Cell Biology Chapter 1 review
Do chloroplasts contain their own DNA and how do they reproduce?
Chloroplasts contain their own DNA, reproduce by dividing in two, and are thought to have evolved from bacteria that were engulfed by an early eukaryotic cell
What is a prokaryotic cell?
Organisms without a nucleus are called prokaryotes-- prokaryotes encompass bacterium and archaea Prokaryotes are typically spherical, rodlike or corkscrew shaped and are generally small Have tough protective coat, or cell wall, surrounding the plasma membrane, which closes a single compartment containing the cytoplasm abd the DNA Cells reproduce quickly by dividing into two-- in optimum conditions they can replicate themselves in up to 20 mins Thanks to their large numbers, rapid growth rates, and ability to exchange bits of genetic material similar to sex, their populations can evolve fast , rapidly acquiring the ability to use a new food source or resist being killed by a new antibiotic
What is a perioxome?
Peroxisomes are small, membrane enclosed vesicles that provide a safe environment for a variety of reactions in which hydrogen peroxide is used to inactivate toxic molecules
How many membranes does mitochondria have?
Under an electron microscope, individual mitochondria are found to be enclosed in two separate membranes, with the inner membrane formed into folds that project into the interior of the organelle
How are genomes more than just genes?
Vast bulk of our DNA does not code for proteins or functional RNA molecules Instead it includes a mixture of sequences that help regulate gene activity, plus sequences that seem to be dispensable The large quantity of regulatory DNA in eukaryotic cells allows for enormous complexity and sophistication in the way different genes are brought into action at different time and places The DNA can program the growth, development and reproduction of living cells and complex organisms The genome directs the manufacturing of the parts of the cell it needs to function and reproduce
How do viruses reproduce?
Viruses are compact packages of genetic information -in the form of DNA or RNA - encased in protein but they have no ability to reproduce themselves independently, therefore they get themselves copied by parasitizing the reproductive machinery of the cells they invade
What is the electron microscope?
instrument that illuminates a specimen using beams of electrons to reveal and magnify the structures of very small objects such as organelles and large molecules
What is the Fluoroscopy technique?
instrument used to visualize a specimen that has been labeled with a fluorescent dye:samples are illuminated with a wavelength of light that excites the dye, causing it to fluoresce
What are lysosomes?
lysosomes → are small irregularly shaped organelles in which intracellular digestion occurs, releasing nutrients from ingested food particles and breaking down unwanted molecules for either recycling within the cell or excretion from the cell
How do cells vary?
-->Cells vary just as widely in their shape and function : example would be a nerve cell (which receive signals from other extended nerve cells) vs a paramecium that is submarine shaped and covered with thousands of cilia to sweet the cell forward by a sinus beating --> Cells also are diverse in their chemical requirements→ some require oxygen to live and for others this gas is deadly also some cells consume little more than air, sunlight and water as their raw materials; others need a complex mixture of molecules produced by other cells
How do the variations reflect differences in cell function?
-->These differences in size, shape and chemical requirements often reflect differences in cellular function -->Some cells are specialized in production of particular substances, such as hormones, starch,fat, latex or pigments Others are like engines, like muscle cells that burn fuel to do mechanical work
What are some features of brewers yeast and what have we learned from them?
-Small single cell fungus -Reproduces rapidly -Relatively immobile -Rigid cell wall -Possesses mitochondria but not chloroplasts -When nutrients are abundant, it reproduces almost as fast as bacterium -We have learned the cell division cycle, the machinery that governs cell division
There is a continual exchange of what and where does it occur in the cell?
A continual exchange of materials takes place between the ER, the golgi apparatus, lysosomes, and outside of the cell The exchange is mediated by transport vesicles that pinch off from the membrane of one organelle and fuse with another (like tiny soap bubbles budding and rejoining larger bubbles)
If these cells contain the exact same copy of DNA, How do they differentiate to ultimate perform different functions?
All of these differentiated cells are generated during embryonic development from a single fertilized egg cell and all contain identical copies of the DNA of the species The varied characters come from the way that the individual cells use their genetic information → different cells express different genes→ which means that they use their genes to produce some proteins and not others, depending on their internal state and on cues that they and their ancestor cells have received from their surroundings -- mainly signals from other cells in the organism
Do cells have similar chemistry, even though they vary from the outside?
Although cells are infinitely varied when viewed from the outside, they are fundamentally similar inside
what dictates the appearance and behaviour of a cell?
Appearance and behaviour of cells are dictated by their protein molecules→ which serve as structural supports, chemical catalysts, molecular motors etc
What are some features of bacteria?
Bacteria have the simplest structure and come closest to showing us life stripped down to its essentials Bacterium contains essentially no organelles-- not even a nucleus to hold its DNA This property - the presence or absence of a nucleus- is used as the basis for a simple but fundamental classification of all living things
What is a eukaryotic cell?
