Cell Organisation and Organelle Function Flashcards
What is the Cell Theory?
The Cell Theory is a fundamental principle of biology that states:
- all living organisms are composed of one or more cells
- cells are the smallest units of life
- new cells come only from pre-existing cells by cell division
What are the two categories of life?
Prokaryotes anf eukaryotes
What are Prokaryotes?
Prokaryotes are a category of life that have:
- simple cell structure
- no nucleus
What are the 2 major categories of Prokaryotes?
Bacteria and archaea
What are Eukaryotes?
Eukaryotes are a category of life that have:
- more complex cells
- DNA enclosed within a membrane-bound nucleus
- internal membranes that form organelles
What are some examples of Eukaryotes?
Animals, plants, fungi, and protists
What are some characteristics of Bacteria?
- small cells, 1 μm – 10 μm in diameter
- very abundant in the environment & our bodies
- vast majority of bacteria are not harmful to humans
- some species can cause disease
What are some characteristics of Archaea?
- small cells, 1 μm – 10 μm in diameter
- less common than bacteria
- often found in extreme environments
Where is DNA located in Eukaryotic cells?
DNA is housed inside a membrane-bound nucleus
What are organelles in Eukaryotic cells?
Specialized compartments that carry out specific functions
What are the types of organelles present in eukaryotic cells?
- membrane-bound compartments
- non-membrane bound structures
What are some membrane-bound compartments in the organelles of eukaryotic cells?
- endoplasmic reticulum
- Golgi apparatus
- mitochondria
- chloroplasts (in plant cells)
What are some non-membrane bound structures in the organelles of eukaryotic cells?
- cytoskeleton
- ribosomes
What is the function of organelles in Eukaryotic cells?
Carry out specialized functions such as:
- protein synthesis
- energy production
- intracellular transport
Are all Eukaryotic cells the same size and shape?
No, there is a wide variety of cell sizes, shapes, and functions, particularly between specialized cell types.
What are the typical components inside the plasma membrane of a typical bacterial cell?
- cytoplasm
- nucleoid region (DNA locateed)
- ribosomes (protein synthesis)
What are the typical components outside the plasma membrane of a typical bacterial cell?
- cell wall (support & protection)
- glycocalyx
- appendages (pilli & flagella)
What is the glycocalyx in a bacterial cell?
Sticky layer of carbohydrates that helps to:
- trap water
- provide protection
- help evade the immune system
What are appendages in a bacterial cell?
Structures that extend from the cell surface, e.g.:
- pilli (used for attachment)
- flagella (used for movement)
What are some of the organelles present inside a typical animal cell?
- nucleus
- endoplasmic reticulum
- mitochondria
- Golgi apparatus
- plasma membrane
- ribosomes
(all membrane bound except plasma membrane)
What is the nucleus in an animal cell?
Contains the chromosomes
What is the endoplasmic reticulum in an animal cell?
The ER is a network (=reticulum) of membranes that form flattened, fluid-filled tubules or cisternae - where proteins are modified & sorted.
What is the mitochondria in an animal cell?
Responsible for producing ATP, the cell’s main energy source.
What are the main structural features of mitochondria?
- mitochondria have an outer and inner membrane
- which surround the intermembrane space and the mitochondrial matrix
What are some other functions of mitochondria besides ATP production?
Also involved in the synthesis, modification, and breakdown of several types of cellular molecules
What is the Golgi apparatus in an animal cell?
A stack of flattened, membrane-bounded compartments/organelles in cells
What are some other names for the Golgi apparatus?
- Golgi body
- Golgi complex
- Golgi
How do vesicles transport materials within the Golgi apparatus in animal cells?
Vesicles transport materials between stacks in animal cells
What are the three overlapping functions of the Golgi apparatus?
The three overlapping functions of the Golgi apparatus are protein:
- secretion
- processing
- sorting
What is the plasma membrane in an animal cell?
A thin, flexible, and selectively permeable barrier that surrounds the animal cell.
