Section 2 : Cells

Question 1

What is a cell?

Answer 1

A small membrane-bound structure containing several smaller structures called organelles

Question 2

List the differences between a prokaryote and a eukaryote

Answer 2

Prokaryote» doesn’t have a nucleus ( bacterial cells), simpler, smaller 0.1- 5 um, unicellular, no membrane bound organelles

Eukaryote- does have a nucleus ( animal+ plant cells ), complex, larger 10-100 um, usually multicellular, has membrane bound organelles

Question 3

What are membranes in cells made of?

Answer 3

Lipids ( phospholipid bilayer)

Question 4

What is the role of the cell membrane?

Answer 4

The cell membrane holds a cell together and controls what leaves the cytoplasm as it is a selectively permeable barrier.

Question 5

What is the role of the cytoplasm?

Answer 5

The cytoplasm functions to support and suspend organelles and cellular molecules in its jelly like substance called cytosal. Many cellular processes also occur in the cytoplasm such as protein synthesis, respiration. Helps to move materials such as hormones asunder the cell and also dissolves cellular waste.

Cytosol → liquid
cytoplasm → cytosol +organelles except nucleus
Protoplasm → cytoplasm + nucleus

Question 6

What is the role of the nucleus?

Answer 6

The nucleus is the largest organelle in a eukaryotic cell and stores all of the cells DNA /genetic material.

Question 7

What is the nuclear envelope?

Answer 7

A double membrane that surrounds the nucleus Souter membrane affen has ribosomes on its surface and controls entry and exit of materials in and out of nucleus and contains the reactions taking place within it

Question 8

What is the nuclear envelope?

Answer 8

A double membrane that surrounds the nucleus Souter membrane affen has ribosomes on its surface and controls entry and exit of materials in and out of nucleus and contains the reactions taking place within it

Question 9

What is the nucleolus?

Answer 9

When not dividing, DNA is arranged loosely as chromatin in this denser region. Manufactures ribosomal RNA and assembles the ribosomes. May be more than one nucleolus in a nucleus.

Question 10

What do the nuclear pores do?

Answer 10

Allows various substances to pass through and large molecules such as messenger RNA out of nucleus. Typical around 3000 pares in each nucleus.

Question 11

What is the role of ribosomes?

Answer 11

Small non-membranous organelles which are responsible for translating proteins and are formed of RNA ribosomal RNA = rRNA and a protein. They can be found in rough er cytoplasm and nuclear surface.

Question 12

Which type of ribosomes do each a prokaryote and a eukaryote have?

Answer 12

Prokaryote → 70’s ribosomes
Eukaryote → 80’s ribosomes

Question 13

What is the role of the rough endoplasmic reticulum?

Answer 13

Series of membrane-bound sacs (cisternae) studded with ribosomes responsible for protein synthesis and packages the new proteins into a membrane -bound sac (vesicle) for transport

Question 14

What is the role of the smooth endoplasmic reticulum?

Answer 14

Series of branching tubes which lack ribosomes on its surface and synthesises, stores and transports lipids and carbohydrates.

Question 15

What is the role of the Golgi apparatus?

Answer 15

Stacks of parallel, flattened membrane pockets called cisternae formed through the fusing of vesicles which modifies proteins and lipids, concentrates them, packs them into vesicles and secretes them from the cell.

Question 16

What are lysosomes and what are their roles?

Answer 16

Lysosomes are formed when vesicles produced by the Golgi apparatus contain enzymes such as protease s lysozymes, and lipases. They destroy bacterial cell walls, breakdown damaged or old organelles, release enzymes for extra cell digestion, autolysis/cell suicide

Question 17

What is the role of the mitochondria?

Answer 17

Generates ATP through aerobic respiration

Question 18

What is the structure of the mitochondria?

Answer 18

1. About 1 micrometer long and is surrounded by 2 membranes
2. Inner membrane is coated in enzymes which catalyse the reactions of aerobic respiration to produce ATP
3. The inner layer folds inwards to form the CRISTAE and the cristae project into a liquid called the MATRIX
4. They have their own loop of DNA and 70’s ribosomes

Question 19

What is the cytoskeleton?

Answer 19

Any protein that gives the cell structure

Question 20

What is the role of the microtubules?

Answer 20

They are the main component of a cell’s cytoskeleton and they connect the cell’s organelles to each other to keep them in place and they can also alter their length to affect the shape of the cell or cause it to more.

Question 21

What is the role of centrioles?

Answer 21

Involved in cell division and co-ordinate the nucleation and growth of microtubules in all eukaryotes except higher plants

Question 22

What 3 structures do plant cells contain that animal cells do not?

Answer 22

Permanent vacuole, chloroplasts, cell wall (made of cellulose)

Question 23

What is the structure and role of the vacuole?

Answer 23

The vacuole consists of a membrane called the TONOPLAST, filled with cell sap a watery solution of diff substances including sugars, enzymes etc. They are important in keeping the cell firm I when vacuole is full of sap cell is turgid.

Question 24

What is the structure and role of the cell wall?

Answer 24

Gives structure and support and is made of the polysaccharide cellulose ,can act as a by carb varying the amount of cellulose it holds.

Does not completely seal off from neighbours, there are pores called plasmodesmata which connect cells
together by their cytoplasm, enabling exchange and transport of substances.

Question 25

What is the role of chloroplasts?

Answer 25

Use CO2, water and light energy to build sugars /carry out photosynthesis and are present in all green plants and have a green pigment called chlorophyll

Question 26

What is the structure of a chloroplast?

Answer 26

1. They are surrounded by a double membrane, filled with the liquid STROMA and contains stacks of THYLAKOID MEMBRANES called GRANA
2. The thylakoid membranes are the site of photosynthesis an excess glucose is stored in the chloroplasts as a starch in a starch granule
   3 They have their own loop of DNA and 70 ribosomes