1.1 Introduction To Cells Flashcards
The cell theory States that;
1- All living things are composed of cells
2- cells are the smallest unit of life
3- All cells come from pre-existing cells
Common features of cells;
1- All cells are surrounded by a membrane which separates the cell content from the surrounding
2- All cells contain genetic material
3- All cells carry out chemical reactions
4-All cells produce energy (ATP) to carry out all the cell activities
Strained muscle cell is Atypical because;
1- much larger size than most animal cells
2- has many nuclei (multinucleated)
Giant Algea is atypical because;
Much simpler structure
Unicellular (carry out all functions of life) but has a much larger size than a typical cell; length could reach 100 mm (e.g Acetabularia)
Aseptate Fungal Hyphea is Atypical because;
there are no septa – each hypha is one long continuous cell that is not separated by septa.
Each hypha is has many nuclei.
Red Blood cells are atypical cells because;
biconcave disks that carry oxygen to different tissues.
lack a cell nucleus, cellular organelles and cannot synthesize proteins
Unicellular organisms carry out how many functions and what are they?
Metabolism – chemical reactions inside the cell (e.g cell respiration to release energy).
Growth – an irreversible increase in size.
Response – the ability to react to changes in the environment.
Reproduction – producing offspring either sexually or asexually.
Nutrition – obtaining food, to provide energy and the materials needed for growth.
Homeostasis – keeping conditions inside the organism within tolerable limits.
Excretion – getting rid of the waste products of metabolism.
Define autotroph and heterotroph
Autotroph: synthesize its organic matter from inorganic matter. (e.g by photosynthesis)
Heterotroph: obtain organic matter from other organisms.
What are the importance of the surface area to volume ratio as a factor limiting the cell?
Cells don’t grow indefinitely; they reach a certain size and then divides.
As cells grow, the surface area to volume ratio decreases.
The surface area controls the rate of exchanging material and heat /the rate of diffusion through cell membrane(proportional relationship).
The volume controls (proportional to):
The rate of heat production
The rate of waste production
The rate of resource consumption
As cells grow, the volume increases faster than the surface area.
As a result, material and heat cannot be exchange fast enough to remove waste and heat, and provide enough resources to be consumed in the cell’s metabolism; the cell becomes unable to meet the needs of the cell. Therefore, the cell divides.
Therefore, the ratio limits the size of the cell.
Multicellular organisms
Multicellular organisms show emergent properties.
Emergent properties arise from the interaction of component parts
The whole is greater than the composition of its parts.
For example: cells form tissues, tissues form organs, organs form organ systems and organ systems form multicellular organisms.
For example your lungs are made of many cells. However, the cells by themselves aren’t much use. It is the many cells working as a unit that allow the lungs to perform their function.
Differentiation in Multicellular organisms
Differentiation is the process where a less specialized cell becomes a more specialized cell.
Cells develop in different and specific way.
Examples of differentiated cells and their specialized functions:
Red blood cells are specialized to carry oxygen
Muscle cells – contraction and relaxation to help in movement
A group of differentiated cells form a tissue.
Cells differentiate to develop specialized tissues to carry out specialized functions
Example of a tissue:
a group of nerve cells make up a nerve tissue
Cells contain all the genes of the organism.
Differentiation involves the expression of some genes and not others in a cell’s genome.
Stem cells
Stem cells: are cells that have the capacity to divide and differentiate along different pathways (pluripotent).
Stem cells are undifferentiated cells.
The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development
Sources of stem cells:
Embryonic stem cells – used to replace damaged cells e.g brain cells
Adult stem cells such as bone marrow hematopoietic cells
Cord stem cells – obtained from the umbilical cord/placenta
Diseases treated using stem cells: leukemia, heart diseases, lymphoma, diabetes, etc.
Treating Leukemia
(Disease: Leukemia)
Source: Stem cells obtained from bone marrow (hematopoietic cells)
Method: Bone marrow transplants
Stem cells found in the bone marrow (hematopoietic cells) give rise to the red blood cells, white blood cells and platelets in the body.
Stem cells (hematopoietic cells) are removed from the bone marrow of the patient or donor by using a needle which is inserted into the pelvis (hip bone).
The patient is given high doses of chemotherapy, the chemotherapy kills the cancer cells but also the normal cells in the bone marrow. This means that the patient cannot produce blood cells.
After the chemotherapy treatment the patient will have a bone marrow transplant in which the stem cells are transplanted back into the patient through a drip, usually via a vein in the chest or the arm.
Stargardt’s disease
(disease: Stargardt’s disease)
What is the Stargardt’s diseas?
Full name: Stargardt’s macular dystrophy
Genetic disease that develops in children between 6 and 12.
Due to a recessive mutation, that causes a membrane protein used for active transport in retina cells to malfunction.
As a consequence, photoreceptive cells in the retina degenerate. So vision becomes progressively worse and could lead to loss of vision and blindness.
Source: Stem cells obtained from embryos.
Method: using developed methods, embryonic stem cells could develop into retina cells and then those cells are injected into the eyes.
Sources of stem cells;
Embryos – embryonic stem cells
Cord blood – blood extracted from umbilical cord
Adult tissue such as bone marrow.