What are the functions of the plasma membrane?
- transports molecules in & out of the cell with selective permeability
- cell signaling using membrane receptors to respond to external stimuli
- cell adhesion to other cells or the extracellular matrix to maintain cell structure & organization
What are ribosomes in an animal cell?
Responsible for synthesizing polypeptides, which are the building blocks of proteins
What are the primary differences between plant cells and animal cells?
Plant cells lack lysosomes & centrioles but have:
- large central vacuole & chloroplasts
- cell wall made of carbohydrate & protein
What is the function of the central vacuole in plant cells?
Storage and regulation of cell volume
What is the purpose of the cell wall in plant cells?
Provides support and protection for the cell
Does the size and shape of eukaryotic cells vary?
Yes, the size and shape of eukaryotic cells show great variation
Can cells with the same genome have different morphologies?
Yes, even cells that share the same genome can have very different morphologies
What largely determines the characteristics of a cell?
The proteome
How does a single organism produce different types of cells if the DNA is identical in each cell?
Cell differentiation
- even though the DNA is identical in each cell of an organism,
- different types of cells can be produced by expressing different sets of genes
- which leads to the production of different proteomes (protein populations)
How does the size of a cell affect its surface area-to-volume ratio?
As cells get larger, the SA to V ratio gets smaller
How does the surface area-to-volume ratio affect cell function?
- as SA to V ratio decreases
- cells struggle to import & export enough material
- which affects cell function
What is the surface area-to-volume ratio of a cell with a radius of 1 micrometer?
A cell with a radius of 1μm has a SA:V ratio of 3:1
What is the surface area-to-volume ratio of a cell with a radius of 100 micrometers?
A cell with a radius of 100μm has a SA:V ratio of 0.03:1
What is the cytosol?
Fluid region (subset) of the cytoplasm that is outside the cell organelles but inside the plasma membrane
What is the cytoplasm?
The cytoplasm includes everything inside the plasma membrane, excluding the nucleus, such as:
- cytosol
- endomembrane system
- semiautonomous organelles
What is molecular synthesis and breakdown?
Refer to the processes by which cells build and break down molecules, respectively.
What is cell metabolism?
The sum of all chemical reactions by cells
What is catabolism?
Process by which cells break down molecules into smaller components, usually releasing energy in the process
What is anabolism?
Process by which cells synthesise cellular molecules and macromolecules, usually requiring energy input
What is the central coordinating region for metabolic activities of eukaryotic cells?
The central coordinating region for metabolic activities of eukaryotic cells
What is the cytoskeleton?
A network of 3 types of protein filaments that provide structural support and shape to cells
(cell’s skeleton)
What are the 3 types of protein filaments in the cytoskeleton?
- microtubules
- intermediate filaments
- actin filaments
What are microtubules?
Microtubules are long, hollow cylindrical structures made of protein called tubulin
What is the function of microtubules?
Function in:
- maintenance of the shape of the cell
- organization of cell organelles
- intracellular movement of cargo
- cell motility via cilia & flagella
What are intermediate filaments and where are they not found?
A type of protein filament that is intermediate in size & form twisted, rope-like structures
- not found in plant cells
What is the function of intermediate filaments?
Function in:
- shape of the cell
- providing cells with mechanical strength
- anchorage of cell & nuclear membranes
What are actin filaments also known as?
Microfilaments
What is the function of actin filaments?
Function in:
- shape of the cell
- cell strength
- muscle contraction
- cell movement
- cytokinesis in animal cells
What are actin filaments?
Long, thin fibers made of protein called actin
What are cytoskeleton-associated motor proteins?
A group of proteins that interact with the cytoskeleton and use ATP as a source of energy for movement
What is the role of ATP in motor protein movement?
ATP serves as the source of energy for motor protein movement
What is an example of a motor protein?
Myosin
How do motor proteins (like myosin) move?
Move using their 3 domains:
- 1st: head is released from the filament it is bound to
- 2nd: head cocks forward and binds to the filament further forward than it was originally bound
- 3rd: head cocks backward, moving the tail of the motor protein forward
- this process is repeated for movement
How do motor proteins move along microtubules?
Motor proteins walk along microtubules from one end to the other
How do motor proteins cause filaments to move?
When the filament moves, the motor proteins are fixed in place and cause a filament to move
What happens when filaments bend and how do motor proteins contribute to this process?
When filaments bend, both the motor protein and the filaments are fixed in place so the actions of the motor proteins cause microtubules to bend instead.
What are the main differences between flagella and cilia?
- flagella are usually longer than cilia
- flagella present singly or in pairs, cilia covers all/part of cell surface
What is the structure of flagella and cilia?
Both have a 9+2 microtubule array structure
(slide 19)
How does movement occur in flagella and cilia?
- flagella move in whip-like motion
- cilia move by the propagation of a bend, beginning at the base and moving toward the tip.
What is the endomembrane system?
The endomembrane system is a network of membranes found in eukaryotic cells.
What are the different organelles of the endomembrane system?
The different organelles of the endomembrane system include:
- the nuclear envelope
- endoplasmic reticulum
- Golgi apparatus
- lysosomes
- vacuoles
- plasma membrane
How do different organelles of the endomembrane system communicate with each other?
Different organelles of the endomembrane system may be directly connected to each other or pass materials via vesicles.
What is the nuclear envelope?
The nuclear envelope is a double-membrane structure that encloses the nucleus of eukaryotic cells.
How is the outer membrane of the nuclear envelope connected to the endoplasmic reticulum membrane?
The outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum membrane.
(physically connected & have a similar structure)
What is the function of nuclear pores in the nuclear envelope?
Nuclear pores provide passageways for molecules to move in and out of the nucleus.
Are materials within the nucleus part of the endomembrane system?
No, materials within the nucleus are not part of the endomembrane system.
What are chromosomes?
Chromosomes are structures made up of DNA & proteins called chromatin. They carry genetic information in the form of genes.
What is chromatin?
Chromatin is the complex of DNA & proteins that makes up chromosomes.
What is the nuclear matrix?
The nuclear matrix is a filamentous network of proteins that provides structural support to the nucleus and organises the chromosomes.
What is the function of the nucleolus?
The nucleolus is involved in ribosome assembly, which is the process of making ribosomes, the cellular structures responsible for protein synthesis.
What is the ER lumen?
Internal space or cavity enclosed by the ER membrane to separate it from the cytoplasm.
What is the Rough Endoplasmic Reticulum (rough ER)?
The rough ER is studded with ribosomes and is involved in protein synthesis and sorting.
What is the Smooth Endoplasmic Reticulum (smooth ER)?
The smooth ER lacks ribosomes and is involved in:
- detoxification
- carbohydrate metabolism
- calcium balance
synthesis
- modification of lipids
What is the pathway of secreted proteins through the endomembrane system?
Secreted proteins move sequentially through organelles of the endomembrane system
Who conducted pulse-chase experiments to trace the path of radioactive proteins through the endomembrane system?
George Palade conducted pulse-chase experiments to trace the path of radioactive proteins through the endomembrane system.
Which cells did George Palade study to investigate the pathway of secreted proteins?
Pancreatic cells, whose primary function is protein secretion
What did the dark spots in TEM images reveal during George Palade’s experiments?
The dark spots in TEM images revealed the location of radioactive proteins.
What was the significance of George Palade’s experiments?
Provided the first evidence that secreted proteins are inserted into the rough ER and move through a series of compartments before secretion.
What are vacuoles?
Vacuoles are membrane-bound organelles found in eukaryotic cells.
How do the functions of vacuoles vary?
The functions of vacuoles are extremely varied and differ among cell types and environmental conditions.
What is the function of central vacuoles in plants?
The function of central vacuoles in plants is for storage and support.
What is the function of contractile vacuoles in protists?
The function of contractile vacuoles in protists is for expelling excess water.
