Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

A Level Biology > Unit 2.1 + 2.2 - Cells > Flashcards

Unit 2.1 + 2.2 - Cells Flashcards

1
Q

Function of Cell-surface Membrane. x2

A

Regulates the movement of substances into and out of the cell.

It has receptor molecules on it which allow it to respond to chemicals like hormones.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Structure of Nucleus x4

A

Surrounded by a double membrane called a nuclear envelope.

The nuclear envelope contains many pores called nuclear pores

Contains chromosomes which are made from protein bound linear DNA

Also contains one or more nucleolus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Function of Nucleus x3

A

Controls cells activities by controlling the transcription of DNA which contains instructions to make proteins.

Nuclear pores allow substances to move between the nucleus and cytoplasm.

Nucleolus makes ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Structure of a Mitochondrion x2

A

Oval shaped with a double membrane:

the inner membrane is folded to form structures called cristae which contain enzymes involved in respiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Function of a Mitochondrion x1

A

Site of aerobic respiration and produces ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Function of Chloroplasts

A

site of photosynthesis which occurs in both the stroma and the grana

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Structure of Chloroplasts x 5

A

Small, flattened structure

Surrounded by double membrane

Contains membranes inside called thylakoid membranes.

Thylakoid membranes stack up to form grana

Contains a thick fluid called stroma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Structure of Golgi Apparatus and Golgi Vessicles

A

GA - Group of fluid filled, membrane bound, flattened sacks.

GV - Small fluid filled sack surrounded by a membrane found in the cytoplasm on the edge of the GA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Function of Golgi Apparatus- x2

A

Processes and packages new lipids and proteins.

Makes lysosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Function of Golgi Vessicles

A

Stores lipids and proteins made by the golgi apparatus and transports them out of the cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Structure of lysosomes

A

A type of golgi vesicle that is a spherical organelle, surrounded by a membrane with no clear internal structure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Function of lysosomes

A

Contains digestive enzymes called lysozymes and are used to digest invading cells or to break down worn out components of the cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Structure of rough endoplasmic reticulum and SER

A

RER - A system of membranes enclosing a fluid filled space. Surface is covered with ribosomes.

SER - similar to RER but no ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Function of Rough Endoplasmic Reticulum

A

Synthesises and transports proteins around the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Function of Smooth Endoplasmic Reticulum

A

Synthesises and processes lipids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Structure of Ribosome?

A

Small organelle made of proteins and RNA.

Not surrounded by a membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Function of Ribosomes?

A

Protein synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Structure of cell wall?

A

Rigid structure that surrounds algae, plants and fungi cells.

Made of cellulose in plants and algae but chitin in fungi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Function of the cell wall?

A

Supports cell and prevents it from changing shape or bursting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Structure of the vacuole

A

A membrane bound organelle containing cell sap (Weak solution of sugar and salts)

Surrounding membrane is called the tonoplast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Function of the vacuole?

A

Helps maintain pressure inside the cell

Involved in the isolation of unwanted chemicals inside the cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How does an optical microscope work?

A

Specimens are mounted in water and stained to increase contrast

Rays of light are passed through specimen

Different parts of the specimen absorb different wavelengths of light. More dense = darker

Different shades of light are focused through 2 glass lenses

Image is viewed directly through the eyepiece

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Benefits of an optical microscope?

A

Can be used to view live samples

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Limitations of an optical microscope?

