Year 9 Biology, Topic 1

Question 1

What is a cell?

Answer 1

cells are the smallest living unit of organisms that carry out the 7 life processes. Organelles within a cell have particular functions. Larger structures like tissues and organs are made of cells.

Question 2

What are the 7 living processes?

Answer 2

Movement
Reproduction
Sensitivity- an awareness of changes in their environment.
Nutrition
Excretion
Respiration
Growth

Question 3

What is secretion

Answer 3

The production and release of a useful substance by a gland or cell; also, the substance produced. E.g. hormone secretion

Question 4

What are the 5 organelles within an animal cell?

Answer 4

Nucleus, mitochondrion(singular), ribosomes, cytoplasm, plasma cell membrane.

Question 5

What are the organelles in a plant cell? (8)

Answer 5

Sap vacuole, cellulose cell wall, chloroplast, plasma cell membrane, cytoplasm, ribosomes, mitochondrion, nucleus.

Not in spec: starch grain (respiration without sunlight), vesicles,

Question 6

What are the features of a bacteria cell? (6)

Answer 6

Chromosomal DNA
Ribosomes (smaller)
Cell membrane
Plasmid DNA
Flagellum
Flexible cell wall

Question 7

Give 4 examples of specialist plant cells:

Answer 7

Palisade cell: tall and thin, packed together closely under the upper surface of the leaf. Many chloroplast for photosynthesis
Guard cells: surround the stomata(holes) on the lower surface of the leaf. They open and close to control Gad exchange in the leaf and reduce water loss.
Xylem vessels: transport water to the leaf and strengthen the stem. No organelles or cytoplasm, only the cell wall which is strengthened by rings to hold them open. The wall is waterproof by a chemical called lignin.
Root hair cells: long thin projections called root hairs provide a large surface area to absorb water and minerals from the soil. They do not have chloroplasts or photosynthesis because they are underground.

Question 8

How are the tissues of a leaf adapted?

Answer 8

1.photosynthesis-palisade cells contain many chloroplasts
2.Gas exchange- guard cells control gas exchange and limit water loss
3.and transporting water and sugars(phloem cells).

Leaves are adapted to perform photosynthesis by having a large surface area to absorb sunlight. Light provides energy for the synthesis of glucose from carbon dioxide and water during photosynthesis.

Question 9

What is the main organ of photosynthesis in a plant? What is the equation for photosynthesis

Answer 9

Leaf
The word equation for photosynthesis in the presence of light and chlorophyll is:
Carbon dioxide + water → glucose + oxygen

During photosynthesis, plants make sugars that they use for energy and to make cellulose and starch. (Polymers of glucose)

Question 10

How are sperm cells adapted to their function

Answer 10

1. A long tail for movement so it can swim to the egg
2. The tip of the head contains the acrosome(a small vacuole) which contains enzymes to penetrate the egg cell.
3. Lots of Mitochondria in the middle section for respiration, in order to provide energy for swimming.
4. A haploid nucleus so the offspring will have the right no. Chromosomes when the egg is fertilised.

Question 11

How is a plant cell wall related to its function?

Answer 11

Cellulose cell wall:
Cellulose is a natural polymer made of glucose( a product of photosynthesis) and is the main component found in plant cell walls.This gives the plant cell strength and support.

Question 12

How is a sap vacuole related to its function?

Answer 12

Sap vacuole stores water and minerals, if helps keep the cell turgid to support the plant.

Question 13

What is a starch grain in a plant for?

Answer 13

Sugars are turned into starch and stored here

Question 14

What are the functions of chloroplasts?

Answer 14

Filled with a green chemical, chlorophyll, which absorbs light energy to power photosynthesis.

Question 15

What is the function of plasma membrane?

Answer 15

The plasma membrane controls the entry and exit of substances. In its surface are receptor proteins that detect chemicals such as hormones and send a signal across the membrane which causes the cell to respond.
Osmosis occurs across semi permeable membranes; these have small holes (pores) that allow small soluble molecules to pass through like water.

Question 16

Function of mitochondrion:

Answer 16

Where aerobic respiration happens. It provides chemical energy to power the cell. Sperm cells have lots of mitochondria for swimming

Question 17

Function of cytoplasm:

Answer 17

Cytoplasm is the jelly where most chemical reactions happen. It’s made mostly of water, proteins and minerals

Question 18

Function of the nucleus:

Answer 18

The nucleus contains DNA which is a very long acid that encodes genetic information. It is duplicated before cell division and bundled into chromosomes.

Question 19

Function of ribosomes:

Answer 19

Ribosomes synthesise proteins from amino acids. Some of the proteins are used to repair organelles abs make the cell larger before cell division, others are secreted.

Question 20

Function of vesicles:

Answer 20

Vesicles are small bags that move substances around the cell. In secretion, vesicles move to the plasma membrane where they burst, releasing useful substances into the blood.

