Biology - Paper 1 - FINISH OFF

What are the two types of cells?

• Eukaryotic (plant and animal)

• Prokaryotic (bacteria)

List the components of both plant and animal cells

• Nucleus

• Cytoplasm

• Cell Membrane

• Mitochondria

• Ribosomes

List the additional cell components found in plant cells

• Chloroplasts

• Permanent Vacuole

• Cell wall

What is the function of the cytoplasm?

• Site of cellular reactions

• Transport medium

• Contains enzymes and organelles

What is the function of the cell membrane?

Controls the entry and exit of materials into and out of the cell

What is the function of mitochondria

Site of aerobic respiration

What is the function of the ribosomes?

Site of protein synthesis

What is the function of the plant cell wall?

• Provides strength

• Prevent the cell bursting when water enters

What is the function of the permanent vacuole?

Supports the cell

What is the function of chloroplasts?

Site of photosynthesis

Describe how sperm cells in animals are adapted to their function

• Haploid Nucleus - Contains genetic information

• Streamlined head - Aids swimming

• Long Tail - Aids swimming

• Mitochondria - Provide energy for tail movement

• Acrosome - Contains enzymes that digest the egg cell membrane

Describe how muscle cells in animals are adapted to their function

• Arrangement of protein filaments - Allows them to slide over each other to produce muscle contraction

• Mitochondria - Provide energy for muscle contraction

Describe how root hair cells in plants are adapted to their function

• Large Surface Area - Absorb nutrients and water from surrounding soil

• Thin walls - Do not restrict water absorption

• Mitochondira - Provide energy for active transport of mineral ions in

Describe how Xylem cells in plants are adapted to their function

• No end walls between cells - Provide a continuous route for water to flow

• Lignin - Strengthens cell and withstands pressure

Describe how Phloem cells in plants are adapted to their function

• Sieve plates - let dissolved amino acids and sugars be transported up and down the stem

• Mitochondria - Provide energy needed for active transport of substances along the phloem

What is cell differentiation?

The process by which cells become specialised

Why is cell differentiation important?

Allows production of different tissues and organs that perform various vital functions in the human body

At what point in their life cycle do most animal cells differentiate?

Early

For how long do plant cells retain the ability to differentiate?

Throughout their entire life cycle

What is the purpose of cell division in mature animals?

Repair and replacement of cells

What changes does a cell go through as it differentiates?

Becomes specialised through acquisition of different subcellular structures to enable a specific function to be performed by the cell

Define Magnification

The number of times bigger an image appears compared to the size of the real object

Define resolution

The smallest distance between two objects that can be distinguished

How does a light microscope work?

Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the speciment to be observed

What are the advantages of light microscopes?

• Inexpensive

• Easy to use

• Portable

• Observe both dead and living specimens

What are the disadvantage of light microscopes?

• Limited resolution

How does an electron microscope work?

It uses a bean of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image.

What are the advantage of electron microscopes?

• Greater magnification and resolution

Why do electron microscopes have a greater magnification and resolution?

They use a beam of electrons which has a shorter wavelength than photons of light

What are the disadvantages of electron microscopes?

• Expensive

• Large - Less portable

• Require training to use

• Only dead specimens can be observed

How can the magnification of an image be calculated?

Magnification = size of image / size of real object

What are chromosomes made up of?

Chromosomes consist of DNA molecules combined with proteins. They contain genes which provide the instructions for protein synthesis.

What is a gene?

A section of DNA which codes for a protein

How many chromosomes are found in the nucleus of human body cells?

46

How are the chromosomes arranged in the nucleus of a body cell?

Arranged in pairs - 46 chromosomes form 23 pairs

What are the three main stages of the cell cycle?

1. Interphase

2. Mitosis

3. Cytokinesis

Why is mitosis important?

• Produces identical cells which all have the same genetic information

• Produces additional cells for growth, development, and repair of multicellular organisms

Describe the first stage of the cell cycle

Longest stage - cells grow and increase in mass, replicate DNA, and synthesise more organelles

Describe the second stage of the cell cycle

Each chromosome in a pair are lined up at the cell equator and pulled to opposite poles of the cell. The nucelus divides.

Describe the third stage of the cell cycle

The cytoplasm and cell membrane divide - two identical daughter cells are produced.

What is a stem cell?

An unspecialised cell which is capable of differentiating into other cell types and of self-renewal

What is the function of stem cells in embryos?

Embryonic stem cells can replicate themselves and differentiate into many other types of cells.

Embyonic stem cells may be able to treat conditions such as paralysis and diabetes by dividing to replace damaged cells

What is the function of stem cells in adult bone marrow?

Adult stem cells can differenmtiate into several cell types to replace dead or damaged tissues.

What is the function of stem cells in plant meristems?

Meristem stem cells retain the ability to differentiate into any type of plant cell throughout their lifespan

What is therapeutic cloning?

A cloning method where an embryo is produced with the same genetic makeup as the patient.

The stem cells which originate from the embryo will not be rejected by the patient’s immune system, so it can be used to treat certain medical conditions

What are the advantages of cloning plants using meristem stem cells?

• Can prevent rare plants from becoming extinct

• Can clone large numbers of identical plants with a favbourable characteristic

• Canj produce identical plants for research

What are issues associated with the use of stem cells?

• Many embryonic stem cells are sourced from aborted embyros - some people have an ethical/religious obligation

• Development of stem cell therapies is slow, expensive, and difficult

• Adult stem cells infected with viruses could transfer infections to patients

• If donor stem cells do not have a similar genetic makeup to the patient, an immune response could be triggered

What is diffusion?

The net movement of particles of any substance in solution or of a gas from an area of higher concerntration to an area of low concerntration

What are the three main factors that affect the rate of diffusion?

• Concerntration gradient - larger gradient, faster diffusion

• Temperature - Higher temperature, faster diffusion

• Surface Area - Larger surface area, faster diffusion

How are single-celled organisms adapted for diffusion?

They have a large surface area to volume ratio - maximises the rate of diffusion of molecules to meet the organism’s needs

How is surface area to volume ratio calculated?

Surface Area = Number of sides x (side length x side width)

Volume = Length x width x depth

Ratio = Surface area : Volume

How is the small intestine in mammals adapted for exchange?

Cells in the small intestine have villi. Villi have microvilli to further increase surface area, thin walls, and are close to good blood supply