Cells

Question 1

What is structure and function of the nucleus?

Answer 1

Nucleus - site of DNA replication and transcription and contains genetic code for each cell

Nuclear envelope - double membrane

Nuclear pores - holes on outside

Nucleoplasm - jelly like material on outside

Chromosomes - protein bound, linear DNA

Nucleolus - small sphere where RNA production occurs and makes ribosomes

Question 2

What is structure and function of golgi apparatus?

Answer 2

Golgi apparatus

Structure: Folded membranes making cisternae

Secretary vesicles pinch off cisternae

Function:

Make glycoproteins by adding carbohydrates to proteins

They are then packaged into golgi vesicles and are transported to cell surface membrane

They then fuse with the membrane and the contents are released

Question 3

What is structure and function of mitochondria?

Answer 3

Structure:

Double membrane

Inner membrane called the cristae

Fluid centre called the matrix

Loop of mitochondria RNA

Function:

Site of ATP production and aerobic respiration

DNA to code for enzymes needed in respiration

Question 4

What are the structure and function of chloroplasts?

Answer 4

Structure:

Surrounded by double membrane

Contain thylakoids - folded membranes embedded with pigment

Stroma contain enzymes for photosynthesis

Function:

Site for photosynthesis

Question 5

What is structure and function of a plasma membrane?

Answer 5

Structure:

Phospholipid bilayer: molecules embed within and attached on the outside

Function:

Controls entry and exit of molecules

Question 6

What is function and structure of the Endoplasmic reticulum?

Answer 6

Structure:

RER and SER both have cisternae

RER contains ribosomes on outside

Function:

RER - Site of protein synthesis

SER - synthesis and stores lipids and carbohydrates

Question 7

What is structure and function of lysosomes?

Answer 7

Structure:

Bags of digestive enzymes

Function:

Secrete enzymes to outside of cell to destroy materials

Question 8

What is structure and function of ribosomes?

Answer 8

Structure:

80s larger ribosomes found in eukaryotic cells

70s smaller ribosomes found in prokaryotic cells

Function:

Site of protein synthesis

Question 9

What is structure and function of vacuole?

Answer 9

Structure:

Filled with fluid surrounded by single membrane

Function:

Make cells turgid for support and pigments colour petals to attract pollinators

Question 10

What is structure and function of cell wall?

Answer 10

Structure:

Plants: made of microfibrils of cellulose polymer

Fungi - made of chitin

Function - provide structural strength to wall

Question 11

What are differences between prokaryotic and eukaryotic cells?

Answer 11

Prokaryotic cells are smaller
Have no nucleus
No membrane bound organelles
Smaller ribosomes
Cell wall made of murein

Some prokaryotic cells contain
Plasmids
Capsule around the cell
Flagella

Question 12

What is murein?

Answer 12

A glycoprotein

Question 13

What do eukaryotic cells have instead of a nucleus?

Answer 13

Single circular DNA molecule which is free from cytoplasm and not associated with proteins

Question 14

What is binary fission of prokaryotes?

Answer 14

1. DNA and plasmids replicate.
2. Cell elongates and DNA moves to opposite poles of cell
3. Cytoplasm begins to divide and new cell wall forms
4. Produces 2 daughter cells. Each contain identical DNA loop but have different number of plasmids as they don’t split evenly

Question 15

What is a bacteriophage and its properties?

Answer 15

Virus which attacks bacteria

1000x smaller than bacteria and needs living cell

Consists of RNA protected by protein coat called capsid

Attachment proteins attach to host cells to recognise them

Question 16

What is process of virus replication?

Answer 16

1. Detects host cell by recognising protein marker on membrane and attach with attachment proteins
2. Virus injects genetic material into cell
3. Cell reproduces genetic material and reads it creating new viral proteins
4. Virus leaves cell by destroying cell and affects different cells

Question 17

What is function of plasmids, capsule and the flagella?

Answer 17

Plasmids are small loops of DNA which only carry a few genes

Capsule - slimy layer made of protein which prevents bacteria drying out

Flagella - rotates allowing bacteria to move

Question 18

What is cell fractionation?

Answer 18

Where cells are broken up to release different organisms they contain

Question 19

How are cells separated?

Answer 19

They are separated based on their sizes via gravity

Question 20

What are steps of ultracentrifugation?

Answer 20

Step 1 (homogenisation) - cells are broken using a blender - cells must be in a solution

Step 2 (filtration) - blended material is filtered to remove large debris

Step 3 (centrifugation) - Solution is placed in a centrifuge and uses gravity to separate organelles by weight by spinning at different speeds

Each time, the liquid is removed (supernatant) and process is repeated at faster speeds until all organelles are separated

Question 21

What type of organelles are removed at slower speeds?

Answer 21

More dense organelles

Question 22

Which organelles separate first?

Answer 22

1. Nuclei
2. Chloroplasts
3. Mitochondria
4. Lysosomes
5. Endoplasmic reticulum
6. Ribosomes

Question 23

What properties must solution have in ultracentrifugation?

Answer 23

Solution must be:

Ice cold - reduces enzyme activity which may break down cells

Buffered - reduces change in ph so enzymes don’t denature

Isotonic - prevents cells bursting via osmosis - water potential inside and out is equal