IB Biology: Level 1 - Intro to Cells 1.1
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Cell Theory
• All living things are composed of cells • The cell is the Basic unit of life • Cells only come from preexisting cells
7 functions of life:
• Nutrition • Metabolism • Growth • Response to Stimuli • Excretion • Homeostasis • Reproduction
Nutrition (as a function of life)
The process by which living things take in materials from its environment for growth and repair
Metabolism (as a function of life)
Chemical reactions inside the cell, including cell respiration to release energy
Growth (as a function of life)
Cells increase in size over time. When they are large enough and acquire the materials required they may divide
Response (as a function of life)
The ability to react to changes in the environment. Receptors in the plasma membrane detect molecules in the environment and send signals to the internal machinery of the cell
Excretion (as a function of life)
The process by which living things remove waste products produced by the cell’s activities
Homeostasis (as a function of life)
Cells maintain a stable internal environment by carrying out a continuous series of chemical reactions
Reproduction (as a function of life)
Producing offspring either sexually or asexually
Why is the SA to V ratio of a cell important in the limitation of a cell size?
If a cell grew infinitely large it would reach a point where this balance between SA and V become imbalanced, meaning it used substances more quickly than it could obtain them. At this point cellular activity decrease and/or ceases.
What arises from the interaction of component parts of a cell?
Emergent Properties
How can it be that all of an organism’s cells have the same genetic information, but the cells have a wide variety of shapes and functions?
All cells are coded, meaning each cell has genes that are expressed, or ‘turned on’ and ‘turned off’. This is because that certain types of cells only require certain genes to create the proteins relevant to that cell.
What are key properties of a stem cell?
-undifferentiated (not specialized) -ability to self-renew -ability to give rise to various types of cells
Two types of stem cells:
Adult and Embryonic
Adult Stem Cells
-Found in adult tissue (e.g. neural cells, cardiac muscle, bone marrow) -Can self-renew many times (but limited) -Multipotent (only give rise to become cells in the tissue they came from)
Embryonic Stem Cells
-Can self renew forever -Come from the blastocyst stage of an embryo -Pluripotent (can give rise to become almost anything in body)
Totipotent Cells
A potency of a stem cell that allows it to differentiate into absolutely everything include supporting structures of pregnancy
Multipotent Cells
A potency of a stem cell that allows it only to differentiate into the cells from their tissue of origin
Pluripotent Cells
A potency of a stem cell that allows it to differentiate into almost every cell, excluding supporting structures of pregnancy
What factors make striated muscle cells an exception to the cell theory?
-each cell is much larger than most animal cells -each cell has many nuclei
What factors make Giant algae an exception to the cell theory?
-large unicellular organism -can grow up to 100mm despite having only one nucleus -An organism of this size would be expected to have more than one cell
What factors make Aseptate Fungal Hyphae an exception to the cell theory?
-Does not have cross walls or septa, and so forms an uninterrupted tube-like structure -Many nuclei spread along tube
Difference in nutrition between Paramecium and Chlamydomonas
Ingests small organisms and digests through vesicals VS contains chloroplast and thereby produces own nutrition
Difference in Metabolism between Paramecium and Chlamydomonas
Both contain enzymes in the cytoplasm which catalyse the metabolic reactions