Cellular Energy

Energy is the ability to do work.

All cells get their energy from their metabolism (food).

Energy required for motion is called KINETIC ENERGY.

Stored energy is called POTENTIAL ENERGY.

Energy can neither be created or destroyed (the 1st LAW OF THERMODYNAMICS), so the amount is always constant (the same).

Energy can be converted from one form to another. When energy is converted from one form to another, some of the energy ends up as heat (the 2nd LAW OF THERMODYMANICS).

ATP (ADENOSINE TRIPHOSPHATE)
– ATP is a molecule present in living organisms, it shuttles energy within the cells.
– ATP is one of the major energy-providing molecules that initiates biochemical reactions throughout the body.
– It is a source of potential chemical energy for most enzyme reactions.
– In the cell’s mitochondria, ATP is constantly generated from food.
– All chemical reactions are the transfer of energy from one molecule to another.
– ATP is an ADENOSINE MOLECULE chemically bonded to 3 PHOSPHATE MOLECULES.
– The chemical bonds connecting each phosphate molecule to the adenosine molecule hold energy.
– Energy is stored when bonds are formed to connect a phosphate molecule to an adenosine molecule. When these bonds are broken the energy is released.
– When a cell needs an ATP’s molecules energy, the last phosphate group breaks off and the energy in the bond is released for use by the cell.
– ATP molecules bind to chemicals within the cell that need the energy. This ensures that the energy is transferred from the ATP molecule to the proper place for use.
– Specialized proteins, called ENZYMES, use the energy released from ATP to do all the work of the cell.
– Enzymes are important biological catalysts; they function in lowering the activation energy needed for chemical reaction to occur.
– Enzymes are neither changed nor used up in the reaction.

ADP (ADENOSINE DIPHOSPATE)
– Once the ATP molecule has released energy by breaking off a phosphate molecule, the ATP molecule only has 2 phosphate molecules and is called ADP (ADENOSINE DIPHOSPATE).
– ADP is like an uncharged battery, it has no energy.
– ADP can have another phosphate molecule join it and become an ATP molecule again.

Types of Tissue

Tissues are groups of cells with a common structure and function.

They work together to perform a particular task.

ORGANS
– Organs are a collection of 2 or more of the basic body tissue types.
– Multiple tissues adapt as a group to perform specific functions and form structures called ORGANS.

ORGAN SYSTEMS
– A collection of 2 or more of the organs that together perform some complex body function.
– The human body is a cooperative of organ systems that are interdependent upon one another, either chemically or physically.

There are 4 main CATEGORIES OF TISSUE:
1.  EPITHELIAL TISSUE (covers and lines the body)
2.  CONNECTIVE TISSUE (binds and supports other tissue)
3.  MUSCLE TISSUE (is involved with movement)
4.  NERVOUS TISSUE (forms a communication network)

1. EPITHELIAL TISSUE

Epithelial tissue is covering and lining tissue, it covers body surfaces in general and lines cavities within the body.

It has little or no intercellular material between its cells.

The free surface of this tissue is exposed either to air or fluid.

The base of the cell is attached to a BASEMENT MEMBRANE (a dense layer of extra cellular material).

The cells are closely joined and may act as a barrier against injury, microbial invasion or fluid loss.

These cells may be specialized for absorption or secretion of chemical solutions.

Epithelial tissue is categorized by the number of LAYERS and the SHAPES of the free surface of the cells.

LAYERS can be:
1. SIMPLE: one layer of cells.
2. STRATIFIED: multiple tiers of cells.
3. PSEUDOSTRATIFIED: one layer that appears multiple because the layers vary in length.

SHAPES include:
1. SQUAMOUS
SIMPLE SQUAMOUS epithelial tissue is thin and leaky.
– These cells aid in the exchange of material by diffusion.
– They line blood vessels and air sacs in the lungs.
STRATIFIED SQUAMOUS tissue regenerates rapidly near the basement membrane.
– New cell are pushed to the free surface as replacements for the cells that are continually sloughed off.
– Stratified Squamous tissue is located on surfaces that are subject to abrasion, like the outer skin.

2. COLUMNAR
– They are like a cytoplasm filled water balloon.
– They are found where secretion or active absorption of substances is an important function, like the intestines, where they secrete digestive juices or absorb nutrients.
STRATIFIED COLUMNAR epithelial tissue line the inner surface of the urinary bladder.
PSEUDOSTRATIFIED CILIATED COLUMNAR epithelial tissue line the nasal passage.

