A2.2: Cell Structure Flashcards
State the three parts of the cell theory.
- All living organisms are made of cells
- Cells are the basic units of life
- All cells arise from pre-existing cells
Compare the use of the word theory in daily language and scientific language.
Daily use:
- Theory is a guess and there is doubt
Scientific use:
- THeory has been proven true through repeated observations and experiments and there is no current doubt
Distinguish inductive from deductive reasoning.
Inductive reasoning:
- Theories developed from observations
Deductive reasoning:
- Using a general premise to form a specific conclusion
Outline the process of inductive reasoning that led to the development of the cell theory.
- 17th century, biologists examined animal and plant tissues and saw every specimen contained at least one or more cells
- Subcellular components have never been seen to perform functions of life whereas full cells have
- Cells have been observed coming from other cells but never observed spontaneous generation
Outline how deductive reasoning can be used to predict the characteristics of a newly discovered organism.
General Premises:
- All organisms are made of one or more cells
- Slime moulds are living organisms
Specific conclusion after a deduction:
- Slime moulds are made of cells
Define magnification
- How much larger an object appears compared to its real size
Given the magnification of the ocular and objective lenses, calculate the total microscope magnification.
Total magnification = Oclar x Objective
Demonstrate how to focus the microscope on a sample.
- Turn the coarse adjustment knob so that the stage moves upward and downward toward the objectives
- Turn the fine adjustment knob for perfect focus
Demonstrate how to make a temporary wet mount and stain a microscopic sample.
- Place sample on slide
- Use pipette to place drop of water on specimen
- Place edge of cover slip over the sample at an angle and carefully lower it into place; preventing air bubbles from being trapped under the cover slip
- if there is to much water, take a piece of paper towel and hold it close to one edge of the cover slip to draw out some water
Define Field of View (FOV)
Diameter of the area visible through the microscope
Describe how to measure the field of view diameter of a microscope under low power.
- Place transparent metric ruler under low power objective lens of a microscope to measure the diameter of field of view on low power magnification
Determine the relationship betw. magnification and FOV
- As magnification increases, FOV is smaller (inverse relationship)
Calculate the field of view diameter of a microscope under medium or high power.
Diameter (at LP) x Magnifictaiton (of LP objective) / Magnification (of HP objective) = Diameter (at HP)
Use a formula to calculate the magnification of a micrograph or drawing.
IAM
- Magnification = Image size / Actual size
If given the magnification of a micrograph or drawing, use a formula to calculate the actual size of a specimen.
IAM
- Actual size = Image size / Magnification
Compare quantitative and qualitative observations.
Quantitative observations:
- involve measuring or counting something and expressing the result in numerical form
Qualitative observations:
- involve describing something in non-numerical terms, such as its appearance, texture, or colour like in Drawing
State the criteria for drawing cell structures
- Title including the magnification of the microscope it is viewed under and how many cells have been drawn. The scientific name is underlined.
- Scale line
- Drawing Magnification (not lens magnification)
- Labelled with straight lines pointing to one side of the drawing
Define resolution and magnification.
Resolution:
- The smallest interval distinguishable by the microscope which then corresponds to the degree of detail visible in an image
Magnification
- How much larger an object appears compared to its real size
Compare the functionality of light and electron microscopes.
Light:
- Uses multiple lenses to blend light and magnify images
Electron:
- Uses electron beams focused by electromagnets to magnify and resolve
Compare the benefits of electron and light microscopes
Light microscope:
- easy to use
- cheaper
- can observe cells alive and dead in colour
- cell movement can be studied
- no need for high-voltage electricity
Electron microscope:
- High resolving power (resolution)
- High magnification
Compare the limitations of electron and light microscopes
Light microscopes:
- Low magnification
- Low resolving power (resolution)
Electron microscopes:
- Expensive
- Requires cells to be dead
- no movement of cells can be seen
- no colour can be seen without stain or dye
- high-voltage electric current is required
State a benefit of using fluorescent stains to visualize cell structures.
Generates particularly bright images
Outline the process of visualizing specific proteins in cells using immunofluorescence technology.
- Label cells with different fluorescently stained antibodies to bind to specific target proteins within a cell
- The protein can be tracked and located as it moves in the cell
Outline the process of producing images of cell surfaces using freeze-fracture electron microscopy.
- involves the rapid freezing of cells and then fracturing them along lines of weakness including the center of membranes
- Surfaces are then etched with a coating creating a replica of the surfaces that can be seen with an electron microscope
Outline the process of visualizing specific proteins using cryogenic electron microscopy.
- A solution with the protein is frozen and bombarded with a beam of electrons
- A computer analyses the patterns of diffraction off the sample to produce an image of the structure
Outline the function of structures that are common to all cells.
- Plasma membrane
- Cytoplasm
- DNA
- Ribosomes
Outline the functions of the following structures of an example prokaryotic cell: cell wall, plasma membrane, cytoplasm, 70s ribosome, and nucleoid DNA.
