Cell Organelles and Features, What To Know

Cellular Structures and Components Relate to Cell Function, Activity

Sep 2, 2009

Eukaryotic Cell and Organelle Diagram, NAI NASA U.S.

Cells that are small and primitive, or large and more complex, are organized to promote their sustenance and survival. Even the simplest of cells are very complex.

Cells are marvelous and mysterious. Scientists study them live, and fix, stain, break open and analyze them. See here what a cell is, and how cells work.

The Universal Code of Life Applies to All Prokaryotes and Eukaryotes

Regardless of cell type, bacterium or mammalian, prokaryote or eukaryote, all cells do similarly:

DNA —> RNA (mRNA, tRNA, rRNA) —> Proteins.

DNA produces three types of RNA, and with the help of enzymes, cell proteins and compounds are made.

A simple bacterium such as Escherichia coli has about 1,000 genes. A human cell has about 25,000 genes. Each gene instructs for one, specific product, more or less. Not all genes work at the same time — some genes are turned on, some are turned off.

Understanding the universal code of life leads us to the next question: what is the minimum requirement for a functional cell?

Cell Essentials and Basic Parts and Features

All cells have:

Cell membrane (plasmalemma), phospholipid diffusion barrier with selective permeability.
Nucleic acids, DNA and RNA (messenger, transfer, ribosomal)
Ribosomes, rRNA and protein complexes; organelles for protein synthesis.
Enzymes, protein catalysts that change molecules.
Cytoplasm, contains abundant water and dissolved and suspended compounds, ions.

Cell Biology of Eukaryotes and Prokaryotes Compared

The universal code of life and essential, common cell parts are basic cell facts. Eukaryotes and prokaryotes differ by the greater complexity of eukaryotes, compared with the simplicity of prokaryotes. Prokaryotes resemble life in a tent or hut, compared with eukaryotic life in a mansion. Prokaryotic Escherichia coli does very well despite its simple structure; human cells, fancier and more complicated, do as well as that type of cell!

Eukaryote organelles and functions:

Double-membraned organelles.

Nucleus with DNA and RNA, and nuclear membrane with pores. Prokaryotic DNA lacks a membrane.
Mitochondria, oxidative organelles with distinctive cristae (folded inner membranes); Mitochondria contain Kreb's cycle enzymes and produce much ATP by oxidative phosphorylation.
Chloroplasts, in plants, have stacked, thylakoid disks (grana) with chlorophyll a and b. Photosynthesis captures light energy, produces ATP and uses CO2 and H2O, to produce sugar and oxygen.

Single-Membrane Organelles.

Endoplasmic Reticulum, sites of protein, hormone synthesis. Rough ER, ribosome organelles attached; smooth ER has no ribosomes.
Golgi Body, membrane system that packages synthesized compounds, and transports or exports them via vesicles.
Vesicles, packages produced from the Golgi body (e.g., lysosomes, peroxisomes, et al.)
Vacuoles, in plants, contain dissolved sugars, amino acids, calcium oxalate crystals or gas.
Leucoplasts, in plants, storage sites for starch
Chromoplasts, in plants, pigment-containing vesicles that give distinctive color.

Other organelles of importance:

Nucleolus, clusters of rRNA within the nucleus.
Microtubules and microtubular structures, 25 nm diameter tubulin proteins that form flagella, cilia, centrioles, mitotic spindle apparatus and kinetchores.
Flagella and Clia, cell movement. Cilia are also important in the respiratory tract and oviducts.
Centrioles, coordinate chromosome movement and separation at mitosis and meiosis.
Kinetochores, sites on chromosomes for attachment to the spindle of mitosis and meiosis.
microfilaments, 5-7 nm, extremely thin actin proteins than interact with myosin to form contractile bodies.
Intermediate filaments, 8-12 nm, stabilizing cytoskeletal proteins that strengthen, shape animals cells. Include: keratins (protein of hair, skin, nails), desmins (cell adhesins), vimentins (membrane support protein and positional proteins), and lamins (fibrous network on inner surface of the nuclear envelope).
Kinesin and Dynein, ATP- powered motor proteins, that move in opposite directions (+ and - poles, respectively) on the spindle or microtubule and break and form new bonds as they do this. They can each also transport vesicles.

In summary, the simplicity and complexity of cells is amazing.

Source

Lodish, H. et al. 2000. Molecular Cell Biology. Fourth Ed., W. H. Freeman and Co., New York, N.Y.

The copyright of the article Cell Organelles and Features, What To Know in Scientific Inquiry is owned by Donald Reinhardt. Permission to republish Cell Organelles and Features, What To Know in print or online must be granted by the author in writing.