UNIT 2 - A 2.2 - Cell Structure Flashcards
What is cytology?
the branch of biology that studies all aspects of the cell
how many micrometers are in a millimeter?
1000
How many nanometers are in a millimeter?
1 000 000
How many nanometers are in a micrometer?
1000
what do microscopes need in order to observe cells and especially their subunits?
high magnification and resolution
What is magnification ?
the increase in an object’s image size compared to its actual size
What is resolution?
the minimal distance between two points/objects at which they can still be distinguished as two
What happens when the resolution of a microscope increases?
the microscope will reveal greater detail
How do light microscopes form an image?
they use light which passes through the specimens
What are stains used for in a light microscope?
to improve the visibility of structures
What do electron microscopes (EMs) use to create an image?
electrons passing through a specimen
What is the order (from largest to smallest) of cells/subunits?
cells, bacteria, viruses, membranes, molecules
What is the field of view/vision?
total area visible when looking through a microscope’s ocular/eyepiece
What are the two general types of micrometers?
ocular and stage
where is the graticule (ocular micrometer) located?
in the eyepiece
How are the units on the graticule calibrated?
using a stage micrometer
How can the size of the image being examined under a microscope be determined?
By comparing the units of the graticule to the know unit size of the stage micrometer
What is the formula to calculate magnification?
measured size of image/actual size of specimen
What benefits do electron microscopes have over light microscopes?
Because electrons have much shorter wave lengths, the EM has a 1000x greater resolving power than a light microscope and the ability to magnify objects over 500000x
What are the two general types of EMs?
scanning electron microscope (SEM) and transmission electron microscope (TEM)
How do SEMs work?
They use a beam of electrons to scan the surface of a specimen
How do TEMs work?
They aim a beam of electrons through a very thin section of specimen which allows its inner structure to be viewed
What are two techniques used when working with an EM?
freeze fracture and cryogenic electron microscopy
What is freeze fracture?
The process of preparing a sample for observation with an EM, involves rapid freezing of specimen, then breaking the specimen apart
What is enabled with the use of cryogenic electron microscopy?
an image to be formed using computers showing the 3D framework of proteins involved with the function of a cell
What are some examples of how our knowledge has been enhanced using cryogenic electron microscopy?
virus composition and structure, cell membrane components and their arrangement, cellular protein synthesis, hereditary expression and regulation
What are the cons of electron microscopes?
They are expensive, require extensive training to operate, and require non-living specimens
What are two preparation techniques developed recently for the study of cells using light microscopy?
fluorescent stains and immunofluorescence
What are fluorescent stains?
substances/dyes that combine with specific cellular components
Why are fluorescent stains used?
They are accepted by certain parts of the specimen after being exposed to UV light and those parts start to fluoresce and assorted colours are produced, allowing for more detailed visibility
What does immunofluorescence allow?
greater visibility of living tissue
How does immunofluorescence work?
because it involves antibodies already combined with dyes, specific antibodies combined with unique coloured dyes recognize and combine with target molecules
What is the technique of immunofluorescence often used for?
Detecting viral proteins that have infected cells
What is the condenser on a light microscope?
Located between the stage and the light source, it has a lens that directs light rays from the light source through the specimen
What is a brightfield microscope?
it uses visible light so the specimen is viewed against a light background
What is a darkfield microscope?
An opaque lens is used in the condenser which blocks direct light, specimen is viewed against a dark background
What is a phase-contrast microscope?
A special condenser is used to show detailed images of a specimen without staining
What structures do all cells contain?
DNA as genetic material, cytoplasm composed of mainly water, plasma membrane composed of lipids surrounding the cytoplasm
What is a cell’s means of storing and transferring information?
DNA
What allows the production of the exact proteins needed for passing distinctive characteristics from cell-cell and organism-organism?
The four different nucleotides making up DNA and their sequences as well as their ability to form big chains
What sort of role do enzymes serve in chemical reactions?
Controlling
What controls the production of enzymes?
DNA
Where is cytoplasm found?
WIthin the boudary of a cell
What is cytosol?
Matrix composed mainly of water which is located in cytoplasm
What does cytosol contain?
