Lecture 1: Review of the cell Flashcards
The discovery of cells is generally credited to
Robert Hooke
Antonie van Leeuwenhoek
First to examine a drop of pond water under the microscope and, to his amazement, observe the teeming microscopic “animalcules” that darted back and forth before his eyes. He was also the first to describe various forms of bacteria, which he obtained from two sources: water in which pepper had been soaked and scrapings from his teeth.
Matthias Schleiden
Concluded that, despite differences in the structure of various tissues, plants were made of cells and the plant embryo arose from a single cell.
Theodor Schwann
Schwann concluded that the cells of plants and animals are similar structures and proposed these two tenets of cell theory:
1. All organisms are composed of one or more cells.
2. The cell is the structural unit of life
Schleiden and Schwann’s ideas on the origin of cells proved to be less insightful because
both agreed that cells could arise from noncellular materials
Rudolf Virchow
Made a convincing case for the third tenet of cell theory:
- Cells can arise only by division from a preexisting cell.
Since the discovery of DNA as the genetic material, a fourth tenet of cell theory is sometimes added:
Cells contain genetic information in the form of DNA, and that information is passed from parent to daughter cell.
Cells Are Highly Complex and Organized
Explain this with examples
- The more complex a structure, the greater the number of parts that must be in their proper place, the less tolerance for errors in the nature and interactions of the parts, and the more regulation or control that must be exerted to maintain the system. Cellular activities can be remarkably precise. DNA duplication, for example, occurs with an error rate of less than one mistake for every ten million nucleotides incorporated—and most of these are quickly corrected by an elaborate repair mechanism that recognizes the defect.
- Each type of cell has a consistent appearance when viewed under a high-powered electron microscope; that is, its organelles have a particular shape and location, from one individual of a species to another. Similarly, each type of organelle has a consistent composition of macromolecules, which are arranged in a predictable pattern.
Just as individual organisms are generated by reproduction, so too are individual cells. Cells reproduce by division, a process in which ….. prior to…..(2):
- the contents of a mother cell are distributed into two daughter cells.
- Prior to division, the genetic material is faithfully duplicated, and each daughter cell receives a complete and equal share of genetic information
Explain how the plant cell uses energy (generalized)
Virtually all of the energy utilized by life on the Earth’s surface arrives in the form of electromagnetic radiation from the sun. The energy of light is trapped by light absorbing pigments present in the membranes of photosynthetic cells. Light energy is converted by photosynthesis into chemical energy that is stored in energy-rich carbohydrates, such as sucrose or starch.
For most animal cells, energy arrives prepackaged, often in the form of the sugar glucose. In humans, glucose is …..
released by the liver into the blood, where it circulates through the body delivering chemical energy to all the cells. Once in a cell, the glucose is disassembled in such a way that its energy content can be stored in a readily available form (usually as ATP) that is later put to use in running all of the cell’s myriad energy-requiring activities.
. Virtually all chemical changes that take place in cells require
Enzymes
Enzymes
molecules that greatly increase the rate at which a chemical reaction occurs
metabolism
The sum total of the chemical reactions in a cell
How does cells engage in mechanical activities?
Materials are transported from place to place, structures are assembled and then rapidly disassembled, and, in many cases, the entire cell moves itself from one site to another. These types of activities are based on dynamic, mechanical changes within cells, many of which are initiated by changes in the shape of motor proteins. Motor proteins are just one of many types of molecular “machines” employed by cells to carry out mechanical activities.
Cell itself and components in it are moving
Explain how cell respond to stimuli
Covered+ react to+ evoke+ respond
Most cells are covered with receptors that interact with substances in the environment in highly specific ways. Cells possess receptors to hormones, growth factors, and extracellular materials, as well as to substances on the surfaces of other cells. Receptors provide pathways through which external stimuli can evoke specific responses in target cells. Cells may respond to specific stimuli by altering their metabolic activities, moving from one place to another, or even committing suicide.
All living organisms have evolved from a single, common ancestral cell that lived more than three billion years ago:
LUCA
Cells that are present in living organisms, share many features, including a … (3)
common genetic code, a plasma
membrane, and ribosomes.
