Introduction to cells Flashcards
What three principles are stated by the Cell Theory?
- All living things are made of cells
- All the cells originate from pre-existing cells
- Cells are the smallest units of life
What are atypical cells?
Cells that differ from the description specified by the cell theory
Name examples of atypical cells
- Striated muscle cell
- It has multiple nuclei per cell (multinucleated)
- It is much larger than a typical cell - Giant algae: Acetabularia
- Gigantic single-celled algae
- Has a complex structure (three parts) - Aseptate fungal hyphae
- Multinucleated
- No dividing cell wall (share a cytoplasm)
Name examples of unicellular organisms
Bacteria, archaea, unicellular algae and unicellular fungi
What are the 7 functions of life?
Hint: Mr H. Gren
M= metabolism R= reproduction H= homeostasis G= growth R= response/sensitivity E= excretion N= nutrition
What are the descriptions of metabolism, reproduction, homeostasis and growth
Metabolism= the set of life-supporting chemical reactions that take place within the cells Reproduction= production of offspring, to pass on genetic information to the next generation Homeostasis= maintenance of a constant internal environment by regulating cell conditions Growth= increase in size and shape over a period of time
What are the descriptions of response, excretion and nutrition?
Response/sensitivity= respond to stimuli (changes in external environment) Excretion= removal of metabolic waste products Nutrition= intake of nutrients. Plants during photosynthesis and in animals and fungi by absorption of organic matter
What are the characteristics of Paramecium?
- Unicellular
- Lives in an aquatic environment
- Heterotrophs
- Move using their cilia (beat to propel the cell)
Characteristics of Chlamydomonas
- Unicellular
- Smaller than a paramecium
- Contains flagella for movement
- Autotrophs
Explain the functions of life of Paramecium
Metabolism- enzymes catalyse the reactions in the cytoplasm
Growth- increases in size and eventually divides into 2 daughter cells
Response- the cilia detect the stimuli
Homeostasis- excess water is collected and expelled through the plasma membrane (osmoregulation) to maintain water balance
Nutrition- heterotroph, engulfs and absorbs food which is used in the cytoplasm
Reproduction- can perform sexual and asexual reproduction, uses binary fission to produce 2 daughter cells
Excretion- nutrients reach anal pore and is expelled
Explain the functions of life of Chlamydomonas
Metabolism- enzymes catalyse the reactions in the cytoplasm
Growth- uses photosynthesis which increases the size of the cell and divides into 2 daughter cells
Response- contains an eyespot and flagellum to move to a brighter region for photosynthesis
Homeostasis- excess water is collected and expelled through the plasma membrane (osmoregulation) to maintain water balance
Nutrition- uses photosynthesis which occurs in the cytoplasm
Reproduction- can perform sexual and asexual reproduction uses binary fission
Excretion- excretes through the large surface of the plasma membrane
Why is the surface area to volume ratio important?
When a cell grows, its volume increases much more than its surface area. When the SA is too small, not enough nutrition and waste products can pass through the membrane.
When the SA increases, the SA: V ratio is restored
The SA: V ratio limits the overall size of a cell
What are the three steps of the evolution of multicellular organisms?
- Organisms grew larger (could expand further)
- The cells began to adapt to become specialized
- Multicellular organisms displayed emergent properties
What is the definition of emergent properties?
An organism can do more things as different parts collaborate to perform all functions
What is cellular differentiation?
When an unspecialized stem cell changes and carries out a specific function.
Side note, all cells start out as stem cells but during their embryonic development, they become differentiated.
Specialized tissues can develop by cell differentiation into a multicellular organism.
What is an important factor in differentiation?
The only way cells become different cell types is due to the expression of different genes. Only a small part of the genes of the entire genome is activated. The genes give rise to certain properties.
What are stem cells?
They are undifferentiated cells of multicellular organisms that can form more cells of the same type indefinitely.
Can stem cells produce different types of cells?
Stem cells can also give rise to cells that are not the same type by differentiation. These cells have the ability to differentiate into specialized cells when given the right stimulus.
What are the 4 types of stem cells?
- Totipotent stem cells: can differentiate into any type of cell and can give rise to a complete organism. E.g. cell after fertilization
- Pluripotent stem cells: can differentiate into all body cells, cannot give rise to a whole organism.
E.g. embryonic stem cells - Multipotent stem cells: can differentiate into a few closely related types of body cells. E.g. umbilical cord stem cells
- Unipotent stem cells: can only differentiate into their associate cell type. E.g. liver stem cells
Why are stem cells used for therapeutic reasons?
Stem cells have the ability to divide indefinitely and give rise to specific cell types. During the embryonic development, the cells become differentiated.
Give two examples of diseases for which stem cells are used.
Stargardt’s disease
- It is an eye disease that affects a part of the retina which is caused by a recessive genetic mutation in gene ABCA4
- Retinal cells which are derived from human embryonic stem cells are injected into the retina
Leukaemia
- A type of cancer of blood or bone marrow, there are too many white blood cells
- Hematopoietic stem cells (HSCs) which are multipotent and harvested from an umbilical or peripheral blood
- Using chemotherapy and the transplant of HSCs, healthy white blood cells are made
What are the ethical concerns about using stem cells for therapeutic reasons?
Pro:
- Used to eliminate diseases or disabilities
- The death of the donor is not required nor pressure on the body functions
- Unlikely to inflict pain
Con:
- Requires the destruction of embryos in their production
- Terminated early-stage embryos
What is the formula for calculating the Magnification?
M=I/O
M: magnification
I: image size
O: object size/actual size
mm —> um (x1000)
um —> nm (x1000)
Bring to same units
