Cell Biology - P1

Cells:

  • Nucleus - contains genetic material

  • Cytoplasm - where most chemical reactions occur

  • Mitochondria - where most of reaction for aerobic respiration occur (powerhouse of cell)

  • Ribosomes - where proteins are made

  • Cell membrane - controls what goes in and out

  • Cell wall - (made of cellulose) strengthens and supports cell

  • Chloroplasts - where photosynthesis occurs

  • Vacuole - contains cell sap

  • Plasmids - small rings of DNA

  • Animal cell - nucleus, cytoplasm, ribosomes, cell membrane, mitochondria

  • Plant cell - cell wall, vacuole, nucleus, mitochondria, cell membrane, cytoplasm

  • Prokaryotic - no nucleus, cell wall, plasmids, smaller ribosomes, flagella

  • Eukaryotic - nucleus, membrane, organism

Magnification - image size/real size

Cell Division:

  • Chromosomes - coiled up lengths of DNA which carry genes. Found in the nucleus and normally in pairs.

  • Cell cycle - series of stages inn which cell divide and produce new cells

  • Mitosis - the stage of the cell cycle when the cell divides (allows multicellular organisms to grow and replace cells that have been damaged)

Mitosis stages:

  1. the cells DNA is doubled

  2. one set of chromosomes are pulled to each end of the cell

  3. cytoplasm and cell membrane divide

  4. two cells are formed which are identical to each other and to the parent cell

Cell Specialisation and Stem Cells:

  • Differentiation - the process by which a cell changes

Types of specialised cells:

  1. Sperm cell (reproduction) - long tail and streamlined head for swimming

  2. Nerve cell (rapid signalling) - long to cover a larger distance and branched to form a network of connections

  3. Xylem and phloem (transport) - xylems are hollow and phloem have few subcellular structures so substances flow through easier.

  4. Muscle cells (contractions) - Long so they have space to contract, lots of mitochondria for energy

  5. Root hair cell (absorbing water and minerals) - large surface area for absorbing water and mineral ions from the soil.

  • Stem cells - undifferentiated cells which can divide to produce lots more stem cells and can differentiate into many other types of cells.

Transport in Cells:

  • Diffusion - movement of particles from high concentration to low concentration

Factors increasing diffusion:

  • High concentration gradient

  • High temperature

  • Large surface area

  • Osmosis - movement of water molecules across a partially permeable membrane from high concentration to low concentration.

  • Active Transport - the movement of a substance against the concentration gradient. Requires energy from respiration

Exchanging Substances:

  • single celled organism - large SA : vol ratio - enough substances can pass across the outer surface to meet need of organism

  • multicellular organism - small SA : vol ratio - many cells too far away from outer surface to get substances in and out of the way

Exchange surfaces usually have these things:

  1. large surface area (lots can diffuse at once)

  2. thin membrane (short diffusion distance)

  3. efficient blood supply

  4. ventilation

Organs adapted for exchange:

  1. leaves (gas exchange) - flat shape , stomata let gases in and out

  2. gills (gas exchange in fish) - lots of gill filaments, lots of capillaries, lamellae have thin surface layer of cells

  3. small intestine (absorption of food molecules from gut to blood) - single layer of surface cells, covered in villi, capillary network

  4. alveoli (gas exchange) - millions of alveoli, air moves in and out, alveoli have thin walls, capillary network