BSC 310 Lecture Notes - Lecture 7: Phagocytosis, Paramecium, Active Transport

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silvercicada472

24 Jun 2018

School

University of Alabama

Department

BSC

Course

BSC 310

Professor

Julie Olson

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Eukaryotic Cells

Eukaryotic cells are generally larger and more complex than prokaryotic cells. They

also contain a variety of cellular bodies called organelles. The organelles function in the

activities of the cell and are compartments for localizing metabolic function. Microscopic

protozoa, unicellular algae, and fungi have eukaryotic cells.

Nucleus. Eukaryotic cells have a distinctive nucleus, composed primarily of protein and

deoxyribonucleic acid, or DNA. The DNA is organized into linear units calledchromosomes,

also known as chromatin when the linear units are not obvious. Functional segments of the

chromosomes are referred to as genes.

The nuclear proteins belong to a class of proteins called histones. Histones provide a

supportive framework for the DNA in chromosomes. The DNA replicates in eukaryotic cells

during the process of mitosis.

The nucleus of eukaryotic cells is surrounded by an outer membrane called the nuclear

envelope, which is a double-membrane structure consisting of two lipid layers similar to the

cell membrane. Pores exist in the nuclear membrane, and the internal nuclear environment

can therefore communicate with the cytoplasm of the cell.

Within the nucleus are two or more dense masses referred to

as nucleoli (singular,nucleolus). The nucleolus is an RNA-rich area where ribosomes are

assembled before passing out of the nucleus into the cytoplasm.

Cellular organelles. Within the cytoplasm (also known as the cytosol) of eukaryotic cells are a

number of microscopic bodies called organelles (“little organs”). Various functions of the cell

go on within these organelles.

An example of an organelle is the endoplasmic reticulum (ER), a series of membranes that

extend throughout the cytoplasm of eukaryotic cells. In some places the ER is studded with

submicroscopic bodies called ribosomes. This type of ER is referred to as rough ER. In other

places there are no ribosomes, and the ER is calledsmooth ER. The endoplasmic reticulum is

the site of protein synthesis in the cell. Eukaryotic ribosomes are 80S bodies where the

amino acids are bound together to form proteins. The spaces within the ER membranes are

known as cisternae.

Another organelle is the Golgi body (also called the Golgi apparatus). The Golgi body is a

series of flattened sacs, usually curled at the edges. The outermost sac often bulges away to

form droplike vesicles known as secretory vesicles. It is in the Golgi body that the cell's

proteins and lipids are processed and packaged before being sent to their final destination.

Another organelle, the lysosome, is derived from the Golgi body. It is a somewhat circular,

droplike sac of enzymes within the cytoplasm. These enzymes are used for digestion in the

cell. They break down the particles of food taken into the cell and make the products

available to the cell. Enzymes are also contained in a cytoplasmic body called

the peroxisome.

The organelle where much energy is released in the eukaryotic cell is

themitochondrion (plural, mitochondria). The energy released is used to form adenosine

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Document Summary

Eukaryotic cells are generally larger and more complex than prokaryotic cells. They also contain a variety of cellular bodies called organelles. The organelles function in the activities of the cell and are compartments for localizing metabolic function. Microscopic protozoa, unicellular algae, and fungi have eukaryotic cells. Eukaryotic cells have a distinctive nucleus, composed primarily of protein and deoxyribonucleic acid, or dna. The dna is organized into linear units calledchromosomes, also known as chromatin when the linear units are not obvious. Functional segments of the chromosomes are referred to as genes. The nuclear proteins belong to a class of proteins called histones. Histones provide a supportive framework for the dna in chromosomes. The dna replicates in eukaryotic cells during the process of mitosis. The nucleus of eukaryotic cells is surrounded by an outer membrane called the nuclear envelope, which is a double-membrane structure consisting of two lipid layers similar to the cell membrane.

Related Questions

The bacterium E. coli, which is a major model system for the study of genes and DNA, has a singular circular chromosome of about 4x106 bp. In contrast, human diploid cells have __1__ chromosomes, of __2__ different types (donât forget that the X Â¹ Y!). The total amount of DNA found in a haploid cell such as a sperm or egg is called the organismâs âC-valueâ; the human C-value is __3__.

Also in contrast to the E. coli circular chromosome is the fact that eukaryotic chromosomes are not circular, but instead are __4__. Eukaryotic chromosomes are complexed heavily with protein to form a DNA-protein complex generically called __5__. The proteins found can be considered to fall into two general classes: __6__ and __7__. The first class is made up of 5 major proteins called __8__, __9__, __10__, __11__, and __12__. On a weight to weight basis, these proteins make up about __13__% of the total mass of a chromosome. Since these proteins must associate relatively non-specifically with DNA, they are rich in the basic amino acids __13__ and __14__, which gives the proteins a net __15__ charge.

One goal of packaging the DNA into chromatin is to compact the genome so it will fit into a nucleus. The basic unit of chromatin structure is the __16__, which has __17__ base pairs of DNA wrapped around a âcore particleâ composed of __18__ copies each of the core histones. Each nucleosome is separated by a stretch of âlinkerâ DNA so that the repeating unit is approximately 200 bp. Lets do a little arithmetic: If we consider that the nucleosome is approximately __19__ nm in diameter, that there is about 200 bp in this structure, and that 200 bp of DNA would normally occupy __20__ nm if stretched out straight (recall that each base is spaced about 0.34 nm from the next), we can see that the nucleosome alone allows for a __21__-fold compaction ratio.

The nucleosome structure is further compacted by histone __22__, which is not a part of the core particle. Instead, this histone __23__ (does what?) to cause the nucleosomal 10 nm fiber to condense into a higher-order structure referred to as the __24__ nm fiber. In the nucleus, chromosomes do not just float around freely: they are tethered to a proteinaceous structure called the __25__ at specific DNA regions called âSARsâ, which stands for __26__. SARs are rich in topoisomerases, to allow the winding and unwinding of the DNA that accompanies replication and transcription to occur, despite this constraint.

The 30 nm fiber discussed above is the form in which transcriptionally active DNA is believed to exist in the nucleus; however, further condensation leads to a highly condensed inactive form called __27__; in this terminology, the active form is referred to as __28__. The inactive condensed form can be divided into two types: one type is essentially invariant between cell types, and since it is âon all t timeâ, it is referred to as __29__. The other type comes and goes, depending on the expression of the genes present in that region of the chromosome; it is referred to as __30__.

Eukaryotic chromosomes carry the genes, of course, but also have other functional regions. One such region is the place where the spindle apparatus attaches during mitosis and meiosis; this region of the chromosome is called the __31__. Another important part of the linear eukaryotic chromosome is the ends; these are called __32__. In humans, the end of each chromosome is composed of many repeats of the short sequence __33__. One more type of functional region on each chromosome is the place where DNA replication starts; in humans, each chromosome has several of these __34__. Thus, eukaryotic chromosomes carry several different types of functional sequences, which together allow for their __35__ during S phase, __36__ during mitosis and meiosis, and the __37__ of their genes

BSC 310 Lecture Notes - Lecture 7: Phagocytosis, Paramecium, Active Transport

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