Cell - Structure and Organization

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,

Villa Alarife Subject:9th SCIENCE Class: Cell Structure and Organization

Teacher's notes

Objectives

Vocabulary

Link and Learn

Date: June 24

2011

Prepared by Group Work

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LIVING THINGS

What do they all have in common? http://1link.in/upcpc

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THE CELL THEORY 1. All living organisms are made up of cells.

2. The Cell is the Basic Unit of Life.

3. Omni celula et celula.

Cells come from cells only.

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THE CELL THEORY

The Cell Theory http://goo.gl/BBOrY

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THE CELL THEORY

The Cell Theory ­ Song http://goo.gl/HIOBH

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Cells ­ Discovery Channel http://goo.gl/GNhOU

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Cell Animation www.cellsalive.com

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CELLS All organisms are composed of Cells, regardless of the ultrastructure, the cell is the minimum structural, morphological and functional unit of life.

http://goo.gl/2vI3I

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Cell Cycle • Cells also have cycles, different stages happening in a specific sequence and under certain conditions.

• As any other life cycle, it starts by birth (New cell), growth (G1), preparation (S), development and maturation (G2) and reproduction (Cell Division).

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http://goo.gl/5GF2V

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ANIMATION Control of the Cell Cycle http://goo.gl/aWbGX

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Biology ­ McGraw Hill ­ 2002

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Cell Wall

Plasmodesma

Biology ­ McGraw Hill ­ 2002

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CELL: SIZE AND SHAPE 15

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CELL SIZE • All substances that pass in or out of the cells have to go through the surface of the cell.

• The larger the cell, the more nutrients it can take up and more wastes it has to release.

• Cell size is limited by a cell's surface area : volume ratio.

• A cell's ability to exchange materials can be assessed by calculating the cell's surface area : volume ratio.

A m 1 c

B

C m

2 c

m 4 c

Cube A Surface Area of one face Surface Area of Cube Volume of Cube Ratio: Surface Area/Volume

Cube B

Cube C

1 cm x 1 cm = 1 cm2 6 x 1 cm2 = 6 cm2 1 cm x 1 cm x 1 cm = 1 cm3 6 cm2 / 1 cm3 = 6:1

What happens to the surface area/volume ratio as the cube increases in size?

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A m

1 c

B m

2 c

C

4 c

m

D

m

6 c

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SURFACE AREA/VOLUME Cell grows

then

Surface Area/Volume

• Which means that the cell volume increases a lot faster than its surface area.

• As the cell gets bigger, more food and oxygen needs to be absorbed through its surface, eventually becoming too small.

• The cell must now divide or die.

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THE CELL MEMBRANE Surrounding the Cell • The Cell, or Plasma membrane, encloses the cell and separates its contents from its surroundings.

• It's formed by a phospholipid bilayer (5‐10 nm) with proteins embedded in it, contributing to the cell's interaction with its environment.

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Membrane Composition • The Cell Membrane is made out of a sea of phospholipids.

• A Phospholipid is a specialized lipid (biomolecule) made of a phosphate "head", and two fatty acid "tails".

• The phosphate head is polar and is attracted to water.

• The fatty acid tails, instead, are non‐polar and repelled by water.

HYDROPHOBIC

HYDROPHILIC

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LIPID BILAYER STRUCTURE • As there's water inside and outside of the cell, the phospholipids form a double layer called the lipid bilayer.

• The non‐polar tails, hydrophobic, make up the interior of the lipid bilayer; and the polar heads, hydrophilic, point toward the surfaces of the lipid bilayer.

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FLUID MOSAIC MODEL • Singer and Nicholson proposed this theory in 1972, suggesting the cell membrane as a lipid bilayer.

• Further analysis found diverse proteins were located in the cell membrane "floating".

• Some of these are intrinsic proteins, completely spanning the cell membrane.

• Other proteins are extrinsic proteins, found either on the inner or the outer surface.

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ANIMATION Fluid Mosaic Model http://goo.gl/0Whx7

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How fluid is the Membrane?

• Depending on the type of fatty acid, saturated • or unsaturated, the membrane will be more or less fluid.

