2.1.1 - Cell Structure (set A - Euckaryotic Cell Organelle) Flashcards
Define a prokaryotic organism?
Prokaryotes are organisms whose cells lack a nucleus and other organelles, prokaryotes are divided into two distinct groups: the bacteria and the archaea
Define eukaryotic organisms?
A eukaryote is any organism consisting of one or more cells that contain DNA in a membrane-bound nucleus, separate from the cytoplasm - examples are plant, animal, fungi and protists
Explain the structure of the nucleus, make reference to all key parts?
Large organelle containing a dense structure called the Nucleolus and chromatin (DNA) and is surrounded by the semipermeable Nuclear Envelope, a structure composed of an inner and outer nuclear membrane which contain a number of nuclear pores
Explain the main function of the nucleus?
- Controls the cells activities by controlling the transcription of DNA (instructions needed for making proteins), gene expression mitosis and semiconservative replication
- contains DNA coiled around chromatin into chromosomes
Explain what the plant cell wall is?
Rigid structure that surrounds plant cells, made of cellulose microfibrils for mechanical support
- plasmodesmata form part of apoplast pathway to allow molecules to pass between cells
Explain the function of the cell wall?
The cell wall gives the cell structure, which prevents it from changing shape. It also offers a small level of added protection.
Explain what the plasma cell surface membrane is?
The membrane found on the surface of animal cells and the inside the cell wall of plant cells - the cell membrane consists of a lipid bilayer that is semipermeable - composed of proteins and lipids
Explain the function of plasma cell surface membrane?
Regulates the movement of substances into and out of the cell - has receptor molecules on it which respond to chemicals like hormones
What is the lysosome?
A round organelle suspended by a membrane, with no clear internal structure - acts as rubbish bin as they break down excess or worn-out cell parts with digestive enzymes
What is the function of the lysosome?
Contains hydrolytic enzymes 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 are ribosomes?
very small organelle that either floats free in the cytoplasm or are attached to the rough endoplasmic reticulum - made up of proteins and RNA (not surrounded by a membrane)
What is the function of ribosomes?
The site where proteins are made
What is the rough endoplasmic reticulum (RER)?
The RER is a membrane bound organelle located near the nucleus It is made up of thin, fluid filled membranes that are stacked together (cisternae) and is covered with ribosomes
What is the function of rough endoplasmic reticulum (RER)?
Folds and processes proteins that have been made at ribosomes - the site of protein synthesis
What is the smooth endoplasmic reticulum (SER)?
Has the same structure as the rough endoplasmic reticulum but does not have ribosomes
What is the function of the smooth endoplasmic reticulum (SER)?
Responsible for carbohydrate and lipid synthesis, and storage
What is the vesicle?
A small fluid-filled sac in the cytoplasm, surrounded by a membrane
What is the function of the vesicle?
Transports substance in and out of the cell (via the plasma membrane) and between organelles
Where are vesicles formed?
some are formed by the Golgi apparatus or the endoplasmic reticulum while others are formed by the plasma membrane
What are mitochondria?
Usually oval-shaped and have a double membrane - the inner one if folded to form structure called cristae inside is the matrix which contains enzymes involved in respiration
what is the function of mitochondria?
The site of aerobic respiration here ATP is produced - they’re found in large numbers in cells that are very active and require lots of energy such as muscle,brain or liver cells
What is the Golgi apparatus?
A group of fluid-filled membrane-bound, flattened sacs which have vesicles at the edges
What is the function of the Golgi apparatus?
- Processes and modifies new lipids and proteins and packages them into vesicles
- makes lysosomes
- allows internal transport
What are chloroplast?
Small, flattened structures found in plant cells they are surrounded by a double membrane - have thylakoid membranes inside which are stacked up in some parts of the chloroplast to form grana which are linked together by lamellae
What is the function of chloroplasts?
The site where photosynthesis takes place - some parts of photosynthesis happens in the grana, other parts happen in the stroma
What are stoma?
located in the chloroplast and responsible for some photosynthesis - is a thick fluid
What are centriole?
Small, hollow cylinders made of microtubules found in animal cells, but only some plant cells located in the cytoplasm
What are 3 functions of centriole?
- They engage in the arrangement of mitotic spindles during cell division
- organises the microtubules in the cytoplasm
- regulate the position of the nucleus and other organelles in the cell.
What are cilia?
Small ‘hair like’ structures found on the surface membranes of some animal cells - have an outer membrane and a ring of nine pairs of protein microtubules inside with two microtubules in the middle
What is the function of cilia?
Microtubules allow the cilia to move - the movement is used by the cell to move substances along the cell surface - located in the bronchus and moves microbes and debris up and away from the lungs
What are flagellum?
Flagella on eukaryotic cells are like cilia but longer, stick out of the cells surface and are surrounded by plasma membrane - have two microtubules in the centre surrounded by nine pairs around the edge
What is the function of flagellum?
The microtubules contract to make the flagellum move - for example the tail on sperm cells allow it to swim to the egg
What are cytoskeletons?
The cytoskeleton is a network of proteins that forms the internal framework for the cell
What are the three components of the cytoskeleton?
- microfilaments
- microtubules
- intermediate fibres
What are microfilaments?
Fibres made from the protein ‘actin’ they are responsible for movement of the cell and cytoplasm during cytokinesis
What are microtubules?
Formed by protein ‘tubulin’, they polymerise to form tubes that determine the shape of the cell
What are intermediate fibres?
Gives strength to cells and helps maintain integrity
What is the structure of the cellulose cell wall?
Cellulose is a long chain of beta-glucose. Beta-glucose molecules are linked by glycosidic bonds to form linear cellulose chains that are unbranched. Microfibrils are strong fibres that are made of many cellulose chains that are held together by hydrogen bonds.
What is the function of the cellulose cell wall?
- gives the plant mechanical strength
- gives the plant support and its shape
- contents of the plant can ‘push’ against the cell wall (turgid cell), giving the plant support
What is the structure of the large permanent vacuole?
Single membrane bound (membrane called a ‘tonoplast’) contains cell sap - has selectively permeable barrier
- membrane allows control of certain molecules
What is the function of large permanent vacuole?
- stores cell sap
- supports herbaceous plants by making cells turgid
- sugar and amino acids act as temporary food source
What are 5 features of prokaryotes?
- extremely small cells, smaller then eukaryotes
- DNA is circular and free in the cytoplasm
- no nucleus
- no membrane-bound organelles or mitochondria
- small ribosomes
What are 4 features of eukaryotes?
- larger cells
- DNA is linear and enclosed inside the nucleus
- mitochondria and other membrane-bound organelle present
- large ribosomes
how are mitochondrion adapted for increased reactions?
Have crista which are finger like folds in the inner membrane of a mitochondrion, its purpose is to increase the surface area to allow for more reactions to take place
What are cisternae and which organelle of a cell are they located?
Stacks of membrane bound (fluid filled) sacs which form sheets found in the endoplasmic reticulum and Golgi apparatus
What are membranes, what is their function?
Membranes are selectively permeable and control the movement of substances into and out of the cell and organelles