A

2D image
Low mag and res

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
How does a TEM work?
Specimens are prepared with salts of heavy metal and placed in a vacuum An electron generated by an electron gun passes through the sample. More dense regions absorb more electrons and appear darker Electrons are focused through electromagnetic lenses Image is produced on a screen.
26
Benefits of a TEM
Relatively high mag and res
27
Limitations of a TEM
Cannot look at living specimens as in a vacuum 2d image Specimen prep is complex so artefacts can be introduced Sample must be very thin so electrons can pass through
28
How does an SEM work
Specimens are chemically treated and covered with a film of gold An electrons beam is generated by an electron gun onto the specimen Images are formed from the electrons deflecting back from the specimen Electrons focused through electromagnetic lenses 3DImage produced on a screen
29
Benefits of an SEM
3D image Relatively high mag and res
30
Limitations of an SEM
No live specimens due to vacuum Complex prep so artefacts may be introduced
31
Difference between eukaryotic and prokaryotic cells x7
Eukaryotic much bigger Prokaryotic have no membrane bound organelles Prokaryotic has no nucleus and the DNA is found in a circular molecule in the cytoplasm Prokaryotic have smaller ribosomes Cell wall made of murein instead of cellulose or chitin which is found in eukaryotic cell walls Prokaryotic may have a capsule May have one or more plasmids
32
Role of the capsule in bacterial cells?
Protects bacterium from other cells and helps groups of bacteria to stick together for further protection
33
Role of plasmids in bacterial cells
Possesses genes that may aid the survival of bacteria in adverse conditions eg. produces enzymes that break down antibiotics
34
Why are viruses nonliving?
No nucleus Must live off another organism Inert until they enter the host cell and then they can reproduce
35
Describe the structure of a virus?
A **core of genetic material** (DNA or RNA) which is surrounded by a protein coat called a **capsid** which has **attachment proteins** coming off. Some proteins have an envelope that surrounds the capsid made from lipids.
36
Why can viruses not reproduce themselves?
A cellular and contain no mitochondria or ribosomes so can create no proteins.
37
Role of attachment proteins in viruses?
Bind onto suitable host cells
38
Why do viruses make you feel ill?
Destroy/damage cells when they leave the host cell
39
Why are viruses difficult to treat?
They replicate inside host cells which makes them hard to individually target
40
Steps of viral replication?
1. Virus attaches to the host cell receptor proteins 2. Virus releases its genetic material into the host cell 3. The host cell's organelles replicate the genetic material 4. The viral components assemble 5. Replicated viruses are released from the host cell
41
What are the stages of the cell cycle?
Interphase Prophase Metaphase Anaphase Telephase
42
What occurs during interphase
Normal functions Cell's DNA is **unraveled and replicated** Organelles replicate and ATP production increases
43
Describe the structure of a chromosome in mitosis
A chromosome is formed of two **chromatids** joined together by a **centromere** The two chromatids joined by the same centromere are called **sister chromatids**
44
What occurs during prophase?
Chromosomes condense and become shorter and fatter The centrioles move towards opposite ends of the cell and form the spindle fibers Nuclear envelope disappears
45
What occurs during metaphase?
The chromosomes line up down the centre of the cell and become attached to the spindle by the centromere
46
What occurs during anaphase?
Centromeres divide which separates the sister chromatids Spindles contract which pulls the chromatids to opposite centrioles Making the chromatids appear v shaped
47
What occurs during telophase?
Chromatids uncoil and become long and thin again - now called chromosomes Nuclear envelope forms around each group of chromosomes and the cytoplasm divides in two through **cytokinesis** Leaving two identical daughter cells
48
What is the mitotic index?
Shows the proportion of cells undergoing mitosis at a given time
49
Mitotic index = ?
Number of cells in mitosis / total number of cells
50
Time spent in a specific stage of mitosis?
Number of cells in a specific stage of mitosis / total number of cells observed = mitotic index Mitotic index x time for one cycle
51
What chemicals did we use for the mitotic index practical? Why?
Ethanoic alcohol - fixative that preserves cell structure (prevents mitosis) Toluidine blue - Stains chromosomes so they are visible HCl - breaks down cells walls and separates the cells so they can be squashed
52
What are the phases of interphase called? and what happens
G1 S G2
53
What occurs in G1 of interphase
Cell growth New proteins are made Organelles replicate ATP production
54
What occurs in S phase of interphase?
Synthesis phase: DNA replicates
55
What occurs in G2 of interphase?
Cell growth Spindle proteins made ATP production
56
What occurs in M phase of the cell cycle?
Prophase Metaphase Anaphase Telephase
57
How do prokaryotic cells replicate?
Through binary fission
58
Describe the steps of binary fission?
1. Circular DNA (only once) and Plasmids replicate (can be multiple) 2. Circular DNA attaches to cell membrane and the cell elongates - DNA moves to opposite ends 3. Cell membrane begins to grow between the two DNA molecules, this divides the cytoplasm in two 4. New cell wall forms between the two DNA molecules and this divides the cell into two identical daughter cells
59
What is the difference between cell division in cancer and mitosis?
Mitosis = controlled Cancer = uncontrolled
60
How do mutations develop tumors?
Mutations in cell cycle genes, eg the gene that controls cell division lead to uncontrolled growth.
61
How do cancer treatments work? and why are they more likely to kill tumor cells than normal cells?
Try to limit the rate of cell division More likely to kill tumour cells as they replicate more frequently
62
What are phospholipids made from?
Hydrophobic hydrocarbon tail Hydrophilic phosphate head
63
Role of phospholipids in a cell membrane? x3
Allow lipid soluble substances to enter and leave the cell Prevent water soluble substances from entering and leaving the cell Makes the membrane flexible and self sealing
64
Role of proteins in a cell membrane? x5
Structural support Act as channels which transport water soluble substances across the membrane Allow transport through carrier proteins Act as receptors Act as enzymes
65
Function of cholesterol in cell membranes? x3
Reduce lateral movement of other molecules Makes the membrane less fluid at high temperatures Reduces water leakage and dissolved ions from the cell
66
How does cholesterol prevent water leakage in cell membranes?
They are very hydrophobic
67
Structure of a glycoprotein in a cell membrane?
Carbohydrate chain which is covalently bonded to a membrane protein
68
Function of glycoproteins in cell membranes? x3
Allows cells to recognise one another Helps cells to attach to one another and form tissues Acts as receptors
69
Functions of a glycolipid?
Allows cells to recognise one another Helps maintain the stability of a membrane Helps cells to attatch to one another and form tissues
70
2 properties a drug should have if they are to pass quickly through a membrane
lipid soluble uncharged small
71
Why is it called the fluid mosaic model?
Fluid: Phospholipid molecules move relative to one another which creates a flexible structure which is constantly changing shape. Mosaic: Proteins vary in shape and size
72
Why is the resolution higher on an electron microscope than an optical microscope?
Shorter wavelength between electrons in an an electron microscope than the wavelength of light in electron microscopes.
73
Define tumor?
Abnormal mass of cells that are undergoing uncontrolled mitotic division
74
How to prepare a root tip cell squash?
Heat acid in water bath Use a scalpel to cut 1cm from the tip of a growing root. Place in acid. Rinse and place root tip on a microscope slide and cut 2mm from the very tip. Discard the rest Use a mounted needle to break the tip and spread the cells thinly Add a few drops of stain which makes the chromosomes easier to see Place cover slip on top and press down firmly. This makes the tissue thinner allowing light to pass through.
75
76
Difference between DNA in chloroplasts and nucleus ?
DNA is longer in nucleus Not associated with histone proteins in the nucleus Fewer genes in chloroplasts Chloroplasts have circular not linear DNA No introns in chloroplast DNA

A Level Biology (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions