Science review: Cells

Vocabulary

Cell- basic unit of all forms of life

Cell theory- fundamental concept of biology that states that all living things are composed of cells; that cells are the basic units of structure and function in living things; and that new cells are produced from existing cells

Cell membrane- thin, flexible barrier that surrounds all cells; regulates what enters and leaves the cell

Nucleus- structure that contains the cell’s genetic material in the form of DNA

Eukaryote- organism whose cells contain a nucleus

Prokaryote- unicellular organism that lacks a nucleus

Cytoplasm- fluid portion of the cell outside the nucleus

Organelle- specialized structure that performs important cellular functions within a eukaryotic cell

Vacuole- cell organelle that stores materials such as water, salts, protein, and carbohydrates

Lysosome- cell organelle that breaks down lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell

Cytoskeleton- network of protein filaments in a eukaryotic cell that gives the cell its shape and internal organization and is involved in movement

Centriole- structure in an animal cell that helps to organize cell division

Ribosome- cell organelle consisting of RNA and protein found throughout the cytoplasm in a cell; the site of protein synthesis

Endoplasmic reticulum- internal membrane system found in eukaryotic cells; place where lipid components of the cell membrane are assembled

Golgi apparatus- organelle in cells that modifies, sorts, and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or release outside the cell

Chloroplast- organelle found in cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy

Mitochondrion- cell organelle that converts the chemical energy stored in food into compounds that are more convenient for the cell to use

Cell wall- strong, supporting layer around the cell membrane in some cells

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Lipid bilayer- flexible double-layered sheet that makes up the cell membrane and forms a barrier between the cell and its surrounding

Selectively permeable- property of biological membranes that allows some substances to pass across it while others cannot; also called semipermeable membrane

Life is CellularIn 1500s eyeglass makers in Europe discovered that using different glass lenses in combination could magnify the smallest objects to make them easy to see. They built the first true microscope and opened the door to the study of biology.

1665- Robert Hooke used an early compound microscope to look at a thin slice of cork Hooke discovered tiny empty chambers and called them cells.

In Holland Anton van Leeuwenhoek used a single-lens microscope and discovered bacteria.

In 1838, German botanist Matthias Schleiden concluded that all plants are made of cells.

In 1855, German physician Rudolf Virchow concluded that new cells can be produced by the division of existing cells.

These discoveries are summarized in the cell theory, a fundamental concept of biology.

Most microscopes use lenses to magnify the image of an object by focusing light or electron.

A typical light microscope allows light to pass through a specimen and uses two lenses to from an image. The first lens is the objective lens, it enlarges the image of the specimen. The second lens is the ocular lens it magnifies the image still further.

The problem with this microscope is that the light limits the detail, resolution. Another problem is that most living cells are nearly transparent. Using dyes can usually solve this problem.

Light microscopes can be used to see cells and cell structures as small as 1 millionth of a meter.

Another type of microscope is the electron microscope. Instead of using light it uses beams of electrons that are focused by magnetic fields. They offer higher resolution, some can be used to study cellular structures that are 1 billionth of a meter in size.

Two types of electron microscopes are: transmission and scanning.

Transmission electron microscope make it possible to explore cell structure and enlarge protein molecules.

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The scanning electron microscope produces stunning three-dimensional images of the specimen’s surface.

The colors in light micrographs come from the cells themselves or from the stains and dyes used to highlight them. Electron micrographs are black and white; electrons don’t come in light. So scientists often use computer techniques to add “false color” to make structures stand out.

All cells at some point contain DNA, molecule that carries biological information.

All cells are surrounded by a cell membrane, which sometimes is called plasma membrane because many cells in the body are in direct contact with fluid portion of the blood.

Cells fall in two different categories that depend on if they have a nucleus or not.

They are: eukaryote (cells have DNA in the nucleus) and prokaryote (don’t have DNA in the nucleus).

