Topic 1 - CELL BIOLOGY Flashcards
The cell theory is a fundamental idea of biology.
What are the three principles of cell theory?
+1
- All organisms are composed of 1+ cells
- Cells are the smallest unit of life
- All cells come from pre existing cells
The cell contains inherited information (genes) that are used as instructions for growth, functioning and development
What is the method of scientific progress for evidence testing?
- Observation
- Hypothesis
- Test
- Refute (reject) or corroborate (share results)
- If corroborate, then repeat
- Theory is produced
Define unicellular organism
Give examples (2)
Fully functioning as once cell, and can carry out all basic functions of life
Eg.
Paramecium
Chlorella
What are the 7 functions of life?
MR. GREHN
Metabolism - chemical reactions take place in all living organisms eg. Respiration to release energy
Response - reacting to environmental changes
Growth - when enough nutrition is present etc
Reproduction - producing offspring sexually and asexually
Excretion - release of waste materials /chemicals formed inside of the cell
Homeostasis - keeping conditions within tolerable limit
Nutrition - obtaining food to provide energy needed for growth
Features of a LIGHT microscope:
Cost
State of specimen
Magnification
Specimen prep
Appearance of results
Light microscopes are:
Inexpensive
Dead or alive specimen are used
Magnification: 2000 x
Prep of specimen is simple
See in colour
Features of a ELECTRON microscope:
Cost
State of specimen
Magnification
Specimen prep
Appearance of results
Electron microscopes are:
Expensive
Dead specimen are fixed to a plastic slide
Magnification: 50 000 x
Prep of specimen is complex
See in black and white
What is the difference between these two electron microscopes:
Scanning
Transmission
Scanning - takes 3D images, external, colours may be applied, electrons are bounced off the specimen surface
Transmission - 2D, internal, slicing, series of photos in layers (imagine something chopped in half)
What do microscopes do?
Magnify an object, NOT improve detail
Define resolution
What is the result of a higher resolution?
Ability to distinguish between two points
Higher resolution = more detail
How do you concert from:
m -> mm -> um -> nm
m -> mm etc. = x1000
m
How do you calculate magnification?
I A M
Magnification = Image size
—————
Actual size
How do you calculate surface area to volume ratio?
Surface area
——————
volume
Do smaller things have a smaller /larger sa:v ratio?
What does this allow for?
Smaller things have more sa:v ratio
This allows for faster movements and disffusion
How do unicellular eukaryotes reproduce?
Asexually, by binary fission
Or sexually (fusion of gametes to produce a zygote)
Maths calculations
Sphere:
Surface area
Volume
Sa = 4 x pi x r^2
Volume = 4/3 x pi x r^2
What happens to the sa and volume of an object as it’s width increases
As the width increases, both the sa and volume increase
But sa increases at a slower rate than the volume
Define diffusion
Is it less /more efficient in cells with a small sa?
The net movement of particles from area of high conc -> area of low conc
Less efficient in cells with small sa relative to their volume
Why is the controlling factor of a cells size?
How do large organisms overcome this?
Effectiveness of diffusion is the controlling factor
Large organisms overcome this by being multicellular
Single cells organism:
Give an example
Size
Describe sa:v
Are requirements easily met for transport of substances?
What does the plasma membrane do?
Eg. Amoeba
Small
Large sa
Cells requirements met by diffusion /active transport of materials into /out of the cell
Plasma membrane: regulates movements of substances into /out of the cell
Multicellular organism:
Give an example
Size
Describe sa:v
Are requirements easily met for transport of substances?
What specialised features does it have?
Eg. Plants and animals
Large
Have a small sa:v ratio
Requirements are not easily met, need specialised systems to transport the materials needed to /from cells and tissues in the body
Embryonic cells:
Type (—potent wise)
Do they retain their potency?
What are they used for?
How are they obtained?
Is it ethical?
Where are they derived from?
