Biology DP1 term 1 Flashcards
Cell theory states
All living things are composed of cells (or cell products)
The cell is the smallest unit of life
Cells only arise from pre-existing cells
- Cells multiply through division
- All life evolved from simpler ancestors
- mitosis -> genetically identical diploid daughter cells
- meiosis -> haploid gametes
Cell theory exceptions
Striated Muscle cells
- multi-nucleated (>1 nucleus per cell)
- long bois (300mm)
- doesn’t conform w/ standard 1:1 nucleus and cells ratio
Aseptate Fungal Hyphae
- Challenges idea that cell is single unit
· Have continuous cytoplasm (no end cell wall or membrane)
· Cell walls composed of chitin
· Consists of thread-like structures called hyphae
· Hyphae not divided up into sub-units containing single nucleus
· Instead, there are long undivided sections which contain many nuclei.
Giant Algae (acetabularia)
- absolutely fuking massive (5-100mm)
- 3 parts (bottom rhizoid, long stalk, top cap)
- single nucleus
- challenges that cells = simple and small
Functions of life
Metabolism
Response
Homeostasis
Growth
Reproduction
Excretion
Nutrition
(MR H GREN)
Functions of life in Paramecium
- nutrition: feed on micro organisms such as algae and fungus. They sue their cilia to bring food t themselves.
- metabolism: Produce the enzymes they need to break down the food that they intake
- growth: it will grow until its too large and then it will split into two
- response: Using their cilia, they respond and sense their environment
- excretion: Anal pores
- Homeostasis: Two contractile vacuole that allow them to push water out of their being since they have no cell wall to keep water out.
- Reproduction: asexual reproduction through binary fission
Functions of life in Paramecium
(1) Nutrition: Food vacuoles have food to digest where nutrients are absorbed
(2) Metabolism: Enzymes in cytoplasm perform respiration
(3) Growth: Between reproduction, grows through the nutrition and metabolism, creating more enzymes and structures using 70S ribosomes
(4) Response: Cilia: moves the cell through water
(5) Excretion: Membrane controls entrance/exit of materials
(6) Homeostasis: Contractile vacuoles fill with water or expel it to regulate water content in cell
(7) Reproduction: Nucleus divides for asexual reproduction
functions of life in chlorella
Demonstrates functions of life in the following ways:
o Nutrition: Produces its own food by photosynthesis using a chloroplast that occupies much of the cell.
o Growth: Increases in size and dry mass due to photosynthesis and absorption of minerals.
o Response: Reacts to stimuli, e.g. senses where the brightest light is with its eyespot and swims towards it.
o Excretion: Expels waste products of metabolism, e.g. oxygen from photosynthesis diffuses out of the cell.
o Metabolism: Produces enzymes which catalyse many different chemical reactions in the cytoplasm.
o Homeostasis: Keeps internal condition within limits, e.g. expels excess water using contractile vacuoles.
o Reproduction: Reproduces asexually using mitosis or sexually using meiosis and gametes.
Why are cells small?
SA:Vol ratio is large
- diffusion pathways are shorter, so takes less
time/energy to move
- concentration gradients are easier to generate, so more efficient diffusion
- metabolic rate and exchange rate needs to be equal
- metabolic rate - function of mass/volume
- exchange rate - function of surface area
- as cell gets bigger, volume increases faster than SA, so MR>ER
- if exchange rate and metabolic rate not equal, cell will die
- so cell stay small by dividing constantly to maintain SA:vol ratio
How do organisms maximise SA:Volume ratio?
cells divide
- 2 cells more efficient than 1
- allows specialized/differentiated cells = more
complex life
cells compartmentalize
- Organelles (membranes carry out metabolic functions
organelles
- made of membranes to maximize SA
organs
- Small intestine
- Alveoli
- plant roots
Cell differentiation
- All cells of an organism have same Genome
- Not all genes expressed
- new cells get signals to deactivate or
activate(rare) gene - e.g skin cells don’t need haemoglobin so that
gene go bye bye - less active genes = more specialized
specialized tissue
- specialized cell happen cuz differentiation
- 220 in human body
Stem Cells
unspecialized cells:
- can continousily divide/replicate
- differentiate to special cells
Types + differentiation:
- totipotent - any type
- pluripotent - many type
- multipotent - few type
- unipotent - you type
Embryonic stem cell info
Ease of extraction:
- XS embryos from IVF
Ethics
- only got from embryo destruction
Growth potential
- almost unlimited
Tumor risk
- higher risk
Differentiation
- any (totipotent)
Genetic damage
- less than adult cells
Compatibility
- not genetically identical to the patient
adult stem cells info
Ease of extraction:
- difficult to obtain cuz very few and buried deep
Ethics:
- adult can give consent
Growth potential:
- reduced potential
Tumor risk:
- lower risk
Differentiation:
- limited capacity to differentiate
Genetic damage:
- damage cuz mutation through life
Compatibility:
- fully compatible cuz stem cells = genetically identical
Arguments for therapeutic cloning
- Stem cell research = maybe future discoveries + beneficial technologies
- May be used to cure serious diseases or disabilities with cell therapy (replacing bad cells with good ones)
- Transplants are less likely to be rejected as they are cells which are genetically identical to the parent
- Transplants do not require the death of another human
- Stem cells can be taken from embryos that have stopped developing and would have died anyway (e.g. abortions)
- Cells are taken at a stage when the embryo has no nervous system and can arguably feel no pain
- Stem cells can be created without the need for fertilization and destruction of ‘natural’ human embryos
- induced pluripotent stem cells
arguments against therapeutic cloning
- Involves the creation and destruction of human embryos (at what point do we afford the right to life?)
- Embryonic stem cells are capable of continued division and may develop into cancerous cells and cause tumors
- More embryos are generally produced than are needed, so excess embryos are killed
- With additional cost and effort, alternative technologies may fulfill similar roles (e.g. nuclear reprogramming of differentiated cell lines)
- Religious or moral objections due to the ‘playing God’ argument.
- The embryo which is created could potentially be used in IVF and develop into a human fetus, so are we creating human life to destroy it?
- Although cloning humans reproductively is illegal, this has not been ratified by all nations. Potential for a race to clone the first human.
Stargardt’s disease
The problem
•Affects around one in 10,000 children
•Recessive genetic (inherited) condition
•The mutation causes an active transport protein on photoreceptor cells to malfunction
•The photoreceptor cells degenerate
•the production of a dysfunctional protein that cannot perform energy transport
•that causes progressive, and eventually total, loss of central vision
The treatment
•Embryonic stem cells are treated to divide and differntiate to become retinal cells
•The retinal cells are injected into the retina
•The retinal cells attach to the retina and become functional
•Central vision improves as a result of more functional retinal cells
The future
•This treatment is still in at the stage of limited clinical trials, but will likely be in usage in the future
Resolution of light vs electron microscope
Resolution = shortest distance between 2 points that can be distinguished
Electron microscopes have have higher resolutions cuz:
- visible light has wavelength (400-700nm)
- electrons have wavelength (2-12pm)
Define ultrastructure
- structures of specimen, at least 0.1nm in smallest dimension
prokaryotic structure (draw)
Cells wall
- Peptidoglycan layer that protects d
maintains cell shape
Plasma Membrane
- Phospholipid layer w/proteins; controls
movement of stuff inside and out of cell
Nucleoid
- single, free strand of DNA (big one)
Plasmid
- small circle of DNA
70s ribosomes
- site of protein synthesis
pili
- protein filaments; cell adhesion + conjugation
Flagella
- longs structure of cell movement
