1.1 Introduction to Cells

Question 1

What is the first rule of the cell theory?

Answer 1

All living organisms are composed of cells or cell products

Question 2

What is the second rule of the cell theory?

Answer 2

The cell is smallest unit of independent life

Question 3

What is the third rule of the cell theory?

Answer 3

Cells can only arise from pre-existing cells.

Question 4

What is a caveat of the cell theory that are multi?

Answer 4

Striated muscle cells are composed of fused cells that are multinucleated. They are the type of tissue that is used to change the position of our body. They are surrounded by a membrane and are formed by division of pre-existing cells. They have their own genetic material and their own energy release system.Muscle cells fuse to form fibres that may be very long (>300mm)
Consequently, they have multiple nuclei despite being surrounded by a single, continuous plasma membrane
Challenges the idea that cells always function as autonomous units

Question 5

What is a caveat of the cell theory that is large?

Answer 5

Giant Algae are unicellular organisms that are very large in size. They consist of one microscopic cell. They only have one nucleas.

Question 6

What is a caveat of the cell theory that is cont?

Answer 6

Aseptate hyphae. Fungi consist of narrow thread like structures called hyphae. These hyphae are divided up into small cell like sections called septa. However, in aseptate fungi there are no septa. Each hypha therefore has multiple nuclei spread across it.

Question 7

What are the seven functions of life?

Answer 7

Metabolism, Reproduction, Sensitivity, Growth, Homeostasis, Excretion, Nutrition.

Question 8

What are the features of a small surface area to volume ratio?

Answer 8

High metabolic rate, low material exchange and low survival chances.

Question 9

How is magnification calculated?

Answer 9

Magnification = Image Size ÷ Actual Size (MIA)

Question 9

How is actual size calculated?

Answer 9

Actual Size = Image Size ÷ Magnification

Question 10

Light Microscopes…

Answer 10

Use lenses to bend light. Can view living specimens in natural colour. Have lower magnification and resolution.

Question 11

Electron microscopes…

Answer 11

Use electromagnets to focus electrons. Can only view dead specimens in monochrome. Have higher magnification and resolution. Can show cross-sections or surface renderings.

Question 12

What are the three caveats to the cell theory?

Answer 12

Striated muscle cells, Giant Algae, Aseptate hyphae.

Question 13

Features of all cells…

Answer 13

All cells:
- Are surrounded by a membrane
- Contain genetic material
- Have chemical reactions occurring within the cell that are catalysed by enzymes

Question 14

Giant Alga (e.g. Acetabularia) and why it questions the cell theory

Answer 14

Acetabularia can grow to heights of 100 mm, and yet consist of only one cell with a single nucleus
Acetabularia have a relatively complex structure. They are divided into three parts: rhizoid, stalk and cap
The features above question the cell theory because the trend for most unicellular organisms is to be small in size and simple in structure

Question 15

Aseptate fungal hyphae and why it questions the cell theory

Answer 15

Fungi have many long, narrow branches called hyphae
Hyphae have cell membranes, cell walls and some have septa
Aseptate fungal hyphae do not have septa, thus these cells are multinucleated with continuous cytoplasm
This questions the cell theory because the cells have no end walls making them appear as one cell

Question 16

Striated muscle fibres and why it questions the cell theory

Answer 16

Striated muscle fibres (fused muscle cells) are:
Longer than typical cells (up to 300 mm in length in comparison to a cardiac muscle cell which has a length of 100 - 150 µm)
Have multiple nuclei surrounded by a single membrane (sarcolemma)
These features question the cell theory because striated muscle cells are formed from multiple cells which have fused together (which is how they have many nuclei rather than one) that work together as a single unit, challenging the concept that cells work independently of each other even in a multicellular organism

Question 17

Where do metabolic reactions take place?

Answer 17

Metabolic reactions take place in the cytoplasm, including reactions that release energy by respiration.

Question 18

What allows reactions to take place in the cytoplasm?

Answer 18

Enzymes in the cytoplasm are the catalysts that cause these reactions to take place.

Question 19

What is the function of the cell membrane?

