Cell structure of Eukaryotic cells

Question 1

What is the structure of the nucleus?

3 points

Answer 1

1) Surrounded by a double membrane called a nuclear envelope
2) There are pores in the envelope called nuclear envelope
3) Chromatin is the genetic material that wraps itself around histone proteins.When the cell is not dividing chromatin is spread out or extended. When the cell is about to divide, chromatin condenses and coils tightly into chromosomes. These make up nearly all the organisms genome.

Question 2

What is the function of the nucleus?

3 points

Answer 2

1) The nuclear envelope separates the contents of the nucleus from the rest of the cell
2) In some regions the inner and outer nucleus membrane fuse together. At these points some dissolved substances and ribosomes can pass through.
3) The nuclear pores enable larger substances such as mRNA to leave the nucleus. Substances such as some steroid hormones, may enter the nucleus from the cytoplasm via these pores.

Question 3

What is the structure of the nucleolus?

1 point

Answer 3

1) does not have a membrane around it and contains mRNA

Question 4

What is the function of the nucleolus?

1 point

Answer 4

1) It is where ribosomes are made

Question 5

What is the structure of the Rough endoplasmic reticulum?

2 points

Answer 5

1) It is a system of membranes, containing fluid filled cavities (cisternae) that are continuous with the nuclear membrane
2) It is coated with ribosomes

Question 6

What is the function of the Rough endoplasmic reticulum?

2 points

Answer 6

1) It is an intercelluar transport system= the cisternae form channels for transporting one substance to an area of a cell to another
2) It provides a large surface area for ribosomes, which assemble amino acids into proteins.These proteins then actively pass through the membrane into the cisternae and are transported to the Golgi apparatus for modification and packaging

Question 7

What is the structure of the Smooth endoplasmic reticulum?

2 points

Answer 7

1) It is a system of membranes, containing cisternae that are continuous with the nuclear membrane
2) It has no ribosomes on its surface

Question 8

What is the function of the Smooth endoplasmic reticulum?

2 points

Answer 8

1) It contains enzymes that catalyse reactions involved with liquid metabolism such as:
synthesis of cholesterol
synthesis of lipids/phosolipids needed by the cell
synthesis of steroid hormones
2) Involved with absorption, synthesis and transport of lipids (from the gut)

Question 9

What is the structure of the Golgi Apparatus?

1 point

Answer 9

1) consists of a stack of membrane bound flattened sacs. Secretory vesicles bring materials too and from the Golgi Apparatus

Question 10

What is the function of the Golgi Apparatus?

2 points

Answer 10

1) Modifies proteins by:
adding sugar molecules to make glycoproteins
adding lipid molecules to make lipoproteins
being folded into their 3D shape
2) The proteins are packaged into vesicles that are pinched off and then:
stored in the cell/moved to the plasma membrane, either to be incorporated into the plasma membrane, or exported to outside the cell

Question 11

What is the structure of the Mitochondria?

3 points

Answer 11

1) May be spherical/rod shaped/branched and are 2.5 um long
2) surrounded by two membranes with a fluid filled space between them. The inner membrane is highly folded into cisternae
3) The inner part of the mitochondria is a fluid filled matrix

Question 12

What is the function of the mitochondria?

3 points

Answer 12

1) Are the site for ATP production during respiration
2) they are self replicating so more can be made if the cells energy needs to be increased
3) Abundant in cells where much metabolic activity takes place e.g in liver cells and at synapses between neurons where neurotransmitters are synthesized and released

Question 13

What is the structure of the chloroplasts?

5 points

Answer 13

1) large organelles 4-5 um long
2) Found only in plant cells and in some protoctists
3) surrounded by a double membrane/envelope
4) Inner membrane is continuous with stacks of flattened membrane stacks called thylakoids (which resemble piles of plates) which contain chlorophyll. Each stack/pile of thylakoids are called a granum (plural. grana.)
5) The fluid filled matrix is called a stomata

Question 14

What is the function of chloroplasts?

4 points

Answer 14

1) The site for photosynthesis
2) the 1st stage of photosynthesis, when light energy is trapped by chlorophyll and used to make ATP, occurs in the grana. Water is also split to supply hydrogen ions.
3) The 2nd stage, when hydrogen reduces C02, using energy from ATP, to make carbohydrates, occur in the stroma
4) Chloroplasts are abundant in leaf cells particularly the palisade mesophyll layer

Question 15

What is the structure of the vacuole?

2 points

Answer 15

1) It’s surrounded by a membrane called the tonoplast

2) contains fluid to keep the cell turgid

Question 16

What is the function of the vacuole?

3 points

Answer 16

1) Only plant cells have a large vacuole
2) It is filled with water and solutes and maintains cells stability, because when full it pushes against the cell, making the cell turgid
3) If all the plant cells are turgid it helps support the plant, especially in non-woody plants

Question 17

What is the structure of the lysosomes?

