B2.2 Organelles + compartmentalization Flashcards
What do/are the organelles do?
Within most cells are highly specialized structures carrying out functions essential to the cell + organism. These specialized structures are called organelles. Organelles are adapted to their function. Most organelles are membrane bound, allowing compartmentalization with the cell. Not all parts of a cell are considered organelles.
what does compartmentalization allow?
allows unique processes to proceed without interference from chemicals or reactions occurring nearby in the cell
What is important in allowing reactions to occur without interference?
A cell has different reactions occurring in close proximity within it. Selectively permeable membranes are important in allowing these reactions/functions to occur without interfering with on another.
Cell compartmentalization
The isolation of reactions = compartmentalization. The result of which is that cells work more efficiently than if all the reactions were mixed up together.
what is reductionism?
the best way to focus on how cells work at molecular level is to reduce the cell to its component parts and study each part individually. This is an approach where we can study localized parts and reactions and develop understanding of overall reactions of the cell
what are tools used to study cells
- Biochemical fractionation
- Electron microscopy
- Microscopes
study of the cell involves a process called biochemical fractionation, what is biochemical fractionation?
Fractionation refers to the separation and isolation of specific chemicals and/or structures so that detailed research can be carried out. There are several different techniques -> each allows the separation of different parts of the cell. Centrifugation or cell fractionation allows the extraction of organelles from cells.
What is the process of cell fractionation?
Ultracentrifuges are often used for this process. Cells are first mixed in a tube with substances that break down the cell membranes. The sample is then spun at high speeds to isolate the different components by size and shape. Larger and heavier cell components are able to be separated at lower speeds. Once separated, larger + heavier organelles are found at the bottom of the tube
What is Chromatography?
this is very effective at isolating pure substances such as amino acids, proteins, carbohydrates and plant pigments. A mixture of molecules is placed in a separating medium. The molecules separate out depending on their size and the speed with which they travel through the medium. There are several different types of chromotagraphy; these include gel and ion exchange chromotography
In column chromatography, what does in mean when each row has a different color?
The different colors indicate different substances that are isolated from the original compound in the test tubes
What does gel electrophoresis do?
this separates molecules of different types by passing them through a gel using an electrical charge. The molecules are separated based on properties such as size and charge. This technique is commonly used in studies involving nucleic acids
How are organelles separated from the rest of the cell?
Organelles are separated from the rest of the cell by a protective barrier, sometimes involving 2 membranes. This barrier is crucial as it allows the chemical reactions to take place in an organelle without interference from the rest of the cell
Cell wall: organelle? general function?
It is not an organelle. This encloses and protects plant cells
Cytoskeleton: organelle? general function?
It is not an organelle. This maintains the cell shape, anchors organelles, facilitates cell movement
Cytoplasm: organelle? general function?
It is not an organelle. This is the region where most of the metabolic reactions in the cell occur
Nucleus: organelle? general function?
This is an organelle. This is for the genetic control
Vesicle: Organelle? General function?
This is an organelle. storage and support
Ribosomes: organelle? general function?
This is an organelle. Protein synthesis
Plasma membrane: organelle? general function?
This is an organelle. This regulates movement in and out of cell, transports materials to maintain the internal cell environment, cell recognition, and communicatio
Cilia/flagella: organelle? general function?
This is an organelle. This controls movement
Golgi apparatus: organelle? general function?
This is an organelle. This modifies and stores endoplasmic reticulum products, forms lysosomes and transport vesicles
Mitochondria: organelle? general function?
This is an organelle. Cellular energy (ATP) production
Chloroplasts: organelle? general function?
This is an organelle. Role = conversion of light energy into chemical energy
Lysosomes: organelle? general function?
This is an organelle. Role = digest worn out organelles and debris, digest materials brought into the cell by endocytosis
What is the advantage of eukaryotic cells having an nucleus?
allowed some of the important cell processes to take place more efficiently, compared to prokaryotic cells. mRNA must leave the nucleus in order to be transcribed
What are the two cell processes that are responsible for the production of proteins?
Transcription and translation. In transcription, a DNA strand serves as a template or copy strand for the formation of messenger RNA. Translation occurs when ribosomes use the code carried by mRNA to produce a polypeptide/protein. Transcription occurs in nucleus while translation is carried out in the cytoplasm.
what does the separation of transcription+translation do?
The separation of these two cellular processes allows post-transcriptional modification of mRNA to occur in the nucleus before translation happens in the cytoplasm. In prokaryotic cells there is no isolation of these 2 processes + mRNA can immediately come into contact with ribosomes and initiate translation without any modification occurring. The additional step of modification of mRNA in eukaryotes decreases the chances of errors happening in the production of polypeptides and proteins
ALL Eukaryotic cells have compartments/organelles that are involved with…
- Energy production
- Metabolism
- Biosynthesis
- Degradation
does size+quantity of compartments vary?
Yes. They vary depending on the overall function of the cell in which they occur.
EX. acinar cells (certain type of pancreatic cells) that specialize in the secretion of digestive enzymes. They have significantly enlarged endoplasmic reticulum, golgi apparatus, and granule storage compartments
what has compartmentalization allowed?