Answer 19

The cell membrane controls what chemicals enter and exit the cell. It allows the entry of oxygen for respiration.

Question 20

How does excretion take place in a cell?

Answer 20

Excretion takes place in a cell using the cell membrane. Excretion happens simply by waste products diffusing out through the membrane.

Question 21

What is metabolism?

Answer 21

Metabolism includes all of the enzyme-catalysed reactions occurring in a cell, including cellular respiration.

Question 22

What is reproduction?

Answer 22

Reproduction is the production of offspring, this can be either asexual or sexual.

Question 23

What is homeostasis?

Answer 23

Homeostasis is the ability to regulate and maintain internal conditions within tolerable limits, including temperature.

Question 24

What is growth?

Answer 24

Growth refers to a permanent increase in size.

Question 25

What is response/sensitivity?

Answer 25

Response/ sensitivity is the ability to respond to internal or external changes in the environment (stimuli). Thus improving their chance at survival.

Question 26

What is excretion?

Answer 26

Excretion is the disposal of metabolic waste products.

Question 27

What is nutrition?

Answer 27

Nutrition is the aquisition of energy and nutrients for growth and development.

Question 28

What is paramecium?

Answer 28

Paramecium are unicellular protozoans commonly found in freshwater. They range in size from 50 to 320 μm

Question 29

What is chlorella?

Answer 29

Chlorella is a small (2 to 10 μm) unicellular green alga. They are abundant in freshwater and can be found in a symbiotic relationship with Paramecium
As Chlorella are living they carry out all the functions of life, although due to different structures, there are some differences to Paramecium

Question 30

What is a symbiotic relationship?

Answer 30

Any relationship or interaction between two dissimilar organisms.

Question 31

How does metabolism take place in the paramecium?

Answer 31

Metabolic reactions such as respiration and digestion are always taking place in the cytoplasm.

Question 32

How does metabolism take place in the chlorella?

Answer 32

Metabolic reactions take place such as respiration and digestion are always taking place in the cytoplasm.

Question 33

How does reproduction take place in the paramecium?

Answer 33

Reproduction in paramecium generally takes place asexually. After mitosis the two nuclei are separated by constriction of the cytoplasm.

Question 34

How does reproduction take place in the chlorella?

Answer 34

Reproduction in the chlorella takes place as mitosis produces autospores that are released when the parent cell wall breaks down.

Question 35

How does homeostasis take place in the paramecium?

Answer 35

The contractile vacuoles fill up with water and expel the water through the plasma membrane to maintain a constant osmotic potential.

Question 36

How does homeostasis take place in the chlorella?

Answer 36

In the chlorella, extra glucose is stored as starch in pyrenoids to maintain the osmotic potential of the cell.

Question 37

How does growth take place in the paramecium?

Answer 37

Growth takes place in the paramecium as after obtaining the nutrients and assimilating the nutrients, the organisms increase in size until it divides.

Question 38

What does assimilating mean?

Answer 38

Assimilation is the movement of the digested food molecules into the cells of the body from where they are used.

Question 39

How does growth take place in the chlorella?

Answer 39

After consuming and assimilating biomass from food the algae will get larger until it divides.

Question 40

How is response in the paramecium?

Answer 40

Response in the paramecium is the beating of the cilia moves the paramecium through the water in response to changes in the environment.

Question 41

How is response in the chlorella?

Answer 41

Response in the chlorella is chlorophyll pigments located in the chloroplast absorb light.

Question 42

How is excretion in the paramecium?

Answer 42

Excretion in the paramecium includes plasma membrane control the entry and exit of substances including expulsion of metabolic waste

Question 43

For cells to survive, metabolic reactions must be occurring, these reactions depend on…

Answer 43

• Materials constantly being exchanged across the plasma membrane

Question 44

How does paramecium show all the functions of life?

Answer 44

Excretion – the plasma membrane control the entry and exit of substances including expulsion of metabolic waste

Metabolism – most metabolic pathways happen in the cytoplasm

Nutrition – food vacuoles contain organisms the parameium has consumed

Homeostasis – contractile vacuole fill up with water and expel I through the plasma membrane to manage the water content

Growth – after consuming and assimilating biomass from food the paramecium will get larger until it divides.

