1.2: Ultrastructure of Cells Flashcards
1.2.U1 Outline the major differences between prokaryote and eukaryote cells
Prokaryote__Eukaryote
Tiny (0.2-2um) Bigger (10-100um)
Nucleoid (no nuclear membrane) True nucleus
No organelles Organelles present
Flagella rotates Flagella moves laterally
Cell wall of peptidoglycan Cell wall of cellulose (plants) or chitin (fungi)
Smaller 70s ribosomes Larger 80s ribosomes
DNA is circular, naked DNA is linear, with histones
Has plasmids Does not have plasmids
Asexual cell division Asexual or sexual reproduction
1.2.U1 Describe the function in a prokaryotic cell of the cell membrane
Responsible for regulating what materials move into and out of the cell.
1.2.U1 Describe the function in a prokaryotic cell of the nucleoid
The genetic material (DNA)
Circular, naked DNA
1.2.U1 Describe the function in a prokaryotic cell of plasmids
Genetic material often with genes for antibiotic resistance
1.2.U1 Describe the function in a prokaryotic cell of cytoplasm
Gel-like fluid substance, site of many metabolic reactions
1.2.U1 Describe the function in a prokaryotic cell of ribosomes
Build proteins during translation
1.2.U1 Describe the function in a prokaryotic cell of the cell wall
Outer peptidoglycan covering that protects and provides shape to the cell
1.2.U1 Describe the function in a prokaryotic cell of pili
Hair-like structures that help the cell attach to surfaces
1.2.U1 Describe the function in a prokaryotic cell of the capsule
Helps maintain moisture and adhere to surfaces. Protects cell from other organisms.
1.2.U1 Describe the function in a prokaryotic cell of a flagella
Long extensions used in locomotion
1.2.U1 Define extracellular
“Extra cellular” means outside the cell. Any structure outside the cell membrane is considered extracellular:
- cell wall
- pili
- capsule
- flagella
1.2.U1 Contrast the size of eukaryote and prokaryote ribosomes
Prokaryotes have smaller, 70s ribosomes. Eukaryotes have larger, 80s ribosomes. The s stands for Svedberg units (a measure of particle sedimentation rate).
1.2.U2 State the meaning and advantage of eukaryotic cells being “compartmentalised”.
Compartmentalization: the presence of membrane bound partitions (aka. organelles) inside the eukaryotic cell. These compartments allow for:
- Specialization for specific functions without interference from other cell functions. For example, lysosomes can digest cell debris without digesting the cell itself.
- Allows molecules needed for a function (for example enzymes or ions) to reach a higher concentration than if all molecules were diluted in the cytoplasm. For example, the mitochondria accumulate a large H+ concentration which is used to fuel ATP synthesis.
1.2.A2 Define asexual reproduction
Asexual reproduction creates offspring from a single organism. The offspring are genetic clones of that parent.
1.2.A2 Outline the four steps of binary fission
- The (nucleoid) DNA replicates to create an exact genetic copy
- The (new nucleoid) DNA attaches to the cell membrane close to the original
- The cell membrane (and wall, if present) grow, causing the cell to elongate and the DNA molecules to move apart from each other
- The The cell membrane (and wall, if present) pinch inwards, creating two genetically identical cells.
1.2.U4 Define resolution
Resolution is the shortest distance between two points that can be distinguished as separate.
1.2.U4 Compare the maximum resolution of a light microscope with that of an electron microscope
Light microscopes can resolve to about 200nm apart. Electron microscopes can resolve to about 0.2nm apart (1000x better than light).
1.2.U4 List 3 example structures that are visible with electron microscopes but not with a light microscope.
Electron microscopes have stronger magnification and better resolution and therefore can produce images with better detail. For example the ribosomes, Golgi, ER and cytoskeleton are not visible with a light microscope but can be seen with the electron microscope.
1.2.A1 State the function of an exocrine gland cell
Exocrine gland cells synthesize molecules (often protein enzymes) for secretion from the cell into an external space (for example, a salivary gland)
1.2.A1 Describe the function of the following structures in an exocrine gland cell
Plasma (cell) membrane: regulates passage of materials into and out of the cell.
Nucleus: contains the genetic code (used to make proteins) and contains the nucleolus (where ribosomes are synthesized).
Mitochondria: location of cellular respiration used to make ATP. The ATP can then be used to fuel the cells protein synthesis, transport and secretion processes.
Golgi apparatus: modifies proteins before they are used, stored or released from the cell.
Lysosome: contains digestive enzymes that can be used to break apart cellular debris and waste.
Vesicles: transport materials within the cell and out of the cell via exocytosis
Endoplasmic reticulum: ribosomes on the rough ER synthesis proteins which are then moved through the ER and packaged into vesicles for transport.
1.2.A2 State the function of a palisade mesophyll cell
Palisade mesophyll cells are found on the upper surface of a leaf and have the primary job of performing photosynthesis.
1.2.A2 Describe the function of the following structures in a palisade mesophyll cell
Cell wall: provides structural rigidity and support
Plasma (cell) membrane: regulating passage of materials into and out of the cell
Chloroplast: location of photosynthesis
Vacuole: water filled sac that helps maintain cell turgidity
Nucleus: holds DNA, the genetic code for making proteins. Also has the nucleolus, where ribosomes are synthesized
Mitochondria: site of cellular respiration, where glucose chemical energy is converted to ATP chemical energy
***plant cells have other organelles as well, like ER, vesicles and Golgi
1.2.S1 Explain why the ultrastructure of prokaryotic cells must be based on electron micrographs
Ultrastructures are small structures of/in a biological specimen that sre too little to see with a light microscope
1.2.S1 Draw the ultrastructure of E. coli
1.2.S2 Recognise features and identify structures in micrographs of eukaryotic cells.
Given a micrograph, draw and label the ultrastructure of a eukaryotic cell.
1.2.S3 Explain why cells with different functions will have different structures
Cells have different organelles depending on the primary function of the cell type. This allows cells to specialise for a specific task which can lead to increased complexity of the entire organism.
1.2.S3 Identify ultrastructures visible in a micrograph of a eukaryotic cell
Typically visible ultrastructures are:
- nucleus - look for nuclear membrane and the nucleolus
- rough ER - look for long sheets of membrane with little black dots attached (typically close to the nucleus)
- cell membrane - look ofr a thin line around the edge of the cell
- Golgi - look for stacks of membrane, typically further from nucleus
- lysosome - little, clear sacs. Hard to distinguish from vesicles
- mitochondria - often stain dark; look for internal lines
- ribosomes - look like little, dark dots. Can be “free” in the cytoplasm or bound to the rough endoplasmic reticulum
- vesicles - look for smaller clear circles
- chloroplast - typically an oval shape with stacks seen on the inside
- vacuole - looks like a vesicle, but is typically larger in size
- cell wall - thicker, clear line outside of the cell membrane
1.2.S3 Given a micrograph of a cell, deduce the function of the cell based on the structures present
Cells will have specialised shapes given their function. For example:
small intestine villus cell - microvilli increase surface area for absorption; many mitochondria for fueling active transport
hormone secreting cell - many vesicles holding the hormones until secretion
photosynthetic plant cell - chloroplasts for performing photosynthesis
1.2.NOS1 With reference to a specific example, explain how an improvement in apparatus allowed for greater understanding of cell structure
The invention of the electron microscope in 1931 led to better resolution when viewing cells. For example, mitochondrial structure was discovered.
