STRUCTURE AND FUNCTION OF CELLS

 

Sources: Estrella Mountain College online Biology Book, Scott, Forseman Biology, Birthsource.com, Babycenter.com, and Biology by Campbell et.al., University of San Diego.

 

7.1 Cell and Organismal Biology

a. Describe organelles and explain their function in the cell
b. Relate the structure of organelles and cells to their functions
c. Explain the conversion, flow, and storage of energy of the cell
d. Identify the function and explain the importance of mitosis and meiosis as processes of cellular and organismal reproduction
e. Compare single-celled and multicellular organisms, noting the role of cell differentiation in the development of multicellular organisms
f. Describe the levels of organization(e.g., cells, tissues, organs, systems, organisms and ecosystems) in plants and animals
g. Describe the structures and functions of human body systems, including, but not limited to, the skeletal, reproductive, nervous and circulatory systems
h. Explain the major structures and their functions in vascular and non-vascular plants

CLICK HERE TO SEE COMPARISON BETWEEN PLANT AND ANIMALS STRUCTURES AND FUNCTIONS
i. Describe the life processes of various plant groups, including reproduction, photosynthesis, respiration and transpiration -also see the two tables below
j. Explain the reproductive processes in flowering plants
k. Identify examples where the physical principles of fluid flow, optics and mechanics can be applied to living systems

Describe organelles and explain their function in the cell

The drawings to the left represent general cell types. The yellow cell will represent bacteria (an organism of the Kingdom Monera- Prokaryotic cell) as well as a protozoan (an organism from the Kingdom Protista-eukaryotic cell). The cell to the right will represent plant, animal and some cells of the Kingdom Protista.

 

 

 

 

 

SIMILARITIES AMONG THE CELL TYPES

NUMBER/Similarities

DESCRIPTION

Bacterial (Monerans)
Protozoans (Protists)
Plant Cells
Animal Cells
1. DNA/ Chromosomes
Yes
Yes
Yes
Yes
2. Cell membrane
Yes
Yes
Yes
Yes
3. Structures to produce energy for cell- Cell Respiration
No-occurs near cell membrane
Yes- in organelle called mitochondrion
Yes- in organelle called mitochondrion
Yes- in organelle called mitochondrion
4. Structures that make proteins and enzymes for the cell
Yes-poly- (many) ribosomes
Yes- endoplasmic reticulum (organelle)
Yes- endoplasmic reticulum (organelle)
Yes- endoplasmic reticulum (organelle)
5. Cytoplasm
Yes
Yes
Yes
Yes

 

 

Differences Among Cells

 

NUMBER/Differences

DESCRIPTION

Bacterial (Monerans)
Protozoans (Protists)
Plant Cells
Animal Cells
1. Cell Wall
Yes
Yes
Yes
No
2. Nucleus-nuclear membrane
No
Yes
Yes
Yes
3. Fimbria-DNA transfer
Some
No
No
No
4. Vacuoles
No
Yes
Yes
Yes
5. Chloroplasts (organelles) (for photosynthesis)
Yes-blue-green bacteria has a green pigment that makes its own food.
Yes-have a green pigment that makes their own food. Diatoms, Dinoflagelletes, Euglena
Yes
No
6. Flagella-mobility
Yes
Yes
No
No
7. Capsule
Some
No
No
No

 

 

Functions of Cell "Parts: including viruses

 

 

Relate the structure of organelles and cells to their functions

 

 

 

1. Cell Wall- This structure is very rigid (does not change shape or bend). Its purpose in the bacterial cell is to protect the cytoplasm, membrane and all the contents of the cytoplasm.

 

 

 

 

 

 

 

 

2. Cell membrane (Above)- Specialized structures surrounding cells and cell organelles. These membranes are made of lipids and proteins and are selectively permeable. This means that they allow some chemicals to enter or leave the cell but not other chemicals.

  • Under a regular microscope the cell membranes appear like a "single line". Greatly magnified by an electron microscope, they show two layers separated by a space (see above).
  • Scientists first said that the membrane was like a sandwich. The protein was the "bread" surrounding the inside of the sandwich of lipids. This did not explain the selective permeability of membranes.
  • The model was changed (see drawing, upper right). Scientists kept the lipids in the center (orange color) and the round blue spheres covering the internal lipids. They put the specialized proteins (proteins to be explained later in this section) perpendicular (at 90 degrees angle) to the membrane in between the lipid molecules. These proteins go through the entire membrane. These membrane proteins may be lipoproteins (proteins that have lipids chemically attached to them).

See below to learn more about lipids and how they can cause selective permeability in cell membranes.

 

 

Lipids, Cell Membranes and Selective Permeability

 

Selective Permeability

I.. Diffusion

II. Semi-permeable Membranes:

If animal or vegetable tissues are dissolved by ethanol, ether, gasoline, benzene, chloroform, petroleum ether, etc. a portion of the tissue "dissolves" or becomes soluble. The solvents described above cannot dissolve water.

