Module 2: Cells And Microscopy Flashcards
Microscopy, Cell structure, Cell Membranes, Transport Across cell membranes, Cell division, Specialisation and Organisation
Function of Microtubules
Involved in transport of organelles
Make up spindle fibres for cell division
Function of microfilaments
Mechanical strength
Link membrane proteins to cytoplasm proteins
Provide supporting framework
Protein synthesis
1) DNA code to produce protein is converted to mRNA
2)mRNA escapes through nuclear pore
3)mRNA attach to ribosome, protein is synthesised. Ribosome attach to RER. Folded + processed here
4)proteins packaged into vesicles + transported to golgi apparatus
5)proteins are structurally modified. Carbohydrate chains added
6)proteins leave golgi apparatus in a transport vesicle towards the plasma membrane
7)vesicle fuses with cell membrane. Protein is released by Exocytosis
Magnification equation
Image size / actual size
Define Resolution
The shortest distance between two objects, so that they can still clearly be seen separately
Why do we stain samples?
A stain colours some parts of a cell more clearly than others.
E.g: methylene blue stains nucleus stronger blue than cytoplasm.
A stain colours certain parts of a cell when it reacts with chemicals in it
E.g: iodine colours potato starch purple/blue black
This makes them more visible
Maximum Magnifican of:
Light microscopes
Scanning Electron
Transmission Electron
Light: x1500
Transmission: x1,000,000 +
Scanning: x500, 000
Prokaryote
A single-celled Organism that lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle
Function of Cholesterol in the plasma membrane
Gives stability and fluidity
Pulls areas of membrane together
Stops phospholipids from grouping closely and crystallising
Structure andFunction of Channel proteins in membrane
Provides hydrophilic channel that allows passive movement of Polar molecules and ions
Held in place by interaction between hydrophobic core and hydrophobic R-groups of proteins
Intrinsic
Some are Gated
Function of carrier proteins in the membrane
Involved in both passive and active transport
Shaped to fit specific Molecules
Opens at other end
Flip-flop movement
Diffusion
The net movement of molecules from a region of high concentration to a region of lower concentration down a concentration gradient
What is Facilitated diffusion
Where protein carrier molecules within the membrane assist the passage of substances across the membrane in the direction of their concentration gradient
Factors affecting the rate of diffusion
Temperature
Concentration gradient
Stirring/movement
Surface area
Diffusion pathway
Size of molecule (smaller molecule=less energy needed to move them)
Active Transport
The movement of molecules against the concentration gradient. It requires energy in the form of ATP
Bulk Transport (in active transport)
moving large amounts of materials in or out of the cells
Process of Endocytosis
-Materials moved into cell in ‘bulk’
-membrane surrounds material, breaks apart and moves into cell
-Enzymes in the cell break down the material, allowing it to pass through the membrane into the cell
Exocytosis process
-Material is transported to cell membrane in secretory vesicle
-vesicle fuse with cell membrane
-release their contents outside of the cell
Why is active transport needed?
-Carries substances faster
-To accumulate substances into and out of the cell
Osmosis
the Net movement of water from a region of high water potential to a region of lower water potential through a selectively permeable membrane
define Water Potential
The tendency of water molecules to move from one place to another
What is the Water potential of pure water?
ZERO
Water potential is the measure of free…
free energy available for water molecules to move.
This free energy is greatest in pure water.
Hypotonic solution
Solution is less concentrated than cell
Isotonic solution
Solution has same concentration as cell
Hypertonic Solution
Solution has higher concentration than cell
Animal cell placed in Isotonic solution
-No Net gain or loss of water
-The cell’s water content remains steady
Animal cell placed in hypertonic solution
-Cells lose water by osmosis and shrink
-Described as being CRENATED
Animal cells placed in Hypotonic Solution
-Cells gain water by osmosis and Burst
-Bursting of red cells when placed in Hypotonic solution is called Haemolysis
Fully Turgid Plant cell placed in Hypotonic solution
-net movement of water into the cell by osmosis
-Protoplast swells and presses against cell wall
Plant Cell placed in Isotonic solution
-Cell displays incipient Plasmolysis. This is where the membrane is just beginning to pull away from the cell.
