B1.1 - Cell Structure

• Organelles found in both animal and plant cells (eukaryotes)


  Nucleus - Contains genetic material that controls the activities of the cell.

  Cytoplasm - A gel like substance where most of the chemical reactions happen. It contains enzymes that control these.

  Cell Membrane - Holds the cell together and controls what goes in and out.

  Mitochondria - Where most of the reactions for aerobic respiration take place. Respiration transfers the energy required for these cells to work.

  Ribosomes - Where proteins are made through protein synthesis.
• Organisms found in only plant cells

  Cell wall - A rigid structure made of cellulose. It supports and strengthens the cell. Cells of algae (e.g. seaweed) also have one.

  Permanent vacuole - Contains cell sap, a weak solution of sugar and salt.

  Chloroplasts - Where photosynthesis occurs, which makes food for the plant. Contain a green substance called chlorophyll, which absorbs the light required for photosynthesis.
• Prokaryotes Vs Eukaryotes

  Eukaryotic cells are complex, contain a nucleus, and include all animal and plant cells. Eukaryotes are organisms of eukaryotic cells.

  Prokaryotic cells are simpler, don't contain a nucleus, and include bacteria cells. Prokaryotes are organisms of prokaryotic cells.
• Organisms found in bacterial cells (prokaryotes)


  A bacterial cell has cytoplasm (chemical reactions gel) and a cell Membrane surrounded by a cell wall. The cell doesn't have a 'true' nucleus - instead it has a single circular strand of DNA that floats freely in the cytoplasm, and may also contain one or more small rings of DNA called plasmids.
• Relative size of bacterial cells (prokaryotes)


  between ∼0.4–3 µm3 
• Root hair cell function and adaptations

  Function - They absorb water and minerals.

  Adaptation - A long thin 'hair' extends from each cell into the soil increasing the root's surface area. Each root has many thousands of root hairs, which can make the root look furry. 
• Xylem cells function and adaptation

  Function - They transport water and minerals up the stem to leaves and flowers.

  Adaptation - Dead long cells are joined end to end to form a continuous tube. They have no cytoplasm. Their walls contain lignin for strengthening. They're hollow to allow substances to pass through them.
• Phloem cells function and adaptation

  Function - They transport sugars, amino acids, other substances both up and down the stem to leaves, flowers and roots.

  Adaptation - Made of long tube-like living cells joined end to end. They do have cytoplasm. This means that the cells are living. They have very little organisms to allow substances to pass through easier.
• Sperm cells function and adaptation

  Function - Reproduction. They carry half the genetics needed to make a baby, which they carry to the egg (female DNA).

  Adaptation - Long tail and streamlined body to help it swim to the egg. Lots of mitochondria to help provide the energy required to do this. Carries enzymes in the head to digest through the eggs cell membrane.
• Nerve cells function and adaptations

  Function - Specialized for rapid signalling, to carry electrical signals from one part of the body to another.

  Adaptations - These cells are long to cover more distance and have branched connections at their ends to connect to other nerve cells and form a network throughout the body.
• Muscle cells function and adaptations

  Function - Specialized for contraction. Function is to contract quickly.

  Adaptation - Long so they have space to contract and contain lots of mitochondria to transfer the energy needed for contraction.
• Cell Differentiation

  Animals and plants produced by sexual reproduction begin life as a single cell, a fertilised egg or zygote. These cells must divide by mitosis to produce a multicellular organism.

  The cells of multicellular animals and plants must also differentiate, so that its cells develop features that enable them to fulfil specific roles. Cells that have differentiated have become specialised. Without this specialisation, complex multicellular animals and plants would not exist.
• Differences in resolution and magnification in electron and light microscopes

  Light microscopes use light and lense to form an image of a specimen and magnify it.

  Electron microscopes use electrons instead of light to form an image. They let us see smaller things in much more detail e.g. internal structures of mitochondria or chloroplasts.

  Electron microscopes have a higher magnification and resolution (ability to distinguish between two points -> sharper image).