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A-Level Biology > Cell Ultrastructure > Flashcards

Flashcards in Cell Ultrastructure Deck (34)
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1
Q

What is the function of:

a) Nucleus
b) Mitochondria
c) Ribosomes
d) Rough endoplasmic reticulum
e) Smooth endoplasmic reticulum
f) Golgi apparatus
g) Lysosomes
h) Plasma membrane
i) Cytoskeleton
j) Centrioles
k) Chloroplasts

A

a) Controls all the activities of the cell through protein synthesis & contains the genetic material as DNA
b) Responsible for the production of ATP - direct source of energy (responsible for respiration)
c) Conduct protein synthesis
d) Has ribosomes & provides a large SA for plotein synthesis and glycoproteins (protein + sugar)
e) Synthesises, stores & transports lipids & proteins
f) Produces secretory enzymes & carbs. Transports, modifies and stored lipids. Adds carbs to proteins to make glycoproteins
g) Formed from golgi. Contains digestive enzymes that can be released to destroy unwanted/ dead materials
h) Surrounds cells, forming boundary between the cytoplasm and the environment, controlling substances moving in & out of the cell
i) Holds & maintains the structure of the cell membrane
j) Used for cell division by generating the spindle fibres, and responsible for separating chromosomes in mitosis
k) Capturing sunlight to use in photosynthesis

2
Q

What is the function of the nucleus?

A

Controls all the activities of the cell through protein synthesis & contains the genetic material as DNA

3
Q

What is the function of the mitochondria?

A

Responsible for the production of ATP - direct source of energy (responsible for respiration)

4
Q

What is the function of ribosomes?

A

Conduct protein synthesis

5
Q

What is the the function of rough endoplasmic reticulum?

A

Has ribosomes & provides a large SA for plotein synthesis and glycoproteins (protein + sugar)

6
Q

What is the function of smooth endoplasmic reticulum?

A

Synthesises, stores & transports lipids & proteins

7
Q

What is the function of the golgi apparatus?

A

Produces secretory enzymes & carbs. Transports, modifies and stored lipids. Adds carbs to proteins to make glycoproteins

8
Q

What is the function of lysosomes?

A

Formed from golgi. Contains digestive enzymes (lysozymes) that can be released to destroy unwanted/ dead materials

9
Q

What is the function of the plasma membrane?

A

Surrounds cells, forming boundary between the cytoplasm and the environment, controlling substances moving in & out of the cell

10
Q

What is the function of chloroplasts?

A

Capturing sunlight to use in photosynthesis

11
Q

What is the function of centrioles?

A

Used for cell division by generating the spindle fibres, and responsible for separating chromosomes in mitosis

12
Q

What is the function of the cytoskeleton?

A

Holds & maintains the structure of the cell membrane

13
Q

Talk about the nucleus structure

A

Spherical, 10-20 micrometres
Nuclear envelope is a double membrane surrounding it. The outer membrane is continuous with endoplasmic reticulum & has ribosomes close to its surface
Nuclear pores allow large molecules in and out
Contains the nucleolus - small, darker spherical body within.
Chromatin (uncoiled, invisible chromosomes. Chromosomes only formed in mitosis) in the nucleus

14
Q

What is the function of the nucleolus?

A

Manufactures ribosomal RNA and ribosomes. Found as a small, dark spherical body in the nucleus

15
Q

What is the nuclear envelope?

