Topic 1.1: Introduction to Cells Flashcards
Principles of Cell theory
a) All living things are composed of cells
b) The cell is the smallest unit of life
c) Cells only arise from pre-existing cells
Caveats to cell theory
a) Striated muscle fibres
b) Aseptate fungal hyphae
c) Giant algae
Striated muscle fibres
a) Have multiple nuclei despite being surrounded by a continuous plasma membrane.
b) Challenges the idea that cells always function as autonomous units.
Aseptate fungal hyphae
a) Not partitioned by septa and have a continuous cytoplasm along the length of the hyphae.
b) Challenges the idea that living structures are composed of discrete cells.
Giant algae
a) Grow very large sizes
b) Challenges the idea that larger organisms are always made of many microscopic cells.
Unicellular organisms
Smallest organisms capable of independent life
Functions of Life
Metabolism Reproduction Sensitivity Homeostasis Excretion Nutrition Growth
Metabolism
Undertaking chemical reactions
Reproduction
Producing offspring either sexually or asexually
Sensitivity
Responsive to internal and external stimuli
Homeostasis
Maintain a stable internal environment
Excretion
Removal of waste products
Nutrition
Exchange of material and gases with the environment
Growth
Change shape or size
Paramecium
a) Food is enclosed within small vacuoles that contain enzymes for digestion
b) Surrounded by small hairs (cilia) which allow it to move
c) Solid wastes removed via an anal pore
d) Gas exchange via diffusion
e) Divide asexually or by conjugation
Scenedesmus
a) Exchange gases and other materials via diffusion
b) Organic molecules produced via photosynthesis
c) Non-motile autospores via the internal asexual division of the parent cell
What do cells need to survive?
a) Production of chemical energy to survive
b) Exchange of materials with the environment
Rate of metabolism
A function of the cell’s volume
Rate of exchange of materials
A function of its surface area
SA : Vol ratio as a cell grows
As a cell grows, volume increases faster than surface area, leading to a decreased SA:Vol ratio
What happens if metabolic rate exceeds the rate of exchange of materials?
Cell will eventually die
Why do cells divide and remain small?
To maintain a high SA:Vol ratio
Magnification
Formula
Magnification = Image size / Actual size
Emergent Properties
The interaction of individual component produces new functions such as thinking
Organization of Multicellular Organisms
Cells -> Tissues -> Organs -> Organ systems -> Organism
Differentiation
Process where newly formed cells become more specialized and distinct from one another as they mature
What involves differentiation?
Expression of some genes and not others in a cell’s genome
Stem cells properties
Self-Renewal – They can continuously divide and replicate
Potency – Capacity to differentiate into specialized cell types
Types of stem cells
a) Totipotent – Can form any cell type, as well as extra-embryonic tissue
b) Pluripotent – Can form any cell type
c) Multipotent – Can differentiate into a number of closely related cell types
d) Unipotent – Cannot differentiate, but are capable of self renewal
Uses of Stem Cells
Necessary for embryonic development as well as therapeutic uses
Therapeutic Use of Stem Cells
Stem cells can be used to replace damaged or diseased cells with healthy, functioning ones
Example of Stem Cell Therapy
a) Stargardt’s Disease is an inherited form of macular degeneration that causes progressive vision loss to the point of blindness.
b) Caused by a gene mutation in photoreceptor cells
c) Treated by replacing dead cells in the retina with functioning ones derived from stem cells.
