2 1 cell structure and size of specimens

The cell membrane separates cells from their surrounding environment.

The largest organelle within animal cells is the nucleus.

Plant cells have the following structures that are not present in animal cells:

True. Ribosomes are present in plant and animal cells. They are the site of protein synthesis.

Organelles present within animal cells are: Note that structures such as the cell membrane and cytoplasm are not organelles, so are not acceptable answers here.

Ribosomes are the smallest organelle; they are present in both plant and animal cells.

False. The gel-like fluid present in plant and animal cells is the cytoplasm. Chloroplasts are organelles found in plant cells.

False. The role of the nucleus is to store genetic information in the form of DNA. Energy is released by the mitochondria.

The cell membrane controls the passage of substances in and out of the cell.

True. Muscle cells are likely to contain more mitochondria than skin cells. This is because they are more metabolically active, so will need more energy from respiration, the process that occurs inside mitochondria.

True. Mitochondria are responsible for releasing energy through the process of aerobic respiration.

True. Ribosomes are responsible for protein synthesis, the process by which proteins are made.

Cytoplasm is the site of chemical reactions inside cells.

Chloroplasts absorb light energy during the process of photosynthesis.

False. Plant cell walls provide strength and additional structural support for plant cells. It is the membrane that regulates the passage of substances.

The permanent vacuole stores cell sap and provides structural support for plant cells.

False. Animal cells contain mitochondria and ribosomes but do not have cell walls. Cell walls are a feature of *plant *cells.

Three differences between plant and animal cells are:

The permanent vacuole in plant cells is a membrane-bound structure that stores cell sap and helps maintain cell shape.

False. Mitochondria are the site of (aerobic) respiration. Chloroplasts are the site of photosynthesis.

False. The cell membrane does not have a rigid structure so does *not *provide any structural support. Its role is to control what enters and leaves the cell.

The nucleus contains the genetic material, DNA, in both plant and animal cells.

Structural features present in both plant and animal cells are:

False. Plant cells do contain mitochondria. Mitochondria are the site of aerobic respiration, a process that is essential for both plant and animal cells.

New cells are produced by division of existing cells, e.g. by mitosis or meiosis.

Specialised cells are cells that have developed specific characteristics that allow them to perform particular functions.

Red blood cells have a large surface area to increase diffusion of oxygen and contain haemoglobin which binds to and transports oxygen. They have no nucleus to allow more space for haemoglobin.

Examples of specialised plant cells include:

True. Root hair cells have an increased surface area to allow increased absorption of water and mineral ions from the soil.

Examples of specialised animal cells include:

False. Plants have organ systems, e.g. the shoot system contains the stem, leaves and flowers.

Cells are the basic structural units of all living organisms.

Organelles are structures within cells that carry out particular functions, e.g. the nucleus.

The levels of organisation should be listed in the following order:

Muscle is a tissue. It is a group of muscle cells working together to bring about movement.

The organ system responsible for the transport of substances in humans is the circulatory system.

Tissues are groups of similar cells that work together to carry out a specific function.

True. Leaves are plant organs. They contain several tissues, e.g. palisade mesophyll, spongy mesophyll and vascular tissue, that work together to carry out photosynthesis.

The formula for calculating magnification is: magnification = image size ÷ actual size

False. Magnification does not have any units and is just written as, e.g. x10 or 5000x.

The equation for calculating the actual size of a specimen is: actual size = image size ÷ magnification

There are 1000 µm in a mm.

False. 1.2 mm is not the same as 12 000 µm. µm are converted into mm by multiplying by 1000, so: 1.2 x 1000 = 1200 µm