Eukaryotic Cell Structures Flashcards
1
Q
what is the ultrastructure of a cell?
A
- each cell can be regarded as a metabolic compartment where the chemical processes of that cell occur
- cells are often adapted to preform a particular function
- the cells internal structure suites its job which is the ultra structure
2
Q
what is an eukaryotic cell?
A
-it has a distinct nucleus and possesses membrane found organelle which an be seen using electron microscopes
3
Q
what is the nucleus?
A
- the nucleus is the most prominent feature of a eukaryotic cell
- the nucleus contains the organisms hereditary material and controls the cells activities
- it’s usually spherical and between 10 and 20um in diameter
4
Q
what is the nuclear envelope?
A
- it’s a double membrane that surrounds the nucleus
- the outer membrane is continuous with the endoplasmic reticulum of the cell and often has ribosomes on its surface controlling the entry and exit of materials in and out of the nucleus and contains the reactions taking place within it
5
Q
what are nuclear pores?
A
- allows the passage of large molecules such as messenger RNA out of the nucleus
- there are typically around 1000 pores in each nucleus each 40-100nm in diameter
6
Q
what is the nucleoplasm?
A
-the granular, jelly like material that makes up the bulk of the nucleus
7
Q
what are chromosomes?
A
-consist of protein bound linear DNA
8
Q
what are the features of the nucleus?
A
- nuclear envelope
- nuclear pores
- nucleoplasm
- chromosomes
- nucleolus
9
Q
what are the functions of the nucleus?
A
- it acts as the control centre of the cell through the production of mRNA and tRNA and hence protein synthesis
- it retains the genetic material of the cell in the form of DNA and chromosomes
- it manufactures RNA and ribosomes
10
Q
what are mitochondrion?
A
- mitochondria are usually rod-shaped and 1-10um in length
- made up from double membranes, cristae and the matrix
11
Q
what is the double membrane?
A
-the organelle controls the entry and exit of material, the inner of the two membranes is folded to form extensions known as cristae
12
Q
what is the matrix?
A
- makes up the remainder of the mitochondrion
- it contains protein, lipids, ribosomes and DNA that allows the mitochondria to control the production of their own proteins
- many enzymes involved in respiration are found in the matrix
13
Q
what is the crista?
A
- extensions of the inner membrane which in some species extend across the whole width of the mitochondrion
- they provide a large surface area for the attachment of enzymes and other proteins involved in respiration
14
Q
what do mitochondria do?
A
- they are the sites of aerobic stages of respiration
- they are responsible for the production of the energy carrier molecule ATP from respiratory substances like glucose this means that the number and size of mitochondria, cristae are high in cells that have a high level of metabolic activity so require lots of ATP
15
Q
what are chloroplasts?
A
- chloroplasts are organelles that carry out photosynthesis
- they vary in shape and size but are typically disc shaped
- 2-10um long in diameter
- made up of chloroplast envelope, grana and the stroma
16
Q
what is the chloroplast envelope?
A
-a double plasma membrane that surrounds the organelle, it is highly selective in what it allows to enter and leave the chloroplast
17
Q
what are grana?
A
- stacks of up to 100 disc like structure called thylakoids which contain the pigment chlorophyll
- thylakoids have tubular extensions that join up with thylakoids in adjacent grana
- the grana are where the first stage of photosynthesis takes place
18
Q
what is the stroma?
A
-a fluid filled matrix where the second stage of photosynthesis takes place
19
Q
how are chloroplasts adapted to their function?
A
- the granal membranes provide a large surface area for the attachment of chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis which are attached to the membrane in order
- the fluid of the stroma possesses all the enzymes needed to make sugars in the second stage of photosynthesis
- chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis
20
Q
what are endoplasmic reticulum?
A
- it’s an elaborate three-dimensional system of sheet-like membranes which spread through the cytoplasm of the cells
- it’s continuous with the outer nuclear membrane
- the membranes enclose a network of tubules and flattened sacs called cisternae
21
Q
what is the function of rough endoplasmic reticulum?
A
- provides a large surface are for the synthesis of proteins and glycoproteins
- provides a pathway for the transport of materials especially proteins thoroughly the cell
22
Q
what is the function of smooth endoplasmic reticulum?
A
- synthesise, store and transport lipids
- synthesis, store and transport carbohydrates
23
Q
Where is the Golgi apparatus found?
A
-occurs in almost all eukaryotic cells and is similar to the SER in structure except that it is more compact
24
Q
what are the functions of the Golgi apparatus?