It has allowed a division of labor within the cell, with specific tasks carried out by a single organelle or organelle-like structure. Enzymes can be kept in the areas where they will be most effective. Keeping reactions separate in different parts of the cell means that the metabolites and enzymes for each particular process can be concentrated in a particular area. This ensures that pathways run smoothly, can be easily controlled and do not interfere with eachother
What do lysosomes participate in?
Lysosomes participate in the breakdown of wastes and cellular components that need to be replaced. This breakdown requires some potentially destructive enzymes that could cause severe damage to the cell if they were not isolated by the membrane.
what is the result when endocytosis occurs?
When endocytosis occurs, the result is often a phagocytic vacuole. This vacuole is a means of protecting the cellular contents from potential damage when phagocytosis occurs
what happens one the phagocytic vacuole is formed?
the phagocytic vacuole will move around in the cell unit it contacts a lysosome. The vacuole then fuses with the acidic lysosome, allowing inactivation and digestion of the threat.
What is phagocytosis?
This plays a key role in defending cells against invading pathogens. This is a cellular process for ingesting and elimination particles larger than 0.5 micrometers in diameter/pathogens
What challenges does compartmentalization present?
The fact that each area or organelle carries out one specific function means that the cell must develop a means of integrating all the separate functions. To accomplish this, some organelles are connected in a functional series, allowing the chemical pathways important to the cell to take place. Membrane pumps and carriers have evolved so that the products of one organelle can enter another, and important cell reactions can occur.
What is cellular respiration?
this is the process by which glucose is used to produce adenosine triphosphate; this molecule then provides the energy needed for cell reactions. Respiration is a very complex series of chemical reactions, most of which occur in the mitochondrion.
What is the mitochondrion?
An organelle found in most cells, in which the biochemical processes of respiration and energy production occur. It has a double membrane, the inner part being folded inwards to from layers (Cristae). This is the site of aerobic respiration
what adaptations has the mitochondrion undergone to produce ATP?
Several key adaptation that make it highly efficient at producing ATP through aerobic respiration.
- Double membrane structure -> The inner membrane houses the electron transport chain and ATP synthase, while the outer membrane allows necessary molecules to enter, ensuring a controlled and efficient ATP production process.
- Cristae - increased surface area for ETC proteins and ATP synthase
- Selective permeability + transport proteins
Overall equation for cellular respiration is;
C(6)H(12)+6O(2)->6C0(2)O+energy. This equation shows aerobic respiration because it includes oxygen as a reactant.
why do all organisms carry out respiration?
All organisms must have the ability to produce ATP for energy, and therefore, all organisms carry out respiration
what happens if there is a defect in any of the mitochondrial regions or structures?
This can cause ATP production to be diminished and even eliminated. Mitochondrial defects in children can lead to muscle weakness and affect mental development.
Mitochondrion structure; Outer mitochondrial membrane, description + function
A membrane that separates the contents of the mitochondrion from the rest of the cell
Mitochondrion structure; Matrix
An internal cytoplasm-like substance that contains the enzymes for the first stages of respiration that take place in the mitochondria
Mitochondrion structure; Cristae
Tubular regions surrounded by membranes that increase the surface area for reactions that take place towards the end of respiration (oxidative phosphorylation)
Mitochondrion structure; inner mitochondrial membrane
A membrane that contains the carriers and enzymes for the final stages of respiration (electron transport chain and chemiosmosis)
mitochondrion structure; space between inner+outer membranes
a reservoir of hydrogen ions (protons), allowing a high concentration of protons.
what is the chloroplast?
is a double-membrane organelle found in plant cells, it is responsible for photosynthesis. It contains chlorophyll, a green pigment that absorbs light energy to drive the conversion of carbon dioxide and water into glucose and oxygen. They have their own DNA and ribosomes, supporting the endosymbiotic theory.
equation of photosynthesis
6CO(2)+12H(2)O+ light-> C(6)H(12)O(6)+6H(2)O+6O(2). In photosynthesis chemical bonds are made to produce carbon compounds. the raw materials of photosynthesis are carbon dioxide + water with light providing energy. Photosynthesis is essentially the reverse of respiration
What types of processes are respiration and photosynthesis?
Respiration is a catabolic (breakdown, releases energy) process, whereas photosynthesis is anabolic (builds up, uses energy) process
In what organisms does photosynthesis occur in?
In autotrophs. These organisms make their own food
Chloroplast structure; extensive membrane surface area of the thylakoids
greater absorption of light by photosystems
Chloroplast structure; small space (lumen) and low volumes of fluid within the thylakoids,
Faster accumulation of protons to create a concentration gradient
Chloroplast structure; stroma region similar to cytoplasm of the cell and the matrix of the mitochondrion
Provides a region where the enzymes necessary for the Calvin cycle can work
Chloroplast structure; double membrane on the outside
isolates the working parts and enzymes of the chloroplast from the surrounding cytoplasm
What does the nuclear envelope do?
This is a double membrane, that provides an area where DNA can carry out its functions without being affected by processes occuring in other parts of the cell. The nucleus is bordered by a double membrane and is the region where DNA resides in.