Response – the wave action of the cilia moves the paramecium in response to changes in the environment, e.g. towards food.

Reproduction – The nucleus can divide to support cell division by mitosis, reproduction is often asexual

Question 45

How does chlorella show all of the functions of life?

Answer 45

Excretion – the plasma membrane control the entry and exit of substances including the difussion out of waste oxygen

Metabolism – most metabolic pathways happen in the cytoplasm

Nutrition – photosynthesis happens inside the chloroplasts to provide the algae with food

Reproduction – The nucleus can divide to support cell division, by mitosis (these cells are undergoing cytokinesis)

Growth – after consuming and assimilating biomass from food the algae will get larger until it divides.

Response – the wave action of the cilia moves the algae in response to changes in the environment, e.g. towards light.

Homeostasis – contractile vacuole fill up with water and expel I through the plasma membrane to manage the water content

Question 46

As organisms increase in size their surface area to volume ratio…

Answer 46

decreases. This means there is less surface area for the absorption of nutrients and gases and the secretion of waste products. The greater volume results in a longer diffusion pathway to the cells and tissues of the organism.

Question 47

What is the endosymbiotic theory?

Question 48

What is the plasma membrane responsible for?

Answer 48

The plasma membrane is responsible for import and export inside the cell.

Question 49

What does a larger surface area to volume ratio mean? (advantages)

Answer 49

A larger surface area to volume ratio means that the cell can act more efficiently. For every unit of volume that requires nutrients or produces waste, there is more membrane to serve it.
- Diffusion pathways are shorter
and hence more efficient. Molecules do not have to travel so far to get in or out of the cell so it takes less time and (if active transport) energy.
- Concentration gradients are easier to generate.
this makes diffusion more efficient. ex. takes more solute to make 10% solution in 100ml than 1000l.

Question 50

What does a larger surface area to volume ratio mean? (disadvantages)

Answer 50

A larger surface area to volume ratio means that mammals lose heat

Question 51

Nucleas

Answer 51

The nucleas contains the chromosomes, which consist of DNA associated with histone proteins. Uncoiled chromosomes are spread through the nucleas and are called chromatin. The nucleas is where DNA is replicated and transcribed to form mRNA . This is exported via the nuclear pores to the cytoplasm.

Question 52

Nuclear membrane

Answer 52

The nuclear membrane is double and has pores through it.

Question 53

Explain the benefits and limitations of using cubes to model the surface area and volume of a cell.

Answer 53

Benefit is that the cubes can be manipulated, visualized and easily measured. Cells are difficult to manipulate because of their microscopic size and variability in shape.
Limitation is that most cells are not cubic in shape.

Question 54

List three adaptations of cells that maximize the SA: volume ratio.

Answer 54

1) cells have evolved structures that increase the amount of surface area. In a neuron cell this is through how there is a long extension of the cell membrane.
2) The thin flattened shape to increase sa:v ratio is the red blood cell.
3) the epithelial cell in the small intestine has bristle like extensions called microvilli.

Question 55

Explain why cells are often limited in size by the SA:V ratio.

Answer 55

As a cell grow, eventually the surface area can no longer serve the requirements of the cell. the nutrients in and waste out of the cell membrane for example.
A decreasing surface area to volume ratio will stimulate cell division through mitosis. By dividing, the size of the cell is reduced and kept within Surface Area to volume limits.

Question 56

Define and provide an example of a multicellular organism.

Answer 56

A multicellular organism contains more than one cell within them. eg a leaf.

Question 57

Define and provide an example of a unicellular organism.

Answer 57

A unicellular organism only contains one cell. Eg yeast cell.

Question 58

Define “emergent property.”​

Answer 58

Emergence takes place when an entity is observed to have properties its parts do not have on their own.

Question 59

Outline the organisation of cells in a multicellular organism

Answer 59

Cells of the same type may group together to form tissues. Different tissues interact to form functional organs. Organs combine to create organ systems.