Bigger and more elaborate that bacteria and archaea Some live independent lives as single celled organisms such as amoeba and yeast Others live in multicellular assemblies All of the more complex multicellular organisms such as plants, animals and fungi and formed from eukaryotic cells
The cell is FAR from static, explain
Cell interior is in constant motion Cytoskeleton is a dynamic jungle of protein ropes that are continually strung together and taken apart - its filaments can assemble and then disappear in a matter of minutes Motor proteins use the energy stored in molecules of ATP to trundle along these tracks and cables, carrying organelles and proteins throughout the cytoplasm
"all present day cells have apparently evolved from the same ancestral cell", explain how this may occur?
Cells reproduce by replicating its DNA and then dividing into two-- creating two daughter cells that are exactly identical to the parental cell (ideally). There can be mutations during DNA replication that can change the DNA for the worse, better or neutrally viable Cells inherited their genetic information from the same common ancestor-- supposed that it contained a prototype of the universal machinery of all life on Earth today
Briefly state how cells are similar in terms of their molecules and genes?
Cells resemble one another in details of their chemistry and they are composed of the same sorts of molecules, which participate in the same sorts of chemical reactions In all organisms, genetic information, in the form of genes,, is carried in DNA molecules This information is written in the same chemical code, constructed out of the same chemical building blocks, interpreted by the same chemical machinery, and replicated in the same way when an organism reproduces Thus in every cells, the long DNA polymer chains are made from the same set of four monomers (A&T, G&C), called nucleotides strung together in different sequences to convey information In every cell, the information encoded in the DNA is read out, or transcribed into a chemically related set of polymers called RNA Then a subset of these RNA molecules is in turn translated into proteins (another type of polymer)
What is the structure of chloroplasts and where are they located?
Chloroplasts are large, green organelles that are found only in the cells of plants and algae, not in the cells of animals or fungi More complex structure than a mitochondria; in addition to two surrounding membranes, they possess internal stacks of membranes containing the green pigment chlorophyll
Whats is the FUNCTION of chloroplasts
Chloroplasts carry out photosynthesis→ trapping the energy of sunlight in their chlorophyll molecules and using this energy to drive the manufacture of energy rich sugar molecules. In the process they release oxygen as a molecular by product Plant cells then can extract this stored chemical energy when they need it, by oxidizing these sugars in their mitochondria, just as animal cells do Chloroplasts enable plants to get their energy directly from sunlight and they allow plants to produce the food molecules- and the oxygen- that mitochondria use to generate chemical energy in the form of ATP
Why is the cytoskeleton essential in both plant and animal cells?
Cytoskeleton is essential to plant cells as it governs the internal organization and structure of the cell and its shape as the plant cell is boxed in by an extracellular matrix, it is also essential to animals cells which are free moving, bends and stretches. In a plant cell, the cytoskeleton drive organelles, in a constant stream, around the cell interior via cytoskeletal tracks Both cell types rely on the cytoskeleton to separate the internal components into 2 daughter cells during division
So, what is each cell capable of?
Each cell is capable of carrying out the variety of biological tasks, depending on the environment and it's history, and it selectively uses this information encoded in its DNA to guide these activities
Tell me some differences in the genomes of prokaryotic cells, eukaryotic cells
First thing we note while looking at an organism's genome is its overall size and how many genes it packs into that length of DNA Prokaryotes have very little excess genetic baggage and nucleotide-for-nucleotide, they squeeze a lot of information into their small genomes Eukaryotic genomes are much larger, there is 700x more DNA than e-coli Genome of an amoeba contains 100x more than ours When genes from different organisms have very similar nucleotide sequences, it is highly probable that they descended from a common ancestral gene Such genes and the proteins they make are said to be homologous
What is the purpose of the genome?
Genome→ the entire sequence of nucleotides in an organism's DNA→ provides a genetic program that instructs the cell how to behave --->For the cells of plant and animal embryos , the genome directs the growth and development of an adult organism with hundreds of different cell types --->With an individual plant or animal, these cells can be extraordinarily varied Fat cells, skin cells, bone cells, nerve cells etc.
What features does electron microscopy allow you to see in terms of detail when viewing the cell
Highest magnification for finest detail = electron microscope Organelles → separate, recognizable substructures with specialized structures Membrane that separates the interior of the cell from the exterior environment is called the plasma membrane, while all the membranes surrounding organelles are called the internal membranes
What does a light microscope allow you to see in terms of the cell
If you cut a small and thin slice of suitable plant or animal tissue and view it using a microscope (light) you will see that the tissue is divided into thousands of small cells. These cells can be closely packed or separated from one another by an extracellular matrix (a dense material often made of protein fibers embedded in a polysaccharide gel Each cell is 5-20 micrometers in diameter
What is the cytoskeleton?
It is composed of three types of filaments, the thinnest are actin filaments: they are abundant in all eukaryotic cells but are in very large numbers in muscle cells (where they are significant for muscle contraction) Thickest filaments are called microtubules: they help to pull duplicated chromosomes to either end of the cell during division into two daughter cells Lastly, there are intermediate filaments which serve to strengthen the cell
How are materials transferred between organelles
Membranes also form many different types of small transport vesicles that ferry materials from one membrane enclosed organelle to another
What is the function of mitochondria?
