Chapter 4 - Cell structure Flashcards
Hierarchy from cells to organism
Cells to tissues to organs to organ systems to organisms
Prokaryotic cell size range
.1 - 5 micrometers
Eukaryotic cell size range
10 - 100 micrometers
In order to look at cells in a microscope what must happen?
They must be stained since they are transparent, the staining process kills them
Oil immersion allows lenses to magnify to what power?
1000x
How are electron microscopes different than regular microscopes?
They use a beam of electrons rather than light, this allows for higher magnification providing great detail. This is because electrons have a very short wavelength while photons are much longer.
What is the difference between a scanning electron microscope and a transmission electron microscope?
Scanning electron microscope visualizes surface characteristics, while a transmission electron microscope penetrates the cell surface to study internal structure
Who coined the term cell for box like structures they observed in cork?
Robert Hooke
Who observed bacteria and protozoa(paramecium) in the 1670s
Anton Van Leeuwenhoek
Plants have cell walls while animals have…
Cell membranes
Who proposed the unified cell theory in the 1830s?
Matthias schleiden, and Theodor Schwann
What are the 3 things listed by the unified cell theory?
1) all living things are composed of one or more cells
2) the cell is the basic unit of life
3) new cells arise from prexisting cells
Prokaryotic cells are mostly what?
Bacteria
What are the 4 common features of all cells? (eukaryotic and prokaryotic)
1) plasma membrane (protective covering that separates the cells external from internal environment)
2) cytoplasm (includes a cells interior components suspended in a jelly like substance called Cytosol)
3) DNA (genetic material which dictates inheritance and controls metabolism)
4) ribosomes (synthesize proteins)
Are viruses or prions considered living? If so which ones, or are both?
None of them are
Most distinctly what do prokaryotic cells lack that eukaryotic cells have?
First they are unicellular instead of multicellular, they lack a membrane bound nucleus and membrane bound organelle’s
Where is prokaryotic DNA found in a cell?
The nucleoid region
What type of cell walls can bacteria have?
They have a peptidoglycan cell wall that is either gram positive or gram negative
It is a protective layer that helps maintain a specific shape, and prevents them from dehydration
How can you tell if a bacteria is gram positive or gram negative?
By a process called a gram staining process, if it is blue it is positive, if red it is negative
Many bacteria have capsules which allows them to attach to surfaces, what is the capsule made out of?
Polysaccharides
Some bacteria’s have a structure to help them move (locomotion). What is the structure called?
Flagellum
what does a pili allow to happen in bacteria?
Exchange of DNA in a process called bacterial transformation
What does fimbriae allow bacteria to do?
Attach to other cells
The small cell size of prokaryotic cells allows for what in terms of getting things in and out of the cell?
It allows ions, organic molecules, and waste products to diffuse quickly though the cells interior
Different from eukaryotic cells which have a much more sophisticated way of transportation
Why is it an advantage size wise for cells to be small? In terms of volume and radius?
Smaller spheres have a much larger surface area to volume than large spheres
Multiple foldings of a plasma membrane allows what?
An increase in surface area
This is how a lot of eukaryotic cells have adapted allowing them to become larger
Form follows
Function
What does organelle literally mean?
Little organ
What are the 2 forms DNA takes?
Chromatin is the unwound form, and chromosomes are the condensed form
What does the plasma membrane seperate?
The internal from the external environment of the cell
You can identify the cell on the plasma membrane by what molecules?
The glycoproteins
What type of bilayer does the plasma membrane have, and what is embedded in them?
It has a phospholipid bilayer with proteins embedded in them
How does water get into a plasma membrane?
Through small channels call aquaporins
What can and can’t go straight through a plasma membrane? Ions, oxygen, carbon dioxide, organic molecules, ammonia
Ions, oxygen, and carbon dioxide can go right through. Organic molecules and ammonia can’t go straight through.
Plasma membranes may fold into microvili like in the small intestine, what does this increase?
Surface area!
What is the region between the plasma membrane and the nucleus?
The cytoplasm
What gel like material does the cytoplasm contain?
Cytosol
Other than Cytosol what else does the cytoplasm contain?
A cytoskeleton and organelles suspended in the Cytosol, and many dissolved molecules and ions including many types of proteins
How much of the cytoplasm is water?
70-80%
What is the most prominent organelle in a eukaryotic cell?
The nucleus
What does the nucleus house?
DNA, which is responsible for reproduction and directing the cells production of proteins and ribosomes
What is the membrane for the nucleus called?
