A Science teacher by trade, I've also been known to be found teaching Maths and PE! However, strange as it may seem, my real love is designing resources that can be used by other teachers to maximise the experience of the students. I am constantly thinking of new ways to engage a student with a topic and try to implement that in the design of the lessons.
A Science teacher by trade, I've also been known to be found teaching Maths and PE! However, strange as it may seem, my real love is designing resources that can be used by other teachers to maximise the experience of the students. I am constantly thinking of new ways to engage a student with a topic and try to implement that in the design of the lessons.
This concise lesson covers the content of specification point 5.1.5 (l) of the OCR A-level Biology A specification which states that students should be able to demonstrate and apply an understanding of the action of neuromuscular junctions. Due to a number of similarities between these structures and cholinergic synapses, this lesson uses prior knowledge of these connections between neurones to build a good understanding of the junctions. Students will discover that the events that occur at an axon tip mirror those which happen at the pre-synaptic bulb and this is then developed to look at the differences in terms of the events once the acetylcholine has bound to its receptor sites. There is a focus on the structure of the sarcolemma and time is taken to explain how the action potential is passed from this membrane to the transverse tubules in order to stimulate the release of calcium ions from the sarcoplasmic reticulum. As a result, this lesson ties in nicely with the following lesson on the contraction of skeletal muscle and students will be able to link the binding to troponin in that lesson to the release of these ions from this lesson.
Both of the main tasks of the lesson have been differentiated so that students of all abilities can access the work and make progress.
This lesson has been designed for those students studying on the OCR A-level Biology course and ties in nicely with the other uploaded lessons on module 5.1.5 (Animal and plant responses)
This is a highly-detailed and fully-resourced lesson which covers the part of specification point 6.4.3 of the AQA A-level Biology specification which states that students should be able to describe the roles of the hypothalamus, posterior pituitary and ADH in osmoregulation. Students learnt about the principles of homeostasis and negative feedback in an earlier lesson, so this lesson acts to build on that knowledge and challenges them to apply their knowledge. A wide range of activities have been included in the lesson to maintain motivation and engagement whilst the understanding and prior knowledge checks will allow the students to assess their progress as well as challenge themselves to make links to other Biology topics.
The lesson begins with a discussion about how the percentage of water in urine can and will change depending on the blood water potential. Students will quickly be introduced to osmoregulation and they will learn that the osmoreceptors and the osmoregulatory centre are found in the hypothalamus. A considerable amount of time is taken to study the cell signalling between the hypothalamus and the posterior pituitary gland by looking at the specialised neurones (neurosecretory cells). Links are made to the topics of neurones, nerve impulses and synapses and the students are challenged to recall the cell body, axon and vesicles. The main section of the lesson forms a detailed description of the body’s detection and response to a low blood water potential. The students are guided through this section as they are given 2 or 3 options for each stage and they have to use their knowledge to select the correct statement. The final task asks the students to write a detailed description for the opposite stimulus and this task is differentiated so those who need extra assistance can still access the work.
This lesson has been written for students studying on the AQA A-level Biology course and ties in nicely with the other uploaded lessons which cover this specification point as well as the whole of topic 6.
This clear and concise lesson explains how the inheritance of two or more genes that have loci on the same autosome demonstrates autosomal linkage. The engaging PowerPoint and associated resource have been designed to cover the part of point 7.1 of the AQA A-level Biology specification which states that students should be able to use fully-labelled genetic diagrams to interpret the results of crosses involving autosomal linkage.
This is a topic which can cause confusion for students so time was taken in the design to split the concept into small chunks. There is a clear focus on how the number of original phenotypes and recombinants can be used to determine linkage and suggest how the loci of the two genes compare. Important links to other topics such as crossing over in meiosis are made to enable students to understand how the random formation of the chiasma determines whether new phenotypes will be seen in the offspring or not. Linkage is an important cause of variation and the difference between observed and expected results and this is emphasised on a number of occasions. The main task of the lesson acts as an understanding check where students are challenged to analyse a set of results involving the inheritance of the ABO blood group gene and the nail-patella syndrome gene to determine whether they have loci on the same chromosome and if so, how close their loci would appear to be.
