Quick Review: The nucleus controls most cell processes and contains nearly all the cell’s DNA. The nucleus is surrounded by a nuclear envelope. Most nuclei contain a small dense region called the nucleolus where the assembly of ribosomes takes place. Questions: 1.Where is the genetic material located in a eukaryotic cell? 2.Which type of organelle assembles proteins? 3.What structures do plant cells have that animal cells do not? Std. 7 1c

Quick Review: Most cells get energy from the Sun or from food molecules Mitochondria are organelles that convert the chemical energy stored in food into compounds that are more convenient for the cell to use. Chloroplasts are organelles that capture energy from sunlight to convert carbon dioxide and water into oxygen and sugars. Questions: 1.Do animal cells contain chloroplast? Explain 2.What two reactions take place inside the chloroplasts? Std. 7 1d

Quick Review: During the cell cycle, a cell grows and prepares for division. It divides to form two identical daughter cells, each of which then begins the cell cycle again. All organisms begin their lifer cycles as a single cell. Most unicellular organisms reproduce asexually by a form of mitosis called binary fission. In multicellular organisms, successive generations of embryonic cells form by cell division. Questions: 1.What is DNA replication? During which stage of the cell cycle does it occur? 2. During which phase of mitosis do the chromosomes line up at the center of the cell? 3.What occurs during cytokinesis? Std. 7 1e

Quick Review: Atoms are the basic building clocks of all cells. The most common elements in living things are carbon, oxygen, hydrogen, and nitrogen. Trace elements such as calcium, iron, potassium, phosphorus, sodium, and sulfur are also important. Water molecules are essential for most chemical reactions that take place within living cells. Questions: 1.Which two gases found in the atmosphere are needed by most living things? 2.What property of water molecules enables most chemicals important for life to dissolve in water? Std. 8 6 b.

Quick Review: The body needs water because many of the body’s processes, including chemical reaction, take place in water. Water is needed by plants for the process of photosynthesis. Questions: 1.How do solutions differ from other types of mixtures? 2.How does water’s porperty as a solvent affect the composition of blood, which is mainly water? Std. 8 6 c.

Questions: 1.What is the function of the cell membrane? 2.What other molecules are found in the cell membrane? Std. BI 1. a Quick Review: The cell membrane controls the internal environment of a cell. Materials can move through the membrane by diffusion, osmosis, or active transport. The composition of nearly all cell membranes is a double-layered sheet called a lipid bilayer. Molecules move by diffusion form an area of higher concentration to an area of lower concentration. Water moves in or out of a cell by osmosis based on concentration differences across a cell membrane. Active transport moves materials through a cell membrane against a concentration gradient.

Quick Review: Osmosis is the diffusion of water through a selectively permeable membrane. Substances diffuse from an area of higher concentration to an area of lower concentration. Osmosis is one of several processes that allow cells to maintain homeostasis. Questions: 1.How does a cell keep from taking in excess water? 2.Why can some substances pass through a cell membrane and others cannot? Std. BI 1 a

Quick Review: Cells must move waste products across the cell membrane to maintain homeostasis within the cell. Diffusion, osmosis, and active transport move materials across the cell membrane. Active transport moves materials against a concentration gradient and requires an input of energy from the cell. Questions: 1.Name two differences between active transport and diffusion. Std. BI 1. a

Quick Review: Most cells function best within a narrow range of temperature and acidity. Extreme changes may harm cells because they change the structure of their proteins. Enzymes increase the rate of reaction by reducing the activation energy needed to get the reacting started. Most enzymes are proteins. When conditions are too acidic or too alkaline, enzymes do not work as well and reactions are slower than when the pH is optimal. Questions: 1.What happens to the rate of the reaction in the presence of an acid? 2.What happens to the rate fo the reaction when a base is added? Std. BI 1. b

Quick Review: Enzymes are biological catalysts. They speed up chemical reactions in cells. Substrates bind to the active site on an enzyme. The active site and the substrate have complementary shape. They fit together like a lock and a key. When the reaction is complete the products of the reaction are released and the enzyme is free to start the process again. Questions: 1.How do enzymes speed up chemical reactions? 2.Where on an enzyme does the reaction take place? 3.What would happen if a cell lacked a key enzyme? Std. BI 1. b

Quick Review: Biologists divide cells into eukaryotes, which have a membrane-bound nucleus, and prokaryotes, which lack a membrane-bound nucleus. Prokaryotes are generally smaller and simpler than eukaryotes. Prokaryotes are bacteria. Eukaryotes contain dozens of specialized structure and membranes. Plants, animals, fungi, and protists are eukaryotes. Questions: 1.What invention allowed scientists to discover that living things are made from cells? 2.What other differences do you see between prokaryotic and eukaryotic cells? Std. BI 1. c

Quick Review: A virus has an outer coat of protein and an inner core containing either DNA or RNA. Viruses reproduce by invading a living cell and using the host cell’s machinery to replicate. Questions: 1.How do viruses compare to cells in methods of reproduction? 2.What is one characteristic shared by viruses and cells? Std. BI 1. c Viruses and Cells Structure Reproduction Genetic Code Growth and development Response Obtain and use energy Change over time DNA or RNA core, or capsid Cell membrane, cytoplasm, organelles, nucleus Only within a host cell Independent cell division either asexually or sexually DNA or RNA DNA No Yes; in multicellular organisms, cells increase in number and differentiate. No Yes NoYes yes

Quick Review: During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA. There are three main differences between RNA and DNA: the sugar in RNA is ribose instead of deoxyribose, RNA is generally single stranded, and RNA contains uracil in place of thyamine. Questions: 1.Where in the cell does transcription take place? 2.What RNA nucleotide sequence would be transcribed from the DNA sequence ACG? Std. BI 1. d

Quick Review: Some of the proteins synthesized by the cell are used within the cell; others are exported from the cell. Proteins that are exported from the cell are synthesized on the rough endoplasmic reticulum. The Golgi apparatus modifies, sorts, and packages proteins and other materials for export from the cell. Questions: 1.Are proteins synthesized in the nucleus or in the cytoplasm of a cell? 2.What are the building blocks of proteins? Std. BI 1. e

Quick Review: During photosynthesis, plants and some other organisms use energy from the sun to convert carbon dioxide and water into oxygen and sugars, including glucose. The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH. The Calvin cycle uses ATP and NADPH to produce high- energy sugars. Questions: 1.What is the cycle that produces high-energy sugars during photosynthesis? 2.What are the products of the light-dependent reactions? 3.Where does photosynthesis take place? Std. BI 1. f

Quick Review: Living things get the energy they need from food. Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. Mitochondria are organelles that convert the chemical energy stored in food into compounds that are easier for the cell to use. Questions: 1.What does glycolysis break down? 2.What takes place in the mitochondria? Std. BI 1. g

Quick Review: The four basic types of organic molecules found in all cells are carbohydrates, lipids, proteins, and nucleic acids. Carbohydrates and lipids are used by living things for energy to fuel biological processes. Proteins and nucleic acids are used to build and repair body parts. Questions: 1.What are the monomers that make up each basic type of organic molecule? 2.What two forms of carbohydrates are made from long chains of glucose molecules connected in different arrangements? Std. BI 1. h 3. What two important kinds of molecules in all cells are nucleic acids?

Quick Review: Cell membranes contain a protein called ATP syntase that spans the membrane. As H+ ions pass into the ATP synthase, it spins. Each time it rotates, the enzyme grabs a low-energy ADP and attaches a phosphate forming high energy ATP. Questions: 1.What is the role of ATP synthase during cellular respiration? Std. BI 1. g

Quick Review: The cytoskeleton helps the cell to maintain its shape. It also is involved in cell movement. The cytoskeleton is made up of microfilaments and microtubules. Microfilaments are made up of the proteins actin. Microtubules are made up of proteins called tubulins. Microtubules form cilia and flagella. Questions: 1.What are two functions of the cytoskeleton? 2.How do organisms, such as paramecia, use cilia to move? Std. BI 1. j

Quick Review: The cytoskeleton helps the cell to maintain its shape. It also is involved in cell movement. The cytoskeleton is made up of microfilaments and microtubules. Microfilaments are made up of the proteins actin. Microtubules are made up of proteins called tubulins. Microtubules form cilia and flagella. Questions: 1.What are two functions of the cytoskeleton? 2.How do organisms, such as paramecia, use cilia to move? Std. BI 1. j