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AS Biology (Unit 1: F211) > Cell structures > Flashcards

Flashcards in Cell structures Deck (30):
1

What characteristics must an organism display in order to be classified as living?

- Movement
- Respiration (or some mechanism of producing energy)
- Sensitivity
- Nutrition
- Excretion
- Reproduction
- Growth

2

What organelle can be seen clearly with a CLM?

The nucleus, chloroplast, vacuole... Other features that can be seen but are too small to be clearly defined are called granules.

3

What is the ultrastructure of a cell?

Detailed structure of a cell containing features that can only be seen by a TEM.

4

What is 'Division of labour'?

Each organelle in a cell has a specific role and function, but working together to ensure the survival of the cell.

5

What is the cytoskeleton?

A network of fibres made out of proteins.

6

What is the role of the cytoskeleton?

1. To support the structure of the cell.
2. Actin filaments are able to move against each other, causing the cell to move. They also move around organelles inside the cell.
3. Microtubules are cylinders around 25nm in diameter. They can be involved in transporting chemicals around the cell or transporting organelles around the cell. This involves energy (from ATP) and is carried out by proteins on the microtubules called microtubule motors.

7

Cell features that can be seen with CLM.

- Nucleus
- Chloroplast
- Mitochondria
- Cytoplasm
- Cell surface membrane
- Cell wall
- Vacuole
- Plasmodesma
- Tonoplast
- Chromatin
- Middle lamella

8

Cell features that can be seen with TEM only (ultrastructure).

- Microtubules
- Rough endoplasmic reticulum
- Smooth endoplasmic reticulum
- Ribosomes
- Golgi apparatus
- Lysosome
- Microvilli
- Nuclear pores
- Chloroplast envelope
- Nuclear envelope
- Secretory vesicles
- Golgi vesicles

9

Cell features only present in animal cells.

- Centrioles
- Pinocytotic vesicles 'Secretory vesicles'

10

Cell features only present in plant cells.

- Chloroplast
- Cell wall
- Plasmodesma
- Tonoplast
- Middle lamella
- Grana
- Chloroplast envelope

11

Cell features present in both cell types.

- Nucleus
- Mitochondria
- Cytoplasm
- Cell surface membrane
- Golgi apparatus
- Vacuole
- Ribosome
- Nuclear envelope
- Chromatin
- Microtubules
- Rough ER
- Smooth ER
- Lysosome
- Nuclear pores
- Golgi vesicles

12

What is the nucleus for?

Usually around 10-20 micrometers in diameter. Contains genetic material of cell. Controls the division and activity of the cell. The nuclear envelope consists of two membranes; the outer and inner membrane. It can be continuous with ERs and can be lined with ribosomes. Along the nuclear envelope are many nuclear pores 40-100nm wide that allow and regulates the exchange of chemicals between the nucleus and cytoplasm. The liquid inside the nucleus is known as nuclear sap or nucleoplasm.

13

What's inside the nucleus?

DNA is usually bound to proteins called histones and forms chromatin that coil to form chromosomes.The chromatin on the edges of the nucleus are usually more coiled than the inside. They stain darker and are called heterochromatin whereas the rest on the inside are called euchromatin.There is also one or more spherical structures called nucleoli. They are responsible for synthesising rRNA which is needed in ribosome formation.

14

What are microvilli?

Finger-like projections off the surface of cells that increase cell surface area by up to x25. A surface lined with microvilli is called a brush border and they are usually found on cells specialised for excretion/ absorption, e.g. the illeum lining cells.

15

What is the Rough Endoplasmic Reticulum for?

Consists of a network of flattened membrane sacs called cisternae. Ribosomes are bound onto the surface which is why it looks rough. The ER itself is involved in storage and transport of proteins.

16

What is the Smooth Endoplasmic Reticulum for?

Involved in the synthesis, storage and transport of lipids.

17

What is the structure of mitochondria?

A spherical or sausage-shaped organelle bound with two membranes separated by a fluid filled space; the outer membrane and the inner membrane which is folded into many cristae to increase surface area. The central part of the ribosome is called the matrix and contains a circular ring of DNA, ribosomes and phosphate granules.

18

What is the function of mitochondria?

Site of aerobic respiration (using oxygen to produce energy).Coupled mitochondria produce ATP which is involved in providing energy for most cellular activities.Uncoupled mitochondria produce heat and is involved in keeping an organism warm.

19

What is the Endosymbiont theory of mitochondrial origin?

A very long time ago, the mitochondria was actually a prokaryotic cell that aerobically respired and produced ATP but was one day engulfed by a eukaryotic cell as food. However, instead of digesting the mitochondria, a permenant symbiotic relationship was formed between the mitochondria and eukaryotic cell which involved the mitochondria providing the cell with energy and ATP while the cell provided the mitochondria with a stable environment and a steady supply of nutrients.

20

What evidence is there to support the Endosymbiont theory of mitochondrial origin?

1. The mitochondria contains a circular ring of DNA, like a prokaryotic cell.2. Mitochondria contains free-floating 70s ribosomes, like a prokaryotic cell.3. Inner mitochondrial membrane is of similar composition to membrane of prokaryotic cell.4. Affected by some antibiotics, like prokaryotic cells.

21

What is the structure of ribosome?

Ribosomes are one of the few organelles not bound by its own membrane. There are two types of ribosomes; 70s ribosomes are small and are found in prokaryotic cells, mitochondria and chloroplasts. 80s ribosomes bigger are found in eukaryotic cells.Ribosomes are made out of rRNA and proteins, forming a large and small subunit. In eukaryotic cells, they can be found either floating freely or bound to rough ER.

22

What is the function ribosome for?

Ribosomes are responsible for protein synthesis. They read the instructions of making proteins carried by mRNA molecules and they assemble amino acids to form the required proteins.

23

What is the structure of chloroplast?

Found is plant cells and some protocists. The chloroplast is bound by an envelope consisting of an outer membrane and an inner membrane. The fluid bound by these membranes is called the stroma. The stroma contains flattened membranes called thycaloid which contain the pigment chlorophyll and is where photosynthesis occurs. The chloroplast also contains starch grains (product of photosynthesis) lipid droplets, circular ring of DNA and ribosomes.

24

What is the function of chloroplast?

Site of photosynthesis. Where light energy is used to convert carbon dioxide and water into glucose and oxygen.

25

What is the Endosymbiont theory of chloroplast origin?

Similar to mitochondria.

26

What evidence is there to support the Endosymbiont theory of chloroplast origin?

1. The chloroplast contains a circular ring of DNA, like a prokaryotic cell.2. Chloroplast contains free-floating 70s ribosomes, like a prokaryotic cell.3. Inner chloroplast membrane is of similar composition to membrane of prokaryotic cell.4. Affected by some antibiotics, like prokaryotic cells.

27

What is the structure of Golgi apparatus?

Layers of flattened membranes (cisternae) stacked on top of each other. There are two sides of the Golgi; the forming side where the lipid and protein vesicles are fusing and the maturing side where the Golgi vesicles are diffusing back into the cytoplasm.

28

What is the function of the Golgi apparatus?

The Golgi is involved in the modifying and packaging of chemicals. For example; lipids and proteins into lipoproteins or carbohydrates and proteins into glycoproteins. It then packages them into small, membrane bound vesicles ready for excretion from the cell.

29

`What is the structure of a lysosome?

A membrane bound vesicle containing digestive chemicals and acid to maintain an optimum pH.

30

What is the function of lysosome?

To break down materials inside or outside of the cell. E.g. a white blood cell.