Cells
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What is a prokaryotic cell?
Smaller and simpler - no nucleus
What is a eukaryotic cell?
Complex - contains a nucleus
4 features of a bacteria cell?
• Cell membrane • Cytoplasm • Cell wall • Plasmid rings containing DNA
2 advantages of an electron microscope
• Higher resolution • Higher magnification
2 disadvantages of an electron microscope?
• Expensive • Large - not portable
Equation for magnification?
magnification = image/ real
2 ways sperm cells are specialised?
• Streamlined head to swim quickly • Enzymes on its acrosome to fertilise egg
2 ways nerve cells are specialised?
• Long - cover distance • Branched - connect to other nerve cells
2 ways muscle cells are specialised?
1/ Long - space to contract 2. Lots of mitochondria - energy for contraction
2 ways root hair cells are specialised?
• Long hairs - bigger surface area for absorbing water and mineral ions
2 ways xylem and phloem are specialised?
• Hollow and few subcellular structures - substances can travel through them • strengthened with lignin - strength
Explain the life cycle of a cell
• Cell grows more subcellular organelles • DNA duplicates to form x shaped chromosomes • Chromosomes line up down the centre and the two arms of each chromosome are pulled to either end • Nucleus divides and a membrane forms around the chromosomes • Cell cleaves and two new daughter cells are created
Explain binary fission
• Plasmids and circular DNA replicate • Cell expands and circular DNA move to either end of cell • Cytoplasm divides and new cell walls form • Cytoplasm divides fully - each new cell ahs one copy of circular DNA but various plasmids
What is therapeutic cloning?
An embryo is made to have the same genetic information as a patient
Risk of using stem cells
Stem cells grown in a lab could become contaminated with a virus which could be passed onto a patient
2 ethical reasons against embryonic stem cells
• Embryos can’t consent • Killing potential human life
2 disadvantages of adult stem cells?
• Can only differentiate into certain cells • Painful for patient
Where are the stem cells in a plant?
Meristem
How can stem cells be used to preserve rare plant life
Stem cells can produce clones of whole plants cheaply and quickly
2 things that increase diffusion rate?
• Bigger concentration gradient • Higher temperature
What is osmosis?
The movement of water molecules from a region of higher water concentration to a region of lower water concentration across a partially permeable membrane
How do root hair cells use active transport
When there is more mineral ions in the cell than in the soil, mineral ions move against the concentration gradient into the cell
How is active transport used in the gut?
When there is a lower concentration of nutrients in the gut than the blood, active transport allows nutrients to be taken into the blood
4 ways exchange surfaces are adapted?
• Thin membrane - short diffusion pathway • Large surface area - more space for diffusion • Lots of blood vessels - easy bloodstream access • Ventilated - air can move in and out