What do the nuclear pores do in the nuclear envelope?
The nuclear membrane has many pores that extend through both layers of the envelope. These nuclear pores allow ions and small molecules to diffuse between the nuclear material; the nucleoplasm and the cytoplasm. These pores also control the passage of mRNA, proteins, and RNA protein complexes in+out of the nucleus
Where are the RNA-protein complexes produced
These RNA-protein complexes often become ribosomes. They are produced in a region of the nucleus -> the nucleolus
the outer membrane of the nuclear envelope is continuous with …
the ER of the cytoplasm, an even shares some functions with the ER. Ribosomes are often seen attached to the other nuclear membrane, and this membrane can also form vesicles just like the ER
What does the inner membrane of the nuclear membrane interact with?
it interacts with the inactive form of DNA-> called Chromatin. Which occurs within the nucleolus. This is important in maintaining the shape of the nucleus
What is chromatin?
This is an elongated form of DNA arranged around proteins. Studies indicates that chromatin affects the function of DNA. Changes in chromatin can cause changes in gene expression (these are called epigenetic changes)
What feature of the nuclear envelope is seen during the cell division processes, mitosis and meiosis?
Early in both processes the nuclear membrane breaks down to allow movement of the DNA structures. generally, the nuclear envelope breaks apart, becoming vesicles freely circulating in the cytoplasm. Once the DNA is correctly positioned at the conclusion of the two processes, these vesicles attach to the surface of the highly condensed chromosomes and undergo a series of complex changes to reform the nuclear envelope
What are ribosomes?
these are cytoplasmic organelles found in both prokaryotic and eukaryotic cells. Ribosomes are composed of proteins and a specific type of RNA called ribosomal RNA (rRNA). All ribosomes produce ribosomes. They are responsible for protein synthesis
what is the difference between ribosomes in prokaryotes and eukaryotes?
ribosomes in prokaryotes are slightly smaller than those of eukaryotic cells
what are ribosomes composed of?
They are composed of 2 subunits; large ribosomal subunit (includes a P and an A site), and a small ribosomal subunit (mRNA binding site, where mRNA is positioned for translation)
To what can ribosomes be attached?
They can be attached to rough ER, or they may be free in the cytoplasm of the cell.
How are free ribosomes different than membrane-bound ribosomes?
They produce different proteins. Free ribosomes produce protein that are used within the cell, such as in the supporting cytoskeleton of the cells, they are also used in nucleus, mitochondria and in other organelles not derived from the cell’s inner membrane system. Ribosomes that are membrane-bound produce proteins that are transported through the ER and often are exported from the cell
Which organelles use membrane-bound ribosomes or free ribosomes?
Membrane-bound ribosomes -> Produce proteins for secretion or membrane-bound organelles
Free ribosomes-> Produce proteins for the cytoplasm, nucleus, mitochondria, and other non-membrane-bound organelles.
What proteins are produced by membrane-bound ribosomes and then get sent to golgi apparatus?
Proteins called secretory proteins. Once produced they get sent to the golgi apparatus, where they are properly packaged for cellular exit. Secretory protein examples = Hormones and enzymes
What does the golgi apparatus consist of?
usually consists of flattened sacs. There can be as few as one in single-celled organisms, and more than 20 in some animal cells. These stacks of flattened sacs are called cisternae
When are the sacs (golgi apparatus) especially numerous?
they are especially numerous in cells that are engaged in producing and secreting substances.
What do the opposite sides mean on the golgi apparatus (Cis + Trans side)?
One side of the stack is located near the ER (this is the cis side), the other side is directed towards the plasma membrane (the trans side). Protein or lipid-filled transport vesicles are received on cis side from either ER. As the protein/lipid moves through the cisternae they are modified so that they can carry out the specific function needed. Once modified the final product is then packaged into vesicles that depart from the trans side. Often modification of the substance includes the attachment of a signal chemical that directs the destination of the product.
What is the golgi apparatus?
is a membrane-bound organelle that modifies, sorts and packages proteins and lipids received from the ER for secretion or delivery to other parts of the cell
What happens with the vesicles that leave from the trans side of the golgi apparatus
Some vesicles may become lysosomes within the cell, and others may return to the ER. Many will combine with the plasma membrane and go through the process of exocytosis, resulting in the secretion of the substance out of the cell
What are vesicles?
are small membrane-bound sacs in which various substances are transported or stored in the cell. Examples of vesicles -> lysosomes; contains enzymes necessary for cellular digestion and also for destroying defective or damaged organelles, transport vesicles; which move molecules within the cell
What are Clathrins?
they are proteins in the cell membrane that anchor certain proteins to specific sites, especially on the exterior plasma membrane in receptor-mediated endocytosis. The clathrin proteins line coated pits, allowing the receptors to bind to specific molecules. When an appropriate collection of molecules occurs in the lined pit, the pit deepens and will eventually seal off, forming a vesicle. Because different cells need to take in different molecules, they have specific receptors on their surface
What is the advantage of receptor-mediated endocytosis?
Is that it is quite selective and efficient, especially compared to ordinary endocytosis