3 points

Answer 17

1) Small bags formed from the Golgi Apparatus. Each is surrounded by a single membrane
2) Contains powerful hydrolytic(digestive ) enzymes
3) abundant in phacocytic cells, such as neurophils and macrophages (types of white blood cell) that can ingest and digest invading bacteria i.e bacteria

Question 18

What is the function of Lysosomes?

2 points

Answer 18

1) Keeps the powerful hydrolytic enzymes separate from the rest of the cell
2) Can engulf old cell organelles and foreign matter, digest them and return the digested components to the cell for reuse.

Question 19

What is the structure of the cilia and undulipoda?

3 points

Answer 19

1) Protusions from the cell and are surrounded by the cell surface membane
2) each contain microtubules
3) formed from the centrioles

Question 20

What is the function of the cilia and undulipoda?

3 points

Answer 20

1) The epithelial cells lining your airways each have many of hundreds of cilia that beat and move the bands of mucus
2) Nearly all cell types in the body have one cilium that acts like an antenna. It contains receptors and allows the cell to detect signals about its immediate environment.
3) The only type of cell to have an undulipodium ( a longer cilium) is a spermatozoon which allows it to move

Question 21

What is the structure of the ribosomes?

4 points

Answer 21

1) small spherical cells, about 20 nm long in diameter
2) made of ribosomal RNA
3) made in the nucleolus, as 2 separate sub units, which pass through the nuclear envelope into the cytoplasm then combine
4) Some remain free in the cytoplasm and some attach to the rough endoplasmic reticulum

Question 22

What is the function of the ribosomes?

2 points

Answer 22

1) Ribosomes found on the exterior of the RER are mainly for synthesising proteins that will be exported outside the cell
2) Ribosomes that are free in the cytoplasm, either singularly or in clusters, are primarily the site of assembly of proteins that will be used inside of the cell

Question 23

What is the structure of the centrioles ?

1 point

Answer 23

1) Consists of two bundles of microtubules at right angles to eachother. The microtubules are made of tublin protein sub units and are arranged to form a cylinder

Question 24

What is the function of the centrioles?

How are they involved in the formation of the cilia/undilipodium?

3 points

Answer 24

1) Before a cell divides the spindle,made of threads of tubulin, forms from the centrioles
2)Chromosomes attach to the middle part of the spindle and motor proteins walk along the tubulin threads, pulling the chromosomes to opposite ends of the cell.
3) Centrioles are involved in the formation of the cilia and undilipodium
before the cilia form, the centrioles multiply and line up beneath the cells surface membrane
microtubules then spread outwards, from each centriole, forming a cilia/undilipodium

Question 25

What is the structure of the Cyto skeleton?

4 points

Answer 25

A network of protein structures within the cytoplasm, it consists of:

1) Rod-like microfilaments made of subunits of the protein actin; they are polymers of actin and each microfilament is about 7nm in diameter
2) intermidiate filaments 10nm in diameter
3) Straight, cylindrical microtubules, made of protein sub units called tubulin; about 18-30 nm in diameter
4) The cytoskeleton motor proteins:myosis, kinesis, dyneins are molecular motors. They are also enzymes and have a site that binds too and allows Hydrolosis of ATP as their energy source

Question 26

What is the function of the Cytoskeleton?

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3 points
Quite lengthy will be broken down later
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Answer 26

1) The protein microfilaments in the cells cytoplasm give support and mechanical strength, keeps the cells shape stable and allows movement
2) Microtubules also provide shape and support to cells and helps substances and organelles to move through the cytoplasm of the cell.
a) They form a track in which motor proteins (dyenine and Kinesin) walk and drag organelles from one part of the cell to another
b) They form a spindle before a cell divides. These spindle threads enable chromosomes to be moved within a cell
c) Also make up the cilia and undulipodia, plus centrioles
3) Intermediate filaments are mad up of a variety of proteins they:
a) Anchor the nucleus within a cytoplasm
b) extend between cells in some tissues; between special junctions, enabling cell-cell signalling and allowing cells to adhere to a baseline membane, therefore stabilizing tissue

Question 27

What is the structure of the Cellulose cell wall?

1 point

Answer 27

1) The outside of the plasma membrane made from bundles of cellulose fibers

Question 28

What is the function of the Cellulose cell wall?

Answer 28

1) Absent from animal cells, the cell wall is strong and can prevent plant cells from bursting when turgid (swollen)
2) The cell wall provides
a) strength and support
b) maintains the cell shape
c) contributes to the strength and support of the whole plant
d) are permable and allow solutions (solute and solvent) to pass through
3) Fungi have cell walls that contain chitin not cellulose