3 Cell structure

• Nucleus is the largest organelle and surrounded by a double membrane called the nuclear envelope.
• The nucleus has nuclear pores that allow substances to enter and leave the nucleus.
• DNA (in the nucleus) - when it is not dividing is in the form of chromatin and when it is dividing its in the chromosomes.
• Nucleolus - site of ribosome synthesis
• The nucleus is the control centre of the cell.
• Ribosomes are made up of RNA and protein, they make proteins from amino acids.
• Mitochondria - where respiration takes place, produces ATP which provides energy for cellular processes.
• Mitochondria have an outer membrane and inner membrane with folds called cristae.
• Inside the mitochondria's inner membrane is the matrix, which contains enzymes (protein complexes) that carry out aerobic respiration
• In the cell surface membrane the phosphate head is attracted to water called hydrophilic but the two fatty acid tails repel water called hydrophobic.
• What is the name of the hydrophobic part of the cell surface membrane?

  2 fatty acid tails
• Exocytosis is when substances leave the cell through vesicles forming on the inside of the plasma membrane.
• Phagocytosis is when cells engulf large particles or pathogens by extending pseudopodia around them.
• Glycolipids are molecules found on the outside of the plasma membrane that contain both lipid and carbohydrates.
• Chloroplasts are larger than mitochondria and are surrounded by a double membrane
• True or false chloroplasts are surrounded by a single membrane?

  False, chloroplasts are surrounded by a double membrane (just like mitochondria)
• The thylakoid membranes are stacked into structures called grana which contain the chlorophyll
• Grana are connected together with lamellae. Lamellae acts as cementing material between two adjacent cells.
• Ribosome: a minute particle consisting of RNA and associated proteins found in large numbers in the cytoplasm of living cells.
• Ribosomes bind messenger RNA and transfer the RNA to synthesise polypeptides and proteins.