CellsChapter 3

Cells are the basic units of structure and function of all living things.

Cells were first discovered in the 1600s by Robert Hook.

All living things whether plant or animal , unicellular or multicellular, large or small are composed of cells.

The cell has three major parts: cell membrane, nucleus, and cytoplasm.

Cells

Every cell is surrounded by a cell membrane.

It is sometimes called a plasma membrane. The cell membrane separates the cell from

it’s external environment and from the neighboring cells.

It also regulates the passage or transport of certain molecules into and out of the cell, while preventing the passage of others.

The cell membrane is often called a selective semi-permeable membrane.

Cell Membrane

The nucleus is the most important organelle within the cell.

It has two vital functions: control the activities of the cell and facilitate cell division.

The nucleus is usually located in or near the center of the cell.

It serves as the “brain” for the control of the cell’s metabolic activities and cell division.

The nucleus contains 46 chromosomes.

Nucleus

Brain of the cell!

Cytoplasm is a sticky, semi-fluid material found between the nucleus and the cell membrane.

The cytoplasm is the background for all chemical reactions that take place in a cell.

Embedded in the cytoplasm are organelles, or cell structures that help a cell to function.

Cytoplasm

The centrioles are two cylindrical organelles found near the nucleus in a tiny round body called the centrosome.

During mitosis, or cell division, the two centrioles separate from each other by a thin spindle fiber appartatus.

The spindle fibers attach themselves to individual chromosomes to help in the equal distribution of these chromosomes to two daughter cells.

Centrosome and Centrioles

Endoplasmic reticulum provides passages through which transport of substances occurs in the cytoplasm.

The two types of endoplasmic reticulum are rough and smooth.

Endoplasmic Reticulum

Most of the cell’s energy comes from the mitochondria.

They vary in size and shape. A cell can contain one mitochondria or thousands.

Cells that need the most energy have the greatest number of mitochondria.

Mitochondria are known as the powerhouse of the cell.

It stores adenosine triphosphate (ATP), all living cells need ATP for their activites.

Mitochondria

Mitochondria are rod-shaped organelles that can be considered the power generators of the cell, converting oxygen and nutrients into adenosine triphosphate (ATP). ATP is the chemical energy

"currency" of the cell that powers the cell's metabolic activities.

The Golgi apparatus is also known as Golgi bodies or Golgi complex.

It manufactures carbohydrates and packages secretions for discharge from the cell.

These organelles are abundant in the cells of gastric glands, salivary glands, and pancreatic glands.

Golgi Apparatus

The main overall function of the Golgi apparatus is to take the proteins that are manufactured in the

endoplasmic reticulum, process them according to specific needs and then send them on to their

destinations.

Lysosomes serve as centers for cellular digestion.

They contain powerful digestive enzymes that digest protein molecules.

The lysosomes help to digest old, wornout cells, bacteria, and foreign matter.

Lysosomes are also known as “suicide bags” because if the lysosome ruptures, it will start to digest the cell’s proteins, causing it to die.

Lysosomes

Lysosomes are organelles in the cell. These little parts are very important. They have chemicals in them that digest the wastes

and other bad organelles. When the cell dies the lysosmes work swiftly with their chemicals

and digest the dead cell. Without lysosomes living organisms would become filled with dead cells.

Cytoskeleton is the internal framework of the cell which consist of microtubules, intermediate filaments, and microfilaments.

The filaments provide support for the cells; the microtubules are thought to aid in movement of substances through the cytoplasm.

Cytoskeleton

Cytoskeleton

Cells divide for two purposes: meiosis and mitosis.

The process of meiosis involves reproduction

The process of mitosis involves growth or maintenance of cells in the human body.

Cell Division

During meiosis the female’s egg cell is fertilized by the male’s sperm combining to form a zygote.

The zygote has 46 chromosomes. 23 from each parent.

Over a course of 9 months the zygote will grow into a baby.

Meiosis

Mitosis involves the growth or maintenance of cells in the human body.

All cells do not reproduce at the same rate. Blood-forming cells in the bone marrow,

cells of the skin, and cells of the intestinal tract reproduce continuously.

Muscle cells only reproduce every few years.

Mitosis

Mitosis – growth or maintenance of cell.

The cell membrane controls the passage of substances into and out of the cell.

The physical processes that control the passage of materials through the cell membrane are diffusion, osmosis, filtration, active transport, phagocytosis, and pinocytosis.

Movement of Materials Across Cell Membranes

Diffusion is a physical process whereby molecules of gases, liquids, or solid particles spread or scatter themselves evenly through a medium.