This lesson has been written to tie in with the other 6 lessons from topic 7.1 (Inheritance) and these have also been uploaded
This bundle contains 7 lessons which combine to cover the content of topic 7.1 (Inheritance) of the AQA A-level Biology specification. All 7 are fully-resourced and contain differentiated tasks which allow students of differing abilities to access the work whilst being challenged. They have been designed to include a wide range of activities that check the understanding of the current topic as well as making links between other parts of this topics and topics covered earlier in the course.
The lessons on codominant and multiple alleles and epistasis are free so you can sample the quality of this bundle before deciding to make a purchase
Each of the 4 lessons included in this bundle are fully-resourced and have been designed to cover the content as detailed in topic 7.3 (Evolution may lead to speciation) of the AQA A-Level Biology specification. The specification points that are covered within these lessons include:
Phenotypic variation within a species
The effects of stabilising, directional and disruptive selection
The importance of genetic drift in causing changes in allele frequency
Allopatric and sympatric speciation
The lessons have been written to include a wide range of activities and numerous understanding and prior knowledge checks so students can assess their progress against the current topic as well as be challenged to make links to other topics within this module and earlier modules
If you would like to see the quality of the lessons, download the phenotypic variation lesson which is free
This fully-resourced lesson describes how light intensity, carbon dioxide concentration and temperature limit the rate of photosynthesis. The PowerPoint and accompanying resources have been designed to cover point 5.2.1 (g) (i) of the OCR A-level Biology A specification and also includes a brief consideration of water stress.
The lesson has been specifically written to tie in with the three previous lessons in this module which covered the structure of the chloroplast, the light-dependent and light-independent stages and the uses of TP. Exam-style questions are included throughout the lesson and these require the students to explain why light intensity is important for both reactions as well as challenging them on their ability to describe how the relative concentrations of GP, TP and RuBP would change as carbon dioxide concentration decreases. There are also links to previous topics such as enzymes when they are asked to explain why an increase in temperature above the optimum will limit the rate of photosynthesis. Step by step guides are included to support them to form some of the answers and mark schemes are always displayed so that they can quickly assess their understanding and address any misconceptions.
Hours and hours of planning have gone into each and every lesson that’s included in this bundle to ensure that the students are engaged and motivated whilst the detailed content of topic 2 of the Edexcel International A-level Biology specification is covered. Membranes, proteins, DNA and gene expression represent some of the most important structures, molecules and processes involved in this subject and a deep understanding of their role in living organisms is important for a student’s success.
The 20 lesson PowerPoints and accompanying resources contain a wide range of activities which cover the following topic 2 specification points:
Know the properties of gas exchange surfaces in living organisms
Understand how the rate of diffusion can be calculated using Fick’s Law of Diffusion
Understand how the structure of the mammalian lung is adapted for rapid gas exchange
The structure and properties of cell membranes
The movement of free water molecules by osmosis
The movement across membranes by passive and active transport
The role of channel and carrier proteins in membrane transport
The basic structure of an amino acid
The formation of polypeptides and proteins
The structure of proteins
The mechanism of action and specificity of enzymes
Enzymes are biological catalysts
Intracellular and extracellular enzymes
The basic structure of mononucleotides
The structure of DNA and RNA
The process of DNA replication
The nature of the genetic code
A gene as a sequence of bases on DNA that codes for a sequence of amino acids
The process of transcription and translation
Errors in DNA replication give rise to mutations
Mutations give rise to disorders but many mutations have no observable effect
The meaning of key genetic terms
Understanding the pattern of monohybrid inheritance
Sex linkage on the X chromosome
Understand how the expression of a gene mutation in people with cystic fibrosis impairs the functioning of the gaseous exchange, digestive and reproductive systems
The uses and implications of genetic screening and prenatal testing
Due to the detail included in all of these lessons, it is estimated that it will take in excess of 2 months of allocated A-level teaching time to complete the teaching of the bundle
If you would like to sample the quality of these lessons, then download the rapid gas exchange, osmosis, DNA & RNA, genetic code, genetic terms and cystic fibrosis lessons as these have been uploaded for free.
