(U1) Cells Flashcards
1
Q
What is a chromosome? (3)
A
- A long strand of DNA
- located in the nucleus
- and bound by histones
2
Q
What is in a eukaryotic cell? (7)
A
- a membrane-bound nucleus,
- chromosomes,
- mitochondria,
- endoplasmic reticulum, (smooth and rough)
- ribosomes,
- Golgi apparatus,
- vesicles,
- lysosomes and
- microtubules
3
Q
What size is a eukaryotic cell?
A
10 - 200 µm
4
Q
What size is a prokaryotic cell?
A
Usually less than 5 µm
5
Q
Where is the site of DNA in a eukaryotic cell?
A
The membrane bound nucleus
6
Q
Where are the sites of DNA in a prokaryotic cell? (2)
A
- Loop of DNA sprawled in cytoplasm
- also plasmids which are circular
7
Q
How is DNA organised in a eukaryotic cell? (2)
A
- DNA is linear and in chromosomes
- chromosomes contain DNA in a helical shape and histones
8
Q
How is DNA organised in a prokaryotic cell?
A
In loops without histones
Also in plasmids
9
Q
What size are ribosomes in a eukaryotic cell?
A
Large compared to prokaryotic - 25 nm (80S)
10
Q
What size are ribosomes in a prokaryotic cell?
A
Small compared to eukaryotic - 20 nm (70S)
11
Q
What does synthesis mean?
A
Creation
12
Q
What is chromatin also known as?
A
Uncondensed DNA
13
Q
What are spindle fibres made of?
A
Microtubules made of tubulin (a protein)
14
Q
In centrioles, how are microtubules arranged?
A
Perpendicularly
15
Q
What 3 substances are contained within a nucleus?
What is also found in a nucleus?
A
- heterochromatin (heavily condensed around histones)
- euchromatin (less condensed around histones)
- nucleoplasm
- Nucleoli - most densely packed (with rRNA)
16
Q
What size is a nucleus usually?
How are they enclosed? (2)
A
- 10-30µm
- within an envelope, with some nuclear pores
- continuing into rough endoplasmic reticulum studded with ribosomes
17
Q
What are the functions of ribosomes? (2)
A
- translates mRNA into an amino acid sequence
- formation of polypeptide chains (primary proteins)
18
Q
What are ribosomes (not functions)?
What size are they usually?
A
- bodies of protein and rRNA either in cytoplasm or on the rough endoplasmic reticulum
- 20-25µm
19
Q
How is the rough endoplasmic reticulum structured? (3)
A
- flattened cavities known as cisternae
- covered with ribosomes
- maze like folding
20
Q
What is the structure of the cell surface membrane? (2)
in broad terms - not including glycocalyx etc.
A
Phospholipid bilayer with:
- hydrophilic phospho-glycerol heads and
- hydrophobic hydrocarbon fatty acid tails
- The bilayer consists of polar phospholipid heads facing the extracellular fluid or cytoplasm,
- while non-polar fatty acid tails are in the center.
21
Q
What model describes the arrangement of proteins in the cell membrane?
A
Fluid-mosaic model
This model illustrates how proteins are embedded within the phospholipid bilayer.
22
Q
What types of proteins are found in the cell membrane?
A
Intrinsic (transmembrane) and extrinsic proteins
Intrinsic proteins span the membrane, while extrinsic proteins are attached to the surface.
23
Q
What role does cholesterol play in the cell membrane?
A
- Regulates fluidity and permeability of the membrane
- increases stability
Cholesterol is located among the hydrocarbon tails in animal cell membranes.
24
Q
Can non-polar molecules diffuse through the cell membrane?
A
Yes
Non-polar molecules can easily pass through the phospholipid layers.
25
What types of molecules can move through the membrane besides non-polar molecules?
Smaller molecules such as water and oxygen
## Footnote
These smaller molecules can also diffuse through the membrane.
26
How do **larger molecules** (too big for facilitated diffusion) *move through the cell membrane*?
