Topic 1-Cell Biology

Question 1

What parts of an animal cell is there? What functions do they have?

Answer 1

Nucleus- contains genetic material that controls the activities of the cell. (Contains DNA)
Cytoplasm- gel like substance where most chemical reactions happen.
Cell membrane- holds the cell together and controls what goes in and out.
Mitochondria- where most reactions for aerobic respiration takes place.
Ribosomes- where proteins are made in the cell (protein synthesis).

Question 2

What is only present in a plant cell? What is there function?

Answer 2

Cell wall- made of cellulose. Supports and strengthens the cell.
Permanent vacuole- contains cell sap (a weak solution of sugar and salts)
Chloroplasts- where photosynthesis occurs. Contain a green substance called chlorophyll which absorbs light needed for photosynthesis.

Question 3

What do bacteria cells have?

Answer 3

Cytoplasm 
Cell membrane 
Cell wall
A circular strand of free floating DNA 
Plasmids

Question 4

Light microscopes Vs. Electron microscopes

Answer 4

Light microscopes- use light and lenses to form an image that’s magnified (allows us to see individual cells and large sub cellular structures).
Electron microscopes- use electrons and have a higher magnification, a higher resolution and allow us to see smaller things in more detail.

Question 5

Magnification equation

Answer 5

Magnification= image size
—————-
actual size

Question 6

What is differentiation?

Answer 6

Differentiation is the process by which a cell changes to become specialised to its job.

Question 7

What are sperm cells specialised for and how?

Answer 7

Sperm cells are specialised for reproduction.
Long tail and streamlined head- to help it swim to the egg.
Lots of mitochondria- provides energy that the cell needs.
Carries enzymes- the help digest through the egg cell membrane.

Question 8

What are nerve cells specialised for and how?

Answer 8

Nerve cells are specialised for rapid signalling.
Long- the cover more distance.
Branched connections- to form a network throughout the full body.

Question 9

What are muscle cells specialised for and how?

Answer 9

Muscles cells are specialised for contraction.
Long- space to contract
Lots of mitochondria- generate energy needed for contracting.

Question 10

What are root hair cells specialised for and how?

Answer 10

Root hair cells are specialised for absorbing water and minerals.
Grow long hairs- stick into the ground to give it a large surface area.
Big surface area- absorb water and minerals from the soil.

Question 11

What are phloem and xylem cells specialised for and how?

Answer 11

They’re specialised for transporting substances.
Xylem cells are hollow
Phloem cells have very few sub cellular structures.
So stuff can flow through them.

Question 12

What is the cell cycle?

Answer 12

Growth and DNA replication, mitosis

Question 13

What are stem cells?

Answer 13

Stem cells are undifferentiated cells. They can divide to create more and they can differentiate into different types of cells, depending on what instructions they’re given.

Question 14

Where can stem cells be found?

Answer 14

In human embryos
In adult bone marrow
In meristems of plants

Question 15

How can stem cells be used to treat disease?

Answer 15

Stem cells can be extracted from the bone marrow of a healthy person to replace faulty blood cells in another patient.
Embryonic stem cells can replace faulty cells in sick people.

Question 16

In what type of cloning could an embryo be made to have the same genetic material as a patient? Why’s this a benefit?

Answer 16

Therapeutic cloning, means the cells won’t be rejected by the body.

Question 17

Why people may be against stem cell research?

Answer 17

Human embryos shouldn’t be used for experiments since each one is a potential human life.
Others think that curing existing patients is more important than the use of embryos.
Embryos used are usually unwanted ones from fertility clinics.
In some countries stem cell research is banned, it’s allowed in the UK but by using strict guidelines.

Question 18

What is diffusion?

Answer 18

Diffusion is the spreading out of particles from an area of high concentration to an area of low concentration.

It happens in both gases and solutions

Question 19

What effects the rate of diffusion?

Answer 19

The bigger the concentration gradient the faster the rate of diffusion.
The higher the temperature the faster the rate of diffusion as the particles have more energy.

Question 20

What is osmosis?

Answer 20

Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.

Question 21

What is active transport?

Answer 21

When substances are absorbed against a concentration gradient (from a lower to higher concentration).

Question 22

Examples of where active transport is used.

Answer 22

Root hair cells taking in minerals and water to get minerals from the soil into the plant cell.
Used in the stomach to get nutrients from the blood into the stomach.

Question 23

How alveoli are adapted to maximise diffusion?

Answer 23

An large surface area
A moist lining for dissolving gases
Very thin walls
A good blood supply

Question 24

What are the villi and how are they adapted?

Answer 24

Villi are found in the small intestine.
They increase surface area so digested food is absorbed a lot faster into the blood.
A single layer of surface cells
A very good blood supply- assist quick absorption

Question 25

The structure of a leaf and how it help gases diffuse in and out

Answer 25

Carbon dioxide diffuses into the air spaces, then it diffuses into the cell for photosynthesis.
Carbon dioxide diffuses in via the stomata. The size of the stomata are controlled by guard cells.
Oxygen and water vapour diffuse out as they’re products of photosynthesis.
The flattened shape- increases the area of the exchange surface.
Close the stomata if too much water is being lost then the roots replace the water.

Question 26

Why gills have a large surface area for gas exchange?

Answer 26

Water enters the fish via its mouth and passes through the gills. Oxygen also diffuses from the water into the blood in the gills and carbon dioxide diffuses from the blood into the water.
Each gill has gill filaments which give a large surface area.
The filaments are covered in lamellae- increase surface area also gives a good blood supply which increases the rate of diffusion.
Thin surface layer- minimises the distance that gases diffuse across
Large concentration gradient between blood and water.