Plant Life

Mediterranean Scrub

Mediterranean scrub vegetation is dominated by fire-adapted shrubs. The biome fringes the Mediterranean Sea, for which it is named, but is also found along western coasts of continents in areas with warm, dry summers and moist, cool winters.

Regions with mediterranean vegetation are coastal regions between 30 and 45 degrees north latitude or between 30 and 45 degrees south latitude.

The air circulating around high-pressure zones over adjacent oceans guides storms away from the coast in the warm season but changes position in concert with the tilt of the earth on its axis and brings storms onto the coast in the cool season. As a result, the warm season is dry, and the cool season is moist. Fire is an important component of mediterranean environments, especially after the warm, dry summer.

Membrane Structure

All cells, whether prokaryotic or eukaryotic, are surrounded by a membrane called the plasma membrane, an essential barrier between the external environment and the cytoplasm inside the cell. In addition, eukaryotic cells contain other membranes that are part of a variety of organelles, such as nuclei, plastids, mitochondria, vacuoles, Golgi bodies, and the endomembrane system.

Compartmentalization by membranes allows the function of competing processes, such as respiration and photosynthesis, in separate areas of the same cell. In addition, membranes control which molecules enter or leave the cell and the various organelles.

Finally, proteins associated with membranes are responsible for extracellular interactions and the energy transactions involved in photosynthesis and respiration.

Metabolites are compounds synthesized by plants for both essential functions, such as growth and development (primary metabolites), and specific functions, such as pollinator attraction or defense against herbivory (secondary metabolites).

Metabolites are organic compounds synthesized by organisms using enzyme-mediated chemical reactions called metabolic pathways. Primary metabolites have functions that are essential to growth and development and are therefore present in all plants. In contrast, secondary metabolites are variously distributed in the plant kingdom, and their functions are specific to the plants in which they are found.

Secondary metabolites are often colored, fragrant, or flavorful compounds, and they typically mediate the interaction of plants with other organisms. Such interactions include those of plant-pollinator, plant-pathogen, and plant-herbivore.

Microbial Nutrition and Metabolism

The diverse metabolic activities of microorganisms make them a critical component of all the earth’s ecosystems and a source of many useful products for human industry.

Microorganisms—bacteria, fungi, algae, and protists—are found in every environment on the earth that supports life. Microorganisms have been found in hot springs where temperatures exceed 80 degrees Celsius as well as in rocks of Antarctic deserts.

To ensure survival in a variety of habitats, microorganisms have developed a fascinating variety of strategies for survival. The study of microbial ecology involves consideration of the mechanisms employed by microorganisms to obtain nutrients and energy from their environment.

Microbody - Peroxisome

Microbodies, found in cells, are spherical, membrane-bound organelles that play a part in photorespiration and the conversion of fats into sucrose.

Peroxisomes and glyoxysomes are the two major types of microbodies in plant cells. Their vesicles (“packages”) vary in size from 0.3 to 1.5 micrometers in diameter and are self-replicating.

New microbodies are formed by incorporation of required proteins and lipids from the cytoplasm and subsequent splitting when they reach a certain size. Although structurally similar, their roles, and thus their contents, are different.

An organelle of eukaryotic cells, a mitochondrion is bounded by a double membrane. It is the major source of adenosine triphosphate (ATP), which is derived from the breakdown of organic molecules and contains the enzymes used in the Krebs cycle and the electron transport system.

With the exception of a few metabolically inert types, such as the red blood cells of many higher animals, eukaryotic cells of animals, plants, fungi, and protozoa contain mitochondria.

Most cells contain several hundred. The efficiency of mitochondria in adenosine triphosphate (ATP) production provides the energy source that powers all the varied activities of eukaryotic cells. For these reasons, mitochondria have been aptly termed the “powerhouses” of the cell.

Mitochondrial DNA

Plant cells have three sets of DNA to code for proteins: one set in the chromosomes of the nucleus, another in the chloroplasts, and a third genome in mitochondria. The mitochondrial genomes of higher plants are larger than those of animals and form a complex series of linear and circular molecules of different sizes.

Mitochondria play an essential role in the generation of energy in eukaryotic cells. Mitochondria are the organelles that are the main “chemical factories” of the cell where cellular aerobic respiration—using the Krebs (citric acid) cycle and respiratory electron transport to produce NADH (nicotinamide adenine dinucleotide) and ATP (adenosine triphosphate)—occurs.

In the light microscope, mitochondria look like short rods or thin filaments about 0.5 to 2 microns long. A mitochondrion is made up of a smooth outer membrane and an inner membrane that is folded into tubular shapes called cristae. Many aerobic respiration reactions are catalyzed by enzymes that are bound to mitochondrial membranes.