Everything necessary for a cell to conduct its day-to-day activities: includes different carbon compounds, ions and other inorganic molecules
Where do most chemical reactions within a cell take place?
Within the cytoplasm
What is the major component of the plasma membrane surrounding a cell?
two layers of lipids combined as a bilayer
What does the membrane of a cell control the interactions between?
a cell’s contents and the exterior
What do membrane proteins provide?
identity properties to the cell
What is the diameter of most prokaryotic cells?
less than 1 micrometre
What are two examples of prokaryotic organisms?
bacteria and archaea
What are different factors differentiating prokaryotes?
nutritional requirements, sources of energy, chemical composition and morphology (shape)
What are the features of a prokaryotic cell?
cell wall, plasma membrane, flagella, pili, ribosomes, nucleoid
What does the cell wall of a prokaryotic cell do?
protects and maintains shape, keeps bacterial cell from rupturing when water pressure is greater inside than outside
What is the cell wall of a prokaryote made from?
peptidoglycan
What is peptidoglycan?
a carbohydrate-protein complex
What is the capsule on some prokaryotes?
and additional layer of a type of polysaccharide
What does the capsule do?
makes it possible for some bacteria to adhere to structures such as teeth, skin, and food
What is one major way to classify bacteria?
by their ability to retain a dye called crystal violet
What happens to the cell wall of a “Gram-positive” bacteria when it is exposed to crystal violet?
it takes a violet/blue appearance
What’s the difference between “Gram-positive” and “Gram-negative” bacteria?
“Gram-negative” bacteria don’t retain crystal violet and don’t appear blue/violet when exposed to the dye
What are two examples of Gram-positive bacteria?
Bacillus and Staphylococcus
What are pili?
The hair-like growths on the outside of some bacteria cell walls
What are the functions of pili?
attatchment and sexual reproduction
What is the pili’s function in sexual reproduction?
joining bacterial cells in preparation for the transfer of DNA from one cell to another
What does a prokaryote’s flagella/flagellum do?
Allow a cell to move
Where is the flagellum anchored?
to the cell wall and plasma membrane
Why are there no specialized areas within the cytoplasm of a prokaryote?
Because there are no internal membranes
Where do all cellular processes within a prokaryotic cell occur?
Within the cytoplasm
What are the two subunits of making up ribosomes?
a protein and ribosomal RNA
What does the nucleoid region of a bacterial cell contain?
a single, long, continuous, circular thread of DNA (the bacterial chromosome)
Why are bacterial chromosomes described as naked loops?
Because the DNA of a prokaryotic cell is not associated with histones
What is the nucleoid region of a prokaryotic cell involved with?
cell control and reproduction
What are plasmids?
small, circular, DNA molecules contained in prokaryotes
Though it is not required under normal conditions, what can plasmids help a prokaryotic cell to do?
adapt to unusual circumstances
How do prokaryotic cells divide?
binary fission
What occurs during the process of binary fission?
the DNA is copied, resulting in two daughter chromosomes which become attached to different regions on the plasma membrane and the cell divides into two genetically identical daughter cells
What does binary fission include the use of specialized fibres for?
lengthening of the cell and the newly produced DNA dividing into parts
What do eukaryotic cells occur in?
organisms such as algae, protozoa, fungi, plants, and animals
What are organelles?
non-cellular structures that carry out specific functions
What do organelles allow for in eukaryotic cells which is not a characteristic of prokaryotic cells?
compartmentalization
What does compartmentalization do?
Enables different chemical reactions to be separated and allows chemicals for specific reactions to be isolated which results in increased efficiency
When is compartmentalization especially important?
When adjacent chemical reactions are incompatible
Where does cytoplasm occur?
inside the plasma membrane and outside the nucleus of all eukaryotic cells
What is the fluid portion of the cytoplasm around the organelles called?
Cytosol
What is a cytoskeleton?
small fibres and rods within eukaryotic cytoplasm
What does the cytoskeleton create?
A complex internal structure
What is the difference between eukaryotic and prokaryotic cytoplasm?
Prokaryotic cytoplasm does not have a cytoskeleton
What is the cytoskeleton made of?
protein
What are the functions of the cytoskeleton?
maintaining cell shape, anchoring some organelles, helping cellular movements, providing a means for some organelles to move within the cell
Which fibres do cytoskeletons contain?
actin filaments, intermediate filaments, and microtubules
How can a eukaryotic cell respond to changes in both internal and external environments?