A

A double membrane surrounding the nucleus. Outer membrane has endoplasmic retuculum & ribosomes on its surface

16
Q

Talk about the structure of mitochondria

A

Rod shaped, 1-10 micrometres.
Have a double membrane, inner membrane folded into a cristae. Matrix is the space in the mitochondria
It’s the site of oxidative phosphorylation (getting energy from oxygen to do ADP + P = ATP)

17
Q

Talk about the structure of a ribosome

A

Made of 2 sub units (looks like a snow man)!
Each unit contains ribosomal RNA (r RNA) & protein.
80 S in eukaryotic cells, 70 S in prokaryotic cells (bigger in eukaryotes)

18
Q

Talk about:

a) Rough endoplasmic reticulum
b) Smooth endoplasmic reticulum

A

a) Has ribosomes on its surface. Provides a large surface area for protein synthesis & glycoproteins
b) Lacks ribosomes. Only synthesises, stores & transports lipids & carbs
Both are found continuous with the nuclear membrane

19
Q

Talk about the golgi apparatus structure

A

Stack of flattened membranous discs (like a WiFi symbol, golgi vesicles/ lysosomes - blobs - coming off it)
Adds carbs & proteins to make glycoproteins.
Produces secretory enzymes & carbs
Transports, modifies and stores lipids

20
Q

Talk about lysosomes structure

A

Formed from budding of the golgi apparatus
Contains digestive enzymes, up to 1 micrometre
Has a phospholipid layer
Single membrane
Breaks down material outside of cell/ ingested by phagocytic cells/ worn out organelles/ dead cells

21
Q

Talk about the plasma membranes’ structure

A

Surrounds cells, forming a boundary.

Lined with phospholipids & proteins to control what enters & stays out

22
Q

Talk about the structure of the cytoskeleton

A

Holds the structure of the cell membrane - surrounds the cell

23
Q

Talk about the structure of the centrioles

A

Close to the nucleus - in the centre, a dense area of cytoplasm called the centrosome. Each cell only has a pair of centrioles
Cylindrical - at right angles to each other, create the spindle fibres in mitosis

24
Q

|What is the centrosome?

A

A dense area of cytoplasm where the centrioles are.

25
Q

Talk about the structure of the chloroplasts

A

Have stacked discs called thylakoid
Stack of thylakoids is a granum
Stroma fills the rest of it
Pigment is chlorophyll - absorbs the sunlight

26
Q

What is a stack of thylaoids called?

A

Granum - in the chloroplasts

27
Q

What is centrifugation?

A

A way of separating organelles creating pure samples

28
Q

What is the type of centrifugation we have to worry about called?

A

Differential centrifugation. Separated based on WEIGHT

29
Q

What is a homogenate?

A

The resultant fluid of blending a substance so all the organelles are free from the cells

30
Q

Talk through each stage of differential centrifugation

A

1) Homogenation - cells broken by homogeniser (blender, can just be a mortar and pestle), releasing the organelles. The resultant fluid is called the homogenate, which is filtered to remove large debris (fine cloth used)
2) Must be cold (2C), buffered & in isotonic salt solution to freeze cell from enzyme reactions & osmosis
3) Put the homogenate into a centrifuge tube. The first sample is sampled at a low speed for a short time. The heaviest (nucleus, around 10 mins) forms a layer at the bottom
4) The supernatant (leftovers from first sample) put in a new centrifuge tube & spun at a higher speed for longer. Leaves 2nd heaviest - mitochondria & lysosomes (around 15 mins)
5) Repeat, leaving the rough endoplasmic reticulum & ribosomes (30 mins roughly)

31
Q

What does the homogeniser not damage organelles?

A

Because they are too small

32
Q

Why must the homogenate be kept

a) Cold?
b) Buffered?
c) In an isotonic salt solution?

A

a) To stop all cell activity - no kinetic energy so enzymes inactive, so stops enzyme based reactions
b) To maintain pH, so enzymes and proteins stay unchanged
c) Same concentration as cells, so removes osmotic effects - the water stays

33
Q

What is are the 3 heaviest organelles?

A

Nucleus
Mitochondia (&lysosomes)
Rough endoplasmic reticulum (& ribosomes)

34
Q

What is the supernatant?

A

After centrifuging the first sample, the homogenate left over is the supernatant. Still contains a mix of organelles, and centrifuging it again will create a new pure sample.