Cells: The Basic Units of Life

• The required reading for this chapter is Chapter 1 of Karp.
• Section 1.4 is for interest and has questions in Assignment 1 in Wiley Plus.
• Sections 1.5 and 1.6 are not required.
• Online resources like the glossary, flashcards, quizzes, and practice questions should be used.
• Review the animations titled "The Scientific Method" and "Cell Structure".
• Cells are the basic structural and functional units of living organisms.
• Tissues are cells that aggregate to form a specific function.
• Organs are fully differentiated structural and functional units in animals, specialized for certain functions.
• The discovery of cells followed the invention of the microscope in 1865 by Robert Hooke, refined by Anton Leewenhoek.
• Hooke called the pores inside cork cells because they reminded him of monks' cells.
• Leeuwenhoek first examined pond water under a microscope and observed microscopic "animalcules".

Cell Theory

• Articulated in the mid-1800s by Matthias Schleiden, Theodor Schwann, and Rudolf Virchow.
• All organisms are composed of one or more cells.
• The cell is the structural unit of life.
• Cells arise only by division from a pre-existing cell.
• Cells can grow and reproduce in culture for extended periods.
• HeLa cells are cultured tumor cells from Henrietta Lacks, isolated by George and Martha Gey in 1951.
• Cultured cells are essential for biologists.

Basic Properties of Cells

• Cells are complex and organized and possess a genetic program.
• Genes encode cellular blueprints.
• Cells produce more of themselves through mitosis and meiosis.
• Cells acquire and use energy for development and maintenance, such as photosynthesis and respiration.
• Metabolism is the sum of chemical reactions in cells.
• Cells engage in mechanical activities.
• Cells respond to stimuli.
• Cells are capable of self-regulation.

Cells and Evolution

• Cells from different species share conserved structure, composition, and metabolic features during evolution.
• Genes store information and are blueprints for constructing cellular structures.
• Changes in genetic information (mutations) allow for variation.
• All cells in an organism contain identical copies of DNA but differentiate during development from a single fertilized egg.
• Cells reproduce by division processes in which a "mother" cell's contents are distributed into two "daughter" cells.
• Genetic material is duplicated, and each daughter cell gets a complete, equal share of genetic information before division.
• Animal cells derive energy from photosynthesis products, mainly glucose.
• Animal cells convert glucose into ATP for readily available energy.
• Chemical changes in cells need enzymes to increase the rate at which chemical reactions occur.
• The sum of the chemical reactions is cell metabolism.
• Cells transport materials, assemble and disassemble structures, and move.
• Activities are based on dynamic changes initiated by "motor" proteins.
• Motor proteins are molecular "machines".
• Single-celled organisms move away from objects or toward nutrients.
• Plant and animal cells have receptors.
• Hormones, growth factors, materials, and substances on the surfaces of other cells interact with these receptors.
• Cells may respond to stimuli by changing metabolism, moving, or committing suicide.
• Cells are protected from fluctuations in composition and behavior.
• Feedback circuits maintain appropriate states.
• Constant regulation maintains a complex, ordered state.
• Hans Driesch separated sea urchin embryo cells, and each cell developed into a normal embryo.
• The origin of cells is unknown.
• Cell evolution can be studied by examining living organisms.
• Cells share a common genetic code, plasma membrane, and ribosomes.
• All organisms evolved from a single common ancestral cell over three billion years ago.
• This ancestor is the Last Universal Common Ancestor (LUCA).

Prokaryotic vs Eukaryotic Cells

• There are two basic types of cells: prokaryotic and eukaryotic.
• They are distinguished by size and types of organelles.
• The cells types share ancestry with an identical genetic language
• They also share a common set of metabolic pathways and common structural features.
• Prokaryotic are covered in biology courses.
• The course focuses on mammalian cellular biochemistry and cell biology.

Cell Structure and Function

• Cells vary in structure and function.
• Cell form reflects function and physiology.
• All cells are made of similar chemical molecules.

Eukaryotic Cell Types

• Model organisms include Escherichia coli (bacteria), Saccharomyces (yeast), Caenorhabditis elegans (nematode), Arabidopsis (mustard plant), Mus musculus (mouse), and Zebra fish.
• These organisms are relatively simple, have fast generation times, large offspring numbers, are easy to manipulate in the lab, and are inexpensive to breed.

Sizes of Cells and Their Components

• Cells are measured in micrometers (1 µm = 10⁻⁶ meter) and nanometers (1 nm = 10⁻⁹ meter).
• Lowest size is limited by the number of biomolecules required for existence.
• Rate of diffusion of solutes in the intracellular environment limit the upper size.
• Oxygen must diffuse easily.
• Some eukaryotic cells can be large, like the Acetabularia alga, which is more than 10 cm long.

Synthetic Biology

• It is a field creating a living cell in the lab.
• A modest synthetic biology goal includes developing novel life forms, beginning with existing organisms.
• Possible applications are in medicine, industry, or the environment.

Scientific method and Facts

• The scientific method helps assess new information
• Scientists make a hypothesis as a testable statement that leads to data collection that is then interpreted.
• Occam's razor states that the simplest explanation consistent with observations is the best.
• "Facts" in science are tentative and dynamic,

Hypothesis, Theory and Law

• Hypothesis is a statement consistent with most of the data and takes the form of an explanation that is testable.
• A theory is a hypothesis tested by investigators using different approaches and widely accepted in the scientific community with the example of cell theory.
• A law is a statement of fact of a natural phenomena tested and confirmed with no doubt with the example of thermodynamics.

Learning Objectives

• You should focus on the big pictures and the basic details of the topics presented.
• The three tenants of cell theory should be known.
• You should be familiar with the fundamental differences between procaryotes and eukaryotes.
• You should understand common model organism advantages
• What limits cell size is and how limit varies.
• You should understand the scientific method
• You should be able to identify a hypothesis, theory and law.
• View "The Scientific Method" and "Cell Structure"
• Make sure that terms in the glossary are familiar
• Complete and understand the WileyPlus assignments for chapter 1
• Also complete the problem set for Chapter 1, and the canvas assignment