B2 - Cells and Control Flashcards
(73 cards)
1
Q
Define
chromosone.
A
a coiled up length of DNA molecules
2
Q
What is a
diploid cell?
A
a cell which has two copies of each chromosone
3
Q
What is
mitosis
used for? (2)
A
- growth in multicellular organisms
- replacing cells that have been damaged in multicellular organisms
4
Q
Define
asexual reproduction.
A
the use of mitosis to reproduce
5
Q
What are the
main stages of the cell cycle?
(6 stages)
A
International - Interphase
Propaganda - Prophase
Makes - Metaphase
Animals - Anaphase
Telecommunicate - Telophase
Cylently - Cytokinesis
6
Q
What occurs during
interphase?
(2 things)
A
- the cell grows and increases the amount of subcellular structures (e.g. mitochondria and ribosomes)
- the DNA is duplicated and forms X-shaped chromosones
each ‘arm’ (chromatid) of the chromosone is an exact duplicate of the other
7
Q
What are the
four stages of mitosis?
A
- Prophase
- Metaphase
- Anaphase
- Telophase
8
Q
What occurs during
prophase?
(2 things)
A
- the chromosones condense, getting shorter and fatter
- the membrane around the nucleus breaks down and the chromosones lie free in the cytoplasm
9
Q
What occurs during
metaphase?
(1 thing)
A
the chromosones line up at the centre of the cell
10
Q
What occurs during
anaphase?
(2 things)
A
- spindle fibres pull the chromosones apart
- the chromatids are pulled to opposite ends of the cell
11
Q
What occurs during
telophase?
(2 things)
A
- membranes form around each of the sets of chromosones
- cytokinesis occurs
these become the nuclei of the two new cells - the nucleus has divided
12
Q
What occurs during
cytokinesis?
A
the cytoplasm and cell membrane divide to form two separate cells
(this is part of telophase)
13
Q
What is produced at the end of
mitosis?
A
two genetically identical diploid daughter cells which are genetically identical to the parent cell
14
Q
What equation allows you to calculate
number of cells after multiple divisions of a cell by mitosis?
A
number of cells = 2^number of divisions
N = 2^n
15
Q
Define
growth.
A
an increase in size or mass
16
Q
Define
cell differentiation.
A
the process by which a cell changes to become specialised for its job
17
Q
What are the benefits of
specialised cells?
A
they allow multicellular organisms to work more efficiently
18
Q
Define
cell elongation.
A
the expansion of a plant cell, making the cell bigger and so making the plant grow
19
Q
How does
cancer occur?
(4 steps)
A
- The rate at which cells divide by mitosis is controlled by the chemical instructions (genes) in an organism’s DNA.
- If there’s a change in one of the genes that controls cell division, the cell may start dividing uncontrollably.
- This can result in a mass of abnormal cells called a tumour.
- If the tumour invades and destroys surrounding tissue it is called cancer.
20
Q
When might a doctor choose to investigate a baby’s size?
(4)
A
- if they are above the top percentile line
- if they are below the bottom percentile line
- if their size increases or decreases by two or more percentile lines over time
- if there’s an inconsistent pattern
21
Q
Define
stem cell.
A
an undifferentiated cell
22
Q
Where are
stem cells found in adults?
A
bone marrow
23
Q
What are the differences between
adult stem cells and embryonic stem cells?
(and why?)
A
adult stem cells aren’t as versatile, they can only produce certain cell types
this is because in adults, the stem cells are used to replaced damaged cells (e.g. to make new skin cells or blood cells)
24
Q
Where are
meristems found in plants?
and why?
A
in the areas of the plant that are growing (tips of the roots and shoots)
(this is because they are the only cells that divide by mitosis)
25
# What are the differences between
adult stem cells and meristems?
unlike human stem cells, the meristems produce **unspecialised cells** that can **divide** and **differentiate** into any type of cell **for as long as the plant lives**
26
# What are the
three main risks of stem cells in medicine?
- tumour development
- disease transmission
- rejection
27
# Describe the risk that
tumour development
| from stem cells poses.
Stem cells **divide** very **quickly**. If scientists are **unable to control the rate** at which the transplanted cells divide inside a patient, a **tumour** may develop.
28
# Describe the risk that
disease transmission
| from stem cells poses.