3. CUBOIDAL
SIMPLE CUBOIDAL epithelial tissue is specializes for secretion.
– They can be found in the kidney tubules, the thyroid gland and the salivary glands.

2. CONNECTIVE TISSUE

Connective tissue binds and supports other tissue.

It has a sparse cell population scattered throughout an extensive extracellular matrix;  it has a lot of intercellular material between its cells.

The matrix contains long, slender rods and connective tissue fiber in a substance similar to soft-set gelatin.

This fiber helps connective tissue to do its job, to directly or indirectly connect body parts together.

3 types of FIBERS make up the various types of connective tissue:
1. COLLAGENOUS FIBERS
– They are bundles of fibers containing 3 collagen fibers each.
– These fibers are strong and resist stretching.
– The parallel lines on the palm of your hand are collagen bundles.

2. ELASTIC FIBERS
– They are long threads of the protein, elastin.
– If stretched, this tissue can return to its original shape.

3. RETICULAR FIBERS
– They are branched and tightly woven.
– They join connective tissue to neighboring tissue.

There are 6 CATEGORIES of connective tissue:
1. LOOSE CONNECTIVE TISSUE
– Contains all 3 fiber types; collagen, elastin and reticular.
– Holds organs in place and attaches the epithelium to underlying tissue.
– Contains 2 types of cells:
1. FIBROBLASTS: secrete proteins of extracellular fibers, like collagen.
2. MACROPHAGES: act as the “attack dogs” of the body’s immune system.

2. ADIPOSE TISSUE
– It is a loose connective tissue that is specialized to store fat.
– The fat is stored in adipose cells distributed throughout its matrix.
– Each adipose cell stores one fat droplet, which can vary in size.
– The stored fat insulates the body and is used for fuel when needed.

3. FIBROUS CONNECTIVE TISSUE
– Large numbers of collagenous fibers in parallel bundles makes this tissue very dense.
– This density gives it the great strength needed for tendons (to attach muscle to the bone) and ligaments (to attach bone together at joints).

4. CARTILAGE
– It is the strong and flexible connective tissue found in the skeleton of all vertebrate embryos.
– Most vertebrates convert the cartilage to bone, but they retain cartilage in the nose, ears and trachea.
– It is composed of collagenous fibers embedded in chondroitin sulfate (a protein-carbohydrate).

5. BONE
– Bone is hard, but not brittle or completely solid.
– It is mineralized connective tissue.
– OSTEOBLASTS (bone-forming cells) deposit a matrix of collagen and calcium phosphate that hardens into the mineral hydroxyapatite.

6. BLOOD
– Blood is the only liquid connective tissue in the body.
-It is a liquid extracellular matrix of plasma containing water, salt and proteins.
– Blood contains RED BLOOD CELLS (that transport oxygen), WHITE BLOOD CELLS (for the immune system) and PLATELETS (which are cell fragments that help in the clotting of blood).
– Blood cells are made in the red marrow of long bones.
– Blood vessels and nerve cells occupy slender canals in the bone tissue call HAVERSAIN CANALS.

3. MUSCLE TISSUE

There is more muscle tissue available in the human body than any other type of tissue.

It consist of long, slender muscle fibers, that contract or shorten to create body movement.

There are 3 types of muscle:
1. SKELETAL MUSCLE
– It is multinucleated and is usually attached to bones by tendons.
– Contractions are voluntary.
– This muscle appears striated under the microscope.

2. SMOOTH MUSCLE
– It is found in the walls of the internal organs and arteries.
– The spindle-shaped, uninucleated cells contract involuntarily.

3. CARDIAC MUSCLE
– It is located only in the wall of the heart.
– The cells are striated, uninucleated, and are joined by intercalated disks.
– Contractions are involuntary.

4. NERVOUS TISSUE
– It is the major tissue for communication and control within the body’s internal environment.
– It is designed to sense stimuli.
– It communicates by means of NEURONS (nerve cells).
– The neuron conducts impulses or bioelectric signals.
– It transmits signals from one part of the organism to another.