• The membrane is more fluid when it is composed by more unsaturated fatty acids.

• The shorter the fatty acid tails the more fluid the membrane.

• The membrane is less fluid when it contains more cholesterol (steroid).

ANIMATION Membrane fluidity http://goo.gl/dUnxg 24

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THE NUCLEUS Information Center for the Cell • Is the largest and most easily seen organelle in the eukaryotic cell.

• The Nucleus is the repository of the genetic information that directs all the activities of the cell.

• Most eularyotic cells have a single nucleus, although fungi and others may have several nuclei.

• Many nuclei exhibit a dark‐staining zone called Nucleolus, which is a region of intense RNA synthesis.

Biology ­ McGraw Hill ­ 2002

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Biology ­ McGraw Hill ­ 2002

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ANIMATION The Cell Cycle http://goo.gl/iEmzo

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ENDOPLASMIC RETICULUM Compartmentalizing the Cell • The interior of a eukaryotic cell is packed with membranes, an endomembrane system, dividing the cell in compartments, channeling the passage of molecules through the interior of the cell and providing surfaces for the synthesis of lipids and some proteins.

• The largest of the internal membranes is called Endoplasmic Reticulum (ER), with a similar composition to the plasma membrane.

ROUGH ER (RER) • Its surface is devoted to protein synthesis, with lots of Ribosomes, hence the name.

• Proteins synthesized in the surfaces of the RER are destined to be exported from the cell, with a signal sequence (special sequence of aminoands obtained in the Golgi Apparatus.

SMOOTH ER (SER) • Few or no ribosomes attached, hence the name.

• The SER contains enzymes in the membrane surface to synthesize 2 1 carbohydrtaes and lipids

Biology ­ McGraw Hill ­ 2002

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Biology ­ McGraw Hill ­ 2002

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GOLGI APPARATUS Delivery System of the Cell • Formed by flattened stacks of interconnected membranes. Named after Camillo Golgi, an italian physician that noticed them.

• The Golgi apparatus functions in the collection, packaging, and distribution of molecules synthesized at one place in the cell and utilized at another location in the cell.

• It has a receiving or front face (cis) usually located near the ER, and a back or discharging end (trans).

• The most common process in the Golgi Apparatus is the alteration, addition or modification of short sugar chains, producing glycoproteins or glycolipids coming from the ER. • The modified or altered molecules are collected in the end of the Golgi bodies in folded stacks of membrane called cisternae.

Biology ­ McGraw Hill ­ 2002

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ANIMATION The Golgi Apparatus http://goo.gl/gpy1R

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ANIMATION ER and Golgi http://bit.ly/9mhurr

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VESICLES Enzyme Storehouses LYSOSOMES

• They are membrane‐bounded digestive vesicles that arise from the Golgi Apparatus.

• They contain high levels of degrading enzymes, which catalyze the rapid breakdown of proteins, nucleic acids, lipids, and carbohydrates.

MICROBODIES

• Eukaryotic cells contain a variety of enzyme‐bearing, • membrane‐enclosed vesicles called microbodies, which are found in the cells of plants, animals, fungi, and protists.

• The distribution of enzymes into microbodies is one of the principal ways in which eukaryotic cells organize their metabolism.

Examples: Glyoxysomes (Plants: Have enzymes that convert fats to carbohydrates), Peroxysome (Contains enzyme that catalyze the removal of electrons and associated hydrogen atoms).

Biology ­ McGraw Hill ­ 2002

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http://1link.in/vmdiy

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VIDEO The Fluid Mosaic Model http://bit.ly/aNvFgK

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ANIMATION Endo­ and Exocytosis http://bit.ly/aioHFU

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RIBOSOMES Sites of Protein Synthesis • Ribosomes are made up of several molecules of rRNA (Ribosomal RNA), bound within a complex of several dozen different proteins.

• Ribosomes are among the most complex molecular assemblies found in cells. Each ribosome is composed of two subunits.

• The subunits join to form a functional ribosome only when they attach to another kind of RNA, called messenger RNA (mRNA) in the cytoplasm.

