1. Cells: Agriculture’s Building Blocks
Original Power Point Created by:
Andy Harrison
Modified by GA Agriculture Education Curriculum Office
July 2002

2. Cells All living organisms are composed of cells.
The ability to study cells was first made possible by the invention of the microscope.
An understanding of cells has allowed scientists to develop new products and technology.
Some animals are only single cell organisms, such as the amoeba, paramecia, and protozoa.

3. Cells
One-celled bacteria are important for cattle health and maintenance (ruminant digestion).
Other bacteria are important for converting atmospheric nitrogen to nitrogen for plant use.
In addition, some cells such as the one-celled phytoplankton are food for fish and whales.

4. Cell Characteristics
Animals and plants contain specialized cells, which vary in size and shape
Largest – ostrich egg
Smallest – some bacteria
Cell shape can be round, boxed, long, or string-like.
Other cells, such as amoebas, have the ability to change shape constantly.

5. Reproductive Cells Reproduction begins in the cells.
Male & female reproductive organs produce cells that unite to form new organisms.
All eggs are single cells.

6. Cell Structure – Cell Wall
Plants have a cell wall, animals do not.
Cell wall provides cell shape and protects its contents
The cell wall is composed of cellulose which:
Makes cell walls rigid
Provides support for plant
Used to make paper

7. Cell Structure- Cell Membrane
Located inside the cell wall
Also known as the plasma membrane
All material going in and out of the cell must pass through this membrane
Membrance is semi-permeable; allows certain substances (small molecules and ions [charged molecules]) to pass through

8. Cell Structures- Cell Membrane
Allows water and nutrients into and out of the cell
Transports waste out of the cell
Membrane does this by a process called diffusion.
Diffusion: molecules pass through the membrane from a region of higher concentration to a region of lower concentration

9. Cell Structure- Cell Membrane
Osmosis is the process where water passes through a cell’s semi-permeable membrane from a higher concentration to a lower concentration
The less substance water has in it , the less concentrated
The more substance – more concentrated
Cells draw water inside their membranes to equalize the concentrations on each side of the membrane.

10. Cell Structure- Cell Membrane
Homeostasis: the ability of an organism to remain stable when conditions around it change
Turgid: cells filled with water so that they are taut (firm)
Turgor pressure: helps cells to retain their shape

11. Cell Structure- Nucleus
A relatively large structure
Eukaryotic cells – have nucleus
Prokaryotic – no true nucleus
The nucleus is made of:
Nucleic acids
Proteins
Enzymes

12. Cell Structure- Nucleus
Surrounded by a double-layer membrane
This membrane regulates movement of materials in and out of nucleus, just as the cell membrane regulated movement in and out of the cell itself.
Contains genetic code
Code is located in DNA (Deoxyribonucleic acid)
DNA arranged in threadlike strands called chromosomes
Genes: segments of the chromosome; site of the actual traits

13. Cell Structure- Cytoplasm
Thick clear fluid surrounding nucleus
Constantly moving
Suspends other parts of cell
Contains all essential materials for cell life process

14. Cell Structure- Organelles
Small structures located in cytoplasm
Mitochondria: peanut shaped; break down food and supply cell with energy
Cells requiring more energy (muscles) have a greater number of mitochondria
Vacuoles: storage compartments
Membrane that encloses water and other material
Stores cell waste

15. Cell Structure- Organelles
Microtubules:
Thin hollow tubes
Composed of protein
Function as the “bones” of the cell
In animals, they aid in chromosome movement during cell division.

16. Cell Structure- Organelles
Microfilaments: fine fiber-like structures made of proteins
Help the cell to move by oscillating back & forth
Ribosomes: organelle where protein molecules are assembled
Enzymes: not an organelle, but important compounds composed of proteins that regulate chemical processes in cell

17. Cell Structure- Organelles
Golgi apparatus: shaped like group of sacks bundled together.
Remove water from proteins and prepare it for transport
Lysosomes: digestive units of cells
Digest proteins, carbohydrates, and other molecules, including bacteria and worn out cell parts

18. Cell Structure- Organelles
Plastids: present in plants but NOT in animals
Three types:
Chloroplast: contains chlorophyll, converts sunlight energy to carbohydrates.
Leucoplast: provides storage for cells
Chromoplast: manufactures pigments that give fruits and leaves color

19. Cell Reproduction All growth comes from cells increasing in number
When a cell reaches its maximum size, the cell divides to increase in number.
Original cell: parent cell
New cells: daughter cells

20. Mitosis
Process where the genetic code is duplicated and passed on to daughter cells.
The process is divided into phases:
Interphase
Prophase
Metaphase
Anaphase
Telophase

21. Interphase Phase where cells are not actively dividing
Not actually part of mitosis
Cell begins to synthesize materials and transport them outside of the cell
Cell grows and reaches maximum size
DNA replicates and forms two sets of chromosomes

22. Prophase First actual phase of mitosis
Chromatin appears in the form of distinct shorten rod-like structures
Chromatin is two strands called chromatids that are attached in middle by a centromere
Nuclear membrane begins to dissolve
Nucleus begins to disperse
In place of nucleus , a spindle is formed,
A spindle is football shaped and made of microtubules

23. Metaphase Chromatids move toward center of spindle
When they reach the center, they connect themselves to the fibers of the spindle

24. Anaphase
Pairs of chromatids separate into an equal number of chromatids
Centromeres duplicate
Chromosomes move to opposite end of cell

25. Telophase Chromosomes continue to migrate to the ends of the cell
Remains of the spindle disappear
New membranes are formed around the chromosomes
This forms two new nuclei

26. Cytokinesis Divides the cytoplasm in cell
Separate process from mitosis
In animals, the separation point is the cleavage furrow in the center of the cell
In plants, they form a cell plate and grow outward until cells are separate