**Viruses** live inside cells. If donor stem cells are infected with a virus and isn't picked up, the virus could be **passed on** to the recipient and so make them **sicker**.
29
# Describe the risk that
rejection
| from stem cells poses.
If the transplanted cells aren't grown using the patient's own stem cells, the patient's body may recognise the cells as **foreign** and trigger an **immune response** to try to get rid of them. The patient can take **drugs** to **suppress** this response, but this makes them **susceptible** to **diseases**.
30
# What are the
ethical issues surrounding embryonic stem cell research?
| and what is the counter argument to this?
Some people argue that human embryo's **shouldn't** be used for experiments because each one is a **potential human life**.
## Footnote
Others think that the aim of **curing patients** who are **suffering** should be **more important** than the **potential life** of the embryos.
31
# What is the
spinal cord?
a long column of **neurones** (nerve cells) that run from the **base of the brain** down the **spine**.
32
# What does the
spinal cord
| do?
it **relays information** between the **brain** and the **rest of the body**
33
# What are the
three main parts of the brain?
| (that you need to know about)
- cerebrum
- cerebellum
- medulla oblongata
34
# What are some key points about the
cerebrum?
| (4 points)
- it is the **largest part** of the brain
- it is divided into two halves called **cerebral hemispheres**
- the **right hemisphere** controls **muscles** on the **left side** of the body (and vice versa)
- different parts of the cerebrum are responsible for different things
35
# What are some examples of things that the
cerebrum
| is responsible for?
## Footnote
(5)
- movement
- intelligence
- memory
- language
- vision
36
# What are some examples of things that the
cerebellum
| is responsible for?
## Footnote
(2)
- muscle coordination
- balance
37
# What are some examples of things that the
medulla oblongata
| is responsible for?
## Footnote
(2)
- breathing
- heart rate
| (unconscious activities)
38
# How does a
CT scan
| work?
it uses **x-rays** to produce an **image** of the brain
39
# What does a
CT scan show?
| (and what does it not show?)
it shows the **main structures** in the brain
| it doesn't show the functions of them
40
# How does a
PET scan
| work?
it uses **radioactive chemicals** to show which parts of the brain are **active** when the person is inside the scanner
41
# What does a
PET scan
| show?
it shows **both** the **structure** and the **function** of the brain in **real time**
| this is very detailed
## Footnote
it can also show if areas of the brain are **unusually inactive or active**, so they are useful for **studying disorders** that change the **brain's activity**
42
# What are the difficulties of
treating problems in the CNS?
| (3)
- it is **hard to repair damage** to the nervous system
- if a problem occurs in a part of the nervous system that's **not easy to access**, it can be hard to treat
- treatment for problems in the nervous system may lead to **permanent damage**
43
# What are
sensory receptors?
groups of **cells** that can detect a **change in your environment**
44
# Define
stimulus.
a change in the environment
45
# Define
reaction time.
the **time** it takes you to **respond** to a stimulus
46
# Describe how the
CNS coordinates a response.
| (to a stimulus) (5 steps)
1. A **stimulus** is detected by **receptors**.
2. This information is **converted** to a **nervous (electrical) impulse** and sent along **sensory neurones** to the **CNS**.
3. The CNS **coordinates** the response (impulses travel through the CNS along **relay neurones**).
4. The CNS send information to an **effector** (**muscle** or **gland**) along a **motor neurone**.
5. The effector then **responds** accordingly.
47
# What are some features of
all neurones?
| (2)
- a **cell body** with a **nucleus** (plus cytoplasm and other subcellular structures)
- the cell body has **extensions** that **connect to other neurones**
48
# What is the
structure of a sensory neurone?
| (and each part's purpose)
- one **long dendron** carries nerve impulses from **receptor cells** to the cell body, which is located in the **middle** of the neurone
- one **short axon** carries nerve impulses from the **cell body** to the **CNS**
| receptor cells > dendron ----> cell body --> axon
49
# What is the
structure of a motor neurone?
| (and each part's purpose)
- many **short dendrites** carry nerve impulses from the **CNS** to the **cell body**
- one **long axon** carries nerve impulses from the **cell body** to **effector cells**
| dendrites > cell body -> axon ----> effector cells
50
# What is the purpose of a
myelin sheath?
