Cells: Structure of Eukaryotic Cells - Structure & Function

Question 1

Cell-surface Membrane

Answer 1

• Structure

• Phospholipid bilayer with proteins and cholesterol embedded within it
• Glycolipids and glycoproteins in the surface

• Function

• Regulates the movement of substances into and out of the cell
• Has receptor molecules on it, which allow it to respond to chemicals like hormones

Question 2

Nucleus

Answer 2

• Structure

• Surrounded by a double membrane nuclear envelope with nuclear pores
• Contains chromosomes and one or more nucleolus

• Function

• Contains genetic information (DNA)
• The pores allow substances (e.g RNA) to move between the nucleus and the cytoplasm
• The nucleolus makes ribosomes

Question 3

Mitochondrion

Answer 3

• Structure

• Double membrane organelle
• The inner membrane is folded
• Contains a fluid centre called the matrix - contains enzymes involved in respiration

• Function
- Site of aerobic respiration and ATP production

Question 4

Chloroplasts

Answer 4

• Structure

• Surrounded by a double membrane
• Contains thylakoids, which are folded membrane containing chlorophyll pigments
• Thylakoids are stacked up to form grana
• Grana are linked together by lamella
• Lamella are thin, flat pieces of thylakoid membrane
• Contains a fluid centre, the stroma

• Function

• The site of photosynthesis
• The stroma contains enzymes for the light-independent stage of photosynthesis

Question 5

Lysosomes

Answer 5

• Structure

• A round organelle surrounded by a membrane, with no clear internal structure
• Formed when the Golgi apparatus contains hydrolytic enzymes

• Function

• A type of Golgi vesicle that releases lysozymes
• Can be used to digest invading cells or break down worn components of the cell

Question 6

Ribosome

Answer 6

• Structure

• A very small organelle that floats free in the cytoplasm or is attached to the rough endoplasmic reticulum
• Made up of proteins and RNA
• Not surrounded by a membrane

• Function
- Site of protein synthesis

Question 7

Rough Endoplasmic Reticulum

Answer 7

• Structure

• A system of membranes enclosing a fluid-filled space
• Surface is covered with ribosomes

• Function
- Folds and processes proteins that have been made at the ribosomes

Question 8

Smooth Endoplasmic Reticulum

Answer 8

• Structure

• A system of membranes enclosing a fluid-filled space
• Similar to RER but with no ribosomes on the outer surface

• Function
- Synthesises and processes lipids

Question 9

Cell Wall

Answer 9

• Structure

• Rigid structure found in plants, algae and fungi
• In algae and plants, it is made of cellulose
• In fungi, it is made of chitin

• Function

• Provides structural strength to cells
• Prevents cells from bursting when water enters by osmosis

Question 10

Cell Vacuole

Answer 10

• Found in plants

• Structure

• A membrane-bound organelle found in the cytoplasm
• Contains a weak solution of sugar and salts
• The membrane around a cell vacuole is called the tonoplast

• Function

• Helps maintain pressure inside the cell and keep it rigid - this stops plants wilting
• Store amino acids and sugars

Question 11

What is a vesicle?

Answer 11

• Vesicles are tiny sacs that transport material within or outside the cell
• They contain a liquid or cytoplasm
• They have membranes

Question 12

Golgi Apparatus

Answer 12

• Structure

• A group of fluid-filled membrane-bound flattened sacs
• Vesicles are often seen at the edges of the sacs

• Function

• It processes and packages new lipids and proteins
• Makes lysosomes

Question 13

Golgi Vesicle

Answer 13

• Structure

• A small fluid-filled sac in the cytoplasm surrounded by a membrane
• Produced by the Golgi apparatus

• Function
- Stores lipids and proteins made by the Golgi appatus and transports them out of the cell