Cells

Question 1

What is the structure and function of the membrane?

Answer 1

Structure - phospholipid bilayer, with protein molecules and protein channels integrated within

Function - controls passage of entry of substances in and out of cell, and its the site of cell communication via receptors

Question 2

What is the structure and function of the nucleus?

Answer 2

Structure - membrane bound organelle, with a nucleolus, nuclear envelope, nuclear pore, nucleoplasm and chromatin

Function - Stores DNA (chromatin), nuclear pore allows mRNA and ribosomes to pass through

Question 3

What is the structure and function of the mitochondria?

Answer 3

Structure -

Function - carries out aerobic respiration to produce ATP

Question 4

What is the structure and function of the chloroplast?

Answer 4

Structure - Double membrane bound which contains fluid sacs called thylakoids, each thylakoid is joined by a lamella and each stack of thylakoid is called a
granum

Function -site of photosynthesis

Question 5

What is the structure and function of the Golgi apparatus?

Answer 5

Structure - Stack of curved membranes containing lumen and two faces (cis face and trans face)

Function - Modifies proteins,
Sorts packages and transport molecules around the cell

Question 6

What is the structure and function of the lysosomes?

Answer 6

Structure - Small round membrane vesicles formed by Golgi bodies

Function - Contains digestive enzymes to break down pathogens,old organelles,cells and food molecules

Question 7

What is the structure and function of the ribosomes?

Answer 7

Consists of two separate RNA-proteins
Protein synthesis

Question 8

What is the structure and function of the rough endoplasmic reticulum?

Answer 8

Series of convoluted,flattened sheets
Provides a larger surface area for protein synthesis

Question 9

What is the structure and function of the smooth endoplasmnic reticulum?

Answer 9

Tue like structures located around the RER
Synthesises, stores and transports lipids and carbohydrates

Question 10

What is the structure and function of the vacuole?

Answer 10

Thin membrane filled with fluid
Maintains water potential and keeps the cell turgid

Question 11

Explain the differences between eukaryotic and prokaryotic cells

Answer 11

Eukaryotic cells have a nucleus containing the DNA whereas prokaryotic cells have free-floating DNA

DNA is linear and associated with histone proteins in eukaryotic cells and DNA is circular and not associated with histone proteins in prokaryotic cells

Eukaryotic have larger ribosomes prokaryotic have smaller ribosomes

Prokaryotic cells may have additional organelles e.g. flagellum and capsule (etc.)

Question 12

Explain the structure and function of virus cells

Answer 12

Structure - Cellular non-living cell
Nucleic acid core and a protein coat called a ‘capsid’

Function -  replicated by binding to the host cell and injecting their genetic material into the cell using the hosts machinery to replicate and burst out of the host cell

Question 13

Describe optical microscopes

Answer 13

Use light to form an image

Results in low resolution (200nm max)

Cannot be used to observe smaller organelles e.g. ribosomes, endoplasmic reticulum or lysosomes

Maximum magnification is up to ×1500

Question 14

Describe electron microscopes

Answer 14

Use electrons to form an image

Increased resolution end result in a more detailed image (0.2nm max)

Maximum magnification of up to x1,500,000

There are two types of electron microscopes:
Transmission electron microscopes (TEMs)
Scanning electron microscope (SEMs)


Question 15

State the difference between magnification and resolution

Answer 15

Magnification - how much bigger the image is in comparison to the original object viewed by the naked eye

Resolution - how about a microscope distinguishes between two points that are close together

Magnification is how big an image is and resolution is how clear an image is

Question 16

List the steps of ultracentrifugation

Answer 16

1- Homogenation: cells are blended in a homogeniser forming a homogenate which is then placed into a centrifuge

2-  Filtration: Homogenate is filtered to remove any large bits or debris

3- Ultracentrifugation: Centrifuge is spun at different speeds with separates organelles into sediment or pellets

Question 17

In what stage does DNA replication take place?