Through cytosis or bulk transport
## Footnote
Larger molecules cannot diffuse directly through the membrane.
27
Can polar molecules pass through the phospholipid bilayer?
No
## Footnote
The non-polar fatty acid tails prevent polar molecules from traveling through.
28
What process allows polar molecules to cross the membrane?
Facilitated diffusion
## Footnote
This process involves channel and carrier proteins.
29
How do **carrier proteins** assist in the *movement* of *polar molecules*?
By attaching to polar molecules and changing shape
## Footnote
Carrier proteins have **receptor regions** for polar molecules.
30
What is simple diffusion?
Movement from higher concentration to lower concentration
## Footnote
This process occurs with lipid-soluble substances.
31
When is **active transport** required?
When moving substances *against the **concentration gradient***
## Footnote
Active transport requires **ATP for energy - also proteins**
32
What is the relationship between the number of carrier proteins and the rate of facilitated diffusion?
Greater number of carrier proteins increases the rate
## Footnote
More carrier proteins enhance the movement of polar molecules.
33
How is a **mitochondrion** *structured*? (**5**)
- outer membrane
- inner membrane *folded* into **cristae**
- fluid-filled **matrix** (site of the *Krebs cycle*)
- ribosomes (*70S*)
- mitochondrial DNA
34
What are **mitochondria** *responsible for*?
**Where** does this occur?
- Production of **ATP** by *aerobic respiration*
- cristae
35
How are **chloroplasts** *structured*? (**4**)
- outer envelope
- inner membrane folded into **lamellae**
- lamellae consist of **thylakoid membranes** (***bonded** to chlorophyll molecules*) *stacked into* **grana**
- jelly like **stroma** - contains **lipid droplets** and **starch grains**
36
In which type of organism are chloroplasts found?
Plants (largely)
37
**Why** are *thylakoids stacked* into *grana*? (**2**)
- supports *efficient packing* of *chlorophyll molecules* attached to thylakoids
- **increasing area** for **light absorption**
38
What are **plasmodesmata**?
In what *organisms* is it found?
What is its **purpose**?
- cytoplasm continuous between 2 cells
- plants
- facilitates transport of substances
39
How is the **nuclear envelope** *structured*? (**3**)
- nuclear pores throughout
- rough endoplasmic reticulum *continuous with envelope*
- ribosomes encrust the RER
40
What is the **purpose** of *nuclear pores*?
Allow **large molecules** *in and out* (e.g. rRNA to go to RER)
41
What is the primary **purpose** of the:
- nucleus
- nucleolus
1. Nucleus: Houses **DNA** which *codes for **synthesis** of polypeptides* (base triplets)
2. nucleolus: **synthesises rRNA**, which make up over half the mass of ribosomes
42
How is the **Rough Endoplasmic Reticulum** *structured*? (**2**)
- **flattened cavities** *continuous with nuclear envelope*
- *studded* with **ribosomes**
43
What are the **purposes** of the **Rough Endoplasmic Reticulum**? (**2**)
- primary proteins (*synthesised by ribosomes*) *folded* to form **secondary proteins**
- then **packed into vesicles** to go to the *Golgi*
44
How is the **Smooth Endoplasmic Reticulum** *structured*? (**2**)
- interconnecting *tubules*
- **not studded** with ribosomes
45
What is the *purpose* of the **Smooth Endoplasmic Reticulum**?
*Synthesis* of **lipids** and/or **carbohydrates**
46
How is the **Golgi apparatus** *structured*? (**3**)
- consist of membrane-bound cavities - **cisternae**
- **cis face** *accepts vesicles from RER*,
- **trans face** has *vesicles pinching off* - usually a *bent shape*
47
What is the *purpose* of the **Golgi apparatus**? (**3**)
- **modifies, processes** and **packages** proteins
- *polypeptides combined* (forming **quaternary structure**) *or* a *prosthetic group* is added,
- then packed into **vesicles** for *secretion by exocytosis* (*secretory vesicle*) or *delivery somewhere in cytoplasm* (e.g. as a *lysosome*)
48
What is the *purpose* of **ribosomes**?
