Cytology Flashcards
Ch. 6
All cells have these four things:
- Plasma membrane
- Cytosol
- Chromosomes
- Ribosomes
Where is the DNA found in both eukaryots and prokaryots
Eukaryots = Nucleus
Prokaryots = Nucleoid
Name three differences between eukaryots and prokaryots
Eukaryots:
- Membrane-bound organelles
- DNA found in nucleus
- Cytosol found between plasma membrane and nucleus
Prokaryots
- No membrane-bound organelles
- DNA found in nucleoid
- Cytosol bound by plasma membrane
What is the corrolation between cell size and surface area
When the cell size increases, the surface area to volume ratio decreases and vice versa.
When the volume is increased, more nutrients are required and more waste is produced. If the surface area is decreased, there is a decrease in availible area for materials to flow through the plasma membrane, leading to slower transportation.
What is the nuclear envelope
- Envelope that encloses nucleus to separate from cytoplasm
- It is a double membrane, each layer has proteins and pores for passage
- The envelope membrane is continuous through the pore complexes
What is the function of nuclear pore complexes
Regulate entry and exits of substances coming in and out of the nucleus
What is the nuclear lamina
- Lines the inside of inner nuclear membrane
- Comprised of protein filaments
- Maintains nuclear shape and supports nuclear envelope
- May help organize nuclear material
What is the nuclear matrix
- Protein fibers extending through the nuclear interior
- May help organize genetic material
How many DNA molecules are in a non-replicated chromosome
1
What is chromatin
DNA-protein complex made from histones
What is the nucleolus
- Found in center of nucleus
- Produces and assembles ribosome subunits and rRNA
Are ribosomes membrane-bound
NO
This is why they can be found in prokaryots
What is a ribosome
rRNA-protein complex that carries out protein synthesis
What role fo ribosomes play in carrying out genetic instructions
Concept Check 6.3 - 1
Ribosomes in the cytoplasme translate the genetic message, translated from DNA in the nucleus by mRNA, into a polypeptide chain
Describe the molecular composition of nucleoli and their function
Concept Check 6.3 - 2
Nucleoli consist of DNA and the ribosomal RNAs made according to its instructions, as well as proteins imported from the cytoplasm. Together the rRNAs and the proteins are assembled into ribosomal subunits.
What are the function of the endomembrane system
- Protein synthesis and transport
- Metabolism
- Lipid movement and detox
How is the membrane of the endomembrane system related
- Through direct physical continuity
- Through transfer of membrane segments
What is the endoplasmic reticulum
- Network of membranous tubules (cisternae) where proteins are synthesised and transported [to golgi]
What is the ER lumen
The internal ER compartments / inside cisternae space
What are the four functions of the smooth endoplasmic reticulum
- Lipid synthesis
- Detoxification
- Storage of Ca 2+
- Carb metabolism
Describe the process of protein synthesis in the rough ER
As a polypeptide chain grows from the bound ribosomes, the chain is threaded into the ER lumen through protein-complex pores in the ER membrane. Polypeptides fold into functional shapes as they enter the ER lumen.
What are transport vesicles
Membranous vehicules in transport from one part of a cell to another
What is the golgi apparatus
Warehouse of the cell for:
- receiving
- manufacturing
- sorting
- shipping macromolecuels to other destinations in the cell
Comprised of flattened membrane sacs (cristae) in trans and cis directions
(cis = close to ER, trans = where vesicles pinch off and travel elsewhere)
Which molecules are actually made in the golgi apparatus of plant cells
Pectins and other non-cellulose polysaccharides
What are lysosomes
- Membranous sacs of hydrolytic enzymes
- Used to digest macromolecules
Where are lysosomes made
The rough ER and processed at golgi
What are the two ways in which lysosomes digest substances and desribe the process
- Autophagy = lysosomes fuse with vesicles containing damaged organelles to allow the lysosome hydrolytic enzymes to digest the organelle components
- Phagocytosis = lysosomes fuse with food vacuoles to allow the lysosome hydrolytic enzymes to digest food particles
What are vacuoles
- Large vesicles from the ER / GA
- transport solutes
What are the three main types of vacuoles
- Food vacuoles
- Contractile vacuoles = pump out excess water (protists
- Central vacuoles = absorb water to increase cell sise without making new cytoplasm (plants)
What is the mitochondrion
- Site of cellular respiration
- Double-membrane structure with unique embedded proteins (inner membrane convoluted with folds (cristae)). This divided the mitochondrion into two parts: internal membrane space and mitochondrial matrix
Of what is the mitochondrial matrix made
Enzymes, mitochondrial DNA, ribosomes
What is the chloroplast
Site of photosynthesis in plant cells that contain green pigments (chlorophyll) that is separated by two separate membranes
What is a thylakoid
Flattened interconnected sacs of membrane in the chloroplast
What is a granum
Stacks of thylakoids in the chloroplast
What is the stroma
Fluid outside the thylakoids, containing choroplast DNA, ribosomes, and enzymes
What are peroxisomes
Single-membrane metabolic compartments that convert dangerous hydrogen atoms from a substance.
The H2 is transferred to O2 which forms H2O2 that eventually becomes H2O. This happens during detox in liver a lot
What is a glycosomes
Fat-storing tissue that contains enzymes to initiate conversion of fatty acids to saccharides
Describe two characteristics shared by mitochondria and chloroplasts
Concept Check 6.5 - 3
Mitochondria and chloroplast are not derived from the ER, nor are they connected physically or via transport vesicles to organelles of the endomembrane system. They are both double-membrane structures, which is uncommon in endomembrane system
What is the cytoskeleton
- A network of fibers in the cytoplasme that forms a support structure for the cell and anchorage for organelles
- Helps create folds in plasma membrane to produce vacuoles and is involved in mechanical cell movements with help from motor proteins
Describe microtubules in terms of structure, location, and function
- They are hollow and comprized of 9 tubulin dimers
- They help with cell motility, shape maintenance, and chromosome movement (spindle fibers)
Ex. of function - Guide vesicles from ER to golgi and from golgi to plasma membrane
Describe microfilaments in terms of structure, location, and function
- Two twisted strands of actin
- Helps with cell motility, muscle contractions, shape maintenance
Ex. of function - Bear tension and support cell when stretched / contracted
Describe intermediate filaments in terms of structure, location, and function
- Proteins (eg. collagen, keratin, etc.) coiled in cables
- Helps with shape maintenance, organization, anchorage, formation of nuclear lamina
Ex. of formation - formation of nuclear lamina
True or false:
Organelles must be equipped with motor proteins to be moved along the cytoskeleton
True
What is a centrisome
- Site of microtubule growth
- One centrisome is a pair of two centrioles
One centriole is comprised of 9 sets of 3 microtubules in a ring
Describe cilia in terms of structure, location, and function
- Cilia are comprised of microtubules outside of the cell
- They are short and “beat” to cause movements of the cell / substances in the extracellular environment
Describe flagella in terms of structure, location, and function
- They are microtubule-containing extenstions outside of the cell
- They are long and thin and “whip” outside the cell to move the cell
What is the basal body
The anchorage for cilia and flagella
What are dyneins
Motor protein “arms” that move and connect neighboring doublet microtubules (α-tubulin & ß-tubulin) in cilia and flagella
ATP hydrolysis drives changes in dynein shape that lead to movements of cilia and flagella
What is a cell wall
- An extracellular structure of plant cells that protects, maintains shape, and prevents excessive uptake of water in plant cells
- Made of cellulose (microfibriles) that are embedded in a matrix of proteins and polysaccharides
What are the three components of a cell wall and what are their functions
- Primary cell wall = thin flexible wall on the outside
- Middle lamella = layer of pectins (polysaccharides) between cell walls of adjacent cells
- Secondary cell wall = thick, sturdy cell wall on the inside that acts as structure
What is the extracellular matrix
Comprised of proteins, proteoglycans and carb-containing molecules (eg. collagen, elastin, etc.)
Describe a proteoglycan complex
Hundreds of proteoglycans noncovelently bonded to a single polysaccharide
What are integrins
Membrane proteins with two subunits bind to extracellular matrix on the outside. Associated proteins attached microfilaments on the inside of the cell.
They can transmit signals between the extracellular matrix and the cytoskeleton
What are plasmodesmata
Pathways of cytosol that join the internal chemical environment of adjacent plant cells
Connected between plasma membrane (not plant walls)
What are tight junctions
When cells are pressed together, they are bound and sealed with proteins to form barriers to prevent leakage of liquids between cells through passages
What are desmosome
When cells are attached, desmosomes are formed by protein plaques in the cell membrane, linked by filaments (eg. keratin)
What are gap junctions
Similar to plasmodesmata in that they act as pathways between cells. They are, however, made from proteins, rather than membrane (in plasmodesmata).
Describe the structural and functional differences between the rough and smooth ER
Concept Check 6.4 - 1.
The rough ER is bound by ribosomes while the smooth ER is not. Both types of ER make phospholipids, but membrane proteins and secretory proteins are made by the ribosomes on the rough ER. The smooth ER also functions in detoxification, storage of Calcium ions, and carbohydrate metabolism
Describe how transport vesicles integrate the endomembrane system
Concept Check 6.4 - 2.
Transport vesicles move membrane and the substances they enclose between other components of the endomembrane system
If one centriole is comprised of nine three-microtubule groups, how many microtubules are in a centrisome
54
1 centriole has 27 microtubule and there are 2 centrioles per centrisome
Describe how cilia and flagella bend
Concept Check 6.6 - 1.
Dynein arms, powered by ATP, move neighbouring doublets of microtubules relative to each other. Because they are anchored within the flagellum or cilium and with respect to one another, the doublets bend instead of sliding past each other. Synchronized bending of the nine microtubule doublets brings about bending of both ciliad and flagella
Define gene expression
The process by which information encoded in DNA directs the synthesis of proteins or, in some cases, RNAs that are not translated into proteins and instead function as RNAs
