chp 3 introduction to cells
Mitochondria
(the power plant of the cell) are membrane-bound organelles involved in chemical energy production providing a majority of the ATP used in the cell
describe three types of extension
1. Microvilli, finger-like extensions of plasma membrane, increase the surface area of cells in organs specialized for absorption 2. Cilia are hair-like projections that allow the cilia to be motile. These cellular extensions move in unison to propel substances past the cells where they are found 3. Flagella, found only on sperm cells, beat in a whip-like fashion propelling the entire cell
genes and genetic code
A gene is a long chain of nucleotides is a specific segment of DNA that determines the sequence of amino acids in a protein.
selectively permeable membrane
A membrane that allows certain molecules to cross it while prohibiting the passage of other molecule which is critical to the survival of the cell.
Active Transport via Membrane Proteins
Active transport processes require energy in the form of ATP to proceed as solutes move against their concentration gradients from low concentration to high concentration. Both primary and secondary active transport processes use plasma membrane carrier proteins called pumps.
Active Transport via Vesicles
Active transport using carrier proteins and channels is effective but has limitations. Large polar macromolecules are too big to fit so must be transported by other means namely vesicles. Vesicles are small sacs filled with large molecules too big to transport by other means.
Cell Size and Diversity
Cells vary widely in size and structure to enable them to better perform specialized functions
cellular extensions
Cellular extensions are formed by the inner framework of the cytoskeleton
chromatin and chromosomes
Chromatin consists of one extremely long DNA molecule and its associated proteins that organize and fold the molecule to conserve space During periods of cell division, chromatin threads coil tightly and condense into thick structures Human cells contain 23 pairs of chromosomes, one maternal and one paternal pair.
passive transport
Diffusion is defined as the movement of solute molecules from high to low concentration also known as moving down or with its concentration gradient until equilibrium is reached
Rough endoplasmic reticulum
Endoplasmic reticulum (ER), a large folded phospholipid bilayer continuous with the nuclear envelope, exists in two forms: the rough ER (RER) has ribosomes bound to it and the smooth ER (SER) does not.
phospholipid bilayer
In order for the plasma membrane to form an effective barrier between the ECF and cytosol the molecules that make up the membrane namely the phospholipid bilayer must have two key properties: The molecules must have parts that can interact with the water in both fluid compartments without falling apart. The molecules must have parts that repel water, keeping the ECF and cytosol separated.
summarize mitosis and its phases
Mitosis occurs when newly replicated genetic material is divided between two daughter cells. Mitotic spindles, made of microtubules, form spindle fibers that originate from the cell's centrosome to assist with the division.
Cytoplasmic Organelles
Organelles are the cellular machinery each with specific functions vital to maintaining homeostasis. Some organelles are separated from the cytosol, known as compartmentalization, by a membrane (such as Golgi apparatus, mitochondria, endoplasmic reticulum) while others are not enclosed in a membrane (such as ribosomes and centrosomes)
Peroxisomes
Peroxisomes, a membrane-bounded organelle, use oxygen to carry out several chemical reactions that produce hydrogen peroxide (H2O2).
where are ribosomes found within the cell ? what function do ribosomes serve in these locations ?
Ribosomes are found free in the cytosol usually make proteins that are needed within the cell itself. Ribosomes can also be bound to the membranes of other cellular structures where they produce proteins destined for export outside the cell, for export to the lysosome, or for insertion into a membrane.
Ribosomes
Ribosomes are tiny granular nonmembrane-bound organelles where protein synthesis takes place. Ribosomes are composed of a large and a small subunit each made of ribosomal proteins and ribosomal RNA (rRNA)
Smooth Endoplasmic Reticulum (SER)
Smooth endoplasmic reticulum (SER) is not associated with ribosomes and has essentially no role in protein synthesis but does perform the following vital functions: a. Stores calcium ions. b. Detoxification reactions c. Lipid synthesis
List three variables or factors that determine how a substance is able to move across the plasma membrane by passive or active transport.
Substance may cross the plasma membrane in several ways; some do not require the expenditure of energy (passive transport mechanisms) while other process do require energy (active transport processes). a. The type of substance b. The plasma membrane permeability to the substance c. The concentration of the substance in the cytosol and ECF
phases of cell cycle
The cell cycle includes two main phases: interphase and M phase (cell division). Interphase, a period of growth and preparation for cell division, includes the following 3 subphases: G1, S, and G2. a. G1 phase (1st gap) is the period where a cell performs its normal daily metabolic activities. Production of new organelles, cytoskeleton and other vital proteins highlight this phase. b. S phase (synthesis) is the period where DNA synthesis (replication) occurs. Chromatin unwinds and each base pair is duplicated using an existing DNA strand as a template to build a new strand. DNA replication proceeds in the following steps a) G2 phase (2nd gap) is another period of cellular growth where proteins required for cell division are produced and centrioles are duplicated.
the cell cycle, why is it required ?