Generally, molecules move from an area where they are greatly concentrated to an area where they are less concentrated.

The molecules will eventually distribute themselves evenly, they are then said to be in a state of equilibrium.

Diffusion

The three common states of matter are gases, liquids, and solids.

Molecules will diffuse more quickly in gases and more slowly in solids.

Diffusion occurs due to the heat energy of molecules.

The movement of molecules increases with an increase of temperature.

Oxygen diffuses from the bloodstream (greater concentration) to the cell (lesser concentation).

Diffusion

Osmosis is the diffusion of water or any other solvent molecule through a selective permeable membrane (e.g. cell membrane) from an area of higher concentration to an area of lesser concentration.

A selective permeable membrane is any membrane through which some solutes can diffuse, but others cannot.

Osmosis is important with the administration of IV fluids.

Osmosis

Filtration is the movement of solutes and water across a semi-permeable membrane from an area of higher pressure to an area of lower pressure.

This results from some mechanical force, such as blood pressure or gravity.

An example of filtration is the kidneys.

Filtration

Active transport is a process whereby molecules move across the cell membrane form an area of lower concentration, against a concentration gradient, to an area of higher concentration.

This process requires ATP which is supplied by cell metabolism.

Active Transport

Phagocytosis is also called “cell eating”.

Human white blood cells undergo phagocytosis.

An example is when a person has an ear infection. The white blood cells help to control the bacteria by eating up the harmful bacteria.

Phagocytosis

Most of the white cells carry out phagocytosis, i.e. they collect at the site of infection, engulf and ingest the bacteria, thereby

preventing the spread of infection.

Pinocytosis

“Cell drinking”

There are many kinds of cells of different sizes and shapes.

Some cells look similar, while others look very different. Examples are the nerve cell and the red blood cell (see figure 3-9 on pg 41).

Specialized cells may lose the ability to perform some of their functions.

When nerve cells are destroyed or damaged others cannot be formed to replace the.

When heart cells reach maturity they can no longer divide.

Specialization

Nerve Cell Red Blood Cells

Heart Cells

Disorders of Cell Structure

A tumor results when cell division does not occur in the usual pattern.

If the pattern is interrupted by an abnormal and uncontrolled growth of cells, the result is a tumor.

Tumors are also known as neoplasms. Tumors are divided into two groups: benign

and malignant.

Tumors

A benign tumor is composed of cells confined to the local area. (non-cancerous)

Benign tumors are given other names depending on their type of location. Example: wart or papilloma is a type of tumor of the epithelial tissue.

Most benign tumors can be surgically removed.

Benign Tumor

A malignant tumor is called cancer. Cancerous tumors continue to grow,

crowding out healthy cells, interfering with body functions, and drawing nutrients away from the body tissues.

The malignant tumors can spread to other parts of the body through a process called metastasis.

Malignant Tumor

The following signs and symptoms may be early signs of cancer: changes in bowel or bladder habits, sores that do not heal, obvious changes in a mole or wart, unusual bleeding or discharge, a new lump or thickening in the breast tissue or elsewhere, difficulty swallowing or frequent indigestion, a persistent cough, or hoarseness.

Some Early Signs of Cancer

Diagnostic tests can detect the early stages of cancer.

Some of the test are: x-ray, mammogram, sonogram, and biopsy.

The healthcare worker needs to give the patient information on procedures before any testing begins.

Diagnostic Test for Cancer

Cancer is classified by microscopic examination of the tumor cells removed during surgery.

The tumor, node, and metastasis (TNM) classification is the recommended classification by the American Joint Commission on Cancer.

Cancer Classification

T - describes the size and extent of the main tumor.

N - describes if lymph nodes contain cancer cells and the number of nodes involved.

M - describes if cancer has spread to other parts of the body.

TNM

The treatment of cancer depends on the type of tumor and where it is located.

Treatment includes surgery, radiation, and the use of drugs (chemotherapy).

Disadvantages of cancer treatment include toxic side effects from drugs and tissue damage caused by radiation.

Scientists today are working to develop cancer treatments that are specific to the tumor to help eliminate side effects.

Treatment of Cancer

Aging is a phase of normal development. It is estimated that an older person

possesses 30% fewer cells than a younger adult, because of the slowing of cell division.

Cells also change in their ability to perform specialized tasks.

Aging is not a disease; however, the physiological changes that occur may predispose a person to disease and illness.

Effects of Aging on Cells

Any questions?