The nuclear envelope
What area of the nuclear envelope controls the passage of ions, and other molecules?
The pores
What is the nucleoplasm?
A semi solid fluid inside the nucleus that contains the chromatin (DNA) and the nucleolus
What holds the strands of DNA together?
Histone proteins
What are the differences in chromosomes from eukaryotic and prokaryotic organisms?
Prokaryotes have a single circular chromosome, while eukaryotes have two or more linear chromosomes
What are non reproductive cells called?
Somatic cells
When are chromosomes visible?
When the cell is dividing
When cells are in their growth and maintenance stage the chromosomes are what?
They are unwound
What are unwound chromosomes complexes called?
Chromatin
Why are chromosomes unwound into chromatin?
To make it easy to access the genes
What are condensed chromatin called?
Chromosomes
What are the dark areas within the nucleus?
The nucleolus
What are the main things that the nucleolus contains?
Ribosmal RNA, with associated proteins
rRNA and associated proteins make what once outside of the nucleus?
Ribosmal subunits
Ribosmal subunits assemble once outside where?
The nucleus
Where are proteins made?
In ribosomes
Where are ribosomes found? (A few places)
They can float freely in the cytoplasm, may be attached to the plasma membranes inner surface, or attached to the endoplasmic reticulum (RER)
What organelle are large proteins and RNA complexes?
Ribosomes
Ribosomes consist of what subunits?
Two sub units small and large)
What, how, and where do ribosomes receive instruction?
They receive instructions for protein synthesis from the nucleus in the form of the nucleotide sequence carried by messenger RNA (mRNA)
How does DNA get the sequence to mRNA?
The DNA in the nucleus transcribes the nucleotide sequence of the gene into the nucleotide sequence of the mRNA
What is the ribosomes job once it gets the mRNA?
It translates the nucleotide sequence of the gene (base pair sequence) into a specific order of amino acids of the specific protein being made
What is the master biomolecule of metabolism?
Proteins
Name some things that are made out of proteins? (List a few)
Enzymes
Antibodies
Pigments
Structural components
Surface receptors
Ect…
Ribosomes are more abundant in cell types that produce large amounts of what?
Proteins, e.g. the pancreas
What is the main thing that mitochondria produces?
ATP (adenosine triphosphate) which is the energy currency of cells
How long does ATP last? Long, medium, or short? And when is it made?
ATP is only made when it is needed, it is a short-term energy molecule
What is the main component used to make ATP?
Glucose
What is the name for the chemical process for producing ATP?
Cellular respiration (oxidative metabolism)
Along with glucose what other molecules are essential in cellular respiration, and what is the byproduct?
Oxygen (O2) is essential, CO2 is also a waste product of the reaction
What type of cells would have the highest concentration of mitochondria?
Muscle cells
Mitochondria have what special molecules their self’s that not many other organelles have?
DNA and ribosomes
Inside the mitochondrial membranes what macromolecule is mostly imbedded?
Proteins
The inner membrane of the mitochondria is folded into what? And what is the area inside the inner membrane?
Cristae is the foldings, while the area inside the inner membrane is called the matrix
Are Peroxisomes single or double membranes?
Single
Name the main functions of Peroxisomes
-Oxidize fatty acids and amino acids (break them down
-Have a detoxifying function (e.g. liver cells have an abundance of Peroxisomes)
When Peroxisomes undergo processes what is produced?
Hydrogen peroxide (H2O2) which is toxic to cells
Enzymes in Peroxisomes break down hydrogen peroxide into what?
Water and oxygen
What are glyoxysomes?
They are plant organelles that convert fatty acids into sugars, they also play many roles in metabolism and defend against pathogen’s
What is the main function of vesicles? And what are they made of?
They are made of membrane sacs, they function primarily for transporting materials in cells and can fuse with plasma membrane as well as other membranes in the cell
What are vacuoles and what are they made out of?
They are also made of membrane sacs, and are large plant cells, and some protozoans and store water along with enzymes that digest macromolecules. But their main function is storage (usually of water)
-some animal cells have vacuoles
-vacuoles do not fuse with other membranes like vesicles do
In both plants and animal cells they have a complex network protein fibers within their cytoplasm that does what for cells?
Holds the cells shape, acts as transport conduits, holds organelles in place, and enables some cells to move
Both plant and animal cells have small structures that build and breakdown the protein fiber network, what are they called?
Microtubule organizing centers (MTOC)
Animal cells have centrioles located within a MTOC called what?
A centrosome, some plant cells have centrosomes but not all
Centrosomes have what compositions? And what are they?