Pluripotent - can differentiate into any cells of body, not placental though
Yes, they retain their potency through multiple cell divisions
Used in therapeutic cases - regenerative medicine and tissue replacement
Involves the deliberate creation and destruction of embryos
Unethical
Derived from inner mass of blastocysts (50-150 cells)
Adult stem cells:
Type (—potent wise)
What are they used for?
Is it ethical?
Where are they found?
Multipotent - can differentiate into limited number of cells, usually related to the tissue of origin
Used to treat diseases such as Leukemia and blood disorders
Fewer ethical issues as no embryo destruction involved
Found in (adult): bone marrow, brain, fat, liver (children): umbilical coed blood
Define stem cells
Undifferentiated cells found in multicellular organisms
Unspecialised and can give rise to many cell types that make up tissues and organs of multicellular organisms
Stem cell categories
Define:
Totipotent (totally)
Pluripotent (plural)
Multipotent
Totipotent - differentiate into all cells of an organism
Pluripotent - give rise to any cell of body (not extra embryonic cells eg. Placenta)
Multipotent - give rise to limited cell types related to their tissue of origin
Proteins within a membrane
What is:
Enzymatic action?
Enzymatic action - membrane enzymes have many activities incl. catalysing biochemical reactions inside cells
Eg. Kinase
Proteins within a membrane
What is:
Cell adhesion?
Cell adhesion - allow cells to stick to eo/ and surroundings (proteins located in cell surfaces)
CAM - Cell Adhesion Molecules
Proteins within a membrane
What is:
Pumps for active transport?
Pumps and active transport - special proteins embedded in cell membrane for transport.
Eg. Sodium potassium pump (Na+ -> K- ions)
Use ATP chemical energy
Have receptors that bind to specific molecules and transport them across membrane
Proteins within a membrane
What is:
Channels for passive transport
Channels for passive transport - channel proteins and carrier proteins allow solutes to cross membranes (from tunnel for molecules /ions to cross)
Proteins within a membrane
What is:
Cell to cell communication
Cell to cell communication - receptors relay signals between cell internal /external environments
Membrane signalling involves proteins shaped into receptors embedded in cell membrane that biophysically connect triggers external environment
Proteins within a membrane
What is:
Hormone binding sites?
Amino acid derived proteins bind to receptors in a plasma membrane
This activated a protein which activated adenylyl
Converts ATP -> CAMP (2nd messenger mediates cell specific response)
Hormones react w/ receptors to induce changes in metabolism and activity of cell
What is a passive process?
Do molecules move up /down the conc gradient?
List 3 examples relating to membrane crossing
A process that doesn’t require energy
Molecules move down their conc gradient
- diffusion
- osmosis
- facilitated diffusion
What is an active process?
Do molecules move up /down the conc gradient?
List 2 examples relating to membrane crossing
A process that uses energy in the form of ATP
Molecules move up OR down the conc gradient
- active transport
- bulk transport (eg. Waste /protein particles,, big molecules)
Define diffusion (in terms of membrane crossing)
Conc?
Substances other than water move between the phospholipid molecules or through proteins that posses channels
High -> low conc
Define osmosis (in terms of membrane crossing)
Only water moves through the membrane using aquaporins, which are proteins w/ specialised channels for water movement
Water high -> low conc
Across a pp membrane
What is facilitated diffusion in terms of membrane crossing?
Non channel protein carriers change shape to allow movement of substances other than eager
Proteins help (facilitate) things pass
Define active transport in terms of membrane crossing
Against conc gradient
Low -> high
Requires ATP energy
What is a sodium-potassium pump in terms of membrane crossing?
Action potention for nervous transmission
ATP fuels for proteins that carry the molecule (helps go against the conc gradient)
What is the difference between ENDOcytosis and EXOcytosis?
ENDOcytosis - allows macromolecules to enter the cell
EXOcytocis - allows macromolecule to exit the cell
Define phagocytosis
The intake of large particulate matter
Define pinocytosis
The intake of extra cellular fluids
What is the plasma membrane?
Who has one?
A lipid bilayer w/ proteins moving freely within it
All cells have one (bacteria, fungi, plants etc also have a cell wall outside of the cell membrane)
What is the accepted model for the membrane structure?
