Cell diversity Flashcards
Why do multicellular organisms need to be specialised?
Multiple tasks simultaneously eg. digest, reproduce, protect against disease.
Cells evolved to have more/less organelles and structures became specialised.
How are erythrocytes specialised?
Transport oxygen from lungs to body cells. Biconcave shape - large SA. Oxygen can diffuse in and reach all parts inside cell.
No nucleus - more space for haemoglobin.
Developed cytoskeleton - flexibility. Can bend through narrow capillaries.
How are neutrophils specialised?
Larger than erythrocytes, travel to infection sites by chemotaxis (due to receptors for inflammatory chemicals on surface).
Multi lobed nucleus - move and engulf material easier.
How are sperm cells specialised?
Tail allows them to swim - movement requires ATP from many mitochondria.
Long and thin - streamlined.
Specialised lysosome = acrosome containing lysozyme. Digest out coating of egg cells - nucleus can enter egg for fertilisation.
How are epithelial cells specialised?
Squamous epithelial cells in alveoli. Thin and flat - decreases diffusion distance - rapid gas exchange.
Ciliated epithelial cells in trachea. Tiny hair-like structures = cilia. Move mucus along.
How are palisade cells specialised?
Long and cylindrical - light absorbed.
Tightly packed - gaps between. Allow CO2 through for photosynthesis.
Many chloroplasts - towards edge of cells by big vacuole. CO2 has shorter diffusion distance.
How are guard cells specialised?
Cell walls are thicker in middle but thinner and more flexible at the tips. Contain chloroplasts - make ATP but no sugars.
What is the main function of guard cells?
- Guard cells make ATP through stage 1 of photosynthesis - lowers water potential.
- Water moves into guard cell and pushes against the sides - swell.
- Paired guard cells are pushed apart - open stoma. Gas exchange can occur.
How are root hair cells specialised?
Protein pumps on plasma membrane - transport minerals in. Lowers water potential, so water follows by osmosis.
Protein pumps require ATP - lots of mitochondria.
Protrusions that increase SA for protein carriers (active transport) and water/ion absorption.
What is a tissue?
A group of cells that work together to perform same function.
What are the 4 main tissue types?
Epithelial, connective, muscle, nervous.
What is epithelial tissue?
Forms the lining between different areas of space in body eg. skin, airways. Protects cells, absorb, secrete and excrete molecules.
What is the epithelial tissue made up of?
- Tightly packed epithelial cells joined by tight junctions and proteins.
- Blood vessels not run through - get O2 and nutrients from tissue fluid.
- Exposed to extreme conditions - often damaged. Short cell cycles.
- Some have smooth surfaces, others have projections.
What are examples of epithelial tissue?
Squamous - single layer of flat cells.
Ciliated - layer of cells covered in cilia.
What is connective tissue?
Separated and connected cells, withstand forces. Made of non living proteins and carbs - form extracellular matrix.
eg. elastin, collagen, carbs including hyaluronic acid (traps water). Connecting tissue eg. blood and bone.
What is cartilage?
Connective tissue in joints and around soft tissue. When matrix forms, develops into mature cartilage.
3 types: hyaline, fibrous, elastic.
What is muscle tissue?
Controls movement so is very metabolically active with good blood supply. Made of muscle fibres and myofibrils.
3 types: skeletal, cardiac, smooth.
What is an organ?
A group of tissues that work together to perform a function.
What is vascular tissue?
Transport - xylem and phloem in vascular bundles.
Plants also have epidermal tissue with cuticle.
What is an organ system?
A group of organs that work together to perform an overall life function.
What are examples of stem cell treatments?
Bone marrow - any type of blood cell. Can be used to treat blood diseases.
Diabetes treated with pancreatic cells to become beta cells - make insulin.
Neurodegenerative disorders could be treated by stem cells differentiating into neurones.
How are stem cells important in research?
Test drugs - avoid animal testing but can asses for side effects.
Study how animals/humans develop - study differentiation.
How diseases develop and can be prevented.
What is regenerative medicine?
Stem cells can be grown into specific shape + cell type to be transplanted.
If use patient’s cells, no need for immunosuppressant drugs.
What is a stem cell?
Undifferentiated cells that can express all genes and divide by mitosis.
What is differentiation?
The process by which cells become specialised for different functions.
How do stem cells develop?
Certain genes are switched on/off. Cells take on individual characteristics and adapt to functions when they mature and become specialised.
Cell differentiation.
What is a pluripotent stem cells?
Can differentiate into almost any cell type except placenta cells. eg. embryonic and foetal.
Undergo mitosis continuously for growth and repair.
What are sources of stem cells?
Embryonic - any cell type.
Umbilical cord blood - blood cells.
Adult stem cells - small selection of cell types to replace damage.
Pluripotent can be induced (iPS). Made in lab by switching on certain genes normally expressed.
What is meristem tissue?
An area of unspecialised cells in a plant which can self-renew and differentiate.
Found in cambium of vascular bundles, root and shoot tips.
What are features of meristem?
- Thin cell walls - divide easily.
- No chloroplasts and small vacuole - no photosynthesis.
- When divide, can differentiate into specialised plant cells.
What does the differentiation of meristem tissue into xylem involve?
- Deposition of lignin in cell wall (strong and waterproof).
- Ends of xylem cells break down in differentiation so water etc. travels unobstructed.
What does the differentiation of meristem tissue into phloem/companion cells involve?
- Sieve tubes carry phloem sap, few organelles and have sieve plates
- Companion cells have many mitochondria so can actively pump sugars into sieve tubes (ATP source).
