Chapter 1 Cells

Question 1

What is the formula for magnification?

Answer 1

Magnification=size of image/size of real object

Question 2

What are the advantages and disadvantages of light microscopes?

Answer 2

They are relatively cheap,can be used almost anywhere e.g. schools and can magnify live specimens.
Their magnification is not as high as an electron microscope.
Limited resolution

Question 3

What are the advantages and disadvantages of an electron microscope?

Answer 3

Advantages- they have a high magnification and high resolution
Transmission electron microscope allows you to see in 3D but has a lower magnification.

Disadvantages- very expensive,large and have to be kept in special temperature pressure and humidity controlled rooms.

Question 4

What is the nucleus?

Answer 4

The nucleus controls all the activities of the cell and is surrounded by the nuclear membrane. It contains the genes on the chromosomes that carry out instructions for making the proteins needed to build new cells or new organisms.

Question 5

The cytoplasm

Answer 5

A liquid gel in which the organelles are suspended and where most of the chemical reactions needed for life take place.

Question 6

Cell membrane

Answer 6

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

Question 7

Mitochondria

Answer 7

Structures in the cytoplasm where aerobic respiration takes place, releasing energy for the cell. They are very small.

Question 8

Ribosomes

Answer 8

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

Question 9

Algae

Answer 9

Algae are simple aquatic organisms. They make their own food by photosynthesis and have many similar features to plant cells.

Question 10

What do all plant and algal cells have?

Answer 10

They have a cell wall made of cellulose that strengthens the cell and gives it support.

Question 11

What are chloroplasts?

Answer 11

Chloroplasts are found in all the green parts of a plant. They are green because they contain the green substance chlorophyll. Chlorophyll absorbs light so the plant can make food by photosynthesis . Root cells do not have chloroplasts because they are underground and do not photosynthesise.

Question 12

A permanent vacuole

Answer 12

A permanent vacuole is a space inside the cytoplasm filled with cell sap. This is important for keeping the cells rigid to support the plant

Question 13

Eukaryotic cell

Answer 13

Eukaryotic cells all have a cell membrane, cytoplasm, and genetic material that is enclosed in the nucleus.

Question 14

Examples of an eukaryotic cell

Answer 14

Animal and plant cells

Question 15

What is genetic material?

Answer 15

Genetic material is a chemical called DNA and this forms structures called chromosomes that are contained within the nucleus.

Question 16

What do prokaryotic cells consist of?

Answer 16

Cytoplasm and cell membrane surrounded by a cell wall. The

Question 17

What is a prokaryotic cell

Answer 17

In prokaryote cells, the genetic material (DNA) is not enclosed in a nucleus.

Question 18

In prokaryotic cells where is the genetic material?

Answer 18

The bacterial chromosome is a single loop DNA loop found in the cytoplasm. They may also contain extra small rings of DNA

Question 19

Slime capsule

Answer 19

Some bacteria have a protective slime capsule around the outside of the cell wall.

Question 20

Flagellum

Answer 20

Some types of bacteria have at least one flagellum, that is a long protein strand that lashes about. These bacteria use their flagella to move themselves around.

Question 21

Nerve cells

Answer 21

They are specialised to carry electrical impulses around the body of an animal. They provide a rapid communication system between the different parts of the body.

Question 22

Nerve cells adaptations

Answer 22

.Lots of dendrites to make connections to other nerve cells

. An axon that carries the nerve impulse from one place to another.(very long; the longest axon in your body runs from the base of your spine to your big toe.)

. The nerve endings or synapses are adapted to pass the impulses to another cell or between a nerve cell and a muscle in the body using special transmitter chemicals they contain lots of mitochondria to provide the energy needed to make the transmitter chemicals.

Question 23

What is the job of a sperm cell?

Answer 23

To join with an ovum (egg cell). We call that process fertilisation.

Question 24

Muscle cell

Answer 24

They are specialised cells that can contract and relax to move the bones of the skeleton.

Question 25

Adaptations of striated muscle cells

Answer 25

. They contain special proteins that slide over each other making the fibres contract

. They contain many mitochondria to transfer the energy needed for the chemical reactions that take place as the cells contract and relax

.They can store glycogen, a chemical that can be broken down and used in cellular respiration by the mitochondria to transfer the energy needed for the fibres to contract.

Question 26

Sperm cells

Answer 26

They are usually released a long way from the egg they are going to fertilise. They contain the genetic information from the male parent.

Question 27

Sperm cell adaptions:

Answer 27

A long tail whips from side to side to help move the sperm through water or the female reproductive system

the middle section is full of mitochondria which transfer the energy needed for the tail to work

the acrosome stores the digestive enzymes for breaking down the outer layers of the egg

A large nucleus contains the genetic information to be passed on.