The fluid mosaic model
What was the process of Louis Pasteurs experiment?
- Boil nutrient broth to sterilise it
- Place in 3 flasks, incubation over a period of time
- Sample of each flask is transferred to plate containing afar and was incubated
Flask1 - open
Flask2 - plugged w/ a bung
Flask3 - attached to tunnel w/ distilled water in it
What did Pastuers experiment prove /disprove?
Disproved and falsified the concept of spontaneous generation
What is a scientific theory?
An explanation of a scientific event supported by scientific evidence
What was the main ideas of Lynn Margulis’ endosymbiotic theory? (1981)
- 2 billion years ago, bacteria cell took residence in eukaryotic cell
- the eukaryotic cells acted as a ‘predator’, formed symbiotic relationship
- bacterial cell went through changes to become mitochondrion
What evidence of mitochondrion proves the endosymbiotic theory?
- mitochondrion is same size as bacterial cell
- they both divide by fission
- they both have naked DNA, and so can survive on their own
What modern day evidence is there to support the endosymbiotic theory?
Eg. Protist: Hatena
Slug: Elysia Chlorotica
Hatena: can infest green alga and form symbiotic relationships
Elysia Chlorotica ingests algae. Algae’s chloroplasts retained one the indigestive tract.
Light carries our photosynthesis, and so doesn’t have to move
Large sa to absorb light
Why do cells divide? (4 reasons - 3 mitosis, 1 meiosis)
Mitosis:
Growth
Repair
Replacement of worn out cells
Meiosis:
Reproduction
The cell cycle
What happens in:
G1?
S?
G2?
M?
Growth 1 - major growth, du cellular structures grow. Organelles and proteins replicate
Synthesis - DNA synthesis (DNA replicates)
Growth 2 - DNA condenses from chromatin -> chromosomes. Microtubules begin to form
Mitotic phase - where actual division takes place
What are cyclins?
What do they do?
Cyclins are the proteins that control the cell cycle
They bind to CDK (Cyclin Dependent protein Kinases) and act as activated enzymes to allow cell to pass onto the next phase
What is the G0 phase?
Give 2 examples of cells that enter G0 phase
Some cells stop after G1 and enter a non growing state
Eg. Nerve and muscle cells
Why are the following exceptions to the cell theory:
The alga Caulerpa
Muscle fibres
Some fungi
Caulerpa - consists of one multi-uncleated cell, yet grows to the size of a large plant. Shape maintained by cell wall and microtubules, but there are no separate cells
Muscle fibres - form from the fusion of many myoblasts (individual muscle stem cells) producing large multi-nucleated fibre. These fibres can be 20cm+ long
Fungi - produce hyphae that lack cross walls dividing the hyphae into cells. They are known as asephate hyphae (as opposed to separate hyphae that do not contain cross walls)
Why are cells limited in size?
What happens if they get too big?
They need nutrients and minerals in order to grow
If they get too big then they won’t be able to carry out their functions
How does new evidence influence theories?
Give an example of a theory that was changed
New evidence brings about falsification of other /older theories
Eg. Plum pudding model
What does cholesterol do for membranes?
What would happen wo/ it?
Cholesterol allows for membrane fluidity at a wide range of temps
Wo/ it, it would become rigid
What is polarity /a polar molecule?
When a neutral molecule has a positive area at one end and a negative area at the other
Define these properties of stem cells:
Self renewal
Potency
Self renewal - the ability to divide many times while maintaining an unspecialised state
Potency - the ability to differentiate into specialised cells
Define compartmentalised
Compartmentalised - membrane bound
What is a scientific theory?
An explanation of a scientific event supported by scientific evidence
Define autotrophic
Give an example
Autotrophic - produces own food
Eg. Plants
What is the interphase of the cell division cycle?
What stages does it include?
The largest and longest phases
Incl. G1, S, G2
What is mitotic index?
Tells us what % of cells are in mitosis
How do you calculate mitotic index?
No. Cells in mitosis
————————— x100
Total no. Cells