THE CHEMICALS THAT DISSOLVE IN THE SOLVENTS ABOVE ARE KNOWN AS LIPIDS.

MEMBRANE LIPIDS ARE DIVIDED INTO THE FOLLOWING CATEGORIES

 

 

SELECTIVE PERMEABILITY

Cell Membrane Model below modified and adapted from Scott, Forseman Biology, Copyright 1980

Text for above picture: Cell membranes are a lipid bilayer- The hydrophobic (water repelling) end of the lipid molecules is directed towards the interior of the membrane. The hydrophilic (water loving) end of the lipid molecules is directed towards the inside or outside of the cell. Hydrophobic area is red arrow. Hydrophilic area are blue arrows.

The glycolipids (the molecules that determine the surface properties of the cell) point toward the outside surface of the cell membrane.

Text for drawing above: The round spheres on both sides of the phospholipids and cholesterol represent the polar portion of the lipid molecules. Cholesterol is represented by the black lines in between the phospholipids. The phospholipids cephalin and lecithin are represented in orange.

The word polar means that a molecule (not an ion/electrically charged atom) has areas of positivity and areas of negativity. Water is an example of a polar molecule.

The lipid bilayer is fluid-like, permitting movement of the imbedded lipids and proteins sideways within the membrane.

 

Text for above drawing: A classic experiment showed that imbedded protein molecules could move from place to place on the cell membrane. Membrane fluidity is affected by a) the placement and number of double bonds in the fatty acid molecules of lecithin and cephalin and by b) the amount of cholesterol filling those spaces between the phospholipid molecules. Cholesterol stabilizes the membrane structure.

 

Membrane fluidity is affected by temperature. The mammalian cell membrane is stable at body temperature but is not too rigid. Fish adjust the proportion of different lipids in their cell membranes as they migrate from waters of one temperature to another.

 

 

Lipid bilayers do NOT allow larger ions and polar molecules to be transported across the membrane unaided. (Most materials needing to get into cells are in these categories)

Movement of these substances across the membrane involves imbedded membrane proteins. These proteins may connect to the energy producing organelles of the cell to cause active, aided transport.

 

 

 


Functions of Cell "Parts"-2

 

3. Cytoplasm- Serves as a fluid container for cell organelles. and other cell substances. This is the area in which all of the work of the cell is done and contains all chemicals and structures to do that work: Things occurring within this area: protein synthesis, DNA and RNA synthesis, energy transfer, preparation for cell division.

4. Lysosomes- small enzyme-containing sacks within the cytoplasm of the cell. These enzymes break down food materials into smaller parts. Some enzymes may damage tissues resulting in emphysema or arthritis.

Lysosomal enzymes remove waste materials from cells by degrading them.

 

 

5. Vacuoles- supports cell wall of plant cells; may also digest food particles (together with lysosomal enzymes) remove wastes and store substances.

 

 

6. Nucleus- place within the cell that houses the genetic material (chromosomes) and the nucleolus (produces RNA involved in protein synthesis).

 

 

 

7. DNA/ Chromosomes: see above and it exists as 2 strands that are coiled about each other much like a spiral staircase. More details in next section.

 

 

 

8. RIBOSOMES: Structures that make proteins and enzymes for the cell- In bacteria these are individual ribosomes attached to a strand of RNA. It is the place in bacteria where new proteins are being made. Each individual ribosome is made of two particles. One is a smaller particle, and the other is a larger particle. Both the smaller particle and larger particle are made of r-RNA (ribosomal RNA) and thousands of proteins.

In all other cells protein synthesis occurs along the endoplasmic reticulum. Smooth endoplasmic reticulum has no ribosomes attached to RNA which results in no protein synthesis.

Rough endoplasmic reticulum has ribosomes attached to RNA and active protein synthesis.

 

 

 

 

9. Chloroplasts- organelles within plant cells containing chlorophyl that allow plants to produce food for themselves and for others who eat them. Sun energy strikes the chlorophyl and starts a reaction where sugars are produced. The chlorophyl gives the cells a green color. Their appearance is somewhat like the mitochondria. Cells that have chloroplasts also have energy producing structures whether near the cell membrane (blue green bacteria and Protists) or within the mitochondria of the cell.

 

 

 

 

 

10. Fimbria or Pili- These are tubular structures that are thought to be one way in which bacteria can transfer DNA from one bacteria to another. This transfer results in bacteria gaining new kinds of characteristics.

 

 

 

 

 

 

 

 

11. Flagella- This structure allows bacteria that have them to move around as well as the Protist, Euglena. Flagella are like a propeller that pushes the organism around much like the movements of a snake as it slithers along the ground.

 

 

 

 

 

12. Structures to produce energy for cell: Mitochondria in all cells but bacterial cells. These contain the enzymes necessary for cellular respiration and the production of ATP (see section on biologically important molecules) or chemical energy for all cell activities. Bacteria (Monerans) do not contain this structure. It occurs near the cell membrane.

