2.1.3 - Eukaryotic cells 1

Question 1

define cytoplasm

Answer 1

jelly-like liquid that makes up the bulk of the cell and contains organelles

Question 2

define nucleus

Answer 2

organelle containing the nucleic acids DNA and RNA as well as protein, surrounded by a nuclear envelope with pores

Question 3

define protoplasm

Answer 3

the cytoplasm and nucleus combined

Question 4

what is the Ultrastructure of the cell?

Answer 4

detailed organisation of the cell that can only be visible using an electron microscope

Question 5

What surrounds the nucleus?

Answer 5

• nuclear envelope (double nuclear membrane with pores)

- chemicals pass in and out of the pores so that the nucleus can control events in the cytoplasm

Question 6

what is the nuclear envelope made up of?

Answer 6

• nucleic acids (RNA and DNA) and proteins

Question 7

define chromatin

Answer 7

granular combinations of DNA bonded to protein found in the nucleus when the cell is not actively dividing

Question 8

define the nucleolus

Answer 8

extra dense area of almost pure DNA and protein found in the nucleus involved in the production of ribosomes and control of growth and cell division

Question 9

list the three parts of the nucleus.

Answer 9

1. nuclear envelope
2. chromatin
3. nucleolus

Question 10

define mitochondria

Answer 10

rod-like structures with inner and outer membranes that are the site of aerobic respiration

Question 11

what process occurs at mitochondria?

Answer 11

• aerobic respiration
• this is where simple molecules are oxidised to produce ATP
• this is then used to drive functions of the cell and the organism as a whole

Question 12

How does the number of mitochondria link to the functions of that cell?

Answer 12

• cells that require very little energy (e.g white fat storage cells) will have less mitochondria
• cells with an energy demand (e.g muscle and liver cells) will have large numbers of mitochondria

Question 13

Why do mitochondria have their own genetic material?

Answer 13

• so that when a cell divides, they can replicate themselves under the control of the nucleus
• it is called mitochondrial DNA and is part of the whole genome of the organism

Question 14

define cristae

Answer 14

infoldings in the inner membrane of mitochondria which provide large surface area for aerobic respiration

Question 15

define eubacteria

Answer 15

true bacteria (prokaryotic organisms)

Question 16

what is the endosymbiotic theory?

Answer 16

• suggests that mitochondria and chloroplasts originated as independent prokaryotic organisms
• they began living symbiotically inside other cells as endosymbionts
• over millions of years they have become an integral part of the cell

Question 17

define centrioles

Answer 17

bundles of tubules found near the nucleus that are involved in cell division by the production of a spindle of microtubules (these move the chromosomes to the end of the cell)

Question 18

define cytoskeleton

Answer 18

3D web-like structure made up of microfilaments (protein fibres) and microtubules (protein tubes) that fills the cytoplasm and gives it structure

Question 19

List 3 things the cytoskeleton does

Answer 19

• keeps organelles in place
• gives the cell structure
• enables cell movements and transport within the cell

Question 20

What are microtubules and microfilaments made up of in the cytoskeleton?

Answer 20

microtubules are made up of the globular protein tubulin

Microfilaments are related to actin and myosin and the contractile proteins in muscle

Question 21

What is a key feature of the vacuole?

Answer 21

• they are formed and lost as needed
• major feature of the plant cell
• permanent vacuoles are never seen in animal cells

Question 22

define vacuole

Answer 22

fluid-filled cavity within the cytoplasm of the cell surrounded by a membrane

Question 23

what are contractile vacuoles?

Answer 23

• vacuoles that can fill and empty to control the water content of the cytoplasm (of simple freshwater animals)