1 Cell Biology

• Eukaryotic Cell

  • Large cell
  • genetic material contained in its nucleus
  • contains a nucleus, cell membrane, mitochondria, cytoplasm and ribosomes
  • Exists as either a plant or animal cell
• Function of:

  Vacuole: to store cell sap which supports the plant

  Chloroplast: contain chlorophyll to take in light for photosynthesis

  cell wall: made of cellulose which makes the plant cell rigid and supports the cell

  mitochondria: where aerobic respiration takes place

  ribosomes: where proteins are synthesised (made)

  nucleus: controls the activities of the cell and contains the genetic material

  cytoplasm: where most of the chemical reactions of the cell take place
• Cell differentiation is a process where a cell becomes specialised to perform specific functions in an organism
• Chromosomes are made up of very long thin molecules that is the genetic material in the cell. It is called chromatin
• Bases are the parts of DNA that carry the information. The four different bases are:

  G + C

  and

  A + T
• Why do cells of a multicellular organism need to divide?

  • Making new cells for growth of new tissue
  • Repair of damaged tissue
  • Asexual reproduction to replace worn out cells
• Cell Cycle

  Cytokinesis:

  • Movement of cytoplasm
  • Cytoplasm and cell membranes divide to form two identical daughter cells

  Interphase:

  • Cell grows, increases number of sub cellular structures and organelles like ribosomes and mitochondria
  • DNA replicates to form two copies of each chromosome

  Mitosis:

  • One cell of chromosomes is pulled to each end of the cell and the nucleus divides
• 1. Parent cell with two pairs of chromosomes
  2. Each chromosome replicates itself
  3. Chromosomes line up along the centre of the cell, divide and the copies move to opposite poles
  4. Each daughter cell has the same number of chromosomes and contains the same genes as the parent cell

  A) 1

  B) 2

  C) 3

  D) 4

  
• Part A - eyepiece or lens

  Purpose of part B - to focus the image

  
• Differences between a red blood cell and plant cell:

  • red blood cell has no nucleus
  • red blood cell has no cell wall
  • red blood cell is a biconcave disc
  • plant cells do not contain haemoglobin
  • red blood cells do not contain chlorophyll
  • red blood cell has no chloroplasts
  • red blood cell has no (permanent) vacuole
  • red blood cells are smaller than plant cells
• Why red blood cell bursts in water whereas plant cells don't:

  • Water enters the cell via osmosis
  • Plant cell has a cell wall to prevent it from bursting
• Two aseptic techniques in the agar bacteria investigation:

  • Use sterilised agar
  • Sterilise work surfaces
• Which cell structure in a leaf mesophyll cell is not found in a root hair cell?

  Chloroplasts
• Guard cells control the rate of water loss
• The transpiration stream is when water is taken in by the roots, transported up the plant and lost from the leaves.
• Compare structure and function of xylem and phloem tissue:

  • Xylem is made up of dead cells whereas phloem with living cells
  • Xylem contains lignin whereas phloem contains cytoplasm
  • Both are made of cells
  • Xylem transports water and mineral ions whereas phloem transports dissolved sugars
  • Xylem transports in only one direction (up) from the roots to the shoots whereas phloem in multiple directions to different parts of the plant
• The rate of water loss at midnight was much lower than at 12:00 Explain why:

  • Stomata are almost completely closed at night
  • It's cooler at night
• The structures inside the cell nucleus that contain DNA are chromosomes
• label X - sugar

  
• Structures A, C, G, T are bases

  
• A gene is a length of DNA. The type of substance a gene codes for is protein
• Each stage of the cell cycle:

  1. The cell grows and the chromosomes replicate
  2. One set of chromosomes is pulled to each end of the cell
  3. The cytoplasm and cell membrane divide to form two new cells
• Explain how the spongy mesophyll is adapted for its function

  • lots of air spaces between the cells
  • allowing for faster diffusion of oxygen and carbon dioxide
  • providing carbon dioxide for photosynthesis
• explain one way that xylem is adapted for its function

  • hollow tubes helping water flow more easily

  OR

  • Lignin in walls to strengthen the walls

  OR

  • No end walls, allowing for a constant transpiration stream
• A tissue is a group of similar cells carrying out a similar function
• The type of tissue in plants that contains stem cells is meristem