cells

Plant and animal cells ( ____________________ cells ) have a cell ____________________ , cytoplasm and genetic material enclosed in a ____________________ . Bacterial cells ( ____________________ cells ) are much smaller in comparison . They have cytoplasm and a cell membrane surrounded by a cell ____________________ . The genetic material is not enclosed in a ____________________ . It is a single DNA loop and there may be one or more small rings of DNA called ____________________ .
Most animal cells have the following parts : ? a ____________________ ? cytoplasm ? a cell membrane ? ____________________ ? ribosomes . In addition to the parts found in animal cells , plant cells often have : ? ____________________ ? a permanent ____________________ filled with cell sap . Plant and algal cells also have a cell wall made of cellulose , which ____________________ the cell .
Cells may be ____________________ to carry out a particular function : ? sperm cells , nerve cells and muscle cells in animals ? root hair cells , ____________________ and phloem cells in plants
As an organism develops , cells ____________________ to form different types of cells . ? Most types of animal cell differentiate at an ____________________ stage . ? Many types of ____________________ cells retain the ability to differentiate throughout ____________________ . In mature animals , cell division is mainly restricted to ____________________ and replacement . As a cell differentiates it acquires different sub - cellular structures to enable it to carry out a certain ____________________ . It has become a specialised cell .
An electron microscope has much higher ____________________ and resolving power than a ____________________ microscope . This means that it can be used to study cells in much finer ____________________ . This has enabled biologists to see and understand many more sub - cellular structures .
magni¬cation = size of ____________________ / size of real object
Bacteria multiply by simple cell division ( ____________________ fission ) as often as once every ____________________ minutes if they have enough nutrients and a suitable temperature .
to prepare an uncontaminated culture using ____________________ technique . They should be able to explain why : ? ____________________ dishes and culture media must be ____________________ before use ? ____________________ loops used to transfer microorganisms to the media must be sterilised by passing them through a ____________________ ? the lid of the Petri dish should be ____________________ with adhesive tape and stored ____________________ down ? in school laboratories , cultures should generally be incubated at ____________________ .
The nucleus of a cell contains chromosomes made of ____________________ molecules . Each chromosome carries a large number of ____________________ . In body cells the chromosomes are normally found in ____________________ .
During the cell cycle the genetic material is doubled and then divided into two ____________________ cells . Before a cell can divide it needs to grow and increase the number of sub - cellular structures such as ____________________ and mitochondria . The DNA replicates to form ____________________ copies of each chromosome . In ____________________ one set of chromosomes is pulled to each end of the cell and the nucleus divides . Finally the ____________________ and cell membranes divide to form two identical cells .
Cell division by mitosis is important in the ____________________ and development of multicellular organisms .
A ____________________ cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type , and from which certain other cells can arise from differentiation . Stem cells from human ____________________ can be cloned and made to differentiate into most different types of ____________________ cells . Stem cells from adult bone ____________________ can form many types of cells including ____________________ cells . ____________________ tissue in plants can differentiate into any type of plant cell , throughout the life of the plant . Treatment with stem cells may be able to help conditions such as ____________________ and paralysis .
In therapeutic cloning an embryo is produced with the ____________________ genes as the patient . Stem cells from the embryo are not ____________________ by the patient ? s body so they may be used for ____________________ treatment . The use of stem cells has potential risks such as transfer of viral infection , and some people have ethical or ____________________ objections . Stem cells from meristems in plants can be used to produce ____________________ of plants quickly and economically . ? Rare species can be cloned to protect from ____________________ . ? Crop plants with special features such as ____________________ resistance can be cloned to produce large numbers of identical plants for farmers .

Substances may move into and out of cells across the cell membranes via ____________________ . Diffusion is the spreading out of the particles of any substance in solution , or particles of a gas , resulting in a net movement from an area of ____________________ concentration to an area of lower concentration . Some of the substances transported in and out of cells by diffusion are ____________________ and carbon dioxide in gas exchange , and of the waste product ____________________ from cells into the blood plasma for excretion in the kidney . Factors which affect the rate of diffusion are : ? the difference in concentrations ( concentration ____________________ ) ? the temperature ? the surface area of the membrane . A single - celled organism has a relatively large ____________________ area to ____________________ ratio . This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism .
In ____________________ organisms , surfaces and organ systems are specialised for exchanging materials . This is to allow sufficient molecules to be transported into and out of cells for the organism ? s needs . The effectiveness of an exchange surface is increased by : ? having a large surface area ? a membrane that is ____________________ , to provide a short ____________________ path ? ( in animals ) having an efficient ____________________ supply ? ( in animals , for gaseous exchange ) being ventilated .
Water may move across cell membranes via ____________________ . Osmosis is the diffusion of ____________________ from a dilute solution to a concentrated solution through a ____________________ permeable membrane .
Active transport moves substances from a more dilute solution to a more concentrated solution ( ____________________ a concentration gradient ) . This requires ____________________ from respiration . Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the ____________________ . Plants require ions for healthy growth . It also allows sugar molecules to be absorbed from lower concentrations in the gut into the ____________________ which has a higher sugar concentration . Sugar molecules are used for cell respiration .