- Cell wall: Helps maintain shape and protects the cell from bursting in hypotonic media
- Cell (Plasma) Membrane: a phospholipid bilayer that has hydrophobic and hydrophilic regions
- Cytoplasm: Contains dissolved substances in the cytosol (liquid part) required for metabolic processes
- 70S ribosomes (in prokaryotes): Smaller ribosomes that synthesise polypeptides into proteins during translation
- Nucleoid DNA: All living organisms use DNA as the genetic material and the DNA code has evidence of being universal
Define the term “naked” in relation to prokaryotic DNA.
DNA is not wrapped around histone proteins - this is the case in prokaryotic cell DNA
Compare and contrast prokaryotic and eukaryotic cell structure.
- Both have Ribosomes, DNA, Cell Membrane and Cytoplasm (structures common to all cells)
- Both perform all life processes
Prokaryote:
- Smaller
- No membrane-bound organelles
- Has a nucleoid instead of a nucleus
- Division by binary fission only and not by meiosis or mitosis
- Cell wall made of peptidoglycan and not cellulose or chitin
- Small 70S ribosomes and not 80S
- Unicellular only and not multicellular
- DNA is circular and not linear called plasmids
Eukaryotes:
- opposite
Label a diagram of a eukaryotic cell.
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Free Ribosomes
- Floating in cytoplasm synthesising polypeptides used within the cell
Bound Ribosomes
- Attached to the rER synthesising polypeptides secreted from the cell
Mitochondria
- Adapted for production of ATP as they are the site of aerobic cellular respiration
- Mitochondria evolved by endosymbiosis
Chloroplast
- Contain light-absorbing pigments like chlorophyll that are adapted for photosynthesis as they capture light energy, use it with water and convert it to chemical energy by producing glucose
- Chloroplasts evolved by endosymbiosis
Endoplasmic Reticulum (Rough and Smooth)
rER:
- Flattened membrane sacs containing bound ribosomes and surround the cell nucleus
sER:
- Flattened membrane sacs that synthesise cholesterol, synthesis of phospholipids and form & repair membranes
Golgi Body
Concentrates and packs proteins into vesicles either:
- Within the cell to organelles called lysosomes
- Plasma membrane
- secretion to outside cell via exocytosis
Vesicles (as well as Transport and Secretory)
Membrane-bound sacs that contain and transport material within cells
- Transport: Move molecules between locations inside the cell by budding off
- Secretory: Secrete molecules from the cell via exocytosis - this is how new phospholipids are added to the cell membrane
Vacuoles
- Store water and maintian turgor pressure against the cell wall
Lysosomes
- Spherical, single membrane organelles containing enzymes, working in oxygen-poor and low pH areas, that digest large molecules to recycle the cell components when they are old/damaged
- also has an immune defence by digesting pathogens engulfed by phagocytes
Cytoskeleton of microtubules
- helps cell maintain their shape, organises cell parts and enables cells to move and divide
Centrioles
- Arrange the mitotic spindle during cell division
- Also serve as anchor points for microtubules in the cytoplasm
Microfilaments
- Used for the intracellular transport of organelles and the separation of chromosomes during mitosis
Nucleus
- Contains DNA
- Contains nucleolus where ribosome subunits are made
- Contains a double membrane with pores
List the common processes carried out by all life (MRS C GREN)
- metabolism
- homeostasis
- excretion
- growth
- nutrition
- movement
- reproduction
- response to stimuli.
Define metabolism, homeostasis, excretion, growth, nutrition, movement, reproduction and response to stimuli.
Metabolism:
- Sum of all chemical reactions within a cell
Homeostasis:
- Maintenance of internal environments
Nutrition:
- Obtaining energy and matter; autotrophs use external energy sources to synthesise carbon compounds and heterotrophs use carbon compounds obtained from other organisms to synthesise carbon compounds
Excretion:
- excrete metabolic waste matter
Growth:
- increase in size and mass as well as the transformation of the organism through its lifespan
Reproduction:
- sexual; involving 2 parents and the fusion of haploid sex cells from each parent. asexual; involves only one parent
Coordination:
- Motile organisms are mobile, sessile organisms stay in one place
Response to stimuli:
- recognise and respond to changes in environmental conditions
Describe characteristics of Paramecium or Chlamydomonas that enable it to perform the functions of life.
Characteristics of paramecium enabling it to perform the functions of life:
- Nutrition: eats smaller unicellular organisms
- Metabolism: cytoplasm contains dissolved enzymes catalysing the metabolic reactions
- Growth: Cell wall grows until max SA is reached at which point it will divide
- Reproduction: asexually as the nucleus of the cell divides via mitosis to make other nuclei
- Excretion: waste products excreted through an anal pore
Compare and contrast the structures of plant, animal and fungal cells with reference to cell walls, vacuoles, chloroplasts, centrioles, cilia and flagella.
