Cell biology

• 2 examples of eukaryotic cells

  Plant cell

  Animal cell
• Function of the cell membrane

  Controls the movement of substances in and out of a cell
• Function of the nucleus

  Contains DNA
• Function of the mitochondria

  Where energy is released through respiration
• Function of the ribosomes

  Site of protein synthesis
• Function of cytoplasm

  Jelly like substance where chemical reactions happen
• Function of permanent vacuole

  Contains cell sap
• Function of chloroplasts

  Contains chlorophyll to absorb light energy for photosynthesis
• function of cell wall

  Made of cellulose, which strengthens the cell
• 1 Example of a prokaryotic cell

  Bacteria
• Characteristics of light microscopes

  Uses light to form images

  Can view living samples

  Cheap

  Low res + magnification
• Characteristics of electron microscopes

  Uses a beam of electrons to form images

  Cant view living samples

  Expensive

  High res + magnification
• Sperm cellfunction + adaptation

  Function: fertilise an egg

  Adaptations: Tail to swim, mitochondria for energy
• Red blood cell

  Function: transports oxygen

  Adaptations: no nucleus so more space for oxygen, haemoglobin binds to oxygen, bi-concave disk shape so more surface area
• Muscle cell

  Function: contract and relax

  Adaptation: contains proteins which can contract, mitochondria for energy for contracting
• Nerve cellfunction + adaptation

  Function: carry electrical impulses

  Adaptations: dendrites to make connections, myelin sheath insulates the axon to increase transmission
• Root hair cell

  Function: Absorb mineral ions and water

  Adaptations: Long, increases surface area for absorption, lots of mitochondria for energy
• Palisade cell function + adaptation

  Function: enable photosynthesis

  Adaptation: lots of chloroplasts containing chlorophyll
• Diffusion

  Particles move from high to low concentration

  No energy required
• Osmosis

  Water moves from low solute concentration to high solute concentration

  No energy required

  Plants
• Active transport

  Particles move from low concentration to high concentration

  Energy needed
• Factors affecting rate of diffusion

  Difference in concentration: steeper gradient = faster diffusion

  Temp: higher temp = faster diffusion

  Surface area of membrane: higher SA = faster diffusion
• Why is active transport needed in plant roots?

  movement of mineral ions

  Concentration of mineral ions in the soil is lower than in the root hair cell
• Purpose of active transport in the small intestine

  Sugars can be absorbed
• What is a stem cell?

  An undifferentiated cell
• Types of stem cell

  Mammals: adult stem cells, embryonic stem cells

  Plants: plant meristem
• Adult stem cells (found, differentiate into, adv, disadv)

  Found in specific parts of body, e.g bone marrow

  Differentiate into certain types of cell e.g bone marrow stem cells can only differentiate into types of blood cell

  Adv: fewer ethical issues, relatively safe

  Disadv: Requires a donor, can only turn into certain types of cell
• Embryonic stem cells (found, differentiate into, adv, disadv)

  Found in early human embryos

  Differentiate into any type of specialised cell in the body

  Adv: treat a wide range of diseases, usually no donor needed

  disadv: ethical issues, risk or transferring viruses
• Plant meristem (found, differentiate into, adv, disadv)

  Found in meristem regions in the roots and shoots of plants

  Differentiate into all cell types

  Adv: can clone plants, (rare + desirable traits) quick + low cost

  disadv: cloned plants are identical, so whole crops can be destroyed by a singe disease
• Therapeutic cloning

  Cells from a patients body are used to create cloned early embryos of themself, stem cells of this embryo can be used for medical treatments and growing new organs, same genes are parents so less likely to be rejected
• Stage 1 of cell cycle

  Cell grows bigger, DNA replicates, increase in number of sub-cellular structrures
• Stage 2 of the cell cycle

  Mitosis

  Complete set of chromosomes is pulled to each end of the cell

  Nucleus forms into 2
• Stage 3 of the cell cycle

  Cytoplasm and cell membrane divide to form 2 daughter cells
• Characteristics of eukaryotic cells

  10–100 μm

  Has a nucleus

  More complex than prokaryotic cells

  Has membrane bound organelles (eg. mitochondria)
• Characteristics of prokaryotic cells

  0.1–5 μm

  Singular circular strand of DNA

  Much simpler than eukaryotic cells

  Has no membrane bound organelles