Ultrastructure of the Cell 1.2 Flashcards
State the function of an exocrine gland cell in the pancreas.
Exocrine gland cells synthesize molecules (often proteins) for secretion from the cell into an external space.
Exocrine gland cells of the pancreas secrete enzymes that function in digestion in the small intestine.
Explain how an improvement in apparatus allowed for greater understanding of cell structure.
Technology = machinery and equipment developed from the application of scientific knowledge.
Begets = gives rise to; brings about.
Discovery = the act of finding or learning something for the first time.
Define “resolution.”
Understanding: Electron microscopes have a much higher resolution than light microscopes.
The smallest interval distinguishable by the microscope, which then corresponds to the degree of detail visible in an image created by the instrument.
Compare the functionality of light and electron microscopes.
LIGHT MICROSCOPES
Use lenses to bend light and magnify images.
Used to study dead or living cells in color.
Cell movement can be studied.
Larger field of view.
Objects can be magnified up to 2000X.
Can resolve objects 200 nm apart.
ELECTRON MICROSCOPES
Uses electron beams focused by electromagnets to magnify and resolve.
Requires cells to be killed and chemically treated before viewing.
No movement can be seen.
Without stain or dye, no color can be seen.
Smaller field of view.
Can magnify objects up to 250,000 times.
Can resolve objects that are 0.2 nm apart.
Outline the major differences between prokaryotic and eukaryotic cells.
Prokaryotic Cells
Smaller (about 0.2 - 2 um)
DNA in nucleoid region (no nuclear membrane)
No membrane bound organelles
Cell wall of peptidoglycan
Smaller ribosomes (70s) in cytoplasm
DNA is circular and without histone proteins
Has plasmid DNA
Asexual cell division
Eukaryotic Cells
Bigger (10-100 um)
DNA in a true nucleus
Membrane bound organelles present
Cell wall of cellulose (plants) or chitin (fungus)
Larger ribosomes (80s) in cytoplasm and on ER
//also has 70s ribosomes within mitochondria and chloroplasts//
DNA is linear with histone proteins
Do not have plasmid DNA
Asexual or sexual cell division
Cell Wall Function in Prokaryotic Cells:
All prokaryotic cells have a stiff cell wall, located underneath the capsule (if there is one). This structure maintains the cell’s shape, protects the cell interior, and prevents the cell from bursting when it takes up water.
Plasma Membrane Function in Prokaryotic Cells:
It physically separates the cytoplasm from the outside environment. The plasma membrane also works as a selectively permeable, or semipermeable, barrier that controls what enters and exits the cell.
Cytoplasm Function in Prokaryotic Cells:
The cytoplasm is the gel-like fluid inside the cell. It is the medium for chemical reaction. It provides a platform upon which other organelles can operate within the cell. All of the functions for cell expansion, growth and replication are carried out in the cytoplasm of a cell.
Pili Function in Prokaryotic Cells:
Helps Transformation of DNA between 2 cells.
70S Ribosomes Function in Prokaryotic Cells:
Site for Protein Synthesis
State the function of the prokaryotic cell flagella.
Found in some (not all) prokaryotic cells.
Long extension used for cell locomotion.
Explain why understanding of the ultrastructure of prokaryotic cells must be based on electron micrographs.
“Ultrastructures” are small structures of/in a biological specimen that are too little to see with a light microscope.
Define “asexual reproduction.”
Asexual reproduction creates offspring from a single parent organism.
The offspring are genetic clones of that parent.
Outline the four steps of binary fission.
- The nucleoid DNA replicates to create an exact duplicate copy.
- The nucleoid DNAs attach to the cell membrane.
- The cell membrane (and wall, if present) grow, causing the cell to elongate and the DNA molecules to move apart from each other.
- The cell membrane pinches inward, creating two genetically identical cells.
State the meaning and advantages of eukaryotic cells being “compartmentalized.”
Compartmentalization is the presence of membrane bound partitions (organelles) within the eukaryotic cell. The compartments allow for:
- Specialization of regions within the cell for specific functions.
- Molecules needed for a specific function to be concentrated in a region within the cell.
State structural differences between plant and animal cells.
Animal Cells
No cell wall
No chloroplasts
No large vacuole
Not a fixed shape
Stores carbohydrates as glycogen
Plant Cells
Cell wall
Chloroplasts
Large vacuole
Fixed shape
Stores carbohydrates as starch
Draw and label a diagram of the ultrastructure of a generic animal cell.
