Biology- Cells for January 2023 Test

What parts are found in an animal cell?

Cell membrane, cytoplasm, nucleus, ribosmomes and mitochondria

What parts are found in a plant cell?

Chloroplasts, permanent vacuole, cell wall, cell membrane, mitochondria, nucleus, ribosomes and cytoplasm

What is the function of the cell membrane?

To alllow substances to go in and out of the cell. It has small holes meaning it’s permeable.

What is the function of the cytoplasm?

Where chemical reactions occur.

What is the function of the nucleus?

Contains genetic information and controls the activities of the cell.

What is the function of the ribosomes?

Where protein synthesis is created.

What is the function of the mitochondria?

Site of aerobic respiration, which releases energy for the cell.

What is the function of the cell wall?

Strengthens and supports the plant cell.

What is the function of the chloroplasts?

Where photosynthesis takes place- contains chlorophyll for it.

What are three parts found in both animal and plant cells?

The cell membrane, nucleus and the cytoplasm

What are two differences between prokaryotic and eukaryotic cells?

Prokaryotes are unicellular whereas eukaroytes are multicellular. The DNA of eukaryotes is stored in the nucleus whereas the DNA of prokaryotes is stored in the cytoplasm.

How are muscle cells adapted to their function?

They have many mitochondria to provide them with energy for contraction.

How are nerve cells adapted to their function?

They have a long axon to move the impulse from one part of the body to another.

How are sperm cells adapted to their function?

They have many mitochondria to provide the energy needed for them to swim.

How are xylem adapted to their function?

They have no cytoplasm or end walls so they can form a straight tube allowing water transport.

How are phloem adapted to their function?

They contain sieve tubes which have no nuclei so allow the sugars to transport.

How are root hair cells adapted for their function?

They have a hair-like structure which increases the surface area allowing them to absorb water from the soil.

What is meant by cell differentiation?

The process where young cells take on individual characteristics to reach their specialised form and function.

What is the function of mitosis?

Growth and to replace worn out cells.

Describe the different stages of mitosis

1. The chromosomes pair up
2. The chromosomes line up at the equator
3. The sister chromatids are pulled apart
4. The cell pinches in the middle
5. Two identical daughter cells are produced

What is a stem cell?

Specialised cells produced by the bone marrow

Explain the difference between embryonic and adult stem cells, including the advantages and disadvantages of each.

Stem cells are cells in animals that can continuously undergo cell division. Embryos are made from embryonic stem cells which can develop into any cell type. Adult stem cells are found only in specific areas of the body and can only develop into a limited number of cell types.

Describe what is meant by therapeutic cloning

Therapeutic cloning is the transfer of nuclear material isolated from a somatic cell into an enucleated oocyte in the goal of deriving embryonic cell lines with the same genome as the nuclear donor.

Describe where stem cells are found in plants

Plant stem cells are innately undifferentiated cells present in the meristematic tissues, providing them vitality and a steady supply of precursor cells which later differentiate into various parts or tissues.

Give two uses of stem cells in plants

1. Producing clones quickly and cheaply
2. Growing and replacing specialised tissues

Define the term magnification

Magnification is the ability to make small objects seem larger.

Define the term resolution

Resolution is the ability to distinguish two objects from each other.

Explain the benefits of using an electron microscope

They have a much higher resolution and magnification than light microscopes.

What part of a micrscope would you use to make an image bigger?

Objective lens

What part of a microscope would you use to make an image clearer?

Condenser lens

What two parts of a microscope do you use to calculate magnification?

1. Eyepiece lens
2. Objective lens

What is the formula to calculate magnification?

Image size / actual size

What is the formula to calculate actual size?

Image size / magnification

What is the definition of diffusion?

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

Describe what is meant by a concentration gradient

A concentration gradient occurs when the concentration of particles is higher in one area than another.

Describe how a concentration gradient affects the rate of diffusion

The greater the difference in concentration, the quicker the rate of diffusion.