This bundle contains 10 detailed lesson PowerPoints and the variety of tasks that are contained within these slides and the accompanying resources will engage and motivate the students whilst covering the following specification points within topic 1 of the Edexcel International A-level Biology specification:
The importance of water as a solvent in transport
The difference between monosaccharides, disaccharides and polysaccharides
The relationship between the structure and function of monosaccharides
The formation and breakdown of disaccharides
The relationship between the structure and function of glycogen, amylose and amylopectin
The synthesis of triglycerides
The differences between saturated and unsaturated lipids
The relationship between the structure of capillaries, arteries and veins and their functions
Atrial systole, ventricular systole and cardiac diastole as the three stages of the cardiac cycle
The operation of the mammalian heart and the major blood vessels
The role of haemoglobin in the transport of oxygen and carbon dioxide
The oxygen dissociation curve for foetal haemoglobin and during the Bohr effect
The blood clotting process
If you want to sample the quality of this bundle, then download the glycogen, amylose and amylopectin, cardiac cycle and blood clotting lessons as these have been uploaded for free
This lesson describes how the role of carrier of proteins and ATP in active transport and the co-transport of sodium ions and glucose in the ileum. The PowerPoint and accompanying resources are part of the final lesson in a series of 3 that have been designed to cover the details of point 2.3 of the AQA A-level Biology specification and also includes descriptions of endocytosis and exocytosis
The start of the lesson focuses on the structure of this energy currency and challenges the students prior knowledge as they covered ATP in topic 1.6. As a result, they will recall that this molecule consists of adenine, ribose and three phosphate groups and that in order to release the stored energy, ATP must be hydrolysed. Time is taken to emphasise the key point that the hydrolysis of ATP can be coupled to energy-requiring reactions and this leads into a series of exam-style questions where students are challenged on their knowledge of simple and facilitated diffusion to recognise that ATP is needed for active transport. These questions also challenge them to compare active transport against the forms of passive transport and to use data from a bar chart to support this form of transport. In answering these questions they will discover that carrier proteins are specific to certain molecules and time is taken to look at the exact mechanism of these transmembrane proteins. A quick quiz round introduces endocytosis and the students will see how vesicles are involved along with the energy source of ATP to move large substances in or out of the cell. The students are then shown how exocytosis is involved in a synapse and in the release of ADH from the pituitary gland during osmoregulation which they will cover in later topics. The final part of the lesson describes the movement of sodium ions and glucose from the ileum to the epithelial cells to the blood using a range of proteins which includes cotransporter proteins and students will learn that similar mechanisms are seen in the phloem and in the proximal convoluted tubule.
This detailed lesson describes how the ventilation rate is controlled by the ventilation centre in the medulla oblongata. The engaging PowerPoint and accompanying resource have been designed to cover the second part of point 7.13 (ii) in unit 5 of the Edexcel International A-level Biology specification.
The previous lesson described the control of heart rate so this lesson has been written to tie in with this and to use this knowledge to further the students understanding of the control of ventilation rate. The lesson begins with a focus on the muscles involved in ventilation, specifically the diaphragm and external intercostal muscles, so that students can understand how their contraction results in an increase in the volume of the thoracic cavity. Boyle’s law is briefly introduced to allow students to recognise the relationship between volume and pressure so that the movement of air with the pressure gradient can be described. Time is then taken to consider the importance of inhalation and an exam-style question challenges the students to explain that a constant supply of oxygen to the alveoli is needed to maintain a steep concentration gradient with the surrounding capillaries. The students are then tasked with writing a description of exhalation at rest using the description of inhalation as their guide. The rest of the lesson focuses on the mechanisms involved in increasing the rate and depth of breathing during exercise. Students will use their knowledge of the control of heart rate to recall that chemoreceptors detect changes in oxygen and carbon dioxide and blood pH and that the medulla oblongata processes the sensory information that it receives before coordinating a response. The final task challenges them to use the information provided in this lesson and the previous one to order 10 detailed descriptions so they can form a complete passage about this control system
It’s fair to say that cell structure and biological molecules are two of the most important topics in the OCR A-level Biology A course and all 19 lessons that are included in this bundle have been planned at length to cover the module 2.1.1 & 2.1.2 specification points in the detail required at this level.
The lesson PowerPoints and their accompanying resources contain a wide range of tasks as well as regular checks to allow students to assess their understanding of the current content as well as prior knowledge checks to emphasise the importance of making links to topics in other modules.
The following specification points in modules 2.1.1 (cell structure) and 2.1.2 (biological molecules) are covered by the lessons in this bundle:
2.1.1
The use of microscopy to observe and investigate different types of cell and cell structure in a range of eukaryotic organisms
The use of the eyepiece graticule and stage micrometer
The use of staining in light microscopy
The use and manipulation of the magnification formula
The difference between magnification and resolution
The ultrastructure of eukaryotic cells and the functions of the different cellular components
The interrelationship between the organelles involved in the production and secretion of proteins
The importance of the cytoskeleton
The similarities and differences between the ultrastructure of prokaryotic and eukaryotic cells
2.1.2
The properties and roles of water in living organisms
The concept of monomers and polymers and the importance of condensation and hydrolysis reactions
The chemical elements that make up biological molecules
The structure and properties of glucose and ribose
The synthesis and breakdown of a disaccharide and a polysaccharide by the formation and breakage of glycosidic bonds
The structure of starch, glycogen and cellulose molecules
The relationship between the structure, function and roles of triglycerides, phospholipids and cholesterol in living organisms
The general structure of an amino acid
The synthesis and breakdown of dipeptides and polypeptides
The levels of protein structure
The structure and function of globular proteins
The properties and functions of fibrous proteins
The key inorganic ions involved in biological processes
The chemical tests for proteins, reducing and non-reducing sugars, starch and lipids
If you would like to sample the quality of the lessons included in this bundle, then download the following lessons as they have been uploaded for free:
The use of microscopy
The importance of the cytoskeleton
Properties and roles of water
Glucose & ribose
General structure of an amino acid
Dipeptides, polypeptides and protein structure
All 5 lessons in this lesson bundle are highly detailed to cover the specification points shown below that are found in AS unit 2, topic 1 of the WJEC A-level Biology specification:
The classification of organisms into groups based on their evolutionary relationships
The need for classification
The three-domain classification system
The characteristic features of the five kingdoms of living organisms
The use of physical features and biochemical methods to assess the relatedness of organisms
The concept of species
The use of the binomial naming system
Biodiversity as the variety of organisms found within a specified geographic region
Biodiversity can be assessed in a habitat using Simpson’s index of diversity
Biodiversity can be assessed within a species at a genetic level
Biodiversity can be assessed at a molecular level using DNA fingerprinting
Biodiversity has been generated through natural selection
Anatomical, physiological and behavioural adaptations
As well as the A-level Biology content within the slides, current understanding and prior knowledge checks in the form of exam-style questions, differentiated tasks and quiz competitions are included throughout to allow the students to assess their progress
If you would like to sample the quality of the lessons included in this bundle, then download the classification, species and the binomial naming system lesson as this has been shared for free
This lesson describes the structure of the chromosome, including DNA, histone proteins, chromatids, centromeres and telomeres. The PowerPoint and accompanying worksheets have been primarily designed to cover point 5.1 (a) of the CIE A-level Biology specification but has been specifically planned to provides links to the upcoming topics of the cell cycle, mitosis, meiosis and DNA replication.
The lesson begins with a prior knowledge check, where the students have to recall why the DNA in prokaryotic cells is described as being naked. This re-introduces histone proteins, and then time is taken to describe that the wrapping of DNA molecules around these proteins forms the linear chromosomes in the nucleus of eukaryotic cells. A series of 7 exam-style questions are used throughout the lesson and challenge the students to apply their knowledge and understanding to unfamiliar situations and challenge their knowledge of topics 1 and 2 (cell structure and biological molecules). The mark schemes for all of these questions are embedded into the PowerPoint to allow the students to assess their progress. Moving forwards, a quiz competition is used to introduce the terms diploid, chromatid and centromere and the S phase of interphase in a fun and memorable way. Students will learn that the duplication of chromosomes results in pairs of identical sister chromatids that are joined by a centromere. The importance of the splitting of the centromere in mitosis is explained and then the students are challenged to explain why the non-sister chromatids are involved in crossing over, when variation is needed. The final part of the lesson considers the repetitive nucleotide sequences found on the end of chromosomes that are known as telomeres and students will gain an initial understanding about their structure so they are prepared for the upcoming lesson on their significance
