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Section 2A: Cells (3.1 - Cell structure (Animal cell: Nucleus, golgi…
Section 2A: Cells
3.1 - Cell structure
Animal cell: Nucleus, golgi apparatus, cytoplasm, ribosomes, mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, lysosome and a cell membrane.
Plant cell; cell membrane, cell wall, vacuole, nucleus, mitochondria, chloroplast, golgi apparatus and ribosomes.
Nucleus: Smooth/rough endoplasmic reticulum, nucleolus, nucleotide and nuclear envelope.
Mitochondria: outer membrane, cristate, inner membrane and matrix.
Chloroplast: chlorophyll, outer membrane, inner membrane, intermediate membrane, stroma, thylakoid, lamella and graham.
Nucleus: Is the largest cell organelle and controls all cell activities and holds all genetic information.
Nucleolus: This produces RNA and ribosomes.
Smooth endoplasmic reticulum:Synthesizes lipids and regulates calcium concentration.
Rough endoplasmic reticulum: Contains ribosomes (causing it to be rough) synthesizes proteins.
Golgi apparatus: Processes and packages macromolecules such as lipids and proteins.
Mitochondria: Produce ATP which is chemical energy. Normally labelled the powerhouse of the cell.
Chloroplast: Conducts photosynthesis.
Lysosomes: Enzymes used during digestion.
Ribosomes: Assembles amino acids.
Vacuoles: Holds cell sap which keeps the cell turgid.
Cell wall: Gives sell support
Centrioles: Release spindle fibres during mitosis
Cell membrane: Controls what enters and leaves the cell.
Specialised cell (sperm): Contains acrosome, haploid nucleus, mitochondria and a long tail.
Specialised cell (red blood cell): Haemoglobin, and iron.
3.7 - Mitosis
General: Mitosis is a form of asexual reproduction in gametes which results in two identical daughter cells.
Interphase:
G1 (Gap phase): New cell grows and carries out normal cell functions.
S Phase: DNA is synthesised forming double stranded chromosomes.
G2 (Gap Phase): This is where the cell checks for damage before beginning mitosis.
Prophase:
Chromatin condenses and so can be viewed on a microscope
Centrioles move to opposite poles of the cell
Nuclear envelope and nucleolus break up.
Late prophase: Spindle fibres form.
Metaphase:
Mitotic spindles attach to centromere of each chromosome whilst the chromosomes line up at the equator of the cell.
Anaphase:
Centromeres break splitting chromosomes at the centromere making them daughter chromosomes from sister chromatids.
Cell elongates in preparation for cytokinesis.
Telophase:
New nuclear membrane and nucleolus is formed.
Chromosomes unwind and are no longer visible under a microscope.
Cytokinesis:
Cytoplasm divides forming two new daughter cells
Cell cycle continues
3.3 - Microscopic measurements and calculations
Image size/Actual size = magnification
DM into a M is 0.1
CM into a M is 0.01
MM into a M is 0.001
UM into a M is 0.000001
NM into a M is 0.000000001
3.2 - The electron microscope
Definitions:
Magnification: To enlarge the appearance of the specimen.
Resolution: Too enhance the clarity of a specimen - works with magnification to do so.
Optical:
Overall advantages: Can view living cells, view in colour, and cheaper than electron microscopes.
Overall disadvantages: Has low resolution alongside magnification and so specimens cannot be viewed in great detail and requires a lot f maintenance.
Electron:
Overall advantages: Can view in 3D, allows viewing of cell organelles and has high levels of magnification and resolution.
Overall disadvantages: Cells must be dead to view and cannot be viewed in colour.
TEM (Transmission Electron Microscope): Electrons pass through samples that are normally required to be very thin producing a 2D image.
SEM (Scanning Electron Microscope): Electron beam is directed onto a sample bouncing off it producing a 3D image.
3.8 - The cell cycle
Has two phases
When the cell is replicating organelles - Interphase
When the cell is dividing - Prophase, metaphase, anaphase,telophase, cytokinesis.
3.5 - Analysis of cell components
To analyse cell components this can be done in a number of different ways: microscopy and cell fractionation.
Centrifugation
Density gradient: Cell structures are isolated based on density heaviest first.
Differential: Isolated organisms are separated based on their weight.
Large samples are blended to mix contents and make smaller.
The sample is homogenized to prevent the cell from changing state.
Occurs at low temperatures to prevent any cellular activity occurring.
3.6 - Prokaryotic cells and viruses
Prokaryotes: A single celled organism with no distinct nucleus.
Bacteria cell consists of: Genetic information, Cell membrane, slime capsule, flagella, cell wall and plasmids.
Components float freely within there organelle as they are not membrane bound.
Binary fussion is the process of cell division within prokaryotic cells by:
Circular DNA replicates and attaches to a cell membrane.
Plasmids then replicate.
Cell membrane elongates and pinches in the middle.
A new cell wall forms between the two DNA molecules
This results in two daughter cells with the same amount of circular dNA and a variable number of plasmids.
Virus replication:
Due to viruses not actually being alive they cannot divide and so replicate instead through the use of a host.
They use the proteins on the cell surface of their hist.
They then inject nucleic acid into the host cell which essentially works as 'instructions; to code for new viruses. This occurs during protein synthesis.
3.4 - Eukaryotic cell structure