Topic 3

• description of lysosome

  > round organelle surrounded by membrane

  > no clear internal structure
• function of lysosome

  > release hydrolytic enzyme

  > kept separated from the cytoplasm by a membrane

  > breakdown/ hydrolysed pathogens (invading cell) or worn out cell component
• description of nucleus

  > surrounded by nuclear envelope

  > double membrane

  > have pores

  > contain chromatin which is made from DNA and protein

  > it has a nucleolus
• function of nucleus

  > stores genetic information that codes for protein

  > site of DNA replication

  > site of transcription, producing mRNA

  > nucleolus makes ribosomes

  > pores allow substance move between nucleus and cytoplasm
• description of ribosome

  > free floating in cytoplasm or attached to rER

  > made of protein and RNA

  > no membrane

  > 70s in prokaryotic cells

  > 80s in eukaryotic cells
• function of ribosome

  site of protein synthesis
• description of rER (rough endoplasmic reticulum)

  > surface cover with ribosome

  > fluid filled space enclosed by a system of membrane
• function on rER

  fold and processes protein that have been made at the ribosome
• description of sER

  similar to rER but with no ribosome
• function of sER

  synthesises and processes lipids
• description of Golgi apparatus

  > a group of fluid filled membrane bound flattened sacs

  > formed by the fusion of vesicles from the ER
• function of Golgi apparatus

  > modify, process and package new lipids and protein

  > make lysosome
• function of Golgi vesicle

  transport protein or lipids to their destination
• description of mitochondria

  > oval shaped

  > double membrane

  > inner membrane fold to form cristae

  > matrix inside cristae

  > matrix contain enzyme for respiration
• function of mitochondria

  > site of aerobic respiration

  > ATP production
• description of centriole

  > hollow cylinder

  > made of microtubules
• function of centriole

  involved with the separation of chromosomes during cell division
• description of chloroplast

  > double membrane

  > small, flattened structure

  > inner membrane aka thylakoid membrane
• function of chloroplast

  > site of photosynthesis
• description of cell wall

  > rigid structure

  > made of cellulose
• function of cell wall

  > support and protect the cell
• description of amyloplast

  > single membrane

  > contain starch ganules
• function of amyloplast

  > stores starch grains

  > covert starch to glucose
• description of cell vacuole

  > contain cell sap - a weak solution of sugar and salt

  > vacuole surround by tonoplast (membrane)
• function of cell vacuole

  > maintain turgor pressure in cell

  > contain cell sap - store sugar amino acids, pigment and any waste chemical
• flagellum

  > long, hair like structure

  > rotates allow prokaryotic cell move

  > not all prokaryotic cell have it
• DNA in prokaryotic cell

  > free floating in cytoplasm

  > circular DNA

  > not attached to any histone protein
• what is histone protein

  protein which DNA wraps around
• plasmid

  > small loops of DNA

  > not the main circular DNA molecule

  > contain genes for antibiotic resistance

  > not all prokaryotic cells have it
• what happens during interphase

  Gap phase 1 (G1) - cell grows and new organelles and protein (polymerase, primase, ligase etc.) are made

  Synthesis (S) - cell replicates its DNA ready to divide by mitosis

  Gap phase 2 (G2) - cell keeps growing and proteins needed for cell division are made
• what is mitosis needed for

  > growth

  > repairing damaged tissues

  > asexual reproduction
• what happens in telophase

  > chromatids reach the opposite poles on the spindle

  > uncoil and become long and thin aka chromosomes

  > nuclear envelope forms around each group of chromosomes - 2 nuclei

  > cytoplasm divides forming 2 genetically identical daughter cell
• how does mitosis ensure genetic consistency

  > DNA replication before mitosis

  > arrangement of chromosomes on the spindle and separation of chromosomes to the pole
• what happens in prophase

  > chromosomes condenses, becoming shorter and thicker

  > each chromosomes is visible as 2 strands aka sister chromatids

  > centrioles start moving to opposite poles

  > network of protein fibres (spindle) forms

  > nuclear envelope breaks down

  > chromosomes lie free in cytoplasm
• what happens in anaphase

  > centromeres divide, separating each pair of sister chromatids

  > spindles contract, pulling chromatids to opposite poles
• stages of mitosis

  1. prophase
  2. metaphase
  3. anaphase
  4. telophase
• what happens in metaphase

  > each chromosomes with 2 chromatids line up at the equator of the cell

  > spindle fibre attach to the centromeres of the chromosomes
• explain the importance of meiosis in gametes production

  > to make haploid nucleus from diploid

  > allows genetic variation through independent assortment and crossing over

  > ensure organisms produced by sexual reproduction have the correct number of chromosomes
• what is cancer and why is it considered multifactorial

  > cancer: uncontrolled division of cells which causes tumors to form

  > multifactorial: cause by lots of factors:

  • genetics
  • smoking
  • UV light
  • diet
  • virus infections
• how does epigenetic control work

  > attaching or removing chemical groups to or from the DNA

  > affects how easy it is for enzymes needed for transcription to interact with and transcribe genes