They are MTOCs made of proteins not bound by a membrane and found near the nucleus
What are centrioles?
Pairs of barrel shaped structures made of the protein tubulin of nine microtubule triplets
-found only in animal cells
When do centrosomes duplicate?
Before cell division
What are centrosomes responsible for?
All microtubules organization throughout the cell
What happens if cells have their centromeres removed before cell division?
Cells can still divide
What do lysosomes contain?
Numerous types of digestive enzymes which function at very low pH
What do lysosomes break down?
Proteins, polysaccharides, lipids, nucleic acids, and worn out organelles
Do plant or animal cells have lysosomes? And instead what does the other have?
Animal cells have lysosomes, while plant cells have digestive enzymes in there vacuoles
Where are cell walls seen?
Plant cells, prokaryotes, fungal, and some protistans
Not in animal cells
What is the cell wall external to?
The plasma membrane
What is the function of the cell wall?
To protect the cell, provide support? And give the cells their shape
Prokaryotic cell walls are composed of what
peptidoglycan
Plant cell walls are composed of what?
Cellulose (a polysaccharide of glucose monomers bonded by beta 1-4 linkages)
What are chloroplasts composition? What takes place here?
Chloroplasts are large double membraned organelles where photosynthesis takes place
Like mitochondira, chloroplasts have their own…
Genome, and ribosomes
What components does photosynthesis need?
It uses CO2, H2O, and light energy to produce glucose and oxygen
Photosynthetic organisms are autographs. What does this mean?
They can feed themselves by making glucose and then using it in their mitochondria to make ATP for energy
Animals are heterographs, meaning what?
Feed on others
In chloroplasts the space enclosed by the inner membrane is what? And what does it contain?
The stroma, and it contains fluid filled stacks of membrane disks called thylakoids, stacks of thylakoids are called grana
What are chlorophylls?
They are the green pigments found on thylakoid membranes and capture light. This is why chloroplasts are green.
Photosynthetic protists and photosynthetic bacteria have a difference in possessing chloroplasts. What is the difference?
Photosynthetic protists contain chloroplasts while photosynthetic bacteria (Cyanobacteria) do not contain chloroplasts
The central vacuole main functions?
Maintains water and rigidity, playing a role in cell expansion
The endomembrane system and proteins is what? What do they do?
A group of membranes and organelles that work together to modify, package, and transport proteins, and lipids
What organelles or structures does the endomembrane system and proteins include?
Nuclear envelope, lysosomes, vesicles, endoplasmic reticulum, Golgi apparatus, and the plasma membrane
Does NOT include the mitochondria and chloroplasts
What is the ER? And what does it do?
It is a series of interconnected membrane sacs and tubules that modifies proteins and synthesizes lipids
What does the rough ER mainly do vs the smooth ER?
Rough ER modifies proteins, smooth ER synthesizes lipids
What is the internal hollow space of the ER called?
The lumen or cristernal space
The ER membrane is what?
A phospholipid bilayer embedded with proteins
What is the ER continuous with?
The nuclear envelope
what is on rough ER that is not on smooth ER (or has very few). Where are they attached?
Ribosomes that are attached to its cytoplasmic surface
Where do ribosomes transfer their newly synthesized proteins?
Into the lumen of the rough ER where they undergo structural modifications such as folding
Proteins that are made and are in the rough ER go where?
They can either be incorporated into the cells structure and functions, or it can be secreted from the cell
E.g. enzymes or hormones
What type of lipid does the rough ER synthesize?
Phospholipids
What happens to the Proteins not intended for use in the rough ER?
They are packaged into transport vesicles which bud off from the ends of RERs membranes
RER are more abundant in cells that produce many what?
Proteins, e.g. liver and glands
What are all the functions of smooth ER?
-Synthesis of carbohydrates, lipids including steroid hormones
-detoxification of medication and poisons
-calcium storage (e.g. sarcoplasmic reticulum in muscle cells)
Vesicles that bud off from the RER are moved where?
The Golgi apparatus
What does the Golgi apparatus do to vesicles it receives?
It is stored, tagged, packaged, and distributed
The Golgi is basically a packaging plant
What is the Golgi apparatus made of?
A series of flattened membranes
The Golgi apparatus has a cis and trans face meaning what?
The cis face is incoming and the trans face is outgoing
List the entire process once a vesicle is transported to the Golgi apparatus to when it leaves (be as specific as possible and get all the steps).