-Protoplast ceases to press against cell wall
Plant cell placed in Hypertonic Solution
-Net movement of water out of the cell by osmosis
-Protoplast shrinks
-Protoplast pulled completely away from cell wall
-Cell is fully plasmolysed (flaccid)
What are the 6 stages of cell division?
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
What happens at Interphase in mitosis?
Each chromosome is replicated
What happens at Prophase in Mitosis?
Chromosomes become Condense
. Able to see pair of sister chromatids / chromosomes have become visible
Nuclear envolope and nucleolus breaks down / dissapearred
Centriole goes to each pole to form spindle
What happens at Metaphase in Mitosis?
Chromosomes move to equator and centromeres attach to spindle
What happens at Anaphase in Mitosis?
Replicated sister chromatids that make up chromosome are separated
Centromere splits / Chromatids are separating
Each sister chromatid becomes a chromosome (identical to parent cell)
Spindles shorten and move sister chromatids towards poles
What happens at Telophase in Mitosis?
Chromosomes reach new poles
New nuclear envolope reforms around downs centre of cell
Spindle breaks down
Chromosomes uncoi
Cytokinesis / cell is starting to divide
What is Cytokinesis?
When the cell splits in two, membrane splits
Prophase 1 Meiosis
Homologous chromosomes pair up -> Bivalent
*Crossing over (swapping alleles)
How is Metaphase 1 in Meiosis different to mitosis?
- the homologous pairs of chromosomes assemble along equator instead of the individual chromosomes
Independent assortment of homologous chromosomes occurs (the way the chromosomes align along the equator e.g: Fathers chromosome on one side of equator, Mother on other. A mix..)
Chiasmata
The point of breakage where alleles between homologous chromosomes are swapped
How is Anaphase 1 in Meiosis different to mitosis?
The homologous chromosomes are pulled to opposite poles and chromatids stay joined together/ NO separation of centromere
Telophase II Meiosis
In total, 4 haploid cells (gametes)
How is Telophase 1 in Meiosis different to mitosis?
The reduction of chromosome number from diploid to haploid is complete
n=2
how many cells are produced from meiosis?
4 unidentical cells (due to chromosomes crossing over)
What 3 stages in meiosis lead to genetic variation
1) Prophase 1 -Crossing over of homologous chromosomes (swapping alleles)
2)Metaphase 1- independent assortment of homologous chromosomes (arrangement along equator)
3)Metaphase 2- Independent assortment of sister chromatids
What is a Stem cell
An unspecialised cell that can differentiate into different types of cell
What is a Totipotent stem cell
Can make all cell types
Zygote and early embryo cells are like this
What is a Pluripotent stem cell
Capable of producing all cells derived from a particular germ layer: ectoderm, endoderm, mesoderm.
Present in early embryos
What is a multipotent stem cell
Can make a restricted range of related cell types
E.g: haemopoietic stem cells make red, white blood cells and platelets
What can cambium differentiate into
Xylem and phloem
What is a tissue
Collection of cells that are similar to each other and perform a common function
What is an organ
A collection of tissues working together to perform a particular function
What is an organ system
A number of organs working together to perform an overall life function
How is a palisade cell specialised for its function
Lots of chloroplast to absorb large amounts of light for photosynthesis
How is squamous Epithelial cell specialised for its function
-squat/flat cells
-once cell thick
To create short diffusion distance
How are elastic fibres used in airways
Recoil of alveoli
What is the cell wall of a prokaryote made of
Peptodiglycan
What is the cell wall of plants made of
Cellulose
What is the cell wall of fungi made if
Chitin
Suggest why sexual reproduction in Hydra usually occurs in the winter. When conditions are unfavourable
(some offspring) might survive unfavourable
conditions
(some) offspring have useful alleles
(named) unfavourable conditions mean (all) offspring
might die (if asexual)
Mitosis and meiosis are important in the life cycles of organisms.
