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Year 7 Biology - Cells and systems

Cell membrane	Controls what substances can get into and out of the cell.	Plant and animal cells
Cytoplasm	Jelly-like substance, where chemical reactions happen. In plant cells there's a thin lining, whereas in animal cells most of the cell is cytoplasm.	Plant and animal cells
Nucleus	Controls what happens inside the cell. Carries genetic information. In exams don't call the nucleus the 'brain' of the cell. That is not a good description and will not get you marks.	Plant and animal cells
Mitochondria	Where respiration happens – energy is produced	Plant and animal cells
Chloroplast	Where photosynthesis happens – chloroplasts contain a green substance called chlorophyll.	Plant cells only
Vacuole	Contains a liquid called cell sap, which keeps the cell firm.	Plant cells only
Cell wall	Made of a tough substance called cellulose, which supports the cell.	Plant cells only

Cell organelle functions

Cell membrane

Term	Definition
Antagonistic	Active opposition
Cardiac	Relating to the heart
Diffusion	The passive movement of particles from an area of high concentration to an area of low concentration
Joint	Structure at which two parts of the skeleton are fitted together
Ligament	A short band of tough, flexible fibrous connective tissue which connects bone to bone
Magnification	The enlargement of an object by an optical instrument
Microscope	An optical instrument used for viewing very small objects
Organ	Tissues grouped together
Organelle	The small parts that make up a cell
Resolution	The shortest distance between two points on a specimen that can still be seen as two different points
Respiration	The process of breaking down glucose to release energy
Tendon	A flexible but inelastic cord of strong fibrous collagen tissue connecting muscle to bone
Tissue	Group of similar cells working together

Magnification

Total magnification = magnification of eye piece lens x magnification of objective lens

Surface area = area of each face x number of faces

Volume = height x width x length

The smaller the object, the greater the surface area to volume ratio

The bigger the object, the smaller the surface area to volume ratio

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4 main roles of the skeleton are: movement, support, protection and production of blood cells.
Muscles contract and relax antagonistically
Tendons connect muscle to bone
Ligaments connect bone to bone
Muscles can only contract and relax (NOT push). To move they must work antagonistically in pairs
Diffusion - The movement of particles from an area of high concentration to an area of lower concentration
Unicellular - organisms only made up of one cell e.g. bacteria
Tissue – group of similar cells

Method for creating cheek cell microscope slide

Gently scrape the inside of the mouth using a clean, sterile cotton swab.
Smear the cotton swab on to the centre of a clean microscope slide seconds to get the cells on to the slide.
Add a drop of methylene blue solution on to the smear and gently place a coverslip on top (to cover the stain and the cells).
Any excess solution can be removed by touching one side of the slide with a paper towel or blotting paper.
Place the slide on the microscope for observation using 4 x or 10 x objective to find the cells
Used cotton swabs and cotton towel should be safely disposed of and not left lying on the working table.

Arm muscles

Method for creating onion cell microscope slide

1. Collect a piece of onion.

2. Remove one of the onion layers.

3. Using forceps, carefully peel off the inner skin of the onion layer.

4. Place the onion skin onto a clean glass slide. Use your forceps to keep the onion skin flat on the glass slide.

5. Using a pipette, add one or two drops of dilute iodine solution on top of the onion skin.

6. Place a coverslip on top of the skin.

7. Place the slide on the microscope for observation using 4 x or 10 x objective to find the cells

8. Once the cells have been found, they can then be viewed at higher magnification

Human Skeleton

Year 7 Biology - Cells and systems