Mitochondria are generators of chemical energy for the cell, they harvest energy from the oxidation of molecules, such as sugar, to produce adenosine triphosphate which is the basic chemical fuel that powers most of the cell's activities Because the mitochondria consume oxygen and release carbon dioxide during this process, this is called cellular respiration Without mitochondria, animals, fungi and plants would be unable to use oxygen to break down and extract the energy they need from food molecules that nourish them
Do mitochondria have their own DNA and where are they thought to have come from?
Mitochondria have their own DNA and reproduce by dividing in two Because they resemble bacteria in so many ways, they are thought to have been derived from bacteria that were engulfed by some ancestor of present day eukaryotic cells This created a symbiotic relationship where the eukaryotic cell and the bacteria help one another to survive and reproduce
What are the two domains of prokaryotes?
Most of the prokaryotes familiar from everyday life - the species that live in the soil or make us ill- are bacteria archaea-->thrive in similar environments than bacteria, but also in conditions that are hostile for most other cells such as concentrated brine, volcanic acid springs, sludge in sewage treatment plants etc
What is the GENERAL purpose of organelles?
Most of these structures are involved in the cells ability to import raw materials and export both the useful substances and waste products that are produced by the cell
What features make prokaryotes the most diverse and numerous on Earth?
Most prokaryotes live as single celled organisms, although some join together to form chains, clusters or other organized multicellular structures In shape and structure, prokaryotes appear simple and limited, but in terms of chemistry, they are the most diverse and inventive class of cells They can exploit enormous ranges of habitats and vastly outnumber eukaryotic organisms Some are aerobic (use oxygen to oxidize food molecules; some are strictly anaerobic and are killed in the slightest exposure to oxygen) Mitochondria (energy organelle in eukaryotic cell) is thought to evolve from aerobic bacteria Any organic, carbon containing material can be used as food by one bacterium or another
What is the function of the nucleus ?
Nucleus is usually the most prominent organelle in a eukaryotic cell It is enclosed within two concentric membranes that form a nuclear envelope, and it contains molecules of DNA DNA are extremely long polymers that encode the genetic info of the organism DNA is also present in prokaryotic cells, these cells just don't have a nucleus and don't keep their DNA apart from the rest of the cells contents
What is the significance of endocytosis and exocytosis?
Portions of the plasma membrane tuck inward and pinch off to form vesicles that carry material captured from the external medium into the cell -- this is called endocytosis In the reverse, called exocytosis, vesicles from inside the cell fuse with the plasma membrane and release their contents into the external medium ---->Most of the hormones and signal molecules that allow cells to communicate with one another are secreted by exocytosis
What are proteins built with? how do they vary in shape?
Proteins built from amino acids, all organisms use the same set of 20 amino acids to make their protein , but these amino acids are linked in different sequences, giving each type of protein molecule a different three dimensional shape, just like how different sequences of letters spell different words
What is a protozoan?
Single celled eukaryotes can prey upon and swallow other cells is borne out of the behaviour of many of the free-living, actively motile micro organisms called protozoans -- however, not all protozoans are predators, they can be photosynthetic or carnivorous, motile or sedentary Their anatomy is often elaborate and they can have distinct features such as beating cilia, sensory bristles, photoreceptors, stinging darts, muscle-like contractile bundles etc.. They are intricate and versatile
What have we learned from e-coli?
Small rod shaped cell, normally lives in the gut of humans and other vertebrae From this organism, we learned how cells replicate their DNA and how they decode genetic instructions to make proteins
What is a draw back in cell specialization?
Some modifications specialize a cell so much that they spoil its chances of leaving any descendants → such specialization would be senseless for a cell that lived a solitary life However, in a multicellular organism, there is a division of labour among cells, allowing some cells to become specialized to an extreme degree for particular tasks that they are dependent on their fellow cells for many basic requirements
What is the cytoplasm?
The cytoplasm contains a profusion of other organelles that are surrounded by single membranes Cytosol is the gel-like substance within the cell, it contains a host of large and small molecules, it is the site of many chemical reactions that are fundamental to the cell's existence. Early steps in the breakdown of nutrients of molecules occur in the cytosol (ex→ proteins made from ribosomes occur here)
What aids in maintaining the cell shape?
The cytosol is criss crossed by long fine filaments -->The filaments are seen anchored to one end of the plasma membrane or to radiate out from a central site adjacent to the nucleus
What is the Endoplasmic Reticulum ?
The endoplasmic reticulum (ER) is an irregular maze of interconnected spaces enclosed by a membrane It is here that most cell membrane components, as well as materials destined for export from the cell, are made This organelle is enormously enlarged in cells that are specialized for the secretion of proteins
What does the Golgi apparatus do?
The golgi apparatus are stacks of flattened membrane enclosed sacs which modify the packages molecules made in the ER that are destined to either be secreted from the cell or transported to another cell compartment
What is cell theory?
theory in biology that includes one or both of the statements that the cell is the fundamental structural and functional unit of living matter and that the organism is composed of autonomous cells with its properties being the sum of those of its cells Cells are generated only from pre-existing cells and inherit their characteristics is a fundamental principle.