4.3 Eukaryotic Cells

4.3 Eukaryotic Cells

Many industries follow this philosophy.

Building should be constructed to support the activities that will be carried out inside them.
Several elevator banks should be included in a skyscraper.
The emergency room should be easy to get to.

Our natural world uses the principle of form following function, especially in cell biology, and this will become clear as we explore eukaryotic cells.

Just as your body's organs have specialized functions, the word "organelle" means "little organ."

It should be clear to you that prokaryotic cells have a more complex structure than eukaryotic cells.

Different functions can be separated in different areas of the cell.
The first thing we need to do is look at the two important components of the cell.

The figures show the major components of a typical animal and plant cell.

The plant cell has structures not found in animal cells.
Most cells have no lysosomes or centrosomes.

A cholesterol molecule has two acid chains and a group.

The passage of organic molecule, ion, water, and oxygen into and out of the cell is controlled by the plasma membrane.
Carbon dioxide and ammonia leave the cell when they pass through the plasma membrane.

There is a bilayer of cholesterol andlipids in the erythrocytes.

The small intestine is the organ that absorbs nutrition from food.

This is a great example of form following function.
People with the disease have an immune response to wheat, barley, and rye.
Microvilli are damaged by the immune response and afflicted individuals can't absorb vitamins.
This leads to dehydration.
Patients with the disease have to follow a diet that is free of wheat.

The surface area available for absorption is increased by the appearance of Microvilli.

The microvilli are only on the area of the plasma that faces the cavity from which substances will be absorbed.

The cytoplasm has a semi-solid consistency even though it is 70 to 80 percent water.

There are other organic molecules in the cytoplasm.
There are also simple sugars and derivatives of glycerol.
The nucleus of the cell contains many elements.
The cytoplasm is where many metabolic reactions take place.

The most prominent organelle in a cell is the nucleus.

Let's look at it in more detail.

The nucleus has a gel-like substance called the nucleoplasm.

The ribosome synthesis occurs in the nucleolus.
The nuclear envelope is called the nucleus' boundary.
It has an outer and an inner layer.
There is a continuous nucleus with the reticulum.
Substances can enter and exit the nucleus.

The nuclear envelope's inner and outer membranes are made oflipids.

The nuclear envelope has pores that control the passage of things between the nucleus and the cytoplasm.

You may remember that in prokaryotes, there is a single circular chromosome.

The chromosomes are linear structures.
The nucleus of a cell has a specific number of chromosomes.
In fruit flies, the number is eight, while in humans it is 46.
When a cell is getting ready to divide, chymosomes are only visible.
When the cell is in the growth and maintenance phases of its life cycle, the chromosomes look like an unwound bunch of threads.
The material that makes up the chromosomes is described by chromatin.

ribosomal RNA is found in some of the chromosomes.

Ribosomes can be seen through an electron microscope as clusters or single dots.

They may be attached to the nuclear envelope's outer and inner parts.
ribosomes, which are large andRNA complexes, consist of two large and small subunits, shown in Figure 4.13.
Ribosomes get their orders for synthesis from the nucleus.
The ribosomes translate the code provided by the nitrogenous bases in the mRNA into a specific order of amino acids.
The building blocks of the human body are called mino acids.

Ribosomal assembles are involved in the creation of proteins.

ribosomes are found in practically every cell because they are an essential function of the cell.

Ribosomes are abundant in cells that make a lot of stuff.
The cells that produce the enzymes that are created by the pancreas have many ribosomes.
Another example of form following function is shown.

The process of cellular respiration uses the chemical energy in the food to make the molecule ATP.

This process uses oxygen and carbon dioxide to make a waste product.
The carbon dioxide that you exhale with every breath comes from cellular reactions that produce carbon dioxide as a byproduct.

In keeping with our theme of form following function, it is important to point out that muscle cells have a high concentration of mitochondria.

Your muscles need a lot of energy to work.
When your cells don't get enough oxygen, they don't make much.
In the absence of oxygen, the small amount of ATP they make is accompanied by the production of lactic acid.

Mitochondria have their own ribosomes and DNA.

There is a bilayer embedded in the membrane.
The folds are called cristae.
The area is surrounded by folds.
The cristae and matrix play different roles in cellular respiration.

The electron micrograph shows achondrion.

There is an inner and an outer organelle.
The cristae increase its surface area.
The space between the two membranes is called the intermembrane space.

The oxidation reactions break down the acids.

Many poisons can enter the body.
There are peroxisomes in the cells of the liver.

Plants have peroxisomes that convert stored fats into sugars.

Plant cells have many different types of peroxisomes that play a role in metabolism, pathogene defense, and stress response.

vacuoles are larger than vesicles, but there is a subtle difference between them.

The vesicle membranes can be used with the other systems within the cell.
Some agents break down macromolecules.
The vacuole doesn't have a connection with the other cellular components.

There are some striking differences between animal and plant cells at this point.

The centrosome is a complex found in both animal and plant cells and is associated with the microtubule organizing centers.
Most plant cells do not have a centrosome and lysosomes.
Animal cells do not have a cell wall, a large central vacuole, or specialized plastids.

There are two structures that lie close to each other.

There are nine triplets of microtubules in a centriole.

Two centrioles lie at right angles to each other in the centrosome.

There are nine triplets of microtubules in the centriole.
The microtubule triplets are held together by nontubulin proteins.

The centrosome replicates itself before a cell divides, and the centrioles appear to have some role in pulling duplicated chromosomes to opposite ends of the dividing cell.

The function of the centriole in cell division isn't clear because cells that have had the centrosome removed can still divide.

Most plant cells do not have lysosomes.

In plant cells there are vacuoles.
The lysosomes aid in breaking down a lot of things.
The cytoplasm's are active at a higher pH.
The lysosomes' pH is more acidic than the cytoplasm's.

You can see a structure outside of the plant cell diagram if you look at Figure 4.8.

Some protistan cells have cell walls.
The cell wall is composed of peptidoglycan, a major organic molecule in the plant.
You are tearing the cells with your teeth.

There is a chain of b-glucose molecule connected by a linkage.

The dashed lines at the end of the figure show a number of more units.
The size of the page makes it hard to portray an entire molecule.

Chlorops have their own genes and ribosomes, but they have a different function than the mitochondria.

Photosynthesis uses carbon dioxide, water, and light energy to make oxygen and sugar.

The difference between plants and animals is significant.
Plants can make their own food using sugars that are used in cellular respiration.
Animals must eat their food.

There are a set of stacked fluid-filled sacs in the space between the outer and inner membranes of a chloroplast.

The stack is called a granum.
The fluid surrounds the stroma.

There are three structures in the chloroplast - an outer, an inner, and a thlakoids that are stacked into grana.

The space inside the thylakoid is called the thylakoid space.
The light harvesting reactions take place in the outer part of the stroma, while the sugar synthesis takes place in the inner part.
Chloroplasts have their own genome, which is contained on a single circular chromosome.

Protists have the same cells as plant cells.

Somebacteria perform photosynthesis, but their chlorophyll is not an organelle.