enough to support life. For example, temperaturesinside organisms are not hot enough for chemical reactions to take place quickly. Enzymesincrease the rates of biological chemical reactions.

Inside cells, sequences of chemical reactions take place to support life. These sequences areknown as metabolic pathways. Photosynthesis, respiration, and digestion are all examples ofmetabolic pathways, or sequences. Photosynthesis is the metabolic pathway that produces oxygen and glucose in organisms with chlorophyll. Respiration breaks down molecules called ATP for cells to use as energy. Digestion breaks down food to be used to make energy in the form of ATP. Hydroplasm is not a known metabolic sequence.

Chloroplasts and central vacuole are important organelles in plant cells. Chloroplasts contain chlorophyll and are the site of photosynthesis. Central vacuoles are used to store water in plant cells. All the other organelles listed are important to the function of animal cells and plant cells.

Photosynthesis is the process plant cells use to convert oxygen, water and sunlight into ausable form of energy. The product of photosynthesis is glucose (sugar) molecules. Glucose molecules are a form of potential energy that can be broken down by an organism to produce energy in the form of ATP molecules.

A gene is the basic unit of heredity. Genes are made of DNA sequences and act as instructions for making proteins (although not all genes make proteins). Genes are found on chromosomes.Chromosomes are located in a cell's nucleus.

DNA is made of two strands of nucleotides (basic units of DNA). The DNA molecule looks likea twisted ladder and is referred to as a double helix. Each nucleotide contains a sugar moleculeand a phosphate group, along with a nitrogen base. The sugar molecules and phosphate groupsmake up the sides of the ladder, and the nitrogen bases make up the "steps" of the ladder.

Genes are sequences of DNA on a chromosome. All DNA is located inside a cell's nucleus.

Messenger RNA (ribonucleic acid) transfers genetic information from the DNA in a cell's nucleus to ribosomes. In the ribosome, the information coded onto messenger RNA is used to make proteins.

During meiosis, gametes (sex cells) are formed by reducing the number of chromosomes found in somatic (body) cells by one half. This occurs so that when two gametes, one from each parent, fuse together, the embryo will contain the correct number of chromosomes. Without meiosis, offspring cells would contain double the number of chromosomes of normal adults and they would not be viable.

Biology uses a system of classification to group organisms together based on their characteristics.The levels of classification, from largest (most inclusive) to smallest (most specific), include domain, kingdom, phylum, class, order, family, genus, species.

Prokaryotic and eukaryotic cells both contain DNA. Prokaryotic cells are found in bacteria and their structure is much more simple than eukaryotic cells. Prokaryotic cells have a few simple cellular structures such as a nucleoid region, ribosomes, and a plasma membrane. Eukaryotic cells have more highly developed cellular structures including organelles that support the function of the cell. Golgi apparatus and mitochondria are found in eukaryotic cells. Chloroplasts are found in eukaryotic cells that contain chlorophyll, such as plants.

Organelles are specialized structures in cells that support the cellular functions. For example, mitochondria are organelles that synthesize energy; ribosomes synthesize protein; chloroplasts convert sunlight, carbon dioxide and water into oxygen and sugar.

Unicellular organisms are very small compared to most multicellular organisms. If they were as large as a multicellular organism, their surface area to volume ratio would be too low to support life. Staying small gives unicellular organisms a high surface area to volume ratio. Surface area to volume ratio refers to the amount of surface area on the outside of the cell compared to the cell's volume. Larger cells have less surface area compared to their volume. Molecules move into the cell, out of the cell and through the cell slowly through the cell membrane. Having a large surface area provides more space for molecules to diffuse across the cell membrane and less of a distance to travel inside the cell to supply organelles with materials needed for metabolism.