Describe how temperature affects the rate of diffusion

The higher the temperature, the more kinetic energy the particles will have, so they will mix and move more quickly.

Describe how surface area affects the rate of diffusion

The greater the surface area, the faster the rate of diffusion.

Why do single celled organisms have no need of a transportation system?

They have no need of a transportation system because they have a higher surface area to volume ratio enabling substances to move across the cell membrane.

What are the four ways that alveoli are adapted to exchange materials with blood?

1. They have a large surface area allowing faster substance diffusion across the surface
2. They have thin walls ensuring short diffusion gradients
3. They have good air ventilation so that diffusion gradients can be maintained
4. They have a good blood supply to maintain a high concentration gradient which speeds up the rate of diffusion

What is osmosis?

Osmosis is the movement of water molecules from a solution with a high concentration of water molecules to a solution with a lower concentration of water molecules through a partially permeable membrane.

A carrot was placed in a dilute solution. What will happen to its mass?

The water will move into the carrot via osmosis because the water moves from a lower solute concentration to a higher solute concentration.

The carrot was placed in 0.4 mol/dm 3 solution. Its mass did not change. Explain why this happened.

This happened because the solution outside had less water molecules than the carrot inside??

A carrot was placed in a concentrated solution. What will happen to its mass?

If a cell is placed in a hypertonic solution, water will leave the cell, and the cell will shrink.

What formula is used to calculate the percentage change in mass?

Final mass - initial mass

Why is percentage used instead of change of mass?

To show how big the change was, relative to the existing mass.

What is active transport?

The process of moving molecules across a cellular membrane through the use of cellular energy.

Describe how root hair cells use active transport

They have carrier proteins in their cell membranes that pick up mineral ions which move them across the membrane into the cell against a concentration gradient.

Explain why cells performing active transport require lots of energy

It needs lots of energy because it’s not a passive transport and molecules need to move against a concentration gradient.

What material makes up the cell wall of plants?

Cellulose

What are the 2 types of microscopes?

Light and electron microscopes

What are 2 advantages of using a light microscope?

1. They are small
2. They are lightweight

What are 2 disadvantages of using a light microscope?

1. They don’t have as high a magnification as electron microscopes
2. They don’t have as high a resolution as electron microscopes

What does the term ‘resolution’ mean?

The ability of a microscope to distinguish detail.

What is the difference between resolution and magnification?

Resolution is the ability to distinguish two objects from each other and magnification is the ability to make smaller objects appear larger.

What is the formula for image size?

Actual size x magnification

What is a graticule?

An eyepiece piece used to measure the size of an object when viewed under a microscope.

What is the method used for preparing a plant cell to look under a microscope?

The cell is stained using iodine and a glass coverslip is placed over it.

What is the method used for preparing an animal cell to look under a microscope?

Cell staining

How has electron microscopy increased our understanding of cells?

They have helped to close the gap between optical microscopy of cell architecture and biochemical studies of macromolecules.

What is the smallest unit of length we use in Biology?

Nanometres

How would you convert cm into μm?

Multiply by 10,000

How is magnification different in light and electron microscopes?

The magnification in electron microscopes is higher than the magnification in light microscopes.

How is the resolution different in light and electron microscopes?

The resolution in electron microscopes is higher than the resolution in light microscopes.

Why has the use of electron microscopes led to more discoveries?

They have higher resolutions.

What are the differences between prokaryotic and eukaryotic cells?

Prokaryotic cells are unicellular organisms whereas eukaryotic cells are multicellular organisms.

How is the DNA arranged in a eukaryotic cell?

It is enclosed in a nucleus.

How is the DNA arranged in a prokaryotic cell?

The DNA of prokaryotic cells freely flows in the cytoplasm.

What are plasmids?

Small, circular molecules of DNA found in bacterial ones and similar ones.

What are flagella?

A long whiplike structure by which some tiny plants and animals move.

Which types of cells are examples of eukaryotes?