The fibres of the cytoskeleton can rearrange their protein components
What are actin filaments also called?
microfilaments
What do microfilaments function in?
cell division and cell movement, especially involving contractions in muscle cells
What do intermediate filaments do?
reinforce cell shape, anchor some organelles and function as movement paths throught the cell for some organelles
Where are intermediate filaments found?
Most animal cells
What is the endoplasmic reticulum?
a network of tubulus/channels extending from the nucleus to the plasma membrane
What is the function of the endoplasmic reticulum?
To transport materials throughout the inside of the cell
What is the main difference between smooth ER and rough ER?
smooth ER does not have any ribosomes on its surface, rough ER does
What are the functions of smooth ER?
production of membrane phospholipids and cellular lipids, production of sex hormones, detoxification of drugs in the liver, storage of calcium ions in muscle cells, transportation of lipid-based compounds, helping the liver to release glucose into the bloodstream when needed
What does the rough ER engage in?
Protein development and transportation
What may the proteins synthesized on the rough ER become?
Parts of the membrane, enzymes, or messengers between cells
Which type of ER is closer to the nuclear membrane?
rough ER
Where may ribosomes be found?
Free within the cytoplasm or attached to the rough ER
What are ribosomes always composed of?
a type of RNA and protein
What do the two subunits of ribosomes in prokaryotic cells equal?
70S
What do the two subunits of ribosomes in eukaryotic cells equal?
80S
What are lysosomes?
intracellular digestive centres which are vesicles (sacs)
What are lysosomes bounded by?
a single membrane that contains as many as 40 different enzymes
Why do lysosomes fuse with old/damaged organelles?
to break them down so that recycling of the components may occur
What is phagocytosis?
a type of endocytosis, a means by which material can enter a cell
Why is the interior environment of a functioning lysosome acidic?
Because acidic conditions are necessary for enzymes to hydrolyse large molecules
What does the golgi apparatus consist of?
flattened sacs called cisternae, which are stacked one on top of another
What does the golgi apparatus function in?
collection, packaging, modification, and distribution of materials synthesized in the cell
Where is the cis side of the golgi apparatus?
The side close to the rough ER
What does the cis side of the golgi apparatus receive?
products from the rough ER
Where do the products received from the ER to the cis side of the golgi apparatus go?
into the cisternae of the golgi apparatus
Which side of the golgi apparatus is the discharging side/opposite of the cis side?
the trans side
What happens after the products from the ER move through the cisternae and to the trans side of the golgi apparatus?
vesicles can be seen coming out of the trans side
What is one example of a vesicle produced by the golgi apparatus?
lysosomes
What do vesicles carry?
modified materials wherever they are needed inside or outside the cell
Where are golgi apparatuses found in particular?
in glandular cells such as those in the pancreas
What allows mitochondria to have some of their own independence within the cell?
they have their own DNA
What are the two membranes of mitochondria like?
the outer membrane is smooth while the inner membrane is folded into cristae
What is found inside the inner membrane of mitochondria?
a semi-fluid substance called the matrix
What lies between the two membranes of mitochondria?
the inner membrane space
What does the cristae of a mitochondrion provide?
a large surface area within which the chemical reactions of the mitochondrion occur
What do most mitochondrial reactions involve the production of?
adenosine triphosphate (ATP)
What type of ribosomes are produced and contained within mitochondria?
70S ribosomes
Which types of cells have large numbers of mitochondria?
Cells that have high energy requirements like muscle cells
What is the nucleus of eukaryotic cells?
an isolated region where DNA resides
What is the nuclear envelope?
a double membrane bordering the nucleus
Why is it important that the nuclear envelope allows compartmentalization of the eukaryotic DNA?
Because it provides an area where DNA can conduct its functions without being affected by processes occurring in other parts of the cell
Why does the nuclear membrane not result in complete isolation?
