B2.3 Flashcards
Fertilisation
Multi-step process in which a sperm and eggs fuse to form a zygote
Occurs in sexually producing organisms such as animals and plants
Haploid
Presence of a single set of chromosomes
Gamete
Specialised cells for reproduction like sperm and egg cells in humans
Zygote-embryo
Zygote then divides by mitosis to form an embryo composed of genetically identical cells
Stem cell
Unspecialised cell
Embryonic stem cells
Cells in zygote are unspecialised stem cells but the cells of embryo continue to divide and begin to specialise in structure and function
Gene expression
Process by which the information encoded in a gene is turned into a function
Morphogens
A signalling molecule which impacts gene expression and as a result the differentiation of the cell by regulating cell fate decisions
Example is retinoic acid which diffuses throughout the embryo switching genes on and off and imparting different cell fates depending on its concentration
Stem cell niches
Are sites within the body where a pool of adult stem cells are maintained in preparation for future proliferation and differentiation (gene expressing).
Example is bone marrow which is home to haemopoitic stem cells and give rise to types of blood cells including leucocytes, erythrocytes and thrombocytes
Bone marrow transplants are employed to replace haemopoitic stem cells following chemotherapy for leukemia (blood cell cancer)
Totipotent
Can differentiate into any type of cell including placental cells. Can give rise to a complete organism
Pluripotent
Can differentiate into all body cells but can’t give rise to a whole organism
Multipotent
Can differentiate into a few closely related types of body cells
Unipotent
Can only differentiate into their associated cell type. Such as liver stem cells can only make liver cells
What are the 4 types of stem cells
Totipotent, pluripotent, multipotent and unipotent
Cell size as an aspect of specialisation
Look in book
Apart from remaining small, what other adaptations do cell use to cope with this
Microvilli to increase SA
root hair cells to increase SA
Adaptations to increase SA:VOL ratios of cells?
Flat and long (squamous) will have a higher SA:VOL ratio than cells that are larger or cuboidal in shape.
Tissues lining absorption surfaces will have ruffled projections (villi), while the cells themselves will possess membranous extensions (microvilli)
What examples can you think of that are specialise for material transport?
Red blood cells - cells are thin and flat (bioconcave) and the nuclei is removed to store more haemaglobin
Tubule cells - have villi and microvilli to improve selected reabsorption
Pneumocytes
Line the alveoli and comprise of the majority of the inner surface of the lungs
Type 1 pneumocytes
Involved in process of gas exchange between alveoli and the capillaries
Squamous and really thin (~0.15 micro metres) minimising diffusion distance
Connected by occluding junctions which prevents leakage of tissue fluid into the alveolar air space
Type 2 pneumocytes
Secrete pulmonary surfactant, which reduces surface tension in the alveoli
Are cuboidal in shape and possess many granules called lamellar bodies which reduce surface tension by storing the surfactant
Adaptations of cardiac muscle cells
Cardiac muscle cells - found within the heart tissue and are responsible for the rhythmic beating of the heart
Adaptations
Short and narrow
Not fused together
Connected by gap junctions at intercalated discs allowing electrical conduction between cells
More mitochondria as they are more reliant on aerobic respiration for ATP production
Adaptations of striated muscle fibres
Striated muscle fibres - connect to bones of skeleton and are responsible for locomotion (voluntary movement)
Adaptations
Comprised of long cylindrical fibres
Single continuous plasma membrane and are multinucleate
Packed together in unbranching strands (2-3cm long) and collectively form a muscle bundle
Single functional unit
Adaptations of sperm cell
Acrosome cap contains hydrolytic enzymes, helped sperm penetrate the egg
Centrioles needed by a zygote to divide
Mid-piece contains high number of mitochondria providing ATP needed for tail movement
Flagellum composed of a microtubule structure called the axoneme, bends to facilitate movement
Adaptations of egg cell
Jelly coat is a glycoprotein matrix which acts as a barrier to sperm entry
Corona radiata is an external layer of follicular cells which provide the egg with nourishment
Egg cell arrested in metaphase 2 until it becomes fertilised by a sperm