This bundle contains 19 PowerPoint lessons which are highly-detailed and are fully-resourced with differentiated worksheets. Intricate planning means that the wide range of activities included in these lessons will engage and motivate the students, check on their current understanding and their ability to make links to previously covered topics and most importantly will deepen their understanding of the following specification points in topic 2 (Cells) of the AQA A-level Biology specification:
Structure and function of the organelles in eukaryotic cells
The specialised cells in complex, multicellular organisms
The structure of prokaryotic cells
The structure of viruses which are acellular and non-living
The principles and limitations of optical, transmission electron and scanning electron microscopes
Measuring the size of an object under an optical microscope
Use of the magnification formula
The behaviour of chromosomes during the stages of the cell cycle
Binary fission
The basic structure of cell membranes
The role of phospholipids, proteins, glycoproteins, glycolipids and cholesterol
Simple diffusion
Facilitated diffusion
Osmosis, explained in terms of water potential
The role of carrier proteins and the hydrolysis of ATP in active transport
Co-transport as illustrated by the absorption of sodium ions and glucose by the cells lining the mammalian ileum
Recognition of different cells by the immune system
The identification of pathogens from antigens
The phagocytosis of pathogens
The cellular response involving T lymphocytes
The humoral response involving the production of antibodies by plasma cells
The structure of an antibody
The roles of plasma cells and memory cells in the primary and secondary immune response
The use of vaccines to protect populations
The differences between active and passive immunity
The structure of the human immunodeficiency virus and its replication in helper T cells
How HIV causes the symptoms of AIDS
Why antibiotics are ineffective against viruses
The use of antibodies in the ELISA test
If you would like to sample the quality of these lessons, then download the eukaryotic animal cells, viruses, microscopes, osmosis, lymphocytes, HIV and AIDS lessons as these have been shared for free.
This fully-resourced lesson describes genetic diversity as the number of genes in a population and explains how this is increased by polymorphic gene loci. The engaging PowerPoint and accompanying differentiated resources have been primarily designed to cover the first part of point 4.4 of the AQA A-level Biology specification but also introduces inheritance and codominance so that students are prepared for these sub-topics when covering topic 7 in the following year.
In order to understand that 2 or more alleles can be found at a gene loci, students need to be confident with genetic terminology, so the start of the lesson focuses on key terms including gene, locus, allele, recessive, genotype and phenotype. A number of these will have been met at GCSE, as well as during the earlier lessons in topic 4 when considering meiosis, so a quick quiz competition is used to check on their recall of the meanings of these terms. The CFTR gene is then used as an example to demonstrate how 2 alleles results in 2 different phenotypes and therefore genetic diversity. Moving forwards, students will discover that more than 2 alleles can be found at a locus and they are challenged to work out genotypes and phenotypes for a loci with 3 alleles (shell colour in snails) and 4 alleles (coat colour in rabbits). At this point, the students are introduced to codominance and again they are challenged to apply their understanding to a new situation by working out the number of phenotypes in the inheritance of blood groups. The lesson concludes with a brief consideration of the HLA gene loci, which is the most polymorphic loci in the human genome, and students are challenged to consider how this sheer number of alleles can affect the chances of tissue matches in organ transplantation.
This fully-resourced lesson guides students through the construction of genetic crosses and pedigree diagrams for the inheritance of a single gene. The clear PowerPoint and accompanying resources have been designed to cover point 8.2 (ii) of the Edexcel A-level Biology B specification and includes the inheritance of multiple allele characteristics as well as those that demonstrate codominance.
In order to minimise the likelihood of errors and misconceptions, step by step guides have been included throughout the lesson to support the students with the following:
Writing parent genotypes
Working out the different gametes that are made following meiosis
Interpreting Punnett crosses to work out phenotypic ratios
Students can often find pedigree trees the most difficult to interpret and to explain so exemplar answers are used as well as differentiated worksheets provided to support those students who need extra assistance.
This detailed lesson describes the relationship between the structure, properties and roles of water for living organisms. The engaging PowerPoint and accompanying resource have been designed to cover the details of specification point 2.1.2 (a) of the OCR A-level Biology A course and has been specifically designed to ensure that each role is illustrated using an example in prokaryotes or eukaryotes.
