Biology B2.1 Cells, tissues and organs


Complete overview of AQA additional biology topic B2.1 covering types of cells, parts of cells, specialised cells, what cells do, tissues, types of tissue, organs and organ systems.
Corey Meehan
Note by Corey Meehan, updated more than 1 year ago
Corey Meehan
Created by Corey Meehan about 8 years ago

Resource summary

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Cells All living things are made up of cells. These are tiny microscopic building blocks which form every leaf, every bacterium, every eye every tree and every heart that beats and even every human! You get the picture. Some cells have special qualities which makes them very useful to have.

Animal Cells Theses are as the name suggests the building blocks of animals. All simple animal cells consist of a nucleus, cell membrane and cytoplasm, after all that is what makes them cells! Most animal cells also contain mitrochondria to produce energy and ribosomes which is where protein synthesis happens.

Key Terms The words highlighted in bold are important and you must know the definition of theses for your exams.The definitions appear here in the order the words appear in the main text.Nucleus - Controls the cells activities and contains the cells DNA.Cell Membrane -Controls the movement of materials in and out of the cells.Cytoplasm -Where chemical reactions take place.Mitrochondria - Where energy is released during aerobic respiration.Ribosomes - Where protein synthesis takes place.Protein Synthesis - The process of making a protein.Cell Wall - Made of cellulose to support the cell and give the cell its structure. Permanent Vacuole - Storage for food and other useful substances.Chloroplasts - Contain chlorophyll and release glucose.Chlorophyll - Where photosynthesis takes place to create glucose.Slime Capsule -Helps to protect the cell from environmental hazards such as antibiotics or drying out.Plasmids -Store genetic information and can lead to genetic advances such as antibiotic resistance.Flagella -Allow the bacterium to move.Genetic material -Keeps cells DNA and other genetic information.Bacterial Colonies - Formed when bacteria multiply.Specialised -A type of cell able to perform a special function to complete a task.Multicellular Organisms -An organism that consists of more than one cell usually plants and animals in contrast to a unicellular organism such as yeast.Differentiate -To recogiese something that makes it different.Muscle Tissue -Type of animal tissue which is made up of muscle cells and allows us to move.Glandular Tissue -Type of animal tissue that secretes hormones and other substances.Epithelial Tissue -Type of animal tissue that covers internal and external parts of the body to protect it.Epidermal Tissue -Plant tissue which covers the outside of the plant to protect it and make it ridged.Mesophyll-Plant tissue that can produce glucose through photosynthesis. Xylem and Phloem -Two plant tissue which run parallel carrying mineral ions, glucose and water around the body.Digestive juices -Liquid secreted by glandular tissue containing enzymes which break down food.Organ system -A group of organs working together to complete a task such as digestion.Insoluble molecules -Molecules of food taken into your body which are then broken down through the process of digestion.

Plant and Algal Cells Plant cells are more complex then animal cells, as well as containing all the parts of an animal cell they also contain three other elements. Plants cells have a cell wall to hold the cells shape as well as a permanent vacuole and chloroplast which contain chlorophyll.

Using This Guide:Key terms are in bold and definitions at the side and processes or parts that relate to another resource are in red with the resource close to it in green.

Bacteria Cells Bacteria are very small and can only be seen using a powerful microscope. Bacteria cells contain; cell membrane, cytoplasm, cell wall, slime capsule, plasmids and flagella. You may have noticed that they don't contain a nucleus so instead the have genetic material in the cytoplasm. When bacteria multiply they form a colony. Bacterial colonies can be seen with the naked eye as they are larger.

Yeast Cells Yeast is a single celled organism they contain perts similar to animal and plant cells. Yeast cells contain a nucleus, cell wall, cell membrane and cytoplasm. Yeast is very useful to us and has many uses such as bread making and medicine.

Study Tip ! You should be able to easily identify animal, plant, bacteria and yeast cells in an exam by their parts and features.

Specialised Cells As an organism matures some cells develop into a particular type. Here it is important to note that the structure of a cell links to its function here are some examples; If a cell has many mitochondria it must need a lot of energy, e.g. muscle cells or sperm cells. If a cell has many ribosomes it is making a lot of protein, e.g. gland cells which produce enzymes. Cells with tails can move such as sperm cells. Receptor cells have special structures which enable them to detect stimuli, e.g. the cone cells in your eyes are light sensitive . Neutrons are specialised to carry electrical impulses from receptors to the CNS. Plant cells with many chloroplasts will be photosynthesising, e.g. mesophyll cells in a leaf. Root hair cells increase the surface area of the root so that they can absorb water and mineral ions efficiently.

Study Tip ! Many exam questions will ask you questions about cells you haven't heard of, just identify the parts and then work out the cells function from its structure.

Tissues During the development of multicellular organisms the cells differentiate. Different cells obtain different functions, a tissue is a group of cells with similar structure and function performing a task. Types of animal tissue include; Muscle tissue, which can contract to make an organism move. Glandular tissue, used to produce substances such as enzymes or hormones. Epithelial tissue, which covers some internal and external parts of the body. Types of plant tissues include; Epidermal tissue, which covers the plant. Mesophyll, which can photosynthesise to produce glucose. Xylem and phloem, which transport substances around the plant: Xylem = Water and Phloem = Food

Organs and Organ systems Organs are made of several types of tissue. Animal organs include; eye, salivary glands, larynx, lungs, heart, trachea, oesophagus, mouth, stomach, gall bladder, kidneys, pancreas, rectum, intestines, adrenal gland and reproductive organs. Plant organs include; stem, leaves, roots and reproductive organs. The stomach;Muscular tissue is used to churn the contents.Glandular tissue is used to secrete digestive juices.Epithelial tissue covers the inside and outside of the stomachGroups of organs form organ system to perform an overall function. The digestive system changes insoluble molecules into soluble molecules which can be absorbed into the boys blood stream. A quick overview of the digestive system: The salivary glands produce digestive juices, the stomach and small intestine is where digestion occurs, the liver produces bile, the small intestine is where the absorption of soluble food occurs and the large intestine is where water is absorbed from the undigested food, producing faeces which are expelled through the anus.

Test yourself !When you can answer these five question first time you know the topic! List the structure of a plant cell. Name three parts only a bacteria cell has. What chemical produced by the liver aids digestion? How is a leaf adapted to carry our photosynthesis? Describe in detail what happens to food as it passes through the digestive system. 1 cell membrane, cytoplasm, nucleus, cell wall, vacuole, chloroplasts 2 any 3 from: slime capsule, plasmids, flagella or genetic material3 bile4 the leaf has mesophyll tissue. the mesophyll cells contain chloroplast which can photosynthesise5 the insoluble food is mixed with digestive juices produced by glands. it is digested in the stomach and small intestine. bile is produced in the liver to aid digestion. absorption of the soluble food takes place in the small intestine. water is absorbed by the large intestine.

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