Cell Division (Cellular Reproduction) Part 4 of 4

PROKARYOTE CELL DIVISION: BINARY FISSION
– Prokaryote cells represent the most primitive living form of cells.
– They divide in a less complex manner the Eukaryote cells, called BINARY FISSION.
– It is not enough to just divide in half; each cell must pass along its’ genetic information to future generations of cells.
– When a cell reproduces, each daughter cell must receive a complete copy of all of the essential genetic material.
– Before a cell divides, the parent cell produces a copy of all the required genetic information. This duplication of the genetic material is called REPLICATION.
– Prokaryote cells have one circular chromosome, prior to cell division, the single chromosome replicates. The 2 strands move to opposite ends of the cell.
– The cell doubles in size, the plasma membrane grows inward, producing a new cell wall as it goes.
– When the new cell wall is in place it “pinches” off and the cell divides into 2. Producing 2 genetically equal daughter cells. Each daughter cell contains a entire set of genetic material.
– Binary Fission is fast, under ideal conditions it can be completed in 20 – 30 minutes.

Cell Division (Cellular Reproduction) Part 3 of 4

SEXUAL REPRODUCTION

The exchange of genetic material between two cells is a sexual union.

Cells exchange or mix their genetic material together, producing unique, yet related cells.

The exchange is accomplished by a sexual union of 2 cells that separate after the genetic exchange occurs.

The process of genetic-recombination between 2 cells is know as CONJUGATION.

GAMATES are the sex cells found in multicellular sexual organisms. There are 2 types of sex cells, MALE and FEMALE.

Sex cells divide in a special process called MEIOSIS.

Meiosis is a longer process than mitosis.

Meiosis only occurs in the germ cells (gametes) of sexually reproducing organisms.

Meiosis is a process of cellular division where the genetic material is reduced by half in the newly created cells.

Sex cells have half the number of chromosomes as the DIPLOID CELL (all cells that have a full number of chromosomes are called diploid) or parent cell and are called HAPLOID CELLS.

Meiosis forms 4 haploid cells that contain half as many chromosomes as the parent cells.

When each parent donates half of the chromosomes, the offspring will have the full number of needed chromosomes.

In sexual reproduction, genetic material from the male and female are put together, a process called FERTILIZATION, to produce a new cell, called a ZYGOTE (a diploid cell that has the full number of needed chromosomes). The new cell must have the same number of chromosomes as each parent. Meiosis ensures that each parent donates only half of the needed chromosomes.

Meiosis allows for genetic variability among organisms.

There are 2 divisions in Meiosis and each includes 4 stages; Prophase, Metaphase, Anaphase and Telophase.

The 2 divisions separate attached chromosomes and produce a total of 4 haploid nuclei.

The actions of Interphase, during the cell cycle are the same for sex cells. DNA replication only occurs once during the Interphase before Meiosis I.

MEIOSIS I
Meiosis I is call the reduction division stage because it separates HOMOLOGOUS chromosomes(matched copies of chromosomes) into 2 different daughter nuclei.

1. Prophase I
– The chromosomes begin to coil-up and condense.
– The homologous chromosomes move next to each other, a process called SYNAPSIS. This action forms a four-part structure called a TETRAD, consisting of 2 sets of sister CHROMTIDS (a chromatid is one copy of a doubled chromosome).
– At the time of the synapsis, genetic material may recombine into a new arrangement, a process called GENETIC RECOMBINATION.
– Also during synapsis the chromatids may exchange genetic material, a process called CROSSING OVER. This is another way that the genes are shuffled, ensuring that each offspring has a random combination of traits from both parents.

2. Metaphase I
– The homologous pairs prepare for separation.
– The homologous pairs line-up at the METAPHASE PLATE/equatorial plane (the center of the cell).
– Spindle fibers help move the chromatids into position and attach to the sister chromatids.

3. Anaphase I
– One chromatid from each of the homologous pairs moves toward a separate pole.
– The attached spindle fibers pull the chromatid toward the poles.
– The homologous pairs separate with sister chromatids remaining together.
– As a result each daughter cell will have half the number of chromosomes of its parent cell.

4. Telophase I
– During Telophase I there is some uncoiling of the chromosomes. The nuclear membrane reappears and cytokinesis produces 2 daughter cells.
– 2 new daughter cells are formed, with each daughter cell containing only one chromosome of the homologous pair.
– The 2 new daughter cells each have half the number of chromosomes of the original parent cell.
– Even though the chromosome number is halved, there is still double the amount of chromosomes necessary for the final product. This is why the cell undergoes the 4 stages; prophase, metaphase, anaphase and telophase, one more time in MEIOSIS II.
– Meiosis II reduces the sister chromatid to a single chromosome.