Moved first to the cis face and empties their contents into the lumen of the Golgi’s lumen, as the proteins or lipids are moved through the Golgi apparatus they may have short sugar molecules added to them, and are often tagged with phosphate or other small molecules. The modified and tagged molecules are packaged into secretory vesicles that bud off the trans face of the Golgi, some of which move back into the cell while others move to the plasma membrane for export
Salivary glands and cells of the immune system have an abundance of what organelle?
Golgi
Golgi in plant cells also synthesize what for the cell wall?
Polysaccharides
What do lysosomes do?
They function as digestive organelles and recyclers
How do lysosomes act as immune cells?
They kill pathogens that may enter the cell through phagocytosis or endocytosis
What is phagocytosis and endocytosis in terms of killing pathogens?
Phagocytosis is engulfing a pathogen while endocytosis involved folding of the cells membrane around the pathogen, then the lysosomes with hydrolysis enzymes fusses with the vesicles emptying the enzymes into it destroying the pathogen
What is the cytoskeleton? What are its functions?
It is a network of protein fibers that help maintain the cells shape, secures some organelles in place, facilitates the movement of vesicles and the cytoplasm, and enables some cells to move
What are the 3 types of fibers that make up the cytoskeleton?
Microfilaments, microtubules, and intermediate filaments
Microfilaments composition
Made up of two intertwined strands of actin protein and are also known as actin filaments (which are composed of globular subunits)
Microfilaments function
Cellular movement by acting as a track for the movement of myosin (a motor protein)
What are some examples of important cellular movements that microfilaments help control
Cell division, cytoplasmic streaming, and animal muscle contraction
Intermediate filaments are composed of what?
Fibrous protein strands wound together
What do intermediate filaments do?
Play a part in structural holding of the cells shape and anchoring organelles like the nucleus in place (acts as a scaffolding)
E.g. keratin
Microtubules composition
Made of hollow tubes of alpha-tubulin and beta-tubulin (globular proteins)
How do the microtubules function? What do they do?
They provide a track on which vesicles move through the cell and pull replicated chromosomes to the opposite ends of the cell, they disassemble and reform quickly m
-Microtubules form flagella, cilia, and centrioles
What is the biggest and smallest component of the cytoskeleton in terms of diameter?
Microtubules are the widest while microfilaments are the thinnest
What is the main thing flagella and cilia both function to do?
Aid movement
What are flagella and what features do they have?
They are long hair structures that extend from the plasma membrane and allow the entire cell to move
E.g. sperm
-very few cells have more than one flagella
What are cilia’s features? And what is their function?
They are short, hairlike structures that extend from the plasma membrane and occur along the entire surface of the cell and allow for the movement of entire cells or move substances along the cells surface
E.g. the trachea and fallopian tubes
Both flagella and cilia are composed of what?
Microtubules in a 9 + 2 array that has a ring of nine microtubules surround a single microtubule dublet in the center
In animals the extracellular matrix (ECM) which are the materials produced in the outside of cells is composed primarily of what?
Collagen, and proteoglycans attached to integral proteins via fibronectin
What does the ECM do?
It holds cells together forming tissues and produces protein receptors
E.g. hormone attachment
When a receptor molecule of the ECM gets triggered what happens?
It changes the microfilaments conformation just inside the cell inducing chemical signals that turn on or off genes thus activating specific actions of the cell
How does receptor signals work in the example of damage to endothelial cells lining blood vessels?
Th chemical signal initiated changes the ECM which causes platelets to adhere, smooth muscles in the blood vessels to contract, and the production of clotting factors
What are plasmodesmata? What type of cells are they found in?
Found in plant cells
They act as channels between adjacent plant cells cell walls allowing for movement of nutrients from one cells cytoplasm to another cells cytoplasm in plant vascular tissue (phloem)
Do tight junctions allow for passage between cells? Where are tight junctions found?
No, they are a watertight seal between adjacent animal cells
How come tight junctions act as a seal?
Because proteins hold the cells tightly against each other and do not allow passage of materials between cells through the extracellular space
-common in epithelial cells for example holding cells of the urinary bladder epithelium together
Do desomsomes or gap junctions allow for the passage of materials or molecules?
They both do
What do desmosomes do?
They allow adjacent cells to be held together with some stretch possible such as in the skin, heart, and muscle cells. They are like spot welds holding adjacent animal cells together
What are Cadherins?
They are short structural transmembrane glycoproteins that hold plaques with keratin together
What do gap junctions do? And what are they?
They are channels between adjacent cells that allow for transport of ions, nutrients, and other substances
What are gap junctions composed of?
Six connexin proteins
E.g. cardiac muscle
