A-Level Biology CELL STRUCTURE

What is the role of vesicles during protein production?

Proteins are transported from the RER to the Golgi apparatus in vesicles After the Golgi apparatus, protein s enter more vesicles to be transported around the cell.

What is the plasma membrane?

The membrane found on the surface of animal cells and just inside the cell wall of plant cells and prokaryotic cells. Regulates the movement of substances into and out of the cell. It also has receptor molecules on it, which allow it to respond to chemicals like hormones.

What is the role of the Golgi apparatus during protein production?

The proteins my undergo further processing (e.g sugar chains are trimmed or added)

What is the eyepiece graticule and the stage micrometer?

- An eyepiece graticule is fitted onto the eyepiece. It's like a transparent ruler with numbers, but no units. So when you look through the eyepiece you'll see a scale. - The stage micrometer is placed on the stage- it is a microscope slide with an accurate scale (it has units) and its used to work out the value of the divisions. on the eyepiece graticule at a particular magnification.

What are the steps to using a light microscope?

1) start by clipping the specimen onto the stage. 2) select the lowest- powered objective lens. 3) se the course adjustment knob to bring the stage up to just below the objective lens. 4) look down the eyepiece. Use the course adjustment knob t one the stage downwards, away from the objective lens, until the image is roughly in focus. 5) adjust the focus with the fine adjustment knob, until you get a clear image of what's on the slide. 6) if you need to see the slide with greater magnification, swap to a higher-powered objective lens and refocus.

What are the four main functions of the cytoskeleton?

1)The microtubules and microfilaments support the cells organelles, keeping them in position. 2)They also help strengthen the cell and maintain its shape. 3)They are responsible for the transport of organelles and materials within the cell. 4)The proteins of the cytoskeleton can also amuse the cell to move.

What is the Golgi apparatus?

A group of fluid-filled, membrane-bound, flattened sacs. Vesicles are often seen at the edge of these sacs. It processes and packages new lipids and proteins. It also makes lysosomes.

What is the nucleus?

A large organelle surrounded by a nuclear envelope which contains many pores. The nucleus contains chromatin which is made from DNA and proteins and often a structure called the nucleolus. The nucleus controls the cells activities (as it is responsible for DNA transcription) DNA contains instructions make proteins. The pores allow substances (e.g.RNA) to mov between the nucleus and the cytoplasm. The nucleolus makes ribosomes.

What is the cytoskeleton?

A network of protein filaments that help maintain the structure of the cell.

What is the cell wall?

A rigid structure that surrounds plant cells. It is mainly made of the carbohydrate cellulose. Supports plant cells.

What is a lysosome?

A round organelle surrounded by a membrane with no clear internal structure. Contains digestive enzymes. These are kept separate from the cytoplasm by the surrounding membrane, and can be used to digest invading cells or to break down worn out components of the cell.

What is a vesicle?

A small fluid-filled sac in the cytoplasm surrounded by a membrane. Transports substances in and out of the cell (via the plasma membrane) and between organelles. Some are formed bu the Golgi apparatus or the endoplasmic reticulum, while others are formed at the cell surface.

What is a chloroplast?

A small, flattened structure fund in plant cells. It's surrounded by a double membrane and also has membranes inside called thylakoid membranes. These membranes are stacked up in some parts of the chloroplast to form grana. Grana are linked together by lamellae- thin, fat pieces of thylakoid membrane. The site where photosynthesis takes place. Some parts of photosynthesis happen in the grana, and other parts happen in the stroma (a thick fluid found in the chloroplasts)

What is the rough endoplasmic reticulum (RER)?

A system of membranes enclosing a fluid-filled space. The surface is covered with ribosomes. Folds and processes proteins that have been made at the ribosomes.

What is a ribosome?

A very small organelle that either floats free in the cytoplasm or is attached to the rough endoplasmic reticulum. It is made up of proteins and RNA. It is not surrounded by a membrane. The site where proteins are made.

What are flagella?

Flagella on eukaryotic cells are like cilia, but longer. They stick out from the cell surface and are surrounded my The plasma membrane. Inside they're like cilia too- two microtubules in the centre and nine pairs down the edge. The microtubules contract to make the flagellum move. Flagella are used like outboard motors to propel cells forward (e.g when a sperm cell swims)

What are mitochondria?

It's usually oval-shaped. It has one double membrane- the inner one is folded to form structures called Cristae. Inside is the matrix, which contains enzymes involved in respiration. The site of aerobic respiration, where ATP is produced. Mitochondria are found in large number in cells that are very active and require a lot of energy.

What is the magnification equation?

Magnification= image size/size of object

What is the role of the rough endoplasmic reticulum during protein production?

New proteins produced at the RER are folded and processed there.

What are the roles of ribosomes during protein production?

Ribosomes- proteins are made at the ribosomes- the ribosomes on the rough endoplasmic reticulum make proteins tat are exerted from the cell or attached to the cell membrane, whereas the free ribosomes in the cytoplasm make ribosomes that stay in the cytoplasm.

What is a scanning electron microscope?

Scans a beam of electrons across the specimen. This knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image. Lower resolutions than TEM. Produce 3D images.

What is the smooth endoplasmic reticulum (SER)?

Similar to the RER, but with no ribosomes. Synthesises and processes lipids.

What are cilia?

Small, hair like structures found on the surface membrane of some animal cells. In cross-section, they have an outer membrane and a ring of nine pairs of protein microtubules inside with a singe pair of microtubules in the middle. The microtubules allow the cilia to move. This movement is used by the cell to move substances along the cell surface.

What is a centriole?

Small, hollow cylinders, made of microtubules (tiny protein cylinders). Found in animal cells but only some plant cells. Involved with the separation of chromosomes durning cell division.

TOPIC: CELLS AND ORGANELLES

TOPIC: CELLS AND ORGANELLES

TOPIC: HOW MICROSCOPES WORK

TOPIC: HOW MICROSCOPES WORK

TOPIC: ORGANELLES WORKING TOGETHER

TOPIC: ORGANELLES WORKING TOGETHER

What is a light microscope?

They use light. Have a lower resolution than electron microscopes. They have a maximum resolution of bout 0.2 micrometers. Usually used to look at whole cells or tissues. The maximum magnification is about x500.

What is a laser scanning confocal microscope?

They're a special type of light microscope that uses laser beams to scan a specimen that's usually tagged with a fluorescent dye.

What is a transmission electron microscope?

Use electromagnets to focus a beam of electrons, which is then transmitted through the specimen to produce 2D images. Provide high resolution images. Can be used look at internal structures of organelles.

What is resolution?

ability of a lens to distinguish between objects which are close together & expressed as a distance.

What is magnification?

the ratio of an object's image size to its real size.