- **translate mRNA** into an **amino acid sequence**
- polypeptide *synthesis* (**primary protein**)
49
What are **ribosomes** *made of*? (**2**)
- rRNA and
- protein / amino acids
50
What are **lysosomes**?
How are they **structured**?
- A form of **vesicle** used to carry **hydrolytic enzymes** to *breakdown worn out organelles*
- thick membrane - phospholipid bilayer
51
What are **vesicles** used for?
Where do they come from?
- **storage or transport** of substances e.g. structural proteins.
- Either to *site in cytoplasm* or *cell surface membrane* (where they *fuse* with membrane and *release substance out of cell*)
- bud off from trans face of Golgi apparatus
52
What is the name of the **membrane** of a **vacuole**?
The tonoplast
53
How do *fungal cells reproduce*?
Budding
54
Give the **equation** between *magnification and lengths*.
What **unit** should lengths be in?
- M = I/A
Magnification = image length / actual length
I
M A
- µm (micrometers) (1mm = 1000 µm)
55
What is **resolution**? (**2**)
- the ability to *discriminate fine detail*
- between *2 separate* neighbouring *points*
56
Why are some *organelles* **not always visible** when using a *microscope*?
Some in different section / not in plane
57
What is the **difference** between a:
- *scanning* electron microscope (SEM)
- *transmission* electron microscope (TEM)
TEM =
- more expensive
- higher resolution
- images not 3d - SEM opposite
## footnote
SEM = better for modelling external structure due to modelling in 3D
58
What is the **main advantage** of *using a **light** microscope* instead of an *electron microscope*?
- can be used to view **living cells**
- images are in **colour**
59
What is the **main advantage** of *using an **electron** microscope* instead of a *light microscope*?
- higher resolution images
- higher magnification
60
What is the **cell wall** made of in:
- bacteria
- fungi
- plant cells
1. Bacteria = peptidoglycan
2. Fungi = chitin
3. Plant = cellulose
61
How do **fungi** *feed*?
Fungi are **heterotrophic**:
- **Saprophytic** digestion
- then *absorb* breakdown products
62
What are **microfilaments**?
What **size** are they?
What is their *role* in cells?
- rod-like structures made of *contractile* **Actin and Myosin proteins**
- 7nm
- provide **support** and **aid movement**.
63
What is the primary purpose of **microtubules** in cells?
Structural support as part of the **cytoskeleton**
64
What is a **vacuole**?
**Where** is it found? (*generally*)
What is its **purpose**?
- large vesicles which hold cell sap
- *plant* cells (**central and permanent**) and *fungal* cells
- provides *structural support* through **turgor pressure**
65
What **substance** is *not* seen in a **prokaryotic cell envelope**?
Cholesterol
66
What is **different** about **how plant cells feed** compared to animal and fungal cells?
- **plant** cells are **photoautotrophic**
- **animal** and **fungal** cells are **heterotrophic**
67
*How* is **energy stored** in:
- plant cells
- animal cells
- fungal cells?
- plant = starch grains
- animal = glycogen granules
- fungal = glycogen granules
68
**Where** are **microtubules** found in:
- prokaryotic
- eukaryotic organisms?
- prokaryotic = only in **flagella**
- eukaryotic = **centrioles** in *animal* and *plant* cells + **cytoskeleton**
69
Name **3 structures** which contain **microtubules**
State the **arrangement** of these microtubules.
- **flagella** - *9+2 arrangement*
- **cilia** - *9+2 arrangement*
- **centrioles** - *9 triplets arrangement*
70
What are **microvilli** and what is their **function**?
- *finger-like folds* of the *cell-surface membrane*
- **increases surface area** for diffusion of *molecules and ions*
71
What happens when a *vesicle reaches another membrane*?
The **membrane** of the **vesicle fuses** *with the membrane*
72
What is the *structure* formed when a *lysosome fuses* to a *membrane* called?
A *secondary lysosome* / **phagolysosome**