Plant cells:
- multicellular eukaryotes with a cell wall made of cellulose
- large permanent vacuole used to store water and cause turgor pressure against cell wall
- centrioles present in male gametes
- cilia and flagella present in male gametes
Animal cells:
- multicellular eukaryotes having no cell wall
- small temporary vacuoles used to expel waste
- centrioles present and used to arrange mitotic spindle during cell division and serve as anchor points for cilia and flagella
- cilia and flagella present including in male gametes
Fungal cells:
- unicellular OR MULTICELLULAR eukaryotes with a cell wall made of chitin
- large permanent vacuole used to store water and cause turgor pressure against cell wall
- no centrioles
- no cilia and flagella
All have:
- nucleus
- 80S ribosomes
- rER and sER
- Golgi body
- Vesicles
- Lysosomes
- Mitochondria
- Cytoskeleton
Describe features of skeletal muscle fibers that make them an atypical cell.
- extremely large skin cell
- contains more than one nucleus
Describe features of aseptate fungal hyphae that make them an atypical cell.
- not divided into individual cells but rather continuous structures
- contains more than one nucleus
Describe features of red blood cells that make them an atypical cell.
- RBCs are a eukaryotic cell without a nucleus
- also no mitochondria
Describe features of phloem sieve tube elements that make them an atypical cell.
- phloem sieve tube elements are eukaryotic cells without organelles
Compare the number of nuclei in aseptate fungal hyphae, skeletal muscle, red blood cells and phloem sieve tube elements.
No nuclei:
- RBC
- Phloem Sieve Tube Elements
Many nuclei:
- Aseptate fungal hyphae
- Skeletal muscle
Recognize features and identify structures in micrographs of prokaryotic cells (inclusive of the plasma membrane, nucleoid region, ribosomes and cell wall).
- No membrane bound organelles
- Cell wall external to the plasma membrane
- Nucleoid region with DNA are squiggly lines across the middle
Recognize features and identify structures in micrographs of eukaryotic cells (inclusive of the plasma membrane, nucleus, mitochondrion, chloroplast, vacuole, rough and smooth endoplasmic reticulum, Golgi apparatus, secretory vesicle, ribosomes, cell wall, cilia, flagella and microvilli).
Plant cells:
- always multicellular
- larger
- larger vacuole
Animal cells:
- no cell wall
- rounded shape
- larger too
rERs are lines with dots inside found near the nucleus
sERs are flattened membrane sacs found further from the nucleus
Golgi body are flattened stacks where the inside of the stack is clear
Lysosomes are bound by a single membrane and are darker
Chloroplasts are large double membranes structures with lines going across
Vacuoles are clear and fill most of the cell volume
Vesicles are dark due to proteins being stored and transported and are circles
Centrioles contain 9 groups of 3 microtubules with circular symmetry
Cilia are long extensions projecting from cell membrane
Microvilli are smaller and more compact projections
Given a micrograph, draw and label the ultrastructure of a prokaryotic cell.
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Given a micrograph, draw and label the ultrastructure of a eukaryotic cell.
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Explain the origin of mitochondria and chloroplast with reference to the endosymbiosis
- Ancestors of mitochondria may have been aerobic-respiring bacteria living inside a larger host cell and instead of being digested, some remained alive and continued to respire aerobically within the host cell
- mitochondria are likely to have evolved first as all eukaryotes have it but only some have chloroplasts
- Ancestors of chloroplasts may have been photosynthetic bacteria living inside a larger host cell and instead of being digested, some remained alive and continued to photosynthesize within the host cell
Explain the origin of mitochondria and chloroplast with reference to infolding
Organelles like ER, nuclear envelop and Golgi body have evolved from inwards folds of the plasma membrane of ancestral prokaryotic cells allowing them to carry out more complex chemical reactions
Describe the genetic, structural and behavioural evidence for the endosymbiotic theory.
Genetic:
- Both have circular naked DNA
- Both share common DNA sequences
- Both have 70S ribosomes
Structural:
- Both have the same size and shape
- Both have a double membrane
Behavioural:
- Both move independently within the eukaryotic cell
- Both reproduce independently through a process similar to binary fission
- Both are inhibited by antibiotics as are prokaryotes
Outline the benefits of cell specialization in a multicellular organism.
Different cells can:
- Focus on fewer tasks at once and do the work more efficiently whilst saving energy by not performing other tasks
- Have specialised structures and metabolism
- evolve faster in that particular task
Define differentiation.
- The development of specialised structures and functions in cells
Describe the relationship between cell differentiation and gene expression.
- Differentiation occurs when different cell types express different genes
State the frequency of the evolution of multicellularity
repeatedly
List groups of organisms that are multicellular.
- All animals
- All plants
- Most fungi
- Most algae
Outline the steps in the evolution of multicellularity.
2 steps:
1. Formation of cellular clusters from single cells
2. Differentiation of the cells within the cluster for specialised functions
State the 2 hypotheses for how cells may have formed clusters
- A group of independent cells came together
- When a unicellular organism divides, the daughter cells fail to separate resulting in an aggregate of identical cells
State the selective advantage clusters of cells have over cells living independently
- Cells can begin to serve specialised functions which can occur through the differentiation of cells