it acts as an **electrical insulator**, **speeding up** the electrical impulse
51
# What is the
structure of a relay neurone?
| (and each part's purpose)
- many **short dendrites** carry nerve impulses from **sensory neurones** to the **cell body**
- an **axon** carries nerve impulses from the **cell body** to **motor neurones**
| dendrites ---> cell body ----> axon
52
# Define
synapse.
the **connection** between **two neurones**
53
# What occurs at a
synapse?
| (3 steps)
1. The nerve impulse reaches the end of the neurone.
2. The nerve signal is transferred by chemicals called **neurotransmitters**, which **diffuse** across the gap.
3. The neurotransmitters then set off a **new electrical signal** in the **next** neurone,
## Footnote
The **transmission** of a nervous **impulse** is **very fast**, but it is **slowed down** a bit at the synapse because the **diffusion** of neurotransmitters across the gap takes **time**.
54
# Define
reflex.
| and state why it is helpful.
an automatic, rapid response to stimuli
| it can reduce the chances of being injured
55
# Define
reflex arc.
the passage of information in a reflex
| (from a receptor to effector)
56
# How does a
reflex work?
| (4 steps)
1. A **stimulus** is detected by receptors.
2. **Impulses** are sent along a **sensory neurone** to a **relay neurone** in the CNS.
3. The impulses then travel along the **motor neurone** to the **effector**.
4. The effector then causes the muscle or gland to respond.
57
# How does a
reflex protect the eye from bright light?
| (2 steps) and why?
1. **Light receptors** in the eye detect a very bright light and send a message along a **sensory neurone** to the brain.
2. The message then travels along a **relay neurone** to a **motor neurone**, which tells **circular muscles** in the **iris** to **contract**, making the pupil smaller.
| this is because **very bright light** can **damage** the eye
58
# What is the purpose of the
cornea?
to **refract** light into the eye
59
# What is the purpose of the
iris?
to control **how much light** enters the **pupil**
60
# What is the purpose of the
lens?
**refract light**, **focusing** it onto the **retina**
61
# What is the
retina?
the **light sensitive** part of the eye that is covered in receptor cells called **rods** and **cones**, which detect light
62
# What are
rods?
receptor cells that are more sensitive in **dim light** but **can't** sense colour
63
# What are
cones?
receptor cells that are sensitive to different **colours** but are not so good in dim light
64
# How does the information from the light get to the
brain?
The information from light is converted into **electrical impulses**. The **optic nerve** carries these impulses from the receptors to the **brain**.
65
# How does the eye focus light onto the retina to look at
distant objects?
| (2 steps)
1. The **ciliary muscle relaxes**, which allows the **suspensory ligaments** to **pull tight**.
2. This pulls the lens into a **less rounded shape** so light is refracted **less**.
66
# How does the eye focus light onto the retina to look at
close objects?
| (2 steps)
1. The **ciliary muscle contracts**, which **slackens** the **suspensory ligaments**.
2. The lens becomes a **more rounded shape** so light is refracted **more**.
67
# What is
long-sightedness?
| and why does this occur?
when people are **unable to focus** on **near** objects
## Footnote
This occurs when the **lens** is the wrong shape and doesn't **bend** the light enough or the **eyeball** is too **short**.
Light from near objects is brought into focus **behind** the **retina**.
68
# What type of lens fixes
long-sightedness?
a **convex lens**
69
# What is
short-sightedness?
| and why does this occur?
when people are **unable to focus** on **distant** objects
## Footnote
This occurs when the **lens** is the wrong shape and bends the light **too much** or the **eyeball** is too **long**.
Light from distant objects is brought into focus **in front** of the **retina**.
70
# What type of lens fixes
short-sightedness?
a concave lens
71
# What is
colour blindness?
When people **can't tell the difference** between **certain colours**.
## Footnote
The most common form of this is **red-green** colour blindness.
This occurs when red or green **cones** in the **retina** are **not working properly**.
There's **no cure** for colour blindness at the moment because the cone cells **can't** be **replaced**.
72
# What is a
cataract?
a **cloudy patch** on the **lens**, which stops light from being able to **enter the eye** normally
73
# What are the consequences of a
cataract?
| and how can this be treated?
the person might experience colours looking **less vivid** and have difficulty seeing in **bright light**
| replacing the faulty lens with an **artificial one**
