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Biology Gcse > Topic 1 - Cell Biology > Flashcards

Topic 1 - Cell Biology Flashcards

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1
Q

Main structures in an animal cell

A 
Cytoplasm
Cell membrane
Nucleus
Mitochondria
Ribosomes
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2
Q

The nucleus

A

Contains genetic material that controls the activities of the cell

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3
Q

Cell membrane

A

Controls the passage of substances such as glucose and mineral ions into the cell and the movement of substances such as urea and hormones out of the cell

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4
Q

Cytoplasm

A

A liquid gel in which the organelles are suspended and where most of the chemical reactions needed for life take place - contains the enzymes that control these chemical reactions

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5
Q

Mitochondria

A

Where aerobic respiration takes place and where energy is released for the cell

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6
Q

Ribosomes

A

Where protein synthesis takes place, making all the proteins needed in the cell

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7
Q

3 extra features in a plant cell

A

Vacuole
Cell wall
Chloroplasts

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8
Q

Chloroplasts

A

Contain green pigment chlorophyll, absorbs sunlight so that the plant can make food by photosynthesis

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9
Q

Vacuole

A

Space in the cytoplasm filled with cell sap which keeps the cells rigid

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10
Q

Cell wall

A

Made of cellulose- strengthens and supports the cell

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11
Q

Eukaryotic cells

A

Plant and animal cells

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12
Q

Prokaryotic cells

A

Bacteria - single celled living organisms
Cell wall does not contain cellulose
No nucleus - dna is a single loop in the cytoplasm
May contain plasmids which are small rings of dna - they code for very specific features like antibiotic resistance
Some have a protective slime capsule
Some have a flagellum

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13
Q

What is a flagellum

A

A long protein strand that lashes about - bacteria use their flagellum to move themselves around

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14
Q

What is cell differentiation

A

As an organism develops, cells differentiate to form different types of specialised cells.
Animal cells- differentiate at an early stage of development
Plant cells - often retain the ability to differentiate throughout life
As a cell differentiates it gets different sub-cellular structures that enables it to carry out a particular function
It becomes specialised

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15
Q

Nerve cells function

A

Carry electrical impulses round the body of an animal.

Provide a rapid communication system between the different parts of the body

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16
Q

Nerve cells adaptations (3)

A

Lots of dendrites to make connections with other cells
An axon that carries the nerve impulse from one place to another which can be very long
Synapses that can pass the impulses to another cell using special transmitter chemicals - they contain lots of mitochondria to provide energy for making the chemicals

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17
Q

Muscle cell functions

A

To contract and relax

Striated muscle cells work together in tissues called muscles

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18
Q

Muscle cell adaptations (3)

A

They contain special proteins that slide over each other making the fibres contract
Contain many mitochondria to transfer the energy needed for the chemical reactions that take place as cells contract and relax
Store glycogen which can be broken down to use in cellular respiration

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19
Q

Sperm cell functions

A

Travel to and fertilise the egg cell

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20
Q

Sperm cell adaptations (4)

A

A long tail to move the cell
The middle section is full of mitochondria to release energy for the movement of the tail
The acrosome stores digestive enzymes for breaking down the outer layers of the egg
A large nucleus containing the DNA to be passed on

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21
Q

Root hair cell function

A

Absorb water (via osmosis) and dissolved mineral ions (via active transport) from the soil for the plant

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22
Q

Root hair cell adaptations (3)

A

Greatly increase the surface area available for water to move into the cell
Have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell
They have lots of mitochondria that transfer the energy needed for the active transfer of mineral ions into root hair cells

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23
Q

Photosynthetic cells

A

Make their own food bus photosynthesis

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24
Q

Photosynthetic cell adaptations (3)

A

They contain chloroplasts containing chlorophyll that absorb sunlight needed for photosynthesis
Usually positioned in continuous layers in the leaves and outer layers of the stem of a plant so they absorb as much light as possible
They have a large permanent vacuole that helps keep the cell rigid and help support the cell

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25
Q

Xylem cell function

A

A transport tissue in plants that carries water and mineral ions from the roots to the highest leaves and shoots. Also important in supporting the plant

26
Q

Xylem cell functions (2)

