Structure of eukaryotic cells

Question 1

Eukaryote

Answer 1

any organism that has one or more cells that contain DNA in the nucleus, seperate from the cytoplasm
* animals
* plants
* fungi
* protists

Question 2

Nucleus structure

Answer 2

largest cell organelle that contains the organisms hereditary material and controls the cells activities.
Contains components such as:
1. Nuclear envelope- double membrane that surrounds the nucleus. outer membrane is continuous with the ER and often has ribosomes on its surface. controls the entry and exit of materials
2. Nuclear pores- allow the passage of large molecules, e.g mRNA out of nucleus
3. Nucleoplasm- jelly-like material that makes up bulk of nucleus
4. Chromosomes- consist of protein-bound, linear DNA
5. Nucleolus- small spherical region within the nucleoplasm that makes rRNA and assembles ribosomes

Question 3

Nucleus function

Answer 3

• acts as control centre of cell through production of mRNA and tRNA
• retains genetic material of cell in the form of DNA + chromosomes
• manufactures rRNA and ribosomes

Question 4

Mitochondria structure

Answer 4

rod shaped structure made up of
1. Double membrane- that controls the entry and exit of material
2. Cristae- inner fold of a membrane that forms extensions to provide a large suface area for enzymes and other proteins
3. Matrix- liquid that makes up remainder of mitochondrion containing protein, lipids, ribosomes, DNA and enzymes involved in respiration

Question 5

Function of mitochondria

Answer 5

site of aerobic respiration
* responsible for the release of ATP

Question 6

Chloroplast structure

Answer 6

disc shaped organelles that carry out photosynthesis
1. Chloroplast envelope- double plasma membrane that surrounds organelle, selective in what it allows to enter and leave the chloroplasts
2. Grana- stacks of 100 disc like structures called thykaloids, the first place of photosynthesis takes place
3. Thylakoids- contain the photosynthetic pigment, chlorophyll, some have tubular extensions that join uo with thylakoids in adjacent grana
4. Stroma- fluid-dilled (matrix) where the second stage of photosyntheis takes place, contains starch grains

Question 7

Chloroplast function

Answer 7

• Granal membranes provide a large surface area for chlorophyll attachment, electron carriers and enzymes that carry out the first stage of photosynthesis
• Fluid stroma processes all the enzymes needed to make sugars in the second stage of photosynthesis
• Chloroplasts contain DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis

Question 8

Rough endoplasmic reticulum

Answer 8

RER
ribosomes are present on the outer surfaces of the membranes
* provide a large surface area for protein synthesis and glycoproteins
* provide a pathway for the transport of materials

Question 9

Smooth endoplasmic reticulum

Answer 9

SER
lacks ribosomes on its surface, often more tubular in appearance
* synthesises, stores and transports lipids
* synthesises, stores and transports carbohydrates

Question 10

Golgi apparatus structure

Answer 10

transports and modifies proteins
1. Cisternae- stack of membranes that make up flattened sacs
* Proteins and lipids produced by ER are passed through here
2. Golgi vesicles- transport modified proteins and lipids, move to the cell surface where they can fuse with the membrane and release their contents to the outside

Question 11

Functions of Golgi apparatus

Answer 11

• add carbohydrate to proteins to form glycoproteins
• produce secretory enzymes
• secrete carbohydrates
• transport, modify and store lipids
• form lysosomes

Question 12

Lysosome stucture

Answer 12

produced by Golgi apparatus
* contain enzymes such as proteases and lipases
* contain lysozymes, enzymes that hydrolyse cell walls

Question 13

Lysosome function

Answer 13

• contains hydrolytic enzymes that hydrolyse material ingested by phagocytic cells
• release enzymes to the outside of the cell (exocytosis) in order to destroy material around the cell
• completely break down cells after they have died

Question 14

Ribosomes

Answer 14

small cytoplasmic granules found in all cells, site of protein synthesis
* occur in cytoplasm or are associated with RER
* 80s- found in eukaryotic cells, 25nm diameter
* 70s- found in prokaryotic cells, mitochondria and chloroplasts, slightly smaller

Question 15

Cell wall structure

Answer 15

PLANTS
* consist of microfibrils of the polysaccharide cellulose that contribute to the overall strength of the cell wall
* contain a thin layer of middle lamelllae that marks the boundary between adjacent cell walls
FUNGI
* made of a nitrogen-containing polysaccharide chitin

Question 16

Cell wall functions

Answer 16

• provide mechanical strength in order to prevent the cell from bursting through osmotic pressure

Question 17

Vacuole structure

Answer 17

fluid filled (cell sap) sac bounded by a single membrane
* plants contain one large permanent vacuole
* Tonoplasts- single membranes around vacuoles
* contains a solution of mineral salts, sugars, amino acids, wastes and pigments

Question 18

Vacuole fuctions

Answer 18

• full of cell sap which keeps cells turgid and firm
• this prevents plants from wilting, less cell sap= flacid

Question 19

Cell specialisation

Question 20

Organs

Question 21

Organ systems