* Muscle cells
* Plant cells
* Stem cells

State 3 main parts of eukaryotic cell

1. The ribosomes
2. The plasma membrane
3. The cytoplasm

Which types of cells are examples of prokaryotes?

* Bacterial cells
* Archaeal cells

Which are usually bigger; prokaryotic cells or eukaryotic cells?

Eukaryotic cells are usually bigger than prokaryotic cells.

What is an ‘order of magnitude’?

10 to the nth power

What cell organelles do bacterial cells NOT have?

* Mitochondria
* Chloroplasts

How are sperm cells adapted to their function?

* Have a haploid nucleus containing genetic material needed for fertilisation
* Have many mitochondria for swimming energy
* Have acrosomes in the head containing enzymes to help the sperm penetrate an egg
* Have a tail so they can swim

How are nerve cells adapted to their function?

They have a long fibre (axon) so they can carry messages up and down the body over long distances.

How are muscle cells adapted to their function?

* Have filaments of protein that slide over each other to cause muscle contraction
* Have many mitochondria to provide energy for contraction

How are root hair cells adapted to their function?

They have a large surface area to maximise absorption.

How are xylem cells adapted to their function?

They lose their end walls to form a long hollow tube and are strengthened by lignin.

How are phloem cells adapted to their function?

* Have sieve tubes which have no nuclei and their cytoplasm connects from one cell to the next to help transport
* Sieve tubes have companion cells which provide energy for substance transport when attatched to each other

What are 3 substances that can move via diffusion in animal cells?

1. Oxygen
2. Glucose
3. Carbon dioxide

What factors increase the rate of diffusion?

* Surface area
* Temperature
* Concentration gradient

Why is diffusion faster with an increase of temperature?

The higher the temperature, the more kinetic energy the particles will have, so they will move and mix more quickly.

Give an example of diffusion

A spray of perfume or room freshner will get diffused into the air by which we can sense the odour.

What is osmosis?

Osmosis is the movement of water molecules from an area of higher water concentration to an area of lower water concentration across a semipermeable membrane.

How is a root hair cell adapted for osmosis?

It has a large surface area to increase the rate of absorption.

What does the term solvent mean?

A substance in which a solute dissolves to produce a homogeneous mixture.

What does the term solute mean?

A substance that dissolves in a solvent to produce a homogeneous mixture.

What does the term hypertonic mean?

Hypertonic has a lower concentration of fluid, sugars and salt than blood.

What does the term hypotonic mean?

Hypertonic has a higher concentration of fluid, sugars and salt than blood.

What does the term isotonic mean?

Isotonic has a similar concentration of fluid, sugars and salt than blood.

What does it mean when the net movement of water is zero?

It means there is no net movement of water molecules.

Describe the method for the required practical that investigates osmosis

* Peel the potato
* Use a cork borer to produce three cylinders of potato- it gives them all the same diameter
* Use a scalpel to trim the cylinders to the same length (around 3cm)
* Measure the length of each cylinder using a ruler and the mass of each cylinder using a balance
* Now place each cylinder into a test tube. Add 10㎤ of a 0.5 molar sugar solution to the first test tube
* Add 10㎤ of 0.25 molar sugar solution to the second test tube and 10㎤ of distilled water to the third test tube
* Leave the potato cylinders overnight to allow osmosis to take place
* Now remove the potato cylinders and roll on a paper towel to remove any surface moisture
* Measure the length and mass of the cylinders again

What is the difference between osmosis and diffusion?

Osmosis only allows solvent molecules to move freely, but diffusion allows both solvent and solute molecules to move freely.

What is active transport?

The process of moving molecules across a cellular membrane through the use of cellular energy.

What is required for active transport?

Active transport requires energy.

What is a concentration gradient?

A concentration gradient occurs when the concentration of particles is higher in one area than another.

Why do cells that carry out active transport have so many mitochondria?

To provide energy via respiration because active transport isn’t a passive process.