A-Level Biology OCR B H422

(i) the importance of microscopy in the development of the cell theory as a unifying concept in biology and the investigation of cell structure

To include the use of the light microscope, transmission and scanning electron microscopes and recent developments such as the confocal scanning microscope.

(ii) the preparation of blood smears (films) for use in light microscopy

To include how blood smears are made and the interpretation of stained material. Practical work to be carried out in accordance with current CLEAPSS® guidelines. Also see Section 5. PAG1

the procedure for differential staining

To include the use of Leishman’s stain to identify leucocytes in blood smears.

(i) the structure of animal cells as illustrated by a range of blood cells and components as revealed by the light microscope

To include red blood cells (erythrocytes), platelets, neutrophils, lymphocytes and monocytes as specialised cells with particular functions related to their structures.

(ii) the observation, drawing and annotation of cells in a blood smear as observed using the light microscope

PAG1

the linear dimension of cells and the use and manipulation of the magnification formula

$\text{magnification} = \dfrac{\text{image size}}{\text{actual size}}$

PAG1

practical investigations using a haemocytometer to determine cell counts

To determine the mean numbers of erythrocytes and convert to a concentration (to include details of dilutions and calculations). PAG1

the principles and use of flow cytometry in blood analysis

To include the use of fluorescent labels. Details of the use of different lasers is not required.

the ultrastructure of a typical eukaryotic animal cell, such as a leucocyte, as revealed by an electron microscope

To include the structure and function of the following: plasma membrane, Golgi apparatus, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER), ribosomes, lysosomes, vesicles, mitochondria, cytoskeleton, centrioles. nucleus and nucleolus.

(i) the ultrastructure of a typical eukaryotic plant cell such as a palisade mesophyll cell and a prokaryotic cell, as revealed by an electron microscope

To include the structure and function of  chloroplasts, large vacuole, tonoplast and the cell wall in plant cells, circular DNA, plasmids, mesosome, pili and flagella in prokaryotic cells.

(ii) the similarities and differences between the structure of eukaryotic plant and animal cells, and between eukaryotic and prokaryotic cells

practical investigations using a graticule and stage micrometer to calculate and measure linear dimensions of cells

To include the calibration of an eyepiece graticule using a stage micrometer, calculating the area of the field of view and measuring the sizes of organs, tissues, cells and organelles and calculating their magnification. PAG1

how the plasma membrane is composed of modified lipids and how the structure of triglycerides and phospholipids is related to their functions

To include reference to fatty acids, glycerol, phosphate groups, ester bonds and hydrophobic/hydrophilic properties.

the fluid mosaic model of the typical plasma membrane

To include the location and function of phospholipids, intrinsic proteins, extrinsic proteins, cholesterol, glycolipids and glycoproteins.

the movement of molecules across plasma membranes

To include diffusion and facilitated diffusion as passive methods of transport across membranes AND active transport, endocytosis and exocytosis as processes requiring ATP as an immediate source of energy.

practical investigation(s) into factors affecting diffusion rates in cells

To include the use of model cells and tissues such as beetroot. PAG8

the roles of membranes within and at the surface of cells

the interrelationship between the organelles involved in the production and secretion of proteins

To include the role of the cytoskeleton and motor proteins, the nucleus, ribosomes, RER, Golgi and vesicles (no details of transcription and translation are required at this stage).