Cell Components

Question 1

Cell theory

Answer 1

All living organisms are made up of one or more cells

Cells are the basic functional unit (i.e. the basic unit of structure and organisation) in living organisms

New cells are produced from pre-existing cells

Question 2

What’s the cell-surface membrane function?

Answer 2

Controls the exchange of materials between the internal cell environment & the external environment

Question 3

What are the properties of the cell-surface membrane?

Answer 3

It is partially permeable, and fluid - constantly in motion
Primarily made up of phospholipids and proteins

Question 4

What does a cell wall do?

Answer 4

provides structural support to a cell

Question 5

What are cell walls made up of?

Answer 5

They are made up of polysaccharides - cellulose in plants, and peptidoglycan in most bacterial cells

Question 6

How do the cell wall connect to other plant cells?

Answer 6

Narrow threads of cytoplasm (surrounded by a cell membrane) called plasmodesmata connect the cytoplasm of neighbouring plant cells

Question 7

Why are the cell wall made up of cellulose?

Answer 7

As it is a structural polysaccharide, has many hydrogen bonds giving it its strength due tot he inversion of the glucose molecule

Question 8

Chromatin

Answer 8

(linear DNA bound to histone proteins) → forms chromosomes

Question 9

the nuclear envelope

Answer 9

full of pores
pores allow mRNA & ribosomes to leave the nucleus, and enzymes (e.g., DNApol) to enter)

Question 10

Nucleolus

Answer 10

site of ribosome production; some cells have multiple nucleoli

Question 11

Function of mitochondria?

Answer 11

site of aerobic respiration

Question 12

What is the structure of mitochondria?

Answer 12

Surrounded by a double-membrane their inner membrane folds to form cristae

The cristase forms the matrix, where many contains needed for respiration can be found
Small, circular mitochondrial DNA (mtDNA) and ribosomes are also found here

Question 13

What is the function of chloroplast?

Answer 13

Is the site of photosynthesis
The light-dependent stage takes place in the thylakoids
The light-independent stage (Calvin Cycle) takes place in the stroma

Question 14

What is the structure of the chloroplasts?

Answer 14

Surrounded by a double-membrane
Thylakoids (containing chlorophyll) stack → form a granum (grana)

Grana join together to form a lamella (lamellae)

Also contain small, circular DNA and ribosomes are also found here

Question 15

What is the function of Ribosomes?

Answer 15

Site of translation - protein synthesis

Question 16

Where are ribosomes located?

Answer 16

found freely in the cytoplasm of all cells or as part of the rough endoplasmic reticulum

Question 17

What are ribosomes made up of?

Answer 17

Each ribosome is a complex of ribosomal RNA (rRNA) and proteins

Question 18

How is the rough endoplasmic reticulum formed?

Answer 18

Formed from continuous folds of membrane that is attached to the nuclear envelope

Question 19

What is the function of smooth endoplasmic reticulum?

Answer 19

Involved in the production, processing and storage of lipids, carbohydrates and steroids

Question 20

What is the strucutre of Golgi apparatus?

Answer 20

are flattened sacs of membrane

Question 21

What is the job of the Golgi apparatus?

Answer 21

Responsible for modifying proteins and lipids → pack them into golgi vesicles → vesicles transport proteins and lipids to their destination

Proteins that go through the Golgi apparatus are usually exported (e.g. hormones such as insulin), put into lysosomes (such as hydrolytic enzymes) or delivered to membrane-bound organelles

Question 22

What is the large permanent vacuoles?

Answer 22

sacs in plant cells surrounded by the tonoplast - selectively permeable membrane

Question 23

What does large permanent vacuoles do?

Answer 23

Helps maintain turgor pressure in a plant cell

Stores water, salts, minerals, pigments & proteins within a cell

Question 24

Vesicles

Answer 24

Vesicles are membrane-bound sacs for transport & storage

Question 25

What are Lysosome?

Answer 25

specialist forms of vesicles which contain hydrolytic enzymes (enzymes that break biological molecules down)

Question 26

When are lysosome used for?

Answer 26

These enzymes break down waste materials such as worn-out organelles

Cells of the immune system & cells involved in apoptosis use lysosomes a lot