Cell components

• All living organisms are made of one or more cells and all cells are surrounded by a cell/plasma membrane which provides a barrier between the cytoplasm and the external environment of the cell.
• Prokaryotic cells are believed to be the earliest cells, with a structure similar to that of bacteria.
• Prokaryotic cells are small, between 0.2 and 5µm in size.
• Eukaryotic cells are believed to have evolved from prokaryotic cells.
• The most obvious difference between prokaryotic and eukaryotic cells is that the DNA is no longer free in the cytoplasm but is contained within a nuclear membrane.
• Eukaryotic cells are larger than prokaryotic cells, 10 - 100µm, and have more and different organelles.
• The Cell Theory states:

  All living organisms are composed of cells, they

  may be unicellular or multicellular.

  The cell is the basic unit of life.

  Groups of cells create tissues, organs, and

  organisms.

  Cells can only arise from other cells.
• Prokaryotes are found in bacteria and blue green algae

  (cyanobacteria)
• Eukaryotes are found in plants, animals, fungi and

  protoctista.
• Prokaryotic cells share many of the following features:

  No nucleus

  Folded cell membrane

  Small ribosomes

  Circular DNA and plasmids

  Peptido-glycan cell wall

  Slime coat, muco-polysaccharide

  Cells are usually 0.2 – 2 µm
• Label the parts of the cell

  A) nucleoid (DNa)

  B) flagellum

  C) pilus

  D) plasma membrane

  
• The cell wall is a rigid outer covering made of peptidoglycan
• The capsule is a protective slimy layer which helps the cell to retain moisture and adhere to surfaces
• plasmid is a circular piece of DNA
• The flagellum is a tail like structure which rotates to move the cell
• The pilus are hair-like structures which attach to other bacterial cells
• Ribosomes are the site of protein production
• Eukaryotic cells share many of the following features:

  Nucleus, with nucleolus and chromosomes

  Mitochondria

  Large ribosomes

  Endoplasmic Reticulum

  Lysosomes

  Centrioles

  Cells are usually 5 – 100 µm
• Plant cells also contain the following features:

  Chloroplasts

  Cellulose cell wall

  Permanent vacuole, bound by a TONOPLAST

  NO centrioles
• Organelles are divided into those with a surrounding membrane, MEMBRANE BOUND and those which do not have a membrane, NON-MEMBRANE BOUND.
• Label the diagram

  A) pore

  B) nuclear envelope

  C) chromatin

  
• Nucleus function - Contains the genetic material (DNA) of the cell, site of transcription and acts as a template for DNA replication.
• DNA is surrounded by a double NUCLEAR MEMBRANE or ENVELOPE

  which has many NUCLEAR PORES, these allow RNA and

  ribosomes to leave the nucleus.
• The nucleus contains one or more small spherical bodies called a nucleolus. This produces RIBOSOMES and CHROMATIN, chromosomes in an ‘unwound’ state.
• Mitochondria function - production of ATP in aerobic respiration.
• The mitochondria has a smooth outer membrane and a folded inner membrane which forms CRISTAE.
• In the mitochondria, the cristae provide a large surface area to attach the molecules of ATP production, such as ATP synthetase.
• The internal space of the mitochondria is called the MATRIX. A solution containing many compounds, including lipids and proteins.
• Mitochondria contain small (70S) ribosomes and small circle of mitochondrial DNA (mtDNA).
• Chloroplast function - site of photosynthesis
• Chloroplasts are surrounded by two membranes comprising the chloroplast envelope.
• In chloroplasts, the stroma is fluid filled and contains some of the products of photosynthesis. This takes place during the dark stage
• In the stroma are many flattened sacs called thylakoids, this

  is where the photosynthetic pigment chlorophyll is found
• A stack of thylakoids is called a granum (grana). This

  arrangement produces a large surface area for capturing light

  energy. This is known as the light stage.
• Like mitochondria, chloroplasts have small (70S) ribosomes and circular DNA.
• Smooth ER function – Synthesis and transport of lipids.
• Rough ER function – Protein synthesis
• In the endoplasmic reticulum, double membranes forming a series of flattened membrane sacs (called CISTERNAE) are connected to the nuclear envelope, which metabolises chemicals.
• Rough ER has ribosomes on the outer surface. Smooth ER does

  not.
• Golgi Body Function:

  Producing secretory enzymes, packaged into secretory vesicles.

  Secreting carbohydrates.

  Producing glycoproteins.

  Transporting and storing lipids.

  Forming lysosomes containing digestive enzymes