Differences between the prokaryote and eukaryote cells:

-prokaryote: smaller and simpler, don’t separate their genetic material within a nucleus, they grow, reproduce, respond to the environment, some cases they glide along surfaces or swim through liquids, bacteria are prokaryote.

-eukaryote: larger and complex, contain dozens of structures and internal membrane, the nucleus separates the genetic material from the rest of the cell, they display variety: protists live solitary lives as unicellular organisms and others form large multicellular organisms like plants, animals, and fungi.

Cell structureIt’s easy to divide each cell into two major parts: the nucleus and the cytoplasm.

Prokaryotic cells have cataplasms even though they don’t have a nucleus.

Organelles are called “little organs”.

Comparing the cell to a factory: the different organelles of the cell can be compared to the specialized machines and assembly lines of the factory. Cell like factories follow instructions and produce products.

The nucleus is the main office of the cell because is the control center of the cell. The nucleus contains nearly all the cell’s DNA and the coded instructions for making proteins and other important molecules.

The nucleus is surrounded by a nuclear envelope composed of two membranes. The nuclear envelope is dotted with thousands of nuclear pores, which allow material to move into and out of the nucleus (like messages, instructions, and blueprints moving in and out of the factory’s main office).

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Chromosomes carry the cell’s genetic information are also in the nucleus. The threadlike chromosomes are spread throughout the nucleus in the form of chromatin (a complex of DNA bound to proteins).

Most nuclei contain a small dense region known as the nucleolus (where the assembly of ribosomes begins).

Vacuoles are the place where you store things. They store materials like water, salts, proteins, and carbohydrates. In many plant cells there is a single, large central vacuole filled with liquid. Vacuoles are also found in some unicellular organisms and in some animals.

Contractile vacuole pumps excess water out of the cell. Nearly all eukaryotic cells contain smaller membrane-enclosed structures called vesicles. They store and move materials between cell organelles, as well as to and from the cell surface.

The lysosomes are the cleanup crew. Lysosomes break down lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell. They are also involved in breaking down organelles that have outlived their usefulness. A number of human diseases can be traced to lysosomes that fail to function properly. They are found in animal and plant cells.

Cytoskeleton is the steel or cement beams and by columns that hold up its walls and roof in the factory. The cytoskeleton helps the cell maintain its shape and is also involved in movement. It’s made up of two principal protein filaments, microfilaments and microtubules.

Microfilaments are threadlike structures made up of a protein called actin. They form extensive networks in some cells and produce a tough flexible framework that supports the cell. It helps the cell move.

Microtubules are hollow structures made up of proteins know as tubulins. They play critical roles in maintaining the cell shape. They are important in cell division, where they form a structure known as the mitotic spindle, which helps to separate chromosomes. In animal cell the centrioles (located near the nucleus) are also formed from tubulins. Microtubules help build projections from the cell surface known as cilia and flagella that enable cells to swim rapidly through liquid.

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Proteins are assembled on ribosomes. They produce proteins by following coded instructions that come from DNA.

The endoplasmic reticulum is where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell.

The portion of the endoplasmic reticulum involved in the synthesis of proteins is the rough endoplasmic reticulum, the name is given because of the ribosomes found on its surface. Proteins made on the rough ER include those that will be released from the cell as well as many membrane proteins and proteins destined for lysosomes and other specialized locations within the cell.

The other portion of the ER is the smooth endoplasmic reticulum, because ribosomes are not found on its surface. It contains collections of enzymes that perform specialized tasks, including the synthesis of membrane lipids and the detoxification of drugs.

In eukaryotic cells protein produced in the rough ER move next into the Golgi apparatus. It modifies, sorts, and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or release outside the cell. From the Golgi apparatus proteins are shipped to their final destination inside or outside the cell.

Chloroplast capture the energy from sunlight and convert it into food that contains chemical energy in a process called photosynthesis. Two membranes surround the chloroplast. Inside it there are large stacks of membranes, which contain the green pigment chlorophyll.

Mitochondria convert the chemical energy stored in food into compounds that are more convenient for the cell to use.

