Chapter 3
Cells: Agriculture’s Building
Blocks
Introduction
• Most important was the invention of the microscope in the
1600s.
• Robert Hook termed the tiny spaces “cells”
• Cells vary greatly in size and shape
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Largest is ostrich egg
Smallest is bacteria
Round, square, long, thin plate
Amoebas change shape constantly
• All of agriculture is built around cells.
– Plants and animals grow from cells
– Reproduction begins with cells
– One-celled bacteria digest food in certain animals
Types of Cells
• Prokaryotic Cells
Types of Cells
• Eukaryotic Cells
Cell Components
• Cell wall – cellulose provides rigidity for the
walls of the cell and provides some support
for the entire plant
– Lumber and paper are manufactured from the
cellulose
– Pectin is found in softer plant tissues such as
leaves ad fruit.
• Pectin gives jelly its thick consistency
Cell Membrane
• Inside the cell wall is the cell membrane
• Semi permeable which means that it allows only certain material to
pass through
• Diffusion –molecules in a solution pass through the membrane
from a region of higher concentration to a region of lower
concentration
• Osmosis – diffusion of water
• Homeostasis- the ability of an organism to remain stable when
conditions around it change
• Turgid – when cells are filled with the proper amount of water, cells
are filled out and taut
• In a drought plants are limp and wilted, but as soon as water is
made available, they return to their normal healthy apperance
The Nucleus
• Eukaryotic cells have a nucleus
• Prokaryotic cells do not have a true nucleus
• Composed primarily of nucleic acids, protein,
and enzymes and serves as the control center
for all of the activities of the cell
Cytoplasm
• Is a thick, clear fluid that surrounds the nucleus and it contains all of
the material needed by the cell to conduct life processes.
• Mitochondria – break down food nutrients and supply the cell with
energy
• Vacuoles are organelles that serve as storage compartments for the
cell
• Microtubules act as the bones of the cell
• Microfilaments are fine fiberlike structures composed of protein
• Ribosomes are the sites where protein molecules are assembled.
• Golgi apparatus remove water from proteins and prepare them for
export from the cell
• Endoplasmic reticulum is a large webbing or network of double
membranes that transport material within the cell
• Lysosomes are the digestive units of the cell
Plastids
• Plant cells have organelles called plastids that are present in
animal cells. Three types of plastids exist: chloroplasts,
leucoplasts and chromoplasts.
Cell Reproduction
• Eukaryotic cells divide by a process called
mitosis.
• Activity on mitosis