The cell cycle is a process defined as the ordered series of events from the formation of the cell to its reproduction by cell division. Cell division is required for growth and development as well as for tissue repair and renewal.
types of filaments
The cytoskeleton contains three types of long protein filaments composed of smaller protein subunits that allow for rapid disassembly and reassembly: 1. Actin filaments (microfilaments) 2. Intermediate filaments 3. Microtubules
Cytoskeleton
The cytoskeleton, made of several types of protein filaments, is a dynamic structure able to change its function based on the needs of the cell. The protein filaments play a variety of critical roles in the cell including the following: 1. Give the cell its characteristic shape and size by creating an internal framework. 2. Provide strength, structural integrity, and anchoring sites that support the plasma and nuclear membranes as well as the organelles. 3. allow for cellular movement where the protein filaments are associated with motor proteins.
nuclear envelope
The nuclear envelope, a double phospholipid bilayer, surrounds and encloses the entire contents of the nucleus. Nuclear pores serve to connect the nucleoplasm with the cytoplasm allowing substances to move between the two locations.
nucleoli
The nucleolus (plural, nucleoli) is a region in the nucleus responsible for the synthesis of ribosomal RNA and the assembly of ribosomes.
the nuclues
The nucleus is the governing body that directs the activities of the other cellular components and largely determines the type of proteins and the rate at which the cell makes them The nucleus consists of three main structures: a) Nuclear envelope b) DNA and its associated proteins which form chromatin c) A single nucleolus or multiple nucleoli
The Endomembrane System
The organelles of the endomembrane system form vesicles that exchange proteins and other molecules. The members of the system synthesize, modify, and package molecules produced within the cell. The plasma membrane, nuclear envelope and the following organelles are components of the system
protein synthesis
The process of manufacturing proteins from DNA blueprint using RNA DNA>Translation>mRNA>Transcription>Protein
Introduction to Electrophysiology
There is a separation of charges across the plasma membrane. A thin layer of positive charges lines the outside of the plasma membrane and a thin layer of negative charges lines the inside of the plasma membrane.
Describe the fluid mosaic model
This model describes the plasma membrane as dynamic fluid structure with multiple components, some with the ability to move within phospholipid bilayer as the phospholipids move themselves.
transcription
Transcription is the process of making mRNA copies of DNA, called a transcript, which can exit the nucleus through a nuclear pore. This addresses the issue of getting the code for a protein into the cytoplasm where the ribosomes are found. Transcription, the process of making mRNA, proceeds in 3 general stages: initiation, elongation, and termination
water can move across a plasma membrane by ?
Water can pass through channel proteins known as aquaporins which is the primary route for osmosis of water. A small amount of water is able to pass through the phospholipid bilayer directly.
membrane proteins
a main component of the plasma membrane, exist in two basic types: Integral proteins can span the entire plasma membrane and are called transmembrane proteins when they travel through both layers of the plasma membrane. Peripheral proteins are found only on one side the plasma membrane or the other.
tonicity
a way to compare the osmotic pressure gradient between two solutions, the cytosol and ECF in the body
organelles
are a variety of cellular machines with very specific functions that are suspended in the cytosol and serve to separate the potentially damaging chemical reactions from the surrounding cell structures known as compartmentalization.
Lysosomes
are the organelles responsible for digestion of worn out cell components or whole cells in some cases.
cytoskeleton
consists of a network of protein filaments that supports the cell by creating and maintaining its shape, holding the organelles in place and providing a means of transportation for substances within the cell.
cytoplasm
inside of the cell consists of both the fluid cytosol and the organelles and cytoskeleton embedded within it
cytosol
intracellular fluid, mostly water with with dissolved solutes, storage molecules, and proteins and is the site of many important chemical reactions
Primary active transport
involves a pump in the plasma membrane that binds and transports a solute against its concentration gradient using the energy from the hydrolysis of ATP. The sodium-potassium pump (Na+/K+ pump or Na+/K+ ATPase pump) is most vital for maintenance of Na+ and K+ concentration gradient homeostasis
facilitated diffusion
involves charged or polar solutes such as ions and glucose that cross the phospholipid bilayer with the help of a membrane protein either a carrier or channel
simple diffusion
involves mostly nonpolar solutes like oxygen, carbon dioxide, lipids, and hydrocarbons that are able to pass straight through the phospholipid bilayer without the need for membrane proteins
Exocytosis
is the process where large molecules exit the cell, known as secretion, when vesicles fuse with the plasma membrane opening into the ECF
Gogli Apparatus
located between the RER and the plasma membrane, is a group of flattened membranous sacs filled with enzymes and other molecules Proteins and lipids made by the ER are further modified, sorted, and packaged for export in the Golgi apparatus. Products packaged in the Golgi apparatus can be secreted from the cell by exocytosis, become part of the plasma membrane, or are sent to the lysosome.
translation
occurs at the ribosome where nucleotide sequence of mRNA is translated into an amino acid sequence with the help of transfer RNA Translation is organized into 3 stages, initiation, elongation, and termination, like transcription
overview of cell structure
overview of cell structure reveals that most animal cells have the 3 basic componets: plasma membrane, cytoplasm, and nucleus
osmosis
passive process in which a solvent moves across a membrane from higher to lower solvent concentration
functions of plasma membrane
provides the cell with structural support, a means of communication with its surroundings and other cells, and cell identification
electrical potential
separation of charges creates an electrical gradient, provides energy to do work
nucleus
single roughly spherical organelle, The nucleus is enclosed in a phospholipid bilayer similar to the plasma membrane called the nuclear envelope. The nucleus contains most of the cell's DNA and is the primary location for making most of the RNA.
plasma membrane
surrounds each cell isolating its internal structures and processes from the external environment
osmotic pressure
the driving force exerted by solute molecules that causes water molecules to move from a low solute to high solute concentration
Endocytosis
transports ECF, large molecules, and whole cells into the cell. Types of endocytosis are phagocytosis, pinocytosis, and receptor-mediated endocytosis
Secondary active transport
uses ATP indirectly to fuel a transport pump. ATP is used to create and maintain a concentration gradient one substance. Moving this substance across the plasma membrane down its concentration gradient can be harnessed to move another substance(s) against its concentration gradient