Because it has pores allowing for communication with the cell’s cytoplasm
What does the DNA of eukaryotic cells occur in the form of?
chromosomes
What do chromosomes carry allowing an organism to survive?
all the information necessary for the cell to exist
When is the cell’s DNA in the form of chromatin?
during the phase when the cell is not in the process of dividing and the chromosomes are not visible structures
What is chromatin formed of?
stands of DNA and histones
What structures are the result of the combination of DNA and histones?
nucleosomes
What do nucleosomes consist of?
a strand of DNA wrapped around 8 histones, with a ninth securing the structure
What is a chromosome?
a highly coiled structure of many nucleosomes
What can’t cells do without a nucleus?
reproduce
What would a cell that cannot reproduce likely have?
increased specialization to carry out certain functions
What is an example of a type of cell that does not have nuclei?
human red blood cells
What are nucleoli?
dark areas included in nuclei
What type of molecule are manufactured in nucleoli?
ribosome molecules
What do ribosome molecules do before assembling as ribosomes?
they pass through the nuclear envelope
Where do chloroplasts occur?
only in algae and plant cells
How are chloroplasts similar to mitochondria?
They contain their own DNA and 70S ribosomes
Other than DNA and ribosomes, what do chloroplasts have within their interior?
grana, thylakoids and the stroma
What is a granum made up of?
numerous thylakoids stacked like a pile of coins
What are thylakoids?
flattened membrane sacs with the components necessary for the absorption of light
What is the first step of photosynthesis?
the absorption of light
What is photosynthesis?
a process that converts light energy into chemical energy
What is the stroma compared to?
they cytoplasm of the cell
Where does stroma occur?
outside the grana but within the double membrane
How is reproduction similar between chloroplasts and mitochondria?
they can reproduce independently of the cell
Where does centrosome occur?
in all eukaryotic cells
What does a centrosome in an animal cells consist of?
A pair of centrioles, often at right angles to one another
What are centrioles involved in the assembly of?
microtubules
Why are microtubules important to a cell?
Because they provide structure, allow movement and they are important for cell division
Which cells do not have centrioles?
plant and fungal cells
Why may centrioles not be necessary for the production of microtubules?
Because plants and fungal cells still produce microtubules from their centrosome-like regions
Where are centrosomes located?
at one end of the cell close to the nucleus
What are basal bodies?
structures related to the centrosome of eukaryotic cells
Why don’t all eukaryotic cells have basal bodies?
Because basal bodies are located at the base of cilia and flagella and not all eukaryotic cells have cilia or flagella
What are basal bodies thought to direct the assembly of?
microtubules within the associated cilia or flagella
What appears to produce basal bodies when present?
centrioles
What are vacuoles?
storage organelles
What are vacuoles usually formed from?
the golgi apparatus
What are some examples of substances stored within vacuoles?
potential food, metabolic waste, toxins and water
What does the vacuole in plant cells allow which provides rigidity to the organism?
an uptake of water
What is a central vacuole?
The large singular vacuole in plants
What are the main similarities between prokaryotic and eukaryotic cells?
both have some outside boundary which always involves a plasma membrane, both conduct all the functions of life, DNA is present in both
What are the functions of life?
metabolism, growth, reproduction, response to stimuli, homeostasis, nutrition, excretion, and movement
What is metabolism?
sum of all chemical reactions occuring within an organism
What is nutrition?
The ability to acquire the energy necessary to maintain life
What is growth?
Development of an organism
What is reproduction?
Ability to reproduce offspring
What is response to stimuli?
the organism adapts as the environment changes
What is homeostasis?
maintenance of a constant internal environment
What is excretion?
the ability to release materials not needed/harmful into surrounding environment
What is movement?
ability to change position
How do unicellular organisms maintaine homeostasis?
The cell membrane controls movement of materials in and out of cell
How do unicellular organims conduct excretion?
vacuoles isolate and store waste
What allows unicellular organisms to move in response to changes in the environment?
cilia and flagella
What allows for nutrition in unicellular organisms?
Vacuoles carry out digestion
What allows energy production in unicellular organisms?
mitochondria or areas of enzymes
What provides the building blocks for growth and repair?
ribosomes
What allows multicellular organisms to carry out the functions of life compared to unicellular organisms?