• To make proteins, the ribosome attaches to the mRNA, which is a transcribed copy of a portion of DNA, and uses the information to direct the synthesis of a protein.

Biology ­ McGraw Hill ­ 2002

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http://bit.ly/dkaUkZ

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Organelles that contain DNA Mitochondria MITOCHONDRIA: The Cell's Energy factory

• Mitochondria are bounded by two membranes: a smooth outer membrane and an inner one folded into numerous contiguous layers called cristae (singular, crista).

• The cristae partition the mitochondrion into two compartments: a matrix, lying inside the inner membrane; and an outer compartment, or intermembrane space, lying between the two mitochondrial membranes.

• On the surface of the inner membrane, and also embedded within it, are proteins that carry out oxidative metabolism, the oxygen‐requiring process by which energy in macromolecules is stored in ATP. Biology ­ McGraw Hill ­ 2002

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http://bit.ly/ddPqsO http://bit.ly/ddPqsO

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Organelles that contain DNA Chloroplasts CHLOROPLASTS: The Cell's Energy factory

• Chloroplasts contain the photosynthetic pigment chlorophyll that gives most plants their green color.

• The chloroplast body is enclosed, like the mitochondrion, within two membranes that resemble those of mitochondria. However, chloroplasts are larger and more complex than mitochondria.

• In addition to the outer and inner membranes, which lie in close association with each other, chloroplasts have a closed compartment of stacked membranes called grana (singular, granum), which lie internal to the inner membrane. A chloroplast may contain a hundred or more grana, and each granum may contain from a few to several dozen disk‐ shaped structures called thylakoids.

• On the surface of the thylakoids are the light‐capturing photosynthetic pigments, surrounding the thylakoid is a fluid matrix called the stroma.

Biology ­ McGraw Hill ­ 2002

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Organelles that contain DNA Centrioles CENTRIOLES: Microtubule‐assembly center

• Centrioles are barrel‐shaped organelles found in the cells of animals and most protists. They occur in pairs, usually located at right angles to each other near the nuclear membranes (figure 5.23); the region surrounding the pair in almost all animal cells is referred to as a centrosome.

• Although the matter is in some dispute, at least some centrioles seem to contain DNA, which apparently is involved in producing their structural proteins.

• Centrioles help to assemble microtubules, long, hollow cylinders of the protein tubulin. Microtubules influence cell shape, move the chromosomes in cell division, and provide the functional internal structure of flagella and cilia, as we will discuss later.

• Centrioles may be contained in areas called microtubule‐organizing centers (MTOCs). The cells of plants and fungi lack centrioles, and cell biologists are still in the process of characterizing their MTOCs. Biology ­ McGraw Hill ­ 2002

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ANIMATION The Nucleus and Endomembrane System http://goo.gl/M0myR

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ANIMATION Quiz ­ Cell Organelles http://bit.ly/a3IT4G

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Teacher's Notes This class has been designed to cover the topics of Cell Structure and Organization from Monday, June 20th till Friday, June 24th.

For further knowledge about this topic: 1. Conduct a thorough search under the topic: Cell Structure and Organization on the Web, books and magazines.

2. If findings are not specific, ask your teacher for suggestions.

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Objectives • Identify the two types of cells.

• Describe the structure of the components of the cell.

• Analyze the functional relation of the cell components.

• Evaluate the main processes in the cell.

• Compare and Contrast Prokaryotic and Eukaryotic cells.

Note: All, or most, of the objectives will be covered during class time, however the student must be responsible for those objectives not covered or concluded.

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Vocabulary • • • • •

Cell: Prokaryote: Eukaryote: Organelle: Biochemistry:

Note: Most of the vocabulary words will be covered during class time, however the student must be responsible for those words not covered or concluded.

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Link and Learn You can visit the following websites to improve your understanding on the present topic:

• www.cellsalive.com/ • http://science‐learning2011.wikispaces.com • http://learningandscience.blogspot.com

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Prepared by Gerardo LAZARO SCIENCE Teacher Email: biochemalarife@gmail.com Wiki: http://science‐learning2011.wikispaces.com Blog: http://learningandscience.blogspot.com Twitter: http://twitter.com/glazaro

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