A
- they add carbohydrate to proteins to form glycoproteins
- produce secretory enzymes such as those secreted by the pancreas
- they secrets carbohydrates such as those used in making cell walls in plants
- they transport, modify and store lipids
- they form lysosomes
25
where are Golgi apparatus most well developed?
-secretory cells like the epithelial cells that like the intestine
26
where are endoplasmic reticulum found?
-in cells that manufacture and store large quantities of carbohydrates, proteins and lipids like liver and secretory cells like the epithelial cells that line the intestines
27
what are lysosomes?
- they are formed when the vesicles produced by the Golgi apparatus contain enzymes such as protease and lipases which contain lysozymes, enzymes that hydrolyse the cell walls of certain bacteria
- each one can contain 50 enzymes from the rest of the cell before releasing them either to the outside or into a phagocyte vesicle within the cell
28
what are the functions of lysosomes?
- they hydrolyse material ingested by phagocytic cells like white blood cells
- release enzymes to the outside of the cell in order to destroy material around the cell
- they digest worn out organelles so that the useful chemicals they are made of can be reused
- they completely break down cells after they have died
29
where are lysosomes found?
-they are especially abundant in secretory cells like epithelial cells and in phagocytic cells
30
what are ribosomes?
- they are small cytoplasmic granules found in all cells which may occur in the cytoplasm or be associated with the RER
- they are 80s and 70s ribosomes
- they are the site of protein synthesis
31
what are 80s ribosomes?
-they are 25nm in diameter and are found in eukaryotic cells
32
what are 70s ribosomes?
-they are smaller than 80s ribosomes and are found in prokaryotic cells, mitochondria and chloroplasts
33
what is the structure of ribosomes?
- they have two subunits one large and one small each of which contains ribosomal RNA and protein
- despite their small size they occur in such vast numbers that they can account for up to 25% of the dry mass of a cell
34
what is a cell wall?
- part of all plant cells
- consists of microfibrils of the polysaccharide cellulose embedded in a matrix
- cellulose microfibrils have considerable strength and so contribute to the overall strength of the cell wall
35
what is the features of the cell wall?
- they consist of a number of polysaccharides like cellulose
- there is a thin layer called the middle lamellae which marks the boundary between adjacent cell walls and cements adjacent cells together
36
what are the functions do the cellulose cell wall?
- it provides a mechanical strength in order to prevent the cell from bursting under the pressure created by the osmotic entry of water
- they give mechanical strength the to the plant as a whole
- they allow water to pass along it and so contribute to the movement of water through the plant
37
What are the cell walls of fungi made from?
-a mixture of nitrogen-containing polysaccharide called chitin, a polysaccharide called glycan and glycoproteins
38
what are cell walls of algae made from?
-they are either made from cellulose or glycoproteins or a mixture of both
39
what are vacuoles?
- a fluid filled sac bounded by a single membrane may be termed a vacuole
- there is usually one large central vacuole in mature plant cells
- the singe membrane around a vacuole is allied a tonoplast
40
what are the functions of vacuoles?
- they support herbaceous plants and herbaceous parts of woody plants by making cells turgid
- the sugars and amino acids may act as a temporary food store
- the pigments may colour petals to attract pollinating insects
41
how do you relate cell ultrastructure to function?
- it's possible to deduce the role of a cell by using ultracentrifugation to look at the number and size of organelles it contains
- for example mitochondria produces ATP so cells that have lots of mitochondria must require lots of ATP and therefore have high metabolic rates
42
what do plant vacuoles contain?
-a solution of mineral salts , sugars, amino acids, wastes and sometimes pigments like anyhocyanins
43
What is the nucleolus?
-a small spherical region within the nucleoplasm in manufactures N
44
what is the structure of rough endoplasmic reticulum?
-has ribosomes present on the outer surfaces of the membranes
44
what is the structure of smooth endoplasmic reticulum?
-it lacks ribosomes on its surface and is often more tubular in appearance
44
What is the structure of the Golgi apparatus?
-it consists of s stack of membranes that make up flattened sacs or cisternae with small round hollow structures called vesicles
44
What does the Golgi apparatus do?
- it produces proteins an lipids that are passed through the Golgi apparatus in strict sequence
- the Golgi modifies these proteins often adding non-protein components such as carbohydrate and sometimes labelling them so they can be accurately sorted and sent to their correct destinations
- the modified proteins and lipids are transported in Golgi vesicles which are regularly pinched off from the ends of the Golgi cisternae
- the vesicles may move to the cell surface where they fuse with the membranes and release their contents to the outside