They have organs carrying out all the functions of life
What are the three types of organisms with eukaryotic cells?
plants, animals, and fungi
What are believed to be the first eukaryotes to live on land?
Fungi
How do the three eukaryotic organisms differ in terms of cell wall?
plants= cellulose cell wall
animals= no cell wall
fungi= chitin cell wall
How do the three eukaryotic organisms differ in terms of chloroplasts?
plants= present
animals= not present
fungi= not present
How do the three eukaryotic organisms differ in terms of vacuoles?
plants= one large vacuole
animals= small and numerous
fungi= small and numerous
How do the three eukaryotic organisms differ in terms of their storage of carbohydrates?
plants= stored as starch
animals= stored as glycogen
fungi= stored as glycogen
How do the three eukaryotic organisms differ in terms of cilia and flagella?
plants= usually not present
animals= may be present
fungi= may be present
How do the three eukaryotic organisms differ in terms of shape?
plants= fixed, angular shape
animals= rounded shape
fungi= varying shape
How do the three eukaryotic organisms differ in terms of centrosomes and centrioles?
plants= centrosomes present but not centrioles
animals= both present
fungi= centrosomes present but not centrioles
What allows some eukaryotic cells carry out special functions?
a unique/atypical structure
What is hyphae?
filaments produced by fungi
What does most hyphae consist of?
chains sperated by cross-walls that have pores allowing various organelles and cytoplasm to flow from cell to cell
What is the result of hyphae that do not have cross-walls?
a single mass of cytoplasm (one cell) with more than one nucleus
What does phloem sieve tube elements’ specialized functions allow for?
transportation within a multicellular plant
What is minimal in the cells of phoem slieve tube?
nuclei, ribosomes, cytoskeleton, and cytoplasm
What is needed for ploem sieve tube cells to stay alive?
companion cells
What do red blood cells contain a lot of which combines easily with oxygen?
haemoglobin
What does the shape of red blood cells have a large surface area?
for the absorption and release of oxygen
Why don’t red blood cells have a nucleus?
because it allows them to carry more oxygen
How can skeletal muscle have the specialized function of body movement?
It has specialized proteins arranged in bands that contract and relax
What allows skeletal muscle to have more coordinated protein molecules?
There is limited cell membrane, so the shape is large and tubular and the cells also have multiple nuclei
What does the long and thin structure, along with branched connections allow nerve cells to do?
transmit electrical impulses
What are the specializations of sperm cells?
many mitochondria, tail allowing for movement, head with a tip producing an enzyme allowing for egg penetration
What specializations do the cells in the lungs have to help move mucus and other particles up and out of the airways?
they have cilia (little hairs) which work in unison
What are the key points of the endosymbiotic theory?
- 2 billion years ago, large cell with nucleus and able to sexually reproduce engulfed small prokaryote that could produce energy
- a mutual beneficial (symbiotic) relationship developed forming one organism
- smaller cell went through changes to become a mitochondrion
How did the larger cell help the bacteria prokaryote in the endosymbiotic theory?
it provided protection and carbon compounds
How did the smaller cell end up helping the larger cell (after changes) in the endosymbiotic theory?
It provided ATP
What evicence supports the endosymbiotic theory involving mitochondria compared to bacteria?
roughly same size, and divide by binary fission
What evidence supports the endosymbiotic theory involving mitochondria compared to prokaryotes?
they have their own 70S ribosomes, they have their own DNA which occurs in aw circular ring, inner membrane composition is similar, and RNA present in mitochondrial ribosomes resembles to prokaryote ribosomes
What evidence supports the endosymbiotic theory with mitochondria by itself?
they divide independently of host cell, they produce their own proteins with their 70S ribosomes, and they have two membranes consistant with engulfing process
Other than mitochondria, which organelle also provides evidence to the endosymbiotic theory?
chloroplasts
Other then endosymbiosis, what other process helped the development of the cell?
compartmentalization
What does compartmentalization result in?
specializations within the cell
How is the nucleus an example of compartmentalization?
it has a protective membrane which enables DNA molecules to function without interference from other reactions in the cytoplasm
How is the mitochondrion an example of compartmentalization?
it produces the energy necessary for the cell to carry out the functions of life
What alters gene expression in the cells of multicellular organisms?
differing environments
