1.1 Introduction to cells Flashcards
3 core ideas of cell theory
- Cell is the smallest structural unit of life
- Cells can only arise from pre-existing cells
- All living organisms are made of cells
Evidence that organisms are made of cells
- Cells divide and multiply by meiosis or mitosis
- Cells are divided into little compartments when observed under the microscope
- Organelles are specialized structures with specific functions and which cannot survive alone
Atypical examples that disprove cell theory + what they disprove
- Striated muscle cell: Defies that cells should have one nucleus
- Aseptate hyphae: Defies that cell should be a single unit. Usually hyphae have multiple septa to divide.
- Giant algae: Defies idea that a cell should be simple and small. It could exceed 7cm. It is also complex with long stalks and a cap of long branches
7 functions of life
MR H GREN
Functions of life in a paramecium
Reproduction: Large nucleus Response: Cilia Nutrition: Food vacuole Homeostasis: Contractile vacuole Excretion: Cell membrane Metabolism: Cytoplasm
Functions of life in chlorella
Reproduction: Nucleus Nutrition: Chloroplasts Metabolism: Cytoplasm Homeostasis: Contractile vacuole Excretion: Plasma membrane
Importance of SA:V ratio
- If ratio is too small, substances cannot enter cells as quickly and waste products will accumulate
- Cells may overheat as heat is produced faster than it’s released from surface
How do they maintain SA:V?
- Shorter diffusion pathways
- Concentration gradients should be easy to generate
- Folding if membranes to increase SA
Emergent properties and function
Properties that arise from interaction between component parts. It allows multicellular organisms to complete functions that could not have been done by individual cells
Advantages of emergent properties
- Efficient as cells carry out fewer roles faster and so they save energy
- Cells can develop ideal structure for their function to increase efficiency
In which cell is entire genome active?
Totipotent
How do newly formed cells become specialized?
- Cells receive signals to deactivate certain genes
- Deactivated genes are tightly packed into heterochromatin
- Other genes are expressed, loosely packed into euchromatin
- Cells become specialized as genes repressed and expressed are different
How many different specialized cell types exist currently?
220
What is a stem cell?
They are undifferentiated cells that can form more cells of the same type and from which other type of cells can arise from differentiation.
Totipotent
Differentiate into any cell type and can give rise to a complete organism eg. Zygote
Pluripotent
Can self-replicate and differentiate into many types of cells but cannot give rise to a complete organism eg. Embryonic stem cells from blastocyst
Multipotent
Can differentiate into few closely related cells but more limited eg. Adult and cord cells
Unipotent
Can regenerate but only differentiate into cell type it arose from eg. Muscle and skin cells
Stargardt’s macular dystrophy
- Recessive genetic condition
- Mutation causes active transport protein on photoreceptor cells to malfunction and degenerate
- Causes progressive loss of central vision
How does stem cell treatment work for macular dystrophy
Stem cells are divided and differentiated to become retinal cells. They are injected into retina where they hopefully attach and restore vision. Currently only viable treatment
Leukemia
- Cancer of the blood or bone marrow
- Results in abnormally high amounts of poorly functioning white blood cells
How does stem cell treatment work for leukemia?
- Uses hematopoietic stem cells which are harvested from marrow, peripheral blood or cord cells
- Chemo or radiotherapy can be used but it destroys healthy bone marrow so HSC is injected into bone marrow to form new WBCs.
- Less rejection of patient’s own HSC compared to marrow transplants
Differentiation in embryo, cord blood and adult stem cells
Embryo: Differentiate into any type
Cord + Adult: Limited capacity
Genetic damage in embryo, cord blood and adult stem cells
Embryo + Cord: Less chance of genetic damage
Adult: Due to accumulation of mutations throughout life, genetic damage can occur