Cell membrane shown as a single continuous line
Nucleus drawn with double membrane and nuclear pores
Mitochondria with a double membrane, the inner one folded into internal projections, shown no larger than half the nucleus
Rough endoplasmic reticulum drawn as a multi-folded membrane with dots on surface
Golgi apparatus drawn as a series of enclosed sacs with evidence of vesicle formation
80S ribosomes drawn as small discrete dots (not circles) in cytoplasm and on rER
lysosome and vesicles drawn as circles with single line
State the function of an exocrine gland cell in the pancreas.
Exocrine gland cells synthesize molecules (often proteins) for secretion from the cell into an external space.
Exocrine gland cells of the pancreas secrete enzymes that function in digestion in the small intestine.
Describe the function of the plasma membrane in an exocrine gland cell.
Forms the boundary of the cell, acts as a selective barrier allowing certain materials to pass into and out of the cell.
Describe the function of the nucleus in an exocrine gland cell.
Contains most of the genes that control the eukaryotic cell, contains the nucleolus and chromatin.
Describe the function of the mitochondria in an exocrine gland cell.
The location of aerobic cellular respiration used to make ATP.
Describe the function of the Golgi apparatus in an exocrine gland cell.
Consists of flattened membranous sacs; receives transport vesicles from the ER,
modifies proteins produced in the ER, produces secretory vesicles
Describe the function of the lysosomes in an exocrine gland cell.
Contains digestive enzymes that are used to break apart cellular debris and waste.
Describe the function of the vesicles in an exocrine gland cell.
Transport materials within the cell and out of the cell via exocytosis.
Describe the function of the endoplasmic reticulum in an exocrine gland cell.
Ribosomes on the ER synthesize proteins which are then moved through the ER and packaged into vesicles for transport.
Identify the nucleus in a micrograph of a eukaryotic cell.
Often stained a darker color, look for a nuclear membrane and the nucleolus.
Identify the Golgi apparatus in a micrograph of a eukaryotic cell.
Look for stacks of lines, without little dark dots attached.
Typically further from the nucleus than ER.
Identify the lysosome in a micrograph of a eukaryotic cell.
Little sacs, often a light grey color.
Hard to distinguish from vesicles.
Identify the vacuole in a micrograph of a eukaryotic cell.
Clear sac, typically larger in size than a vesicle or lysosome. More prevalent in plant cells than in animal cells.
Identify the flagella in a micrograph of a eukaryotic cell.
Long tail-like structure emerging from the main cell body.
Identify the cell wall in a micrograph of a eukaryotic cell.
Rigid outermost layer of a plant cell, external to the cell membrane. Thicker than the cell membrane.
State the function of the prokaryotic cell capsule.
Found in some (not all) prokaryotic cells.
Helps the cell maintain moisture and adhere to surfaces. Protects the cells from other organisms.
Contrast the size of eukaryotic and prokaryotic ribosomes.
Prokaryotes have a smaller, 70s ribosome.
Eukaryotes have a larger, 80s ribosome. Although, the mitochondria and chloroplasts within eukaryotic cells have 70s ribosomes.
(The “s” stands for Svedberg unit, a measure of particle sedimentation rate)
Draw the ultrastructure of E.coli, including the cell wall, pili, flagella, plasma membrane, cytoplasm, 70s ribosomes, and nucleoid with naked DNA.
Cell wall drawn uniformly thick and outside the cell membrane
Capsule drawn outside the cell wall
Pili drawn as hair-like structures connected to cell wall
Flagellum drawn at one end only and longer than pili
Cell membrane represented by a continuous single line
70S ribosomes drawn as small discrete dots (not circles)
Nucleoid DNA shown as a tangled line not enclosed in membrane
Plasmid drawn as a small circular ring of DNA
Cytoplasm labeled within the cell
Draw and label a diagram of the ultrastructure of a generic plant cell.
Cell wall drawn on outside perimeter with two continuous lines to indicate the thickness
Cell membrane shown as a single continuous line
Nucleus drawn with double membrane and nuclear pores
Vacuole drawn with a single continuous line
Chloroplast drawn with a double line and internal stacks of thylakoid
Mitochondria with a double membrane, the inner one folded into internal projections, shown no larger than half the nucleus
80S ribosomes drawn as small discrete dots (not circles) in the cytoplasm and on rER
Explain why cells with different functions will have different structures.
Cells will have different types and/or quantities of organelles depending on the primary function of the cell type.
This allows for cells to specialize for a specific task.
