Cell Structure

• Describe the general structure of eukaryotic cells

  Cell surface membrane

  Mitochondria

  Ribosomes

  Smooth ER

  Rough ER

  Nucleus

  Golgi apparatus

  Lysosome

  Chloroplast

  Cell wall

  Vacuole
• Describe the structure of the cell-surface membrane

  Hydrophilic phosphate head (point to/are attracted to water)

  Hydrophobic fatty acid tail (point away/repel water)

  Proteins
• Describe the function of the cell-surface membrane

  Selectively permeable → enables control of passage of substances in and out of cell

  Molecules, receptors or antigens on surface → allow cell recognition and signalling
• Describe the structure of the nucleus

  Nuclear envelope: nuclear pores, double membrane

  Nucleoplasm

  Nucleolus (dense region)

  Histone bound linear DNA
• Describe the function of the nucleus

  ● Holds / stores genetic information which codes for polypeptides (proteins)

  ● Site of DNA replication

  ● Site of transcription (part of protein synthesis), producing mRNA

  ● Nucleolus makes ribosomes / rRNA
• Describe the structure of a ribosome

  ● Made of ribosomal RNA and protein (two subunits)

  ● Not a membrane-bound organelle
• Describe the function of a ribosome

  Site of protein synthesis (translation)
• Describe the function of rough ER

  ● Ribosomes on surface synthesise proteins

  ● Proteins processed / folded / transported inside rER

  ● Proteins packaged into vesicles for transport eg. to Golgi apparatus
• Describe the function of smooth ER

  Synthesises and processes lipids
• Describe the function of Golgi apparatus

  Modifies proteins and lipids

  Packages proteins/lipids into golgi vesicles

  Produces lysosomes
• Describe the function of golgi vesicles

  transports proteins/lipids
• Describe the function of lysosomes

  Release hydrolytic enzymes (lysozymes)

  To break down / hydrolyse pathogens or worn-out cell components
• Describe the structure of mitochondria

  Outer membrane

  Cristae

  Matrix containing 70s ribosomes and circular DNA
• Describe the function of mitochondria

  ● Site of aerobic respiration

  ● To produce ATP for energy release

  ● Eg. for protein synthesis / vesicle movement / active transport
• Describe the structure of chloroplasts in plants and algae

  Double membrane

  Stoma

  Thylakoid membrane

  70S ribosomes

  Circular DNA

  Lamella

  Grana
• Describe the function of chloroplasts in plants and algae

  Absorbs light energy for photosynthesis

  To produce organic substances eg. carbohydrates / lipids
• Describe the structure of the cell wall in plants, algae and fungi

  ● Composed mainly of cellulose (a polysaccharide) in plants / algae

  ● Composed of chitin (a nitrogen-containing polysaccharide) in fungi
• Describe the function of the cell wall in plants, algae and fungi

  ● Provides mechanical strength to cell

  ● So prevents cell changing shape or bursting under pressure due to osmosis
• Describe the function of the cell vacuole in plants

  ● Maintains turgor pressure in cell (stopping plant wilting)

  ● Contains cell sap → stores sugars, amino acids, pigments and any waste chemicals