INTERKENSIS
A brief period of rest called INTERKENSIS separates Meiosis I from Meiosis II.

It is sometimes called INTERPHASE II, however no DNA is replicated, because the chromosomes are already doubled.

MEIOSIS II
The 2nd stages of Meiosis are called; Prophase II, Metaphase II, Anaphase II and Telophase II.

These 4 stages ensure that each of the 4 cells created, has a single copy of each chromosome.

Sister chromatids become separated into different nuclei during Meiosis II.

1. Prophase II
– The chromosomes condense and move toward the equatorial plane (the center of the cell), where the centromeres will attach to the spindle fibers.

2. Metaphase II
– The chromosomes line-up along the metaphase plate/equatorial plane.
– The chromosomes attach to the spindle fibers and are moved into position at the center of the cell.

3. Anaphase II
– The centromeres split and the sister chromatids move toward opposite poles.

4. Telophase II
– The chromosomes unwind, the nuclear membrane reforms and the cell divides.
– Cytokinesis ends the process with 4 separate haploid cells forming.
– Both cells from the beginning of Meiosis II were products of a single cell that began at the start of Meiosis I. Since both of these cells divided again, the end result of Meiosis is: From one cell we get 4 cells.
– Each of the 4 cells is a haploid cell (a cell with half the number of chromosomes).

Cell Division (Cellular Reproduction) Part 2 of 4

EUKARYOTE CELL DIVISION: MITOSIS AND MEIOSIS

Division of Eukaryote cells involves a series of steps that are different from the process that Prokaryote cells go through to divide, a process called BINARY FISSION.

Cell division is more complicated in Eukaryote cells. The cells are larger and more complex.

The material must be distributed evenly and each daughter cell must have a new nuclear membrane.
Cell division may occur by either mitosis or meiosis, depending on what type of cell is involved.

All one cell organisms reproduce by mitosis.

Mitosis is used by multicellular organisms for growth and repair of all its cells, except sex cell or GAMATES.

The division of Eukaryote cells into daughter cells occurs in 2 stages:
– 1. The nuclear contents are divided by mitosis or meiosis, a process called KARYOKINESIS.
– 2. The cell division of the rest of the cell, a process called CYTOKINESIS.

MITOSIS

Mitosis is the process where the genetic material of the cell is equally divided into 2 complete cells.

Mitosis is divided into 4 stages; PROPHASE, METAPHRASE, ANAPHASE and TELOPHASE.

1. Prophase
– Prophase is the longest stage of Mitosis.
– For cell division to occur, the already replicated chromosome must be pulled apart.
– The chromosome that was doubled during S phase of Interphase, begins to coil, thicken and shorten, in order to be more easily moved during the process of cell division.
– A chromosome at Prophase becomes “X” shaped. It consists of joined CHROMITIDS, which are the doubled DNA structures from the S phase of Interphase.
– The structure that joins the chromatids is called a CENTROMERE.
– While the chromosomes are recoiling (pulling apart), the nucleoli and nuclear membrane are disappearing.
– At the same time spindles are forming that will help to align and move the chromosomes.
– The CENTRIOLES being to move to opposite ends of the cell.
– The centrioles line-up long, thin, wire-like structures called SPINDLE FIBERS across the length of the cell. (These spindle fibers will help line-up the chromosomes during the next phase of mitosis, Metaphase).
– The chromosomes move toward the middle of the cell.
– By the end of Prophase the nuclear membrane is broken down.

2. Metaphase
– In Meta phase the doubled chromosomes line up at the center of the cell.
– The centromeres divide in two.
– Metaphase last only as long as the chromosomes remain lined-up along the center of the cell.

3. Anaphase
– In Anaphase the 2 complete sets of chromosomes being to move toward opposite corners (poles) of the cell.
– Each chromosome appears to be dragged along by its centromere, which is attached to a spindle fiber.
– The division of the cytoplasm, or CYTOKINESIS, begins at the end of Anaphase.

4. Telophase
– Telophase is the last stage of mitosis.
– The chromosomes reach their respective sides (poles) of the cell. While this is occurring the cell’s plasma membrane pinches in from both sides, enclosing the chromosomes, creating two separate cells.
– The chromosomes then uncoil and the nucleus reappears.

Mitosis ends when the new daughter cells go their separate ways.