(a) Hydra is a small animal that lives in fresh water. When environmental conditions are
favourable, Hydra reproduces asexually. Large numbers of offspring can be produced in this
way.
Suggest why Hydra reproduces asexually when conditions are favourable.
genetically identical offspring
offspring produced , rapidly / in large numbers
(all) offspring will , find conditions favourable / have
same adaptations
show the main differences in structure between glucose and
starch.
Glucose Starch
monomer polymer
monosaccharide polysaccharide
no glycosidic bonds glycosidic bonds
C6H12O6 / more H and O C6H10O5 / less H and O
what are homologous chromosomes
Homologous = same
A pair of chromosomes with the same structure and genes, one from mum and one from dad
Phospholipids bilayers act as a barrier to most ______-_____ substances (the non-polar fatty acid tails prevent ____ or ____ from passing across the membrane)
water-soluble
polar molecules or ions
There are three main receptor types:
(the roles)
Signalling receptors for hormones and neurotransmitters
Receptors involved in endocytosis
Receptors involved in cell adhesion and stabilisation (as the carbohydrate part can form hydrogen bonds with water molecules surrounding the cell
Transport proteins create ______channels to allow ____ + _____ molecules to travel through the membrane
hydrophilic
ions and polar
The permeability of cell membranes is affected by different factors or conditions, such as:
Temperature
Solvent concentration
How do organic solvent conc. affect the structure and permeability of the plasma membrane
Organic solvents can increase cell membrane permeability as they dissolve the lipids in the membrane, causing the membrane to lose its structure
As temperature increases, lipids become more ____
This increased fluidity reduces the _____ of the cell membrane as a barrier to polar molecules, meaning polar molecules can pass through
fluid
effectiveness
At higher temperatures, any diffusion taking place through the cell membrane will also occur at a _______(due to increased kinetic energy)
higher speed
At higher temperatures, any diffusion taking place through the cell membrane will also occur at a _______(due to increased kinetic energy)
higher speed
How does increasing temperature effect the permeability and structure of the plasma membrane (in terms of proteins)
At a certain temperature (often around 40°C) many proteins (including those in cell membranes) begin to denature
This disrupts the membrane structure, meaning it no longer forms an effective barrier
As a result, substances can pass freely through the disrupted membrane
This process is irreversible
How does Surface Area effect the rate of diffusion
A larger surface area which diffusion is taking place, the greater the number of ions or molecules that can cross it at one moment, therefore the faster it diffuses
G1 CHECKPOINT
- chromosomes are checked for damage. If damage is detected then the cell does not advance into the S phase until repairs have been made
Checkpoint During S phase
- chromosomes are checked to ensure they have been replicated. If all the chromosomes haven’t been successfully replicated then the cell cycle stops
G2 phase checkpoint
During G2phase- an additional check for DNA damage occurs after the DNA has been replicated . The cell cycle will be delayed until any necessary repairs are made
Metaphase checkpoint
During metaphase- the final check determines whether the chromosomes are correctly attached to the spindle fibres prior to anaphase
The movement from one phase to another is triggered by chemical signals called…….
Cyclins
G1 phase
G1phase–Gstands forgrowth
Cells make the RNA, enzymes and other proteins required for growthduring the G1phase
S phase of interphase
TheDNA in the nucleus replicates
Synthesis of DNA
Identical sister chromatids are made
G2 phase cell cycle
During the G2phase, thecell continues to grow and the new DNA that has been synthesised is checkedand any errors are usually repaired
Other preparations for cell division are made (eg. production of tubulin protein, which is used to make microtubules for the mitotic spindle)