A

The xylem cells are alive when they are first formed but a special chemical called lignin builds up in spirals in the cell walls. The cells die and form long hollow tubes that allow water and mineral ions to move easily through them
The pirates of lignin in the xylem cells make them very strong and help them withstand the pressure of water moving up the plant and support the stem

27
Q

Phloem cell functions

A

Transport tissue that carries food made by photosynthesis around the body of the plant
Made up of cells that form tubes like xylem cells but they do not become lignified and die. The dissolved food can move up and down the phloem tubes to where it is needed

28
Q

Phloem cell adaptions (2)

A

The cell walls between the cells break down to form special sieve plates which allow water carrying dissolved food to move freely up and down the tubes to where it is needed
Phloem cells are supported by companion cells which have mitochondria that transfer the merely needed to move dissolved food up and down the phloem

29
Q

What is diffusion

A

The spreading out of the particles of a gas or any solute resulting in the net movement of particles from an area of higher concentration to an area of lower concentration

30
Q

Rates of diffusion

A

The greater the difference in concentration, the faster the rate of diffusion
Diffusion occurs down a concentration gradient
An increase in temperature makes diffusion take place more rapidly as the particles move quicker

31
Q

What dissolved substances move in and out of your cells via diffusion?

A 
Simple sugars (glucose)
Gases (oxygen and carbon dioxide)
Waste products (urea)
32
Q

Diffusion of oxygen + co2 in the body

A

Oxygen needed for respiration passes from air in the lungs to your red blood cells through cell membranes via diffusion
Then diffuses from red blood cells to cells in the body where it is needed
Carbon dioxide diffuses from body cells to red blood cells to the air in the lungs (the opposite way to oxygen - known as gas exchange)

33
Q

How might individual cells be adapted to make diffusion easier and more rapid?

A

By increasing the surface area of the cell membrane (ie. folding up the cell membrane of a cell)

34
Q

What is osmosis

A

The moment of water from an area of higher concentration to an area of lower concentration across a partially permeable membrane

35
Q

What is an isotonic solution

A

If the concentration of solution outside the cell is the same as the internal concentration

36
Q

What is a hypertonic solution

A

If the concentration of solutes in the solution outside the cell is higher than the internal concentration

37
Q

What is a hypotonic solution

A

If the concentration of solutes in the solution outside the cell is lower than the internal concentration

38
Q

Osmosis in animals

A

If outside is much more dilute, water will move in and may cause the cell to burst
If outside is much more concentrated, water will move out and cause the cell to shrivel up and no longer survive
Therefore internal water balance must remain constant

39
Q

Osmosis in plants

A

Water moves into plant cells by osmosis. This causes the vacuole to swell which presses the cytoplasm against the cell wall
Pressure builds up until no more water can enter the cell (turgor)
Turgor pressure makes the cells hard and rigid keeping the stem and leaves of the plant firm

40
Q

Why must the fluid surrounding plant cells always need to be hypotonic to the cytoplasm, with a lower concentration of solutes and a higher concentration of water?

A

This keeps water moving in by osmosis and the cells remain turgid.
If the surroundings are hypertonic water will leave and there will be no pressure on the cell walls so they come flaccid and the plant wilts
If more water is lost then the vacuole and cytoplasm shrink and the cell membrane pulls away from the cell wall. This is called plasmolysis

41
Q

What is active transport

A

The movement of substances against a concentration gradient across a partially permeable membrane
Energy is needed from respiration

42
Q

Active transport in root hair cells

A

The conc of mineral ions inside the cell is higher than the conc in the soil but the cell needs to absorb mineral ions for healthy growth so the mineral ions move into the cell via active transport

43
Q

Active transport in the gut

A

Sometimes there’s a lower conc of glucose and amino acids in the gut than the blood but active transport allows nutrients to be taken into the blood against the concentration gradient and transported to cells for respiration

44
Q

Gas exchange in the lungs

A

The lungs contain millions of alveoli where gas exchange takes place.
The alveoli are specialised for diffusion because they have a large surface area, a moist lining for dissolving gases, very thin walls, and a good blood supply

45
Q

exchange in the small intestine

A

The inside of the small intestine is covered in millions and millions of villi
They increase the surface area so that digested food is absorbed much quicker into the blood
They have a single layer of surface cells and a very good blood supply to assist quick absorption