As this is the first lesson in the biological molecules sub-module (2.1.2), which is a topic that students tend to find difficult or potentially less engaging, the planning has centred around the inclusion of a wide variety of tasks to cover the content whilst maintaining motivation and engagement. These tasks include current understanding and prior knowledge checks, discussion points and quick quiz competitions to introduce key terms and values in a memorable way. The start of the lesson considers the structure of water molecules, focusing on the covalent and hydrogen bonds, and the dipole nature of this molecule. Time is taken to emphasise the importance of these bonds and this property for the numerous roles of water and then over the remainder of the lesson, the following properties are described and discussed and linked to real-life examples:
As a solvent to act as a transport medium in blood plasma
Molecules are attracted by cohesive forces to enable transport in the xylem
High latent heat of vaporisation for thermoregulation
High specific heat capacity for the maintenance of a stable environment
Peak density in the liquid form allowing ice to float
The final part of the lesson introduces condensation and hydrolysis reactions and students will learn that a clear understanding of these reactions is fundamental as they will reappear throughout the module in the synthesis and breakdown of biological molecules.
This lesson describes the mechanisms of ventilation and gas exchange in insects. The PowerPoint and accompanying worksheets are the part of the second lesson in a series of 2 lessons which have been designed to cover the details that are set out in point 3.1.1 (f) of the OCR A-level Biology A specification. The first lesson in this series describes ventilation and gas exchange in bony fish
In the previous lesson, the students were introduced to the different circulatory systems of mammals and bony fish and this knowledge is checked upon at the start of this lesson. This is relevant because the open circulatory system of an insect explains how oxygen is not transported in the blood but instead is absorbed from the body fluid that bathes the tissues. The next part of the lesson describes the structure of the spiracles, tracheae and tracheoles in the tracheal system and explains how this system is responsible for the delivery of oxygen to the open end of the tracheole for gas exchange with this fluid. As the tracheae are supported by chitin, which is similar in structure and function to cellulose and keratin respectively, a series of exam-style questions are used to challenge the students on their knowledge of those polymers from module 2.1.2 (biological molecules). As always, the mark scheme is embedded in the powerpoint so students can assess their understanding and progress. The final part of the lesson describes how squeezing of the tracheoles by the flight muscles and the changes in the volume of the thorax as a result of the movement of the wings are similar to mechanisms observed in mammals.
This lesson looks at the homologous series of alcohols, focusing on the properties that they share and guiding students through naming and drawing displayed formula to represent them. It has been designed for GCSE students and time is taken to embed a few selected key details as dictated by the exam board specification.
The lesson begins with students meeting the formula for ethanol. This substance will provide the backbone to their understanding as they are guided through drawing the displayed formula so they can visualise how it is done and use to draw diagrams for the others. Students are shown how the general formula for the alkanes and alkenes can be worked out and then challenged to use this to work out the general formula for the alcohols. There is a brief look at the reactions with oxygen and the products that can be made depending upon whether sufficient oxygen is available or not.
This detailed lesson describes the structure of a nucleotide and a phosphorylated nucleotide and explains how polynucleotides are synthesised and broken down. The engaging PowerPoint has been designed to cover points [a], [b] and [c] of module 2.1.3 as detailed in the OCR A-level Biology A specification and links are made throughout to earlier topics such as biological molecules.
Students were introduced to the term monomer and nucleotide in the previous module, so the start of the lesson challenges them to recognise this latter term when only the letters U, C and T are shown. This has been designed to initiate conversations about why only these letters were used so that the nitrogenous bases can be discussed later in greater detail. Moving forwards, students will learn that a nucleotide is the monomer to a polynucleotide and that deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are two examples of this type of polymer. The main part of the lesson has been filled with various tasks that explore the structural similarities and structural differences between DNA and RNA. This begins by describing the structure of a nucleotide as a phosphate group, a pentose sugar and a nitrogenous base. Time is taken to consider the details of each of these three components which includes the role of the phosphate group in the formation of a phosphodiester bond between adjacent nucleotides on the strand. At this point students are challenged on their understanding of condensation reactions and have to identify how the hydroxyl group associated with carbon 3 is involved along with the hydroxyl group of the phosphoric acid molecule. A number of quiz rounds are used during this lesson, as a way to introduce key terms in a fun and memorable way. One of these rounds introduces adenine and guanine as the purine bases and thymine, cytosine and uracil as the pyrimidine bases and the students are shown that their differing ring structures can be used to distinguish between them. The remainder of the lesson focuses on ADP and ATP as phosphorylated nucleotides and links are made to the hydrolysis of this molecule for energy driven reactions in cells such as active transport
