biology4alevel600

Describe and interpret drawings and photographs of typical animal and plant cells. Note that plant cells are always surrounded by a cell wall made of cellulose,  never found around animal cells.  Typical animal and plant cells as seen using an electron microscope: 1. Functions of membrane systems and organelles The plasma membrane ( cell surface membrane ) controls what enters and leaves the cell. Many membranes within the cell help to make different compartments for different chemical reactions to take place. The nucleus is surrounded by  nuclear envelope (pair of membranes).  The nucleus contains chromosomes , with very long molecule of DNA (DNA determines the sequences of amino acids to form protein molecules).  A darker area in the nucleus (no membrane) is called nucleolus : here new ribosomes are made, following a code on part of the DNA. Ribosomes (made of RNA & protein) are found free in the cytoplasm + attached to rough endoplasmic reticulum (R...

Most cells are very small, and their structures can only be seen by using a microscope . 1. Light microscopes light rays pass through the specimen on a slide  focused by an objective lens and an eyepiece lens .  ---> magnified image of the specimen on the retina of your eye/screen/camera . 2. Electron microscopes uses beams of electrons   specimen very thin,  placed in a vacuum  to allow electrons to pass through it.  electrons are focused onto a screen/photographic film ---> magnified image of the specimen. 3. Magnification and Resolution Amount of magnification depends on the resolution of the microscope (ability to distinguish 2 objects as separate).  The smaller the objects that can be distinguished --> the higher the resolution.  wavelength: beam of electrons  <<<  light          resolution:   electron microscope >>> light microscope with electron microscope,...

1.1 The microscope in cell studies 1.2 Cells  as the  basic units of living  organisms All organisms are composed of cells. Knowledge of their structure and function  underpins much of biology. The fundamental differences between eukaryotic and prokaryotic cells are explored and provide useful biological background for the section on Infectious disease.  Viruses are introduced as non-cellular structures, which gives candidates the opportunity to consider whether cells are a fundamental property of life. The use of light microscopes is a fundamental skill that is developed in this section and applied throughout several other sections of the syllabus. Throughout the course, photomicrographs and electron micrographs from transmission and scanning electron microscopes should  be studied. Learning Outcomes Candidates should  be able to: 1.1 The microscope in cell studies An understanding of the principles  of microscopy shows why light and electron mi...

• The microscope in cell studies • Cells as the basic units of living organisms • Detailed structure of typical animal and plant cells, as seen using the electron microscope • Outline functions of organelles in plant and animal cells • Characteristics of prokaryotic and eukaryotic cells Learning Outcomes Candidates should be able to: (a) [PA] use an eyepiece graticule and stage micrometer scale to measure cells and be familiar with units  (millimetre, micrometre, nanometre) used in cell studies; (b) explain and distinguish between resolution and magnification (see section 5), with reference to light  microscopy and electron microscopy; (c) describe and interpret drawings and photographs of typical animal and plant cells, as seen using the  electron microscope, recognising the following: rough endoplasmic reticulum and smooth endoplasmic  reticulum, Golgi body (Golgi apparatus or Golgi complex), mitochondria, ribosomes, lysosomes,  chloroplasts, cell surface memb...

Candidates  for   Cambridge   International   AS   Level   Biology   study    the   following   topics: 1      Cell   structure 2      Biological   molecules 3      Enzymes 4      Cell   membranes   and   transport 5      The   mitotic    cell   cycle 6      Nucleic   acids    and   protein    synthesis 7      Transport   in   plants 8      Transport   in   mammals 9      Gas   exchange and   smoking 10    Infectious   disease 11    Immunity Candidates  for   Cambridge   International   A   Level   Biology   study    the   AS   topics    and   the   ...

1 Core syllabus Cambridge International AS Level candidates will study and be assessed on the first eleven sections,  A to K. Cambridge International A Level candidates will study and be assessed on all sixteen sections, A to P. A   Cell Structure B   Biological Molecules C   Enzymes D   Cell Membranes and Transport E   Cell and Nuclear Division F   Genetic Control G  Transport H  Gas Exchange I   Infectious Disease J   Immunity K  Ecology L   Energy and Respiration M   Photosynthesis N   Regulation and Control O   Inherited Change (Gene technology now in section R) P   Selection and Evolution 2 Applications of Biology Cambridge International AS Level candidates will not be assessed on these sections. Cambridge International A Level candidates will study and be assessed on all five sections, Q to U. Q   Biodiversity and Conservation R   Gene Technology (includes some material originally in O) ...