 

 

 

 

 

 

 

13. Capsule- -a gel-like structure that sticks to the cell wall of some bacteria. There are different types of capsules. These capsules protect the bacteria against an organisms defenses. Diseases can be caused more easily in bacteria with capsules than bacteria without capsules.

 

 

 

 

 

3. Explain the conversion, flow, and storage of energy of the cell

Photosynthesis and Cellular Respiration: Summary (Animation)

Click on Green Box to Begin:

1) Photosynthesis and cellular respiration are the basis for the existence of life on this planet. Click on green box to continue..

2) The chloroplast (drawing at the top) and the Mitochondria (lower right of animation) are the organelles in photosynthetic organisms that create and utilize the energy required for cellular functions. Click on green box to continue...

3) Two reactions occur in the chloroplast. One is called the light reaction occurring in the granum (looks like a pile of coins) and the dark reaction occurring in the stroma (looks like bridges between grana). Click on green box to continue...

4) Cellular respiration occurs in the mitochondria in structures called the Cristae. Click on green box to continue.

General Consideration of respiration and photosynthesis. (Click on green box to continue)

5) The energy in light produces chemical energy that is temporarily stored. These reactions are mediated by different enzymes. Click on the green box to continue.

6) Water undergoes an enzymatic reaction producing water and oxygen. The water stays in the grana to continue this part of the light reaction. Oxygen also leaves the cell and enters the atmosphere. Click on green box to continue.

7) The stored energy moves to the stroma as carbon dioxide enters the stroma thus commencing the DARK REACTION. Click on green box to continue.

8) During the dark reaction the stored energy powers the enzymatic synthesis of the sugar glucose from carbon dioxide. Glucose leaves the chloroplast and travels to the mitochondria. Much of the stored chemical energy is transferred to the bonds holding the glucose atoms together. More water is produced in this enzyme reaction. Click on green box to continue.

9) Glucose was actively transported through the membranes of both the chloroplasts and the mitochondria. Once inside the mitochondria, cellular respiration now begins. Click on green box to continue.

10) The reaction takes place in the Cristae. You will now watch the chemical reaction (all steps done by enzymes). Glucose will be broken down and carbon dioxide and water are the products of the reaction. Carbon dioxide leaves the mitochondria. Part of the carbon dioxide is recycled again through chloroplasts. The rest is excreted into the air or through exhalation for mammals/animals. Click on green box to continue

11) Breakdown of glucose also produces chemical energy that is used throughout the entire body for cell and enzyme functions as well as breathing, walking, running... in short.... being able to live and move. The energy is called ATP (adenosine triphosphate). Adenosine is the DNA/RNA purine nucleotide we have already seen. It has three instead of just the one phosphate present in DNA. The other two phosphates have high energy bonds. Click on green box to continue.

12) Water, like carbon dioxide, is recycled to other parts of the organism. It too can be eliminated. Once ATP is used for energy it loses a phosphate and becomes ADP. It is only recycled..not eliminated. Click on green box to reset animation and review it again...or continue by clicking on the right arrow below.

 

 

Identify the function and explain the importance of mitosis and meiosis as processes of cellular and organismal reproduction

Courtesy of University of Utah, Salt Lake City, Utah

 

 

CLICK ON "SUMMARY DESCRIPTION AND ANIMATION FOR CROSSING OVER DURING MEIOSIS" below- Click on the "Refresh" option on the top of the Internet browser of the new window to see the animation once again.

CLICK ON "DETAILED DISCUSSION:CROSSING OVER" BELOW TO LEARN ABOUT CROSSING OVER

 

 

Compare single-celled and multicellular organisms, noting the role of cell differentiation in the development of multicellular organisms

Gene triggers stem cell differentiation- article

Hormonal and Growth Factors controlling mammary gland differentiation

Muscle factors turning on muscle differentiation

 

 

Describe the levels of organization(e.g., cells, tissues, organs, systems, organisms and ecosystems) in plants and animals

Summary of levels of organization

Classification of organisms- details

 

 

 

Identify examples where the physical principles of fluid flow, optics and mechanics can be applied to living systems

States of Matter : Effect on cells, tissues, systems and organisms

 

Heat Capacity of Water and energy: Effect on cells, tissues, systems and organisms

 

Fluidity Properties of water: Effect on cells, tissues, systems and organisms

 

Chemistry Principles: Effect on cells, tissues, systems and organisms

Principles of Optics

Principles of optics: water allows free passage of light, facilitating photosynthesis in plants and single cell organisms with specific organelles. Atomic chemistry: properties of magnetic fields and the function of enzymes at the molecular level, realizing that each atom or protein has a specific electromagnetic orientation. Some evidence exists that abnormalities of cell growth associated with cancer may be associated with an abnormal electromagnetic orientation.

 

Newton's laws of motion (macro-mechanics) facilitating the movement of mammals of all types.

 

 

 

 

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