What is the function of phagocytic vacuoles in protists and white blood cells?
The function of phagocytic vacuoles in protists and white blood cells is for degradation of materials.
What are peroxisomes?
Organelles found in eukaryotic cells that contain enzymes which catalyze certain reactions that break down molecules by removing H or adding O.
What is the byproduct of peroxisomal reactions?
The byproduct of peroxisomal reactions is hydrogen peroxide (H2O2)
What enzyme breaks down hydrogen peroxide in peroxisomes?
Catalase breaks down dangerous H2O2 into water and oxygen within peroxisomes.
What are semiautonomous organelles?
Organelles that are partially self-sufficient in terms of their reproduction and maintenance but still rely on the cell for some resources.
Which organelles are considered semiautonomous?
Mitochondria and chloroplasts
How do semiautonomous organelles reproduce?
By growing and dividing to form new organelles - still depend on the cell to produce material for synthesis of their internal components.
What is the main function of chloroplasts?
Photosynthesis
- Capture light energy and use some of that energy to synthesise organic molecules such as glucose
In what types of organisms are chloroplasts found?
In nearly all species of plants and algae
What is the basic structure of chloroplasts?
Chloroplasts have an outer & inner membrane, which surround the intermembrane space
What is the intermembrane?
A fluid-filled region containing the thylakoid membranes
Do chloroplasts and mitochondria contain their own DNA?
Yes, chloroplasts and mitochondria contain their own DNA, which is separate from the nuclear DNA of the cell.
How do chloroplasts and mitochondria reproduce?
Reproduce by binary fission
What is endosymbiosis?
Endosymbiosis is a theory that explains the origin of eukaryotic cells
What is the origin of mitochondria?
Mitochondria are believed to have originated from purple bacteria, which are a type of α-proteobacteria.
What is the origin of chloroplasts?
Chloroplasts are believed to have originated from cyanobacteria, which are photosynthetic blue-green bacteria.
What is protein sorting?
Proteins are sorted to their correct destination within a cell
What 2 mechanisms are used to sort proteins to different organelles?
- cotranslational sorting
- post-translational sorting
What is cotranslational sorting?
Proteins are destined for the:
- ER
- Golgi
- lysosomes
- vacuoles
- plasma membrane
- secreted proteins
When does sorting begin in cotranslational sorting?
Sorting begins in the cytosol during the early stages of protein production.
What is an ER signal sequence in cotranslational sorting?
A specific sequence of amino acids that serves as a signal for cotranslational sorting.
What is the first step in cotranslational sorting?
The first step is when the signal recognition particle (SRP) binds to the ER signal sequence of the protein being built.
What happens after the SRP binds to the ER signal sequence during cotranslational sorting?
The SRP then binds to an SRP receptor in the ER membrane, releasing the growing protein.
The protein moves through a channel in the ER membrane and is released into the ER lumen.
What is the second step in cotranslational sorting?
Vesicles bud from the ER membrane and fuse with the target membrane (e.g. Golgi apparatus) to deliver proteins to other organelles.
What is post-translational sorting?
For most proteins destined for the nucleus, mitochondria, chloroplasts, and peroxisomes are synthesised in the cytosol and taken up by the target organelle.
What is the matrix-targeting sequence?
(In post-translational sorting)
A short amino acid sequence at one end of a protein that directs the protein to its target organelle
How does a protein get taken up by its target organelle in post-translational sorting?
- matrix-targeting sequence of the protein binds to a receptor on the surface of the target organelle
- protein is then transferred to a channel in the target organelle’s membrane and released into the organelle
What are the characteristics of bacterial cells?
Have:
- cell wall
- plasma membrane
- sometimes flagella
- have ribosomes
- circular chromosome
but lack many organelles found in eukaryotic cells.
What are the characteristics of animal cells?
Have:
- no cell wall
- may have cilia or flagella present
- multiple linear chromosomes
- an endomembrane system
- mitochondria
and other organelles.
