Chapter 3

THE AWESOME CELL!

Cell Diversity

Cells vary in shape, size and internal organization.

All cells have a specific job to do and look and function the best for that job.

White blood cells

Stem cells

Nerve Cells

Heart cells

Skin cells

Plant cells

Review Vocabulary

Eukaryotic cells contain organelles and a nucleus. Prokaryotic cells contain very few organelles and

no nucleus. Bacteria are prokaryotic while plants, animals and

fungi are eukaryotic. Homeostasis (steady environment) must be

maintained in all cells.

Flu virus

T4 Bacteriophage

HIV

A Generalized View of the Cell

A cell is composed of three main sections. The plasma membrane forms the cell’s outer

surface. It regulates the flow of materials into and out of

the cell to maintain homeostasis.

A Generalized View of the Cell

The cytoplasm is all the fluid between the plasma membrane and the nucleus.

The cytoplasm is fluid and contains organelles or mini organs.

The nucleus is the largest organelle and contains all the genetic material for the cell.

The Plasma Membrane

The plasma membrane is a flexible yet sturdy barrier that consists mostly of phospholipids.

The membrane also contains proteins. The plasma membrane is made of a lipid bi-

layer with the hydrophilic heads and hydrophobic tails that face the inside.

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The Plasma Membrane

The plasma membrane is selectively permeable or semi-permeable which allows some substances to cross and denies others.

Many substances require transport proteins to move through the membrane.

Cell Transport

Materials dissolved in body fluids include gases, nutrients, ions and other substances required to maintain life.

Any material dissolved in a fluid is called a solute while the fluid is called the solvent.

Water is the solvent in many cases.

Cell Transport

The amount of solute dissolved in a solution is called the concentration..

A concentration gradient is the difference in concentration between two different areas.

A concentration gradient is like a hill where particles can move “up” or “down” the gradient.

Cell Transport

Passive transport does NOT require energy (ATP) because it moves “down” the gradient.

Active transport requires energy because it moves “up” the gradient.

Passive Transport

Diffusion is the movement of particles from one place to another because of the particle’s kinetic energy.

They always move from high concentration to low concentration until equilibrium is reached.

The can happen in liquids or gases.

Vocabulary Cards

DiffusionPassive transport

Facilitated Diffusion

This process is used for molecules that can’t move quickly through the cell membrane.

Carrier proteins help move the molecules.

Facilitated Diffusion

The molecules still move down the concentration gradient so no energy is required.

Transport of glucose is facilitated diffusion.

Diffusion through Ion Channels

Ions such as sodium, potassium and calcium need a channel protein because they cannot pass through the membrane on their own.

Each type of channel is specific to an ion.

Diffusion Through Ion Channels

Some channels are always open and some have gates that open and close depending on the need for the ion.

Osmosis

Osmosis is the diffusion of water across the cell membrane.

Only water is moved in osmosis. The direction of osmosis depends on the

concentration of molecules outside and inside of the cell.

Hypotonic

If the concentration of molecules outside the cell is lower than the concentration inside the cell’s cytoplasm, then the solution is called hypotonic.

Water will move into the cell to create equilibrium.

Hypertonic

When the solution outside the cell has more molecules than inside the cell, the solution is hypertonic.

Water will move out of the cell to create equilibrium.

Isotonic

Both the solution and the inside of the cell are equal.

Water will move both ways randomly to maintain equilibrium.

Vocabulary CardsHypertonicHypotonicIsotonicOsmosisDiffusion through ion channelsFacilitated diffusion

Active Transport

This type of transport goes up or against the concentration gradient.

Since that is working uphill, energy is required.

This includes: sodium-potassium pump, endocytosis, and exocytosis

Sodium-Potassium Pump

This involves a carrier protein. To function normally, animal cells must have a high

concentration of sodium outside their cells and a high concentration of potassium inside their cells.

The sodium-potassium pump works to maintain these differences.

Sodium-Potassium Pump

As sodium comes into the carrier protein and moves outside the cell, potassium comes into the protein and moves inside.

They switch places.

Endocytosis

Some substances such as food particles are too large to move through the cell membrane.

In endocytosis, the cell encloses external materials in a pouch made from the cell membrane and moves them into the cell.

The pouch is called a vesicle.

Endocytosis

There are two types of endocytosis: pinocytosis involves transport of fluid and phagocytosis involves transport of solids or whole cells.

Many animals use phagocytosis to ingest bacteria or viruses that invade the body.

Exocytosis

Exocytosis is the reverse. In exocytosis, molecules or cells are

transported to the outside of the cell from the inside.

Vesicles are used.

Exocytosis

Cells used exocytosis to release large molecules like proteins into the body from the cell.

Usually the ER and the golgi are involved in this process.