Mitochondria and chloroplasts contain their own genetic information in the form of small DNA molecules.

Cell walls support, shape and protect the cell. Most cell walls are porous enough to allow water, oxygen and carbon dioxide. They provide the strength needed for plants to stand against the force of gravity.

All cells have cell membranes, which almost always are made up of a double-layered sheet called a lipid bilayer. The cell membrane regulates what enters and leaves the cell and also protects and supports the cell.

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Cells remained out of sight until the invention of the...MicroscopeHow did the first true microscope come to be?Eyeglass makers in Europe discovered that using several glass lenses in combination could magnify small objects Robert HookeUsed a compound microscope to examine cork. It seemed to be made of thousands of tiny chambers. He called them cells.Anton van LeeuwenhoekUsed a single-lens microscope to observe pond water and it revealed tiny organisms that were found everywhere, today we call them bacteriaCellsThe basic units of lifeMatthias SchleidenConcluded all plants are made of cellsTheodor SchwannStated all animals are made of cellsRudolf VirchowConcluded that new cells can be produced from the division of existing cellsCell TheoryThe fundamental concept of biology. It states: 1) all living things are made up of cells. 2) Cells are the basic units of structure and function in living things. 3) New cells are produced from existing cells.Most Microscopes use lenses to magnify the image of an object by _____________.Focusing light or electrons.Compound Light MicroscopeIs a typical light microscope that allows light to pass through a specimen and uses two lenses to form an image.Objective lensThe first lens located just above the specimenOcular lensThe second lens that magnifies the image still further.Light microscopes produce clear images of objects only to a magnification of1000 timesUsing chemical stains solves the problem ofThe fact that most living cells are transparent (fluorescence)Electron microscopesUse beam of electrons that are focused by magnetic fields. They offer much higher resolution than light microscopes.Two major types of electron microscopes:

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Transmission and scanning.Transmission electron microscopesMake it possible to explore cell structures and large protein molecules. Beams of electrons can only pass through thin samples making images 2 dimensionalScanning electron microscopesA pencil like beam of electrons is scanned over the surface of the specimen. They produce three dimensional imagesTo prevent electrons from scattering in the air,Samples must be placed in a vacuum and chemically preserved since they have to be nonliving cells and tissuesCell membraneA thin flexible barrier that surrounds a cell.NucleusA large membrane-enclosed structure that contains genetic material in the form of DNA.EukaryotesCells that enclose their DNA in nuclei.ProkaryotesCells that do not enclose their DNA in nuclei.Prokaryotic Cells are generally _____ and ________ than eukaryotic cells.Smaller and simplerOne example of prokaryotesBacteriaEukaryotic Cells are generally _____ and ________ than prokaryotic cells.Larger and more complexEukaryotic cells containA nucleus and many specialized structuresCytoplasmIs the portion of a cell outside the nucleus.OrganellesAre structures that have specialized functions in eukaryotic cellsThe nucleus contains...and controls...DNA; the activity of a cellVacuolesMembrane-enclosed saclike structures that store water, salts, and organic moleculesLysosomesSmall organelles filled with enzymes that break down large molecules and organelles that are no longer usefulThe cytoskeletonA network of protein filaments; it helps that cell maintain its shape and is involved in movementCentrioles

