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Cells

What you need to know

Reflections and Exam tips

 

Cells

A cell is the basic building unit of all living organisms- they are like bricks which make up the living things.

There are 2 types of cells based on their level of complexity:

Eukaryotic cells (eu= true, Karyon= nucleus), so these have a nucleus (DNA surrounded by a membrane). Plants, animals and fungi are in this group.

Prokaryotic cells (pro= before, karyon = nucleus), these don't have a true nucleus, the DNA lies naked in the cytoplasm. Examples are bacteria.

Organisms can be made up of single cells (unicellular) or many cells (multicellular).

Animal cells

Animal cells have:

  • Cell membrane- outer flexible surrounding, controls entry and exit of substances into the cell.
  • Cytoplasm- Jellylike fluid where chemical reactions take place
  • Nucleus- Controls the activities of the cell, contains genetic material (DNA)- Do not say its the brain of the cell
  • Motochrondria- Oval organelles surrounded by 2 membranes, site of respiration- release (don't produce) energy from glucose.
  • Ribosomes- very tiny organelles involved in protein synthesis (join up amino acids). Are found freely floating in the cytoplasm or bound to a system of mebranes called the Rough Endoplasmic Reticulum (ER)

All the components of a cell are called organelles (like small organs). There are many more organelles inside cells, but for now these are the ones that you need to know.

Drawing of an animal cell

Plant cells

Plant cells have:

  • Cell membrane- outer flexible surrounding, controls entry and exit of substances into the cell.
  • Cytoplasm- Jellylike fluid where chemical reactions take place
  • Nucleus- Controls the activities of the cell, contains genetic material (DNA)- Do not say its the brain of the cell
  • Motochrondria- Oval organelles surrounded by 2 membranes, site of respiration- release (don't produce) energy from glucose.
  • Ribosomes- very tiny organelles involved in protein synthesis (join up amino acids). Are found freely floating in the cytoplasm or bound to a system of mebranes called the Rough Endoplasmic Reticulum (ER)
  • *Cell wall- Rigid outer surrounding made of cellulose. Maintains cell shape.
  • *Chloroplasts- oval green organelles, contain chlorophyll to absorb light for photosynthesis
  • *Permanent Vacuole- Fluid filled space, contains cell sap, a solution of sugars and salts. Also maintains cell shape.

Plant cell diagram

Fungal cells

Fungi have:

  • Cell membrane- outer flexible surrounding, controls entry and exit of substances into the cell.
  • Cytoplasm- Jellylike fluid where chemical reactions take place
  • Nucleus- Controls the activities of the cell, contains genetic material (DNA)- Do not say its the brain of the cell
  • Motochrondria- Oval organelles surrounded by 2 membranes, site of respiration- release (don't produce) energy from glucose.
  • Ribosomes- very tiny organelles involved in protein synthesis (join up amino acids). Are found freely floating in the cytoplasm or bound to a system of mebranes called the Rough Endoplasmic Reticulum (ER)
  • *Cell wall- Rigid outer surrounding made of chitin. Maintains cell shape.

Fungi are very diverse, they can be unicellular or multicellular.

 

Bacteria cells

Bacteria are unicelluar (each bacteria is one cell) and prokaryotes (no nucleus).

Their structure is very simple and they lack many organelles. They have:

  • A cell wall (made of murein)
  • Cell membrane- outer flexible surrounding, controls entry and exit of substances into the cell.
  • Cytoplasm- Jellylike fluid where chemical reactions take place
  • Small ribosomes- for protein synthesis
  • DNA (genetic material)-lying naked in the cytoplasm
  • They also have mucus capsule on the outside
  • Tail-like flagella for movement.

Bacteria cell diagram