Cell structure and organisation Flashcards

(28 cards)

1
Q

What can light microscopes show you?

A

objects magnified to 1000x and images are coloured

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2
Q

What can electron microscopes show you?

A

Images magnified to more than 200000x and images are black and white

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3
Q

What is a cell?

A

It is a unit of life. It consists of mass of living matter called protoplasm

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4
Q

What is protoplasm made of?

A

It is made up of three parts : the cell membrane, cytoplasm, nucleus

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5
Q

What is the function of the cell surface membrane?

A

controls the movement of substances in and out of the cell

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6
Q

Characteristics of cell membrane

A
  1. It is partially permeable
  2. It is made of lipid molecules, protein groups and carbohydrate groups
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7
Q

What are the functions of cell wall?

A
  1. It serves as a protection against injury for the plant cells
  2. It gives plant cells a fixed shape
  3. It prevents the plant cells from bursting when too much water enters them
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8
Q

Characteristics of cell wall

A
  1. It is made of cellulose
  2. It is fully permeable to all substances
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9
Q

Which organelles are not able to be seen under the light microscope and only electron microscope?

A

Mitochondria, endoplasmic reticulum, golgi apparatus and ribosomes

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10
Q

What are the functions of a nucleus?

+ nuclear membrane

A
  1. It controls cell activities such as cell growth and repair of worn-out parts
  2. It is essential for cell division
  3. It also contains chromatin ( which consists of DNA and proteins)
  4. It makes mRNA which is used to make proteins that are responsible for traits

Nuclear membrane separates the contents of the nucleus from the rest of the cytoplasm

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11
Q

What is the function of the cytoplasm?

A

It is the site of where chemical reactions occur in a cell

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12
Q

Characteristics of Rough endoplasmic reticulum (RER)

A
  1. It is made up of a network of flattened spaces lined with membranes which are continuous with the nucleus membrane.
  2. Surface appears rough due to ribosomes attached to its surface
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13
Q

Functions of RER

A

It transports proteins made by attached ribosomes to the Golgi apparatus for secretion out of the cell.

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14
Q

Function of ribosomes

attached to RER & free lying in the cytoplasm

A
  • (attached to RER) make proteins that are usually transported out of the cell
  • (lying freely in cytoplasm) make proteins that are used within the cytoplasm of that cell
  • main function is synthesising proteins
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15
Q

Functions of smooth endolasmic reticulum (SER)

A
  1. Synthesises substances such as fats and steroids (sex hormones in mammals are steroids)
  2. converts harmful substances to harmless substances - detoxification
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16
Q

Characteristics of SER

A
  • more tubular than RER
  • does not have ribosomes attached to its membrane
17
Q

Functions of golgi apparatus

A
  • chemically modifies substances made by the endoplasmic reticulum
  • stores & packages these substances in vesicles for secretion out of the cell
18
Q

How are substances synthesised secreted out of the cell?

A
  1. (in the context of protein) proteins are synthesised by ribosomes on the rough endoplasmic reticulum
  2. Small vesicles containing proteins/ substances made by the ER are then pinched off the RER (for proteins) / ER (for substances made by the ER)
  3. These small vesicles fuse with Golgi apparatus, releasing their contents into the Golgi apparatus. The Golgi apparatus carries out chemical modifications to these proteins/ substances.
  4. Secretory vesicles containing the modified proteins/ modified substances then pinches off from Golgi apparatus.
  5. These secretory vesicles move towards the cell surface membrane and fuse with the cell surface membrane and release its contents out of the cell
19
Q

Function of mitochondria

A

It is the site of aerobic respiration where food substances (glucose) are broken down to release energy to be used by the cell to perform cell activities such as growth and repair

20
Q

Function of chloroplasts

A

It contains a green pigment called chlorophyl which is essential for plants to photosynthesise and make food

21
Q

Vacuoles in animals & plants

A

Vacuoles are fluid-filled spaces enclosed by a partially permeable membrane which stores substances within the cell.

Animal cells:
- numerous small vacuoles, contain water and food substances
- exist temporarily

Plant cells :
- large central vacuole, stores cell sap which contains dissolved substances like sugars, mineral salts and amino acids

22
Q

Differences between plant and animal cells

A
  1. Plant cells have cellulose cell walls which are absent in animal cells
  2. Plant cells contain chloroplasts which are absent in animal cells
  3. Plant cells contain a large central vacuole while animal cells have small vacuoles
23
Q

Define differentiation (in terms of specialised cells)

A

The process by which a cell becomes specialised for a specific function

24
Q

Specialised cells : RBC

Adaptations of RBC

A
  1. Contains haemoglobin - which binds reversly to oxygen, so oxygen can be transported from lungs to all parts of the body
  2. Has circular and biconcave - increases SA:V ratio for faster rate of diffusion of oyxgen in and out of the RBC
  3. Lacks nucleus - enables RBC to pack more haemoglobin to bind reversely to more oxygen for faster tranportation of oxygen around the body
  4. Flexible and elastic - enables RBC to be able to change into a bell shape to squeeze through narrow blood capillaries so RBC are in close proximity to body cells, reducing diffusion distance, allowing faster rate of diffusion of oxygen to cells
25
Adaptions of muscle cell
Muscle cells are elongated and cylindrical in shape, contains many **nuclei and mitochondria** 1. Has many mitochondria - to **increase rate of respiration** to release **more energy** for increased contraction of muscle cell 2. Has many nuclei - allow for **cell division**
26
Adaptations of root hair cell
1. *Has a long and narrow outgrowth* - **increase SA:V ratio** to absorb **water molecules** and **dissolved mineral salts** at a **higher rate** 2. *Maintains a lower water potential in vacuole* - allows **water molecules** to **enter** root hair cell via **osmosis** 3. *Numerous mitochondria* - for root hair cell to be able to **release energy** from respiration to carry out **active transport** to **absorb dissolved mineral salts** against **concentration gradient**
27
Explain how a large number of mitochondria in root hair cells allows the plant to survive in soils that contain a short supply of mineral ions. | 3m
* When mineral ions are in short supply, there will be a **lower concentration of mineral ions in soil** than in root hair cells * The large number of mitochondria ensures that the root hair cell can carry out **aerobic respiration** to release **sufficient energy.** * Energy can then be used by the root hair cell to **absorb mineral ions against its concentration gradient** via **active transport**.
28
Explain why liver cells have a large number of mitochondria
* Liver carries out many **metabolic reactions** like **detoxification** and **deamination** * A large no. of mitochondria: required to **release sufficient energy** needed to carry out these reactions **effectively**