Vocabulary CardsActive transportSodium-potassium pumpendocytosisexocytosis

Cytoplasm

This lies between the cell membrane inside of the cell.

It is a fluid that all the organelles float in.

It is sometimes called the cytosol.

Cytoskeleton

Cytoskeleton’s are made of two parts: the microtubules and the microfilaments.

The microtubules assist in cell division by moving the cells apart.

Microfilaments are made of protein and help with muscle contractions.

Both help support the cell and give structure but do allow for movement.

Cilia and Flagella Some cells have

flagella. They usually only have one.

Many cells have cilia which can number in the thousands.

A flagella is like a whip.

Cilia are like tiny paddles.

Cilia and flagella are made of microtubules.

Cilia

Flagella

Ribosomes Ribosomes are the most

numerous of the cell’s organelles.

Ribosomes are made of proteins and RNA.

Ribosomes are responsible for creating proteins.

Ribosomes are found free in the cytoplasm and also attached to the rough ER. (endoplasmic reticulum)

Endoplasmic Reticulum

The ER comes in two varieties, the rough ER and the smooth ER.

The rough ER contains ribosomes and makes proteins.

The smooth ER does not contain ribosomes and makes lipids such as steroids.

The rough and smooth ER are sometimes attach to each other.

Both ER are involved in cell product transport of proteins and lipids.

Ribosomes

Nucleus

Golgi Apparatus The golgi is the

processing, packaging and transport system.

It is a system of membranes that work closely with the ER.

The golgi modifies the products for transport throughout the cell.

Exocytosis moves things out of the cell.

Endocytosis moves things into the cell.

Lysosomes

Lysosomes contain enzymes that help digest proteins, carbohydrates, lipids, DNA and RNA.

These enzymes can also digest old organelles, viruses and bacteria.

Lysosomes are rare in plant cells.

Mitochondria

Mitochondria are the powerhouses of the cell.

Mitochondria create ATP for the cell to use as energy.

One cell many have thousands of mitochondria depending on its function.

Mitochondria have two membranes and have their own DNA which only comes from the mother.

Nucleus

The nucleus is surrounded by a membrane called the nuclear envelope.

The nucleus contains all the DNA for the cell.

It directs all the activities of the cell.

The nuclear envelope contains pores so that RNA can pass into the cytoplasm during protein synthesis.

Nucleolus

The nucleolus is found inside the nucleus.

It is responsible for making the ribosomes.

There is usually only one.

Vocabulary CardsCytoplasmCytoskeletonCilia and flagellaRibosomeEndoplasmic reticulum (rough

and smooth)

Vocabulary Cards

Golgi apparatusLysosomesMitochondriaNucleusnucleolus

Aging and Cells

Gerontology is the scientific study of aging and the problems associated with it.

Although the body can make millions of new cells, many cells such as nerve tissue and some muscle cells have a limited ability to divide or don’t replicate at all.

Aging and Cells

When mitosis slows down, problems can happen which are a normal part of aging.

Telomeres are specific DNA sequences found at the tips of chromosomes.

After each turn of the cell cycle, the telomeres shorten contributing to aging.

Aging and Cells

Free radicals produce damage in lipids, proteins or nucleic acids which contribute the aging.

Decreased skin elasticity causing wrinkles also occurs as free radical damage increases and collagen in the body is depleted.

Aging and Cells

Antioxidants such as vitamin E and C help slow free radical formation.

The rate of aging is a combination of factors including diet, overall health, and genetics.

Cancer• Cancer is a group of diseases

characterized by uncontrolled cell growth.

• The excess tissue is called a tumor.

• The study of tumors is called oncology.

• Malignant tumors are cancerous and often undergo metastasis which means it spreads to other parts of the body.

Causes• Several factors may trigger a normal cell

to lose control.

• Carcinogens are chemical agents of radiation that produce cancer.

• Carcinogens induce mutations that cause permanent change in a subject’s DNA.

• Carcinogens are associated with 60-90% of all human cancers.

Causes• Research is now being directed to cancer

causing genes called oncogenes.

• When activated, these genes can cause cancer in a cell.

• Some cancers have a viral origin.

• Human papillomavirus or HPV causes virtually all the cases of cervical cancer in the world.

• A vaccine now exists for HPV.

Treatment• Many cancers are removed surgically.

• If the cancer exists in many areas of the body, radiation therapy or chemotherapy may be used.

• Chemotherapy involves using drugs to shrink or kill the cancer cells.

Treatment• Radiation therapy breaks chromosomes

which slows or stops the spread of cancerous cells.

• All the therapies target fast growing and dividing cells so there are some side effects to other fast growing body cells.

Treatment• Patients often lose their hair, cells in their

stomach lining and intestines, and have low white blood cell counts.

• Patients are susceptible to infections and have nausea and vomiting.

Vocabulary Cards

carcinogen

oncogene

Metastasis

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