Parts Of A Eukaryotic Cell Flashcards
1
Q
What is the cell surface membrane?
What is this parts function?
A
- it’s the membrane found on the surface of animal cells and is just inside the cell wall of plant cells and prokaryotic cells. It’s made made mainly of lipids (arranged as the phospholipid bilayer) and proteins (these are embedded in the bilayer and receptors are made of these)
- it’s function is to regulate the movement of substances into and out of the cell. It has receptor molecules on it which allows it to respond to chemicals like hormones.
2
Q
What is the cellulose cell wall?
What is this parts function?
A
- a rigid structure that surrounds plant cells. Made mainly of the carbohydrate cellulose (fibres are unbranched and in layers + lots of gaps makes it fully permeable)
- it’s function is to support plant cells
3
Q
What is the nucleus?
What is this parts function?
A
- the nucleus is a large organelle surrounded by a nuclear envelope (double membrane) which contains many pores. The nucleus contains chromatin (made from DNA and proteins named histones) and a structure called the nucleolus. The histones act as “cotton reels” to stop the DNA getting tangled. Unless the cell is about to divide the chromatin is diffuse (uncoiled) so we can’t see distinct chromosomes under the microscope.
- the nucleus controls the cell’s activities (controlling the transcription of DNA). DNA contains instructions to make proteins. The pores allow molecules to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes.
4
Q
What is the ribosome?
What is this parts function?
A
- a very small organelle that’s made in the nucleus and exits via the nuclear pores, that is either floating free in the cytoplasm or is attached to the rough endoplasmic reticulum. It’s made up of proteins and rRNA. Not surrounded by a membrane.
- it’s function is the site where proteins are made
5
Q
What is the rough endoplasmic reticulum?
What is this parts function?
A
- the RER is a system of membranes (made of phospholipid bilayer) enclosing a fluid-filled space (cisterna). The surface is covered with ribosomes.
- it’s function is to fold and process proteins that have been made at the ribosomes
6
Q
What is the smooth endoplasmic reticulum?
What is this parts function?
A
- the SER is a system of membranes (made of phospholipid bilayer) enclosing a fluid-filled space (cisterna). The surface does not however have any ribosomes attached.
- it’s function is to synthesise and process lipids. It’s exact function though may depend of the type of cell; in some endocrine cells the SER makes steroidal hormones from cholesterol.
7
Q
What is the vesicle?
What is this parts function?
A
- is a small fluid-filled sac in the cytoplasm, surrounded by a membrane (made of phospholipid bilayer). (Small temporary vacuole)
- it’s function is to transport substances in and out of the cell (via surface cell membrane) and between organelles. Some are formed by the Golgi apparatus or the endoplasmic reticulum, while others are formed at the cell surface. It forms a small temporary “bubble” which travels along the cytoskeleton tracks within the cell.
8
Q
What is the lysosome?
What is this parts function?
A
- a special sort of vesicle- a round organelle surrounded by a membrane, with no clear internal structure
- it 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. If the digestive enzymes were not compartmentalised in this way, then they would destroy the cell.
9
Q
What is the golgi apparatus?
What is this parts function?
A
- a group of fluid-filled, membrane-bound, flattened sacs (membranes are made of phospholipid bilayer and it has enclosed cisterna) Vesicles are often seen at the edges of the sacs. Lacks bridges of membrane between channels so looks likes “a pile of pitta breads”
- it’s function is to process and package new lipids and proteins. It also makes lysosomes
10
Q
What is the mitochondrion?
What is this parts function?
A
- it’s usually oval shaped. It has a double membrane (made of phospholipid bilayer- inner one is folded to form structures called cristae= this increases the surface area for the final part of aerobic respiration to occur). Inside is the matrix, which contains enzymes involved in respiration and its own independent DNA within it.
- it’s the site of aerobic respiration, where ATP is produced. Mitochondria are found in large numbers in cells that are very active and require lots of energy.
11
Q
What is the chloroplast?
What is this parts function?
A
- a small, flattened structure found 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, flat pieces of thylakoid membrane. (Thylakoid membranes contain chlorophyll which absorbs light energy and is transformed into ATP= used to fix CO2 into glucose in the stroma. This is only possible because of the thylakoid membranes enclose compartments and keep these areas separate from the stroma). Also contains its own DNA, ribosomes and starch for glucose storage
- the site where photosynthesis takes place. Light dependent photosynthesis happens in the grana, and light independent photosynthesis happens in the stroma (a thick fluid found in chloroplast)
12
Q
What is the centriole?
What is this parts function?
A
- small, hollow cylinders, made of microtubules (tiny protein cylinders). Found in animal cells, but only some plant cells. It’s a part of the cytoskeleton and they’re found in pairs and are responsible for making the spindle.
- involved with the separation of chromosomes during cell division
13
Q
What is the cilia?
What is this parts function?
A
- small hair-like structures found on the surface membranes of some animal cells. They are part of the cytoskeleton. In cross-section, they have an outer membrane and a ring of nine pairs of protein microtubules inside, with a single pair of microtubules in the middle (9+2 cross section structure)
- the microtubules allow cilia to move. This movement is used by the cell to move substances along the cell surface.
14
Q
What is the flagellum (undulipodium)?
What is this parts function?
A
- flagella on eukaryotic cells are like cilia but longer. They stick out from the cell and are surrounded by the cell surface membrane. Inside they’re like cilia too- two microtubules in the centre and nine pairs around the edge. (9 + 2 microtubule cross-section). Many prokaryotic cells have flagella but they don’t have the 9 + 2 cross section
- the microtubules contract to make the flagellum move. Flagella are used like outboard motors to propel cells forward.
