Topic 1.1 Introduction to Cells Flashcards
State the 4 Hypotheses of Cell Theory
- All cells exist from pre-existing cells
- Cells are capable of independent existence, and are the smallest unit of life
- All living things are composed of cells
- All actions of the cell are controlled by the chemical reactions occurring in the cell.
Exceptions to cell theory
- Skeletal/Striated Muscle fibres
- Aseptate Fungal Hyphae
- Giant algae
Skeletal/Striated Muscle Fiber
- Each Fiber is very long (30mm compared to 0.03mm)
2. Has hundreds of nuclei (multinucleated)
Aseptate Fungal Hyphae
- Hyphae are thread-like structure that have cell membranes and cell walls
- Each hyphae is a multinucleate coenocyte (multinucleated and enclosed in a single membrane)
- Hyphae is not partitioned by septa, challenges the idea that all organisms are made of discrete cells
How does Giant Algae contradict cell theory
- Each Cell is 7-10cm
2. Contradicts the concept of SA:V ratio for cell size
Purpose of Surface area to Volume Ratio
- Limit the cell size (larger cell has higher SA:V)
- If the ratio is too small, exchange will be very slow –> Overheating, low metabolic rate, accumulation of waste products
Define Metabolism
Conversion of organic molecules/chemical reactions in an organism
Define Response
Reaction to stimuli
Define Homeostasis
Maintaining constant interior environment
Define Growth
Increase in size/mass/number of cells within an organism
Define Reproduction
Production of similar cells/offspring
Define Nutrition
Process by which organism take in and make use of food/nutrients
Define excretion
Elimination of metabolic wastes
What are the structure of Paramecium and their functions?
- Nutrition: Feeds on smaller organisms by ingesting through oral groove and digesting them in vesicles (endocytosis)
- Excretion: Expels waste products of metabolism through the anal pore
- Homeostasis: Expels excess water using contractile vacuole
- Response: Reverse its direction of movement using contractile vacuoles when it touches a solid object
- Reproduction: Reproduces asexually using mitosis or sexually using meiosis and gametes
- Movement: Through the cilia and contractile vacuole
- Metabolism: Produces enzymes which catalyse many different chemical reactions in the cytoplasm
What is the structure of Amoeba?
Pseudopodium are fake arms used for phagocytosis to engulf and ingest food.
What are the structure and function of Chlamydomonas?
- Nutrition: Produces its own food by photosynthesis using a chloroplast that occupies much of the cell
- Response: Senses where the brightest light is with its eyespot and swims towards it
- Excretion: Oxygen from photosynthesis diffuses out of the cell
- Homeostasis: Expels excess water using contractile vacuoles
- Reproduction: Reproduces asexually using mitosis or sexually using meiosis and gametes
What is Gene expression?
- While every cell contains the genetic information to carry out every function, only a small portion of genes is activated/expressed to form a protein
- Cells differentiate by expressing some of their genes but not others
What is cell differentiation
- The process in which young immature (unspecialized) cells take on individual characteristics and reach their mature (specialized) form and function
- The differentiated cells express some genes but not others
- Determined by cell’s position relative to others and by chemical gradient
Different levels of organisation in multicellular organisms
o Tissue – cells that differentiate in the same way and are made up of cells of the same type
o Organs – made up of different tissues working together –> carry out specific function
o System – made up of organs working together –> carry out specific function
o All the systems make an organism
What are Emergent Properties
Emergent properties arise in multicellular organisms from the interaction of the cellular component. (e.g. each cell in a tiger is a unit of life that has its own distinct properties such as sensitivity to light in the retina, but all the tiger cells combined would give additional emergent properties – tiger can hunt and kill)
Properties of stem cells
- Divide Repeatedly to produce copious quantities of new cells
- Not fully differentiated –> can differentiate into different types of cells
Types of Stem Cells (too simple to test)
- Embryonic Cells
- Undifferentiated cells capable of continual cell division and developing into ALL cell types of an adult organism
- Make up the bulk of the embryo as it develops - Adult Stem Cells
- Undifferentiated cells capable of cell divisions –> give rise to a limited range of cells
- Occuring in the growing and adult body, within most organs where they replace damaged cells (bone marrow, brain and liver)
Purpose of stem cells
- Nontherapeutic Purposes- Produce large quantities of striated muscle fibers for human consumption
- Therapeutic Purposes: Treat many diseases such as Stargardt’s disease and Leukemia
Describe how Embryonic Stem Cells are used to treat Stargardt’s disease
- Photoreceptor cells in the macula at the retina degenerate and the vision becomes progressively worse resulting in the loss of vision
- Genetic disease which occurs at ages 6-12
- Caused by recessive mutation of a gene called ABCA4 –> Membrane protein used for active transport into the retina cells to malfunction
- Stem cells are treated so that they divide and differentiate into retinal cells
- These cells are injected into the retina
- The retinal cells attach and become functional –> more functional retinal cells lead to better central vision
Describe how Adult Stem Cells are used to treat Leukemia
- In chemotherapy, cancer cells in the bone marrow procuring excessive numbers of WBC are destroyed but normal stem cells in the bone marrow also get killed
- In the Stem Cell Transplant, a large needle is inserted into a large bone (pelvis)
- Fluid is removed –> stem cells are extracted from the fluid and stored by freezing them (adult stem cells that only produce blood cells)
- A high dose of chemotherapy drugs is given to the patient to kill all the cancer cells in the bone marrow
- Stem cells are returned to the patient’s body –> reestablish themselves in the bone marrow, multiply and start producing WBC and RBC
Sources of Stem Cells
- Embryonic Stem Cells
- Embryos are deliberately created by fertilization and allowing the resulting zygote to develop until it is between 4-16 cells (embryonic stem cells)
- Blood can be extracted from the umbilical cord of a newborn baby and stem cells can be obtained from it (frozen and stored to be used later in the baby’s life) - Adult Stem Cells
- Adult Stem cells can be obtained by extracting them from adult tissue
For Stem Cell treatment
- Early stage embryos are just groups of cells have yet to develop essential features of life
- The embryos lack nervous system –> no suffering during stem cell procedures
- If embryos are produced deliberately, no individual will be denied the chance of life
- Large number of embryos produced by IVF are never used for implantation –> use it to save lives
- Stem cells can be used to replace the organs or tissues that have been lost or damaged in a patient
Against Stem Cell treatment
- An embryo is a human life even at its earliest stage and if it dies it is immoral
- IVF involves hormones for the treatment of women, with some associated risk, as well as an invasive surgical procedure for the removal of eggs
- If women are paid to supply eggs for IVF, this may lead to the exploitation of vulnerable groups of women
- Embryonic stem cells are redundant as adult stem cells can be used without causing loss of life
- There is a danger of embryonic stem cells developing into tumour cells as harmful effects are not known yet
