B2.3-cell specialization Flashcards
steps of zygote formation
-fusion of gametes (genetic material 50% each) leads to zygote (single cell)
-zygotes divide at fast rate (are totipotent stem cells)
-zygote develops into blastocysts through cell division over 5 days
-stems cells differentiate into specialized cells, some genes expressed and others not
morphogens
signaling molecules that control cell differentiation.
signal molecules occur in gradients in different region-resulting in different genes being expressed (different past of embryo develop into different features)
stem cells definition
undifferentiated cells which have the unlimited capacity to divide and can differentiate into specialized cells
merismetic tissue
stem cells found near root/tip of plant composed of rapidly reproducing tissues
stem cell properties
1) can self-renew: can divide into daughter cells or differentiate
2)can replenish dying/ damaged tissues
stem cell niches
1) bone marrow: niche for hematopoietic stem cells which can differentiate into all types of blood cells
2)hair follicles: large pools of epithelial cells found in hair follicles- involved in hair growth/skin regeneration
types of stem cells
1) totipotent stem cells: stem cells that can differentiate into all types of cells or develop into embryo (e.g= zygotes are totipotent)
2)pluripotent: stem cells that can differentiate into almost all types of cells, but not embryo (e.g=embryonic stem cells are pluripotent)
3)multipotent: stem cells can differentiate into limited range of cells (e.g=adult stem cells are mulitpotent)
red blood cell adaptation
-contain haemoglobin that attaches to oxygen
-bioconcave shape
-lack nucleus/mitochondria
-flexible
straited muscle fibers
=specialized cells found in skeletal muscles
-are atypical-multinucleated formed from fusion of cells
-fibers are cylindrical
-contain bands which contribute to movement
V to SA ratios and contriasnts on cell
as the cell grows, metabolism occurs at faster rate then cells ability to transfer materials
-volume increases at higher rate than SA
-cells must have adaptations to allow efficient function: cell may have changes in shapes projections, cell may divide
adaptations to increase SA to V ratio in erythrocytes and proximal convoluted tubules
erythrocytes=
-biconcave shape to increase O2
-flexible
proximal convoluted tubules=
-cube shape-cells packed together for efficiency
-many extensions of cytoplasm(microvilli) to increase SA
-lots of mitochondria
-channels on opposite side to increase SA
what are proximal convoluted tubules
cells that line part of kidney and absorb nutrients
adaptations of type I and II pneumonocytes
alveoli=air sacs, tissue composed of:
1)type 1 pneumonocytes
function: to allow gas exchange between alveoli and capillaries
adaptation: long, thin, flat, share a membrane with lining of capillaries, tightly joined
2)type II pneumonocytes
function: to secrete pulmonary surfactant which reduces surface tension, preventing alveoli from sticking/collapsing and provides liquid for rapid diffusion
structure: cuboid shape, contain microvilli extending to alveoli sac, increasing SA, contain secretory vesicles which release the surfactant by exocytosis
adaptations of cardiac and striated muscle fibers
1) cardiac=located in heart and is responsible for rhythmic beating. Cells are branched and connected by intercalated discs.
-has one nucleus per cell
-composed of microfibrils
2) striated muscles
-long, polynucleated fibers formed from fusion of cells
adaptation of sperm cell
-streamlined shaped, for swimming
-small
-haploid nucleus contain paternal genetic material
-acrosome at tip of head contain hydrolytic enzymes which help sperm fertile egg
-midpiece contain mitochondria and provides ATP for swimming
-flagellum, tail for swimming