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Organelles made form tubulins; they help organize cell division in animal cellsThree kinds of organelles work with the nucleus to make and distribute proteinsRibosomes, endoplasmic reticulum (ER), Golgi apparatusRibosomeSmall particles of RNA and protein found throughout the cytoplasm in all cells; they produce proteins by following coded instructions from DNAThe endoplasmic reticulum (ER):An internal membrane system where lipid components of the cell membrane are assembled, along with proteins and other materialsGolgi apparatus:An organelle that appears as a stack of flattened membranes; it modifies, sorts, and packages proteins and other materials form the ER for storage in the cell or release outside the cellTwo types of organelles act as power plants of the cells.ChloroplastsMitochondriaBoth types are surrounded by two membranesChloroplastsCapture the energy from sunlight and convert it into food that contains chemical energy in a process called photosynthesis. Cells of plants and some other organisms contain chloroplasts, which contain chlorophyllMitochondriaAre found in nearly all eukaryotic cells; they convert the chemical energy stored in food to a usable formCellular BoundariesAll cells are surrounded by a cell membrane. Many cells also have a cell wall. Both cell membranes and cell walls separate cells from the environment and provide support.Cell wallsSupport, shape, and protect the cell. Most prokaryotes and many eukaryotes have them. Animals do not have cell walls. Cell walls lie outside the cell membrane. Most cell walls allow materials to pass through them.Lipid bilayerWhat a cell membrane consists of.   It is a strong but flexible barrier between the cell and its surroundings. They cell membrane regulates what enters and leaves the cell and also protects and supports the cell. Most biological membranes are selectively permeable, allowing some substances, but not others, to pass across them.

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Selectively permeableAllowing some substances, but not others, to pass across them.Describe the relationship between the cytoplasm and the nucleus of a cellThe nucleus of a cell is found in the cytoplasm, but is not part of the cytoplasm. The nucleus and cytoplasm work together to keep a cell aliveWhat does the term organelle mean literally?Little organIn the visual analogy of a cell is a factory, what two functions of the nucleus are represented? How are these functions illustrated?The nucleus act as the office, or control center, as illustrated by the people at the desk. The nucleus is the source of messages, instructions, and blue prints as illustrated by the two workers helping the chain (of RNA) leave the nucleus.Which feature of the nucleus is not clearly shown by the visual analogy?The chromatin is not shownWhat is another possible analogy that could be compared with the structure and function of a cell?The structure and function of an airport control tower could be compared to the structure and function of a cellWhat are vacuoles?Vacuoles are membrane-enclosed saclike structures that store materials such as water, salts, proteins, and carbohydrates.What are the two roles of the central vacuole in plant cells?Storage of materials and support of the cellHow are contractile vacuoles different from other types of vacuoles?Contractile vacuoles pump excess water out of the cell, while other types of vacuoles hold materials inside of cellsWhat is the role of lysosomes in the cell? Why is this a vital role?Lysosomes breakdown large molecules and waste without them clutter could accumulate in the cell, which has been linked to serious human diseasesWhich structures of the cytoskeleton are found in animal cells but not in plant cells?CentriolesWhat other structures of the cytoskeleton would show the same pattern of microtubules as a flagellum?Cilia

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What are ribosomes? What do they do?Ribosomes are small particles of RNA and protein found throughout the cytoplasm. They are involved in synthesis of proteins.In which organelle are the lipid components of the cell membrane assembled?Endoplasmic reticulumWhat is the difference between rough ER and smooth ER?Ribosomes are found on the surface of rough ER. Smooth ER has no ribosomes on its surface.Using the cell as a factory analogy, describe the role of the Golgi apparatus in cells.The Golgi apparatus is like a customization shop in a factory. It puts the finishing touches on proteins before they leave the factory.Suppose a cell's Golgi apparatus does not function properly. How might this problem affect other cells?If the cell manufactures proteins that are normally released to travel to other cells. Those cells would not receive the proteins. The loss of these proteins might cause the "receiver" cells to function poorly.Chloroplasts are....found in animal cellsNever...chloroplasts, mitochondria are surrounded by a double membraneLikeNearly all of the ....in your cells were inherited from your motherMitochondriaBoth chloroplasts and mitochondria... genetic information in the form of DNAContainMost cell...are porous to water and other materials but strong enough to support and protect cellsWallsNearly all of the plant tissue called...is make up of cell wallsWoodBesides supporting and protecting a cell, the cell membrane...what enters and leaves the cell.RegulatesWhat is the function of vesicles in the synthesis of proteins and the release of those proteins outside the cell?Vesicles transport newly synthesized proteins to the Golgi apparatus. After the Golgi apparatus modifies the proteins,

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vesicles transport the modified proteins to the cell membrane, where they are released.

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