Question 28

Root hair cells

Answer 28

Root hair cells help the plant to take up water and mineral ions more efficiently

Question 29

Root hair cells adaptations:

Answer 29

They greatly increase the surface area available for water to love into the cell

They have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell.

They have many mitochondria that transfer the energy need for the active transport of mineral ions into the root hair cells

Question 30

Photosynthetic cells

Answer 30

Help to carry out photosynthesis

Question 31

Adaptations of photosynthetic cells:

Answer 31

They contain specialised green structures called chloroplasts containing chlorophyll that trap the light needed for photosynthesis

They are usually positioned in continuous layers in the leaves and outer layers of the stem of a plant so they can absorb as much light as possible.

They have a large permanent vacuole that helps keep the cell rigid asa result of osmosis. When lots of these rigid cells are arranged together to form photosynthetic tissue they help support the stem. They also keep the leaf spread out so it can capture as much light as possible.

Question 32

Xylem cells

Answer 32

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

Question 33

Xylem cells adaptations:

Answer 33

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, from one end of the plant to another.

The spirals and rings of lignin in the xylem cells make them very strong and help them withstand the pressure of water moving up the plant. They also help support the plant stem.

Question 34

Phloem cells

Answer 34

It is a specialised transport tissues that carries the food made by photosynthesis around the body of the plant.

Question 35

Adaptations of phloem cells:

Answer 35

The cell walls between the cells break down to form special sieve plates. These allow water carrying dissolved food to move freely up and down the tubes to where it is needed.

Phloem cells lose a lot of their natural internal structures but they are supported by companion cells that help to keep them alive. The mitochondria of the companion cells transfer the energy needed to move dissolved food up and down the plant in phloem.

Question 36

What is diffusion

Answer 36

It is the spreading out of particles of any substance. In solution or a gas, resulting in a net movement from and area of higher concentration to an area of lower concentration, down a concentration gradient.

Question 37

What is the rate of diffusion affected by?

Answer 37

It is affected by the difference in concentrations, the temperature, and the available surface area.

Question 38

What moves in and out of cells by diffusion?

Answer 38

Dissolved substances such as glucose and urea and gases such as oxygen and carbon dioxide move in and out of cells by diffusion.

Question 39

What is osmosis?

Answer 39

It is a special case of diffusion. It is the movement of water from a dilute to w more concentrated solution through a partially permeable membrane that allows water to pass through.

Question 40

Isotonic

Answer 40

If the concentration of solutes in the solution outside the cell is the same as the internal concentration, the solution is isotonic to the cell

Question 41

Hypertonic

Answer 41

If the concentration of solutes in the solution outside of the cell is higher than the internal concentration, the solution is hypertonic to the cell.

Question 42

Hypotonic

Answer 42

If the concentration of the solutes in the solution outside the cell is lower than the internal concentration, the solution is hypotonic to the cell.

Question 43

Osmosis in animals

Answer 43

Animal cells can be damaged if the concentration outside the cell changes dramatically.

Question 44

What is turgor?

Answer 44

When the pressure builds up until no more water can physically enter the cell. Turgor pressure makes the cells hard and rigid which in turn keeps the leaves and stems of the plant rigid and firm.

Question 45

Do plants need the fluid surrounding the cells to be hypotonic or hypertonic to the cytoplasm.

Answer 45

They need to be hypotonic. This keeps water moving by osmosis in the right direction and the cells are turgid.

Question 46

What happens if the solution surround the cell is hypertonic.

Answer 46

Water will leave the cell by osmosis. The cells will no longer be firm and swollen- they become flaccid-soft as there is no pressure on the cell walls.

Question 47

What happens if more water is lost by osmosis?

Answer 47

The vacuole and cytoplasm shrink, and eventually the cell membrane pulls away from the cell wall. This is plasmolysis.

Question 48

Active transport

Answer 48

It moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient)

Question 49

What does active transport use?

Answer 49

Active transport uses energy released from food in respiration to provide the energy required.

Question 50

What does active transport allow?

Answer 50

It allows plant root hairs to absorb mineral ions required for healthy growth from very dilute solutions in the soil against a concentration gradient.

Question 51

What does active transport enable?

Answer 51

Sugar molecules used for cell respiration to be absorbed from lower concentrations in the gut into the blood where the concentration of sugar is high.

Question 52

Adaptations for exchanging materials

Answer 52

Having a large surface area over which exchange can take place

Having a thin membrane or being thin to provide a short diffusion path

In animals having an efficient blood supply moves the diffusing substances away from the exchange surfaces and maintains a steep concentration (diffusion) gradient

In animals, being ventilated makes gas exchange more efficient by maintaining steep concentration gradients.

Question 53

Examples of adaptations

Answer 53

Alveoli

Stomata