Answer 17

S phase

Question 18

Define mitosis

Answer 18

A process of nuclear division by which two genetically identical daughter cells are produced from the parent cell

Question 19

How are tumors formed?

Answer 19

Formed from cancer cells
Tutors are formed from uncontrolled cell division

Question 20

What is the main aim of cancer treatments?

Question 21

Explain the stages of binary fission

Answer 21

• Cell replicates it’s DNA
• Cytoplasmic membrane elongates separating DNA molecules
•A cross wall forms; and membrane splits /turns inside out
• Cross wall forms completely
• Two daughter cells are formed

Question 22

Describe the basic structure of a cell membrane

(Use a diagram)

Answer 22

A bilayer consisting of phospholipids integrated with protein channels

Question 23

Describe the structure of a phospholipid

Answer 23

Phospholipid head is composed of a phosphate group and a glycerol, this is hydrophilic which means it’s attracted to water.

Phospholipid tale is composed of two fatty acids, this is hydrophobic which means it repels water.

Question 24

Describe the fluid mosaic model of membranes

Answer 24

Fluid mosaic model is a cell membrane that acts as a barrier and controls what passes in and out of the cell. It consists of organelles like phospholipids, proteins, glycoproteins, glycolipids and cholesterol

Question 25

Explain the role of cholesterol in the membrane

Answer 25

Cholesterol adds rigidity to the cell which reduces lateral movement

Question 26

Explain the role of glycolipids in the cell membrane

Answer 26

Glycolipids are cell-surface receptors which allow cells to adhere and form tissues

Question 27

Explain the function of extrinsic and intrinsic proteins in the cell membrane

Question 28

List three factors that affect membrane permeability

Question 29

How does temperature affect membrane permeability?

Question 30

How does pH affect membrane permeability?

Question 31

How does the use of a solvent affect membrane permeability?

Question 32

List the five ways molecules move through a membrane

Answer 32

Diffusion Facilitated diffusion Co-transport Osmosis Active transport

Question 33

Define diffusion

Answer 33

Net movement of particles from an area of high concentration to an area of low concentration

Question 34

How and what molecules move through the membrane via diffusion?

Question 35

Define osmosis

Answer 35

Net movement of water molecules from an area of high water potential to the area of low water potential across a partially permeable membrane

Question 36

What is the difference between simple diffusion and facilitated diffusion?

Question 37

How and what molecules move through a membrane via facilitated diffusion?

Question 38

Define active transport

Question 39

How and what molecules move through the membrane via active transport?

Question 40

Define co-transport

Question 41

How and what molecules move through the membrane via co-transport ?

Question 42

Explain how channel and carrier proteins work

Question 43

Compare and contrast of active transport and facilitated diffusion 

Question 44

Compare and contrast transmission electron microscopes and scanning electron microscopes

Question 45

What is the equation for magnification?

Answer 45

Question 46

State the conditions needed for cell fractionation and explain the reason behind each

Answer 46

Ice cold - To reduce the activity of enzymes Isotonic - To produce the same water potential and prevent water from moving into the cell so no expansion occurs Buffered - Prevent organelle are proteins from being denatured

Question 47

Name the first stage of mitosis and explain what happens during this phase

Answer 47

-Prophase •Chromosomes condense and become visible •Nuclear envelope breaks down •Centrioles move to opposite poles 

Question 48

Name the second stage of mitosis and explain what happens during this phase

Answer 48

-Metaphase • Centrioles release spindle fibres • Spindle fibres attach to centromeres which joins the two chromatids together forming chromosome •Chromosomes line up at the equator of the cell

Question 49

Name the third phase of mitosis and explain what happens during this phase

Answer 49

-Anaphase • Centimetres divide • Chromatids now move to opposite poles

Question 50

Name the fourth stage of mitosis and explain what happens during this phase

Answer 50

-Telophase • Chromosomes uncoil therefore not visible anymore • nuclear envelope reforms

Question 51

What happens during cytokinesis in mitosis

Answer 51

 Cell membrane splits forming two identical daughter cells