46
Q

Gases exchange in leaves

A

Co2 diffuses I tot he air spaces in the leaf, then it diffuses into the cells where photosynthesis happens
The underneath of the leaf is an exchange surface, it is covered in stomata which co2 diffuses in through
Oxygen and water vapour diffuse out of the stomata
The stomata are controlled by guard cells, these close the stomata is water is being lost too quickly
The flattened shape of the leave creates a bigger surface area making this more effective

47
Q

Gas exchange in fish

A

Gas exchange happens in the gills
Water (containing oxygen) enters the fish through its mouth and passes through the gills
Oxygen then diffuses from the water into the blood in the gills and co2 diffuses from the blood to the water

48
Q

Adaptations of gills for gas exchange

A

Each Gill has lots of Gill filaments which give a large surface area for gas exchange
Gill filaments are covers in lamellae which increase the surface area even more
The lamellae have lots of blood capillaries to speed up diffusion
They also have a thin surface layer of cells to minimise the distance that the gases have to diffuse
Large concentration gradient between water and blood
Conc of oxygen is always much higher in the water than in the blood so as much as possible can diffuse

49
Q

What are stem cells

A

Undifferentiated cells that can divide to produce lots more undifferentiated cells

50
Q

Where are stem cells found

A

In early human embryos - can differentiate into any cell

In an adults bone marrow - can only change into certain types of cell

51
Q

How can stem cells be used to cure disease

A

Embryonic stem cells can be used to replace faulty cells in sick people - you could make insulin producing cells for people with diabetes or nerve cells for people with spinal injuries
Therapeutic cloning can make an embryo have the same genetic information as a patient and therefore the stem cells produced from it would have the same genes and wouldn’t be rejected by the patients body
Stem cells are transferred from the bone marrow of a healthy person to replace the faulty cells of the patient who receives them

52
Q

Risks of stem cells

A

Embryonic stem cells divide and grow rapidly and so there is some concern that they might cause cancer if used to treat people
Also stem cells might be infected with viruses and so could transfer the infections to patients, and immune response could be triggered in the patient and they may need to take an immunosuppressant drug to stop their body rejecting the new cells

53
Q

Ethical problems with stem cell research

A

Every human embryo is a potential human life
However people think that curing living patients is more important than the rights of embryos
Embryos used in research are often unwanted ones from fertility clinics (aborted or donated)
In some countries it is banned, people think a lot of time and money is being wasted and scientists should concentrate on finding and developing different sources of stem cells

54
Q

What are chromosomes

A

Coiled up lengths of DNA molecules found in the nucleus of a cell
Each chromosome carried a large number of genes - different genes control the development of different characteristics
Body cells have 2 copies of each chromosome (one from mum and one from dad)
23 pairs in the nucleus of a body cell

55
Q

What is the cell cycle

A

A series of stages in which body cells in multicellular organisms divide to produce new cells

56
Q

What does mitosis do

A

Produces additional cells needed for growth and development in multicellular organisms, and for the replacement worn out or damaged cells

57
Q

Stage one of the cell cycle

A

The cell grows bigger, increases in mass, and carries out normal cell activities. Most importantly they replicate their DNA to form two copies of each chromosome ready for cell division. They also increase the number of sub-cellular structures such as mitochondria and ribosomes
X-shaped chromosomes are formed (each arm is the exact duplicate of the other)

58
Q

Stage 2 of the cell cycle (mitosis)

A

The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell
Membranes form around each new set of chromosomes - these become the nuclei of the two new cells
Then the cytoplasm and cell membrane divide so that the cell now have 2 new daughter cells
The daughter cells are identical to the parent cell

59
Q

What is a gene

A

A small packet of information that controls a characteristic- a section of dna

60
Q

DNA

A

The unique molecule that makes up your chromosomes

61
Q

Binary fission

A

How prokaryotic cells replicate
A circular DNA and plasmids replicate
The cell gets bigger and the circular DNA strands move to opposite poles (ends of the cell)
The cytoplasm begins to divide and new cell walls begin to form
The cytoplasm divides and two daughter cells are produced
Each daughter cell has one copy of circular dna but can have a variable number of copies of plasmids

62
Q

What is the mean division time

A

The average amount of time it takes for one bacterial cell to divide into two

Biology Gcse (4 decks)

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