LIVROS FOZ PDF Biology Textbook

# LIVROS FOZ ## Intestinal cells have large quantities of mitochondria - Provide energy for diverse transport processes. - Each mitochondrion is composed of a pattern of membranes. - Inner membranes form a set of consistent proteins. - Include an ATP synthase, a molecule that synthesizes adenosi...

# LIVROS FOZ ## Intestinal cells have large quantities of mitochondria - Provide energy for diverse transport processes. - Each mitochondrion is composed of a pattern of membranes. - Inner membranes form a set of consistent proteins. - Include an ATP synthase, a molecule that synthesizes adenosine triphosphate. ## Cells possess a genetic program and the means to use it. - Organisms are built according to information encoded in a collection of genes. - Genes are made of DNA. - The human genetic program holds enough information, when converted into words, to fill millions of pages of text. - The information is packed into chromosomes. - Located in a cell's nucleus. ## Genes are more than storage compartments - They are recipes for building cellular structures. - Instructions for executing cellular activities, - Instructions for making more of themselves. - The molecular structure of genes allows for changes in genetic information - mutations. - Lead to variations among individuals. - This is the basis of biological evolution. - Understanding how cells use and transmit their genetic information has been one of science's major triumphs of recent decades. ## Cells are capable of producing more of themselves - Organisms reproduce through cell division. - Replicated before division. - Each daughter cell receives a complete and equal share of the genetic information. - The division of a human oocyte (egg) cell can lead to an unequal distribution of cytoplasm and genetic information. ## Cells acquire and use energy - All biological processes require energy expenditure. - Most of the energy used by life on Earth comes from the Sun in the form of electromagnetic radiation. - Light energy is trapped by pigment molecules. - Located in the membranes of photosynthetic cells. ## Cells carry out a variety of chemical reactions - The simplest bacterial cell is capable of hundreds of different chemical transformations. - These transformations do not occur significantly in the inanimate world. - Nearly all changes require enzymes, molecules that greatly increase the rate of a chemical reaction. - Metabolism - the sum total of chemical reactions in a cell. ## Cells participate in mechanical activities - Cells are sites of much activity, materials are transported from one place to another. - Structures assemble and disassemble rapidly. - Move themselves from one place to another. - These activities are based on mechanical and dynamic changes within the cell. - Many of these changes are caused by alterations in the shape of motor proteins. ## Cells are capable of responding to stimuli - Some cells respond to stimuli in obvious ways. - For instance, a single-celled protist moves away from a barrier in its path or toward a source of nutrients. - Cells within a plant or animal respond to stimuli in less obvious ways. - Most cells are covered with receptors. - Interact with substances in the environment in very specific ways. - Cells have receptors for hormones, growth factors, extracellular materials, and other cell surfaces. - Cell receptors provide pathways for how external stimuli can trigger specific responses in target cells. - Cells can respond to stimuli by altering their metabolic activities, moving from place to place, or even self-destructing. ## Cells are capable of self-regulation - Cells are robust, they are vigorous and durable. - Protected from dangerous fluctuations in composition and behavior. - If such fluctuations occur, specific feedback loops are activated to bring a cell back to its appropriate state. - Maintaining a complex and ordered state in cells requires constant regulation. - The importance of cellular regulatory mechanisms is most apparent when they fail. - A failure to correct a mistake when DNA is duplicated can result in damaging mutations. - Breakdown in a cell's growth control can lead to a cancerous cell capable of destroying the entire organism. - The discovery of how a cell regulates its activities is a gradually unfolding story. - Cells are highly robust because they have the capacity to self-regulate. ## Cell Example: The Sea Urchin - An experiment by Hans Driesch in 1891 demonstrated that: - The four cells of a sea urchin embryo can be separated. - Each cell can grow into a complete embryo, although smaller. - This demonstrates that each cell retains the complete genetic information necessary for development.