There were two basic classes of cells——distinguished by their — and the —–, or —, they contain
- prokaryotic and eukaryotic
- size
- types of internal structures
- membrane bound organelles
Prokaryotic cells include
bacteria
eukaryotic cells include (4)
protists, fungi, plants, and animals
Eukaryotic cells almost certainly evolved from —- because —, —, —
- prokaryotic ancestors
- both types of cells share an identical genetic language, a common set of metabolic pathways, and many common structural features.
nucleoid
The genetic material of a prokaryotic cell is present in a nucleoid: a poorly demarcated region of the cell that lacks a boundary membrane to separate it from the surrounding cytoplasm.
nucleus
Eukaryotic cells possess a nucleus: a region bounded by a complex membranous structure called the nuclear envelope.
chromatin
the chromosomal DNA of eukaryotes, that is tightly associated with proteins to form a complex nucleoprotein material
Mitochondria
Where chemical energy is made available to fuel cellular activities
Endoplasmic reticulum
Where many of a cell’s proteins and lipids are manufactured
Golgi complexes
Where materials are sorted, modified, and transported to specific cellular destinations
Eukaryotic cells also contain numerous structures lacking a surrounding membrane. Included in this group are (2)
- the elongated tubules and filaments of the cytoskeleton
- ribosomes
What do the elongated tubules and filaments of the cytoskeleton do?
Participate in cell contractility, movement, and support
What do ribosomes do? (2)
Function as “workbenches” on which the proteins of the cell are manufactured. These structures participate in the assembly of proteins by a similar mechanism in both types of cells.
What is a flagellum and how does it work?
The movement of a prokaryotic cell may be accomplished
by a thin protein filament, called a flagellum, which protrudes from the cell and rotates. The rotations of the flagellum, which can exceed 1000 times per second, exert pressure against the surrounding fluid, propelling the cell through the medium.
Prokaryotes are divided into two major taxonomic groups, or domains:
the Archaea (or archaebacteria) and the Bacteria (or eubacteria)
Covalent bonds
What it is+ Why it forms, goberned by what principle?
Pairs of electrons are shared between pairs of atoms.
The formation of a covalent bond between two atoms is governed by the fundamental principle that an atom is most stable when its outermost electron shell is filled.
The formation of a covalent bond is —-, which must be —– at some later time if then bond is to be broken
accompanied by the release of energy
reabsorbed
Polarized
A molecule such that one of the atoms has a partial negative charge and the other a partial positive charge
What are polar molecules + what they usually contain (2)
Molecules, such as water, that have an asymmetric distribution of charge (or dipole) are referred to as polar molecules.
Polar molecules of biological importance contain one or more electronegative atoms, usually O, N, and/or S.
Nonpolar+ex (2)
Molecules that lack electronegative atoms and strongly polarized bonds, such as molecules that consist entirely of carbon and hydrogen atoms. (Symmetic distribution of charge)
Noncovalent bonds
What do they depend and not depend on?
A relatively weak chemical bond based on attractice forces between atoms having an opposite charge.
Tell me about the strength of ionic bonds in cells
The strength of ionic bonds in a cell is generally weak (about 3 kcal/mol) due to the presence of water, but deep within the core of a protein, from which water is often excluded, such bonds can be much stronger.
Hydrogen bonds in biological molecules are easily —.
broken
What happens in a hydrophobic effect?+ ex
In a hydrophobic effect, the nonpolar (hydrophobic)
molecules are forced into aggregates, which minimizes their exposure to the surrounding water molecules.
- basis for the formation of lipid bilayer membranes
Each molecule of water can form hydrogen bonds with as many as —- other water molecules
four
Water molecules form hydrogen bonds with organic molecules that contain polar groups, such as —- and —-, which ensure their —- within the cell.
- amino acids and sugars
- solubility
organic
a chemical with a structure
based on carbon-carbon bonds
biochemicals
The compounds produced by living organisms
Functional groups
Particular groupings of atoms that often behave as a unit and give organic molecules their physical properties, chemical reactivity, and solubility in aqueous
solution
macromolecules
What they are+do
Huge and highly organized molecules that form the structure and carry out the activities of cells. Because of their size and the intricate shapes that macromolecules can assume, some of these molecular giants can
perform complex tasks with great precision and efficiency.
Macromolecules can be divided into four major categories:
Tell me about them
- proteins, nucleic acids, polysaccharides, and certain lipids.
- The first three types are polymers composed of a large number of low-molecular-weight building blocks, or monomers. These macromolecules are constructed from monomers by a process of polymerization.
Metabolic pathway
In the cell, each series of chemical reactions is termed a
metabolic pathway.
Polysaccharides, proteins, and nucleic acids consist of monomers (subunits) linked together by —–
covalent bonds