Question 21

What is chromosomal DNA

Answer 21

(One long circular DNA molecule) - controls the cells activities and replication.

Question 22

What is a plasmid

Answer 22

Small loops (circular molecules) containing a small proportion of the bacterium’s DNA that aren’t part of the chromosome.

Unlike the chromosomal DNA, plasmid DNA can move from one bacterium to another giving variation.

Question 23

What is the function of a flagellum?

Answer 23

Plural=flagella
Long structure that rotated to make the bacterium move.

Extra:)Used to move them away from harmful substances and toward beneficial things like nutrients or oxygen

Question 24

How is an egg cell specialised for reproduction?

Answer 24

1. Cytoplasm contains nutrients to feed the embryo
2. Haploid nucleus so the offspring have the right number of chromosomes when the egg is fertilised by a sperm cell.
3. After its fertilised by 1 sperm, the membrane hardens to stop any more sperm penetrating. To ensure the offspring has the right no. Chromorosmes.

Question 25

Adaptions of ciliated epithelial cells:

Answer 25

General function: Beating cilia move substances

E.g (Lining of the airways contains lots of ciliated epithelial cells)
Cilia on the surface beat to move fluids and particles up the trachea so it doesn’t reach the lungs

Question 26

What is cell elongation?

Answer 26

When something gets longer(such as a cell in a plant root or shoot before it differentiates into a specialised cell)
Plant growth, NOT ANIMAL growth

Question 27

Define an enzyme

Answer 27

Enzymes are proteins that act as biological catalysts which means they are produced by living things and speed up reactions (synthesis and breakdown of substances). They do not get used up in reactions

Question 28

What is enzyme denaturation?

Answer 28

When a change in conditions(pH or temperature) changes the shape of an enzymes active site, by breaking the bonds between the amino acids, so it can no longer catalyse reactions

Question 29

What is (enzyme) activation energy ?

Answer 29

The minimum amount of energy particles must have to be able to react
Enzymes lower activation energy

Question 30

Define lock and key model:

Answer 30

Model that describes the way an enzyme catalysed a reaction when the substrate fits within the active site of an enzyme

Question 31

Define an active site:

Answer 31

The space in an enzyme where the substrate fits during an enzyme-catalysed reaction

Question 32

Optimum pH:

Answer 32

The pH at which an enzyme-catalysed reaction works fastest

Question 33

Optimum temperature

Answer 33

The temperature at which an enzyme-catalysed reaction works fastest

Question 34

Define substrate:

Answer 34

A substance that is changed during an enzyme-controlled reaction.

Question 35

Why does an increase in temperature increase the rate of reaction (enzyme)?

Answer 35

The molecules move faster due to increased kinetic energy, and therefore the substrate and enzyme collide with more often. This means the rate at which the product is formed will increase.

Question 36

How does an increase in temperature (beyond optimum) affect the shape of the active site?

Answer 36

The bonds holding the enzyme in shape break, and the active site changes shape so it can no longer accomodate the substrate. Denatured.

Question 37

What is a microscope?

Answer 37

Microscopes are instruments that produce a magnified image of an object

Question 38

Hypertonic
Hypotonic
Isotonic

Answer 38

Hypertonic: a solution with a higher concentration of salt
Hypotonic: a solution with a lower concentration of salt (more water)
Isotonic: a solution with the same concentration of salt

Question 39

What is the nutritional function of an enzyme?

Answer 39

Catalysing the synthesis and breakdown of substances, such as carbohydrates, proteins and loped but speeding up the rate of reaction

Question 40

Why are enzymes important for life processes

Answer 40

Because reactions happen much faster 👍🏽

Question 41

Affect of pH, temperature and substrate concentration:

Answer 41

pH- Changes in pH also alter the shape of an enzyme’s active site. Each enzyme work bests at a specific pH value (optimum)
Temperature- kinetic energy causes collisions between the substrate molecule and enzyme, extreme change in temp can break the bonds that hold the shape of the active site->denaturation
Substrate concentration -> high concentration means the active sites are often full, low concentrations means active sites are often empty.

Question 42

Calculating percentage change in mass (osmosis)

Answer 42

%change= (final mass-initial mass)/ initial mass *100

Question 43

Effect of substrate concentration on enzyme activity

Answer 43

Substrate concentration -> high concentration means the active sites are often full, low concentrations means active sites are often empty. A continued increase in substrate concentration results in the same activity as there are not enough enzyme molecules available to break down the excess substrate molecules.

Question 44

How is the cell wall of a bacteria related to its function?

Answer 44

Flexible, bacterial cell walls provide structure and protection.

Question 45

Give 7 differences between prokaryotic and eukaryotic (plant or animal) cells:

Answer 45

Prokaryotic cells have no mitochondria
Prokaryotic cells have no chloroplasts
Prokaryotic cells have no nucleus
Prokaryotic cells do not divide by mitosis
Prokaryotic cells have flagella
Cell walls are not made of cellulose