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.
