A2.2 Cell Structure Flashcards
functions of life
Metabolism,
reproduction,
homeostasis,
movement,
growth,
response to stimuli,
excretion (removal of metabolic waste),
nutrition
Cell theory
Living organisms are composed of cells
Cells are the smallest unit of life
Cells come from pre-existing cell
Magnification
the ability to enlarge an object’s image
Resolution
the ability to differentiate two separate objects
Light Microscopes
Use lenses to bend light and magnify images by a factor of roughly 100-fold
Electron microscopes
Use electromagnets to focus electrons resulting in significantly _greater magnifications and resolutions__
Transmission electron microscopes (TEM) pass electrons through specimen to generate a cross-section
Scanning electron microscopes (SEM) scatter electrons over a surface to differentiate depth and map in 3D
Light Microscope advantages
Can observe living specimen
Cheap to use
Portable
Easy to used
Can observed colored specimen
light microscope disadvantages
Low Resolution
Only produced a two- dimensional image
electron microscope advantages
Can view finer details (Higher resolution)
electron disadvantages
Expensive
Difficult to prepare specimen
Not portable
May produce artifacts (structure that is not present in specimen) due to heavy metal staining
Cannot observed colored specimen. (The ‘color’ observed are ‘false-color scanning)
structures of prokaryotic cell
Capsule (Glycocalyx)
Cell wall
Cell membrane
Cytoplasm
Pili
Flagella
Nucleoid region
Plasmid
70S ribosome
capsule (glycocalyx)
Protect the cell from external environment
cell wall (prokaryotic)
Act as a structural support, made up of peptidoglycan
Cell membrane
Control substances going in and out of the cell
cytoplasm
Contain enzymes, site for metabolic reactions
pili
Responsible for exchange of plasmid between bacteria (horizontal gene transfer/sexual reproduction)
Flagella
Responsible for locomotion of the bacterium
Nucleoid region
Contain genetic material of the bacterium
Plasmid
Circular DNA in the cytoplasm
70S ribosome
Site for protein synthesis
Asexual Reproduction of Prokaryotes
binary fission
binary fission
The circular DNA is replicated.
The membrane elongates and pinches off (cytokinesis), forming two cells.
The way of transferring gene is called _vertical gene transfer__
Sexual Reproduction of Prokaryotes
Formation of Conjugation
formation of conjugation
Pili of the donor will be connecting to the recipient.
Conjugation is formed between the donor and recipient.
Replication of the donor plasmid.
Plasmid is transferred to the recipient, and it comes a new donor
structure Eukaryotic Cell – Animal Cell
Nucleus
Cytoplasm
Cell membrane
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Mitochondria
Golgi Apparatus
Vesicles
Lysosome
Peroxisome
80S ribosome
Cytoskeleton
Centriole
nucleus
Contain DNA, control cellular activity
cytoplasm
Contain enzymes, site for metabolic reactions
cell membrane
Control substances going in and out of the cell
Rough Endoplasmic Reticulum
Site for protein synthesis (extracellular proteins)
Smooth Endoplasmic Reticulum
Site for lipid synthesis
mitochondria
Site for aerobic respiration, produces ATP
Golgi Apparatus
Site for modifying and repackaging protein
Vesicles
Transport of substances, mainly protein
Lysosome
Contain hydrolytic enzyme, breaking down pathogens or worn-out organelles
Peroxisome
Responsible for breaking down of lipid
80S ribosome
Site for protein synthesis (intracellular proteins)
Cytoskeleton
Structural support of the cell
Centriole
Responsible for the formation of spindle fibers
Atypical Eukaryotes
red blood cells
Fungal hyphae
Phloem sieve tube
Skeletal muscle
red blood cells
Carries oxygen
Contains haemoglobin
biconcave shape
Do not have a nucleus
fungal hyphae
Fungi may have filamentous structures called hyphae, which are separated into cells by internal walls called septa
Some fungi are not partitioned by septa and hence have a continuous cytoplasm along the length of the hyphae
Challenges the idea that living structures are composed of discrete cells
Phloem sieve tube
In charge of translocation
Specialized cell for transportation of sucrose and amino acid in plant
End wall with pores and __ cellular components
Can only remain alive with the help of companion cell
Skeletal muscle
Muscle cells fuse to form fibres made up of specialised protein that may be very long (>300mm)
Tubular cells with multiple nuclei despite being surrounded by a single, continuous plasma membrane
Allowing more coordinating protein molecules
Prokaryotic Cell vs Eukaryotic Cell (1)
Nucleus absent
No membrane bounded organelles
Capsule present
Contain plasmid
Naked DNA (histone is the clothes, DNA without histone)
70S ribosome
Divide by binary fission
Prokaryotic Cell vs Eukaryotic Cell (2)
Nucleus present
Contain membrane bounded organelles
Capsule absent
No plasmid
DNA associate with histone protein (chromosome)
80S ribosome
Divide by mitosis and meiosis
Endosymbiotic Theory (theory only)
The _origin of eukaryotic cells__ can be explained by the endosymbiotic theory.
Mitochondria are believed to have evolved from aerobic prokaryotes that were engulfed by anaerobic cell.
Chloroplasts are believed to be evolved from photosynthetic bacteria that were engulfed by heterotrophic cell.
Endosymbiotic Theory – Evidence
Mitochondria and chloroplasts have their own DNA which is naked and circular
Mitochondria and chloroplasts have ribosomes that are similar to prokaryotes (70S)
Mitochondria and chloroplasts have a double membrane, and the inner membrane has proteins that are similar to prokaryotes
Mitochondria and chloroplasts are roughly the same size as bacteria and are susceptible to the antibiotic chloramphenicol
Cell Differentiation
All the cells in our body contain the same DNA. (Except sex cell)
Based on the position of the cell, different cells will have different expression
Depending on where the cell is, only some genes in the cell are expressed.
The cell is said to be specialized or differentiate.
Difference between cilia and microvilli
Cilia are motile
Microvilli are non-motile
Cilia involved in movement
Microvilli increase surface area for absorption
Cilia are found in the lumen of the respiratory tract (trachea) and the lumen uterine tube
Microvilli are found on the epithelial cells of the small intestine (villi) and kidney tubules
Central vacuole / Large vacuole
Primarily store water but nutrients, salts, ions, minerals, proteins, pigments, etc. may also be found depending on the type of plant cell
The water inside the vacuole helps to maintain the turgor pressure (the force within the cell that pushes the plasma membrane against the cell wall) within the plant cell (increase the turgidity of the plant cell)
When water goes in and there are no ions inside the cell, it will go out of the cell through osmosis
