Cells and Organelles; The Cell Membrane

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Cells and OrganellesThe Cell Membrane

• Book Reference p.16-p.19

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Do all membranes have the same basic structure?

• Both the cell surface membrane and the membranes
  surrounding certain organelles have the same
  basic structure. Much of the membrane is made up
  of a 'sea' of phospholipids with protein
  molecules 'floating' in between the
  phospholipids.

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Where are proteins located within the membrane?

• What is an intrinsic protein?
• What is an extrinsic protein?
• Why is it called the fluid mosaic model?

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INTRINSIC 1Channel Proteins

• Allow movement of substances, such as glucose,
  across the membrane
• NO ATP REQUIRED

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INTRINSIC 2Carrier Proteins

• Actively transport substances, such as minerals,
  across the membrane
• ATP is REQUIRED

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(a) Channel VS (b) Carrier
Proteins
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Bilayer Phospholipids

• What is the bilayer?
• The phosphate heads are polar molecules and so
  are water-soluble.
• The lipid tails are non-polar and therefore are
  not water-soluble.

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Why do phospholipids have both a hydrophilic and
a hydrophobic part?

• The phosphate heads are polar. Are they
  water-soluble?
• The lipid tails are non-polar. Are they
  water-soluble?

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What is a polysaccharide?

• Clue polymer monomer carbohydrate

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Glycowhat?

• What is the difference between a glycoprotein
  and a glycolipid?

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What is the role of glycoproteins?

• They may help in the recognition of, and
  interaction with, other cells. They may also play
  a part in the recognition of hormones and foreign
  molecules.

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What is the role of cholesterol in the cell
membrane?

• Cholesterol is also present in the membrane. It
  maintains the fluidity and increases the
  stability of the membrane. Without cholesterol
  the membrane would easily split apart

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Cell membrane Functions

• Selectively permeable barrier.
• Structural, keeping the cell contents together.
• Allows communication with other cells.
• Allows recognition of other external substances.
• Allows mobility in some organisms, e.g. amoeba.
• The site of various chemical reactions.

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Cells and OrganellesTissues

• Some organisms do exist as single cells - for
  example, Amoeba,
• but many organisms are multicellular and consist
  of from hundreds to billions of cells.
• The functions of the organism are divided up
  amongst the groups of cells, which become
  specialised for particular roles.
• Specialised cells show division of labour by
  being grouped into tissues.

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What is a Tissue? Definition

• A tissue is defined as a collection of cells,
  together with any extracellular secretion, that
  is specialised to perform one or more particular
  function. Tissues may contain only one type of
  cell, or several types.

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Website Reference www.s-cool.co.ukgo to
Biology and then 1.Cells and Organelles 2.Gas
Exchange3.Transport
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