AQA GCSE Biology - Paper 1.docx

What does a nucleus do? - correct answer It contains genetic material and controls the activities of the cell What does cytoplasm do? - correct answer It's a gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions What does a cell membrane do? - correct answer It holds the cell together and controls what goes in and out What do mitochondria do? - correct answer These are where most of the reactions for aerobic respiration occur. Respiration transfers energy that the cell needs to work What do ribosomes do? - correct answer This is where protein synthesis takes place - where proteins are made in the cell What do cell walls do? - correct answer They are made of cellulose and they support and strengthen the cell What does a vacuole do? - correct answer It contains cell sap and helps maintain the shape of the cell What do chloroplasts do? - correct answer This is where photosynthesis occurs, which makes food for the plant. They contain chlorophyll - a green pigment - which absorbs light needed for photosynthesis What do bacterial cells contain? - correct answer Cytoplasm, cell membrane, cell wall, flagella, ribosomes, mitochondria, slime capsule, plasmids (small rings of DNA) and a single circular strand of DNA that floats freely in the cytoplasm What do bacterial cells NOT contain? - correct answer A nucleus What is the equation for magnification? - correct answer Image size divided by actual size What is differentiation? - correct answer The process by which a cell changes to become specialised for its job What are undifferentiated cells called? - correct answer Stem cells What are sperm cells specialised for and how are they specialised? - correct answer Reproduction - they transport the male DNA to the female DNA -It has a flagella and a streamlined head to help it swim towards the egg -There are lots of mitochondria in the cell to provide the energy needed -It carries enzymes in its head to help digest through the egg cell membranes What are nerve cells specialised for and how are they specialised? - correct answer Rapid signalling - they carry electrical signals from one part of the body to another -They are long to cover more distance -They have branched connections at their ends to connect to other nerve cells and form a network throughout the body What are muscle cells specialised for and how are they specialised? - correct answer Contraction - they need to contract quickly -They are long so they have space to contract -They contain lots of mitochondria to generate the energy needed for contraction What are root hair cells specialised for and how are they specialised? - correct answer Absorbing water and minerals -They are cells on the surface of plant roots which grow into long hairs that stick out into the soil -They have a large surface area for absorbing water and mineral ions from the soil What are chromosomes? - correct answer Coiled up lengths of DNA molecules that are found in the nuclei What do multicellular organisms use mitosis for? - correct answer To grow or replace cells that have been damaged What are stem cells? - correct answer They are undifferentiated cells that divide to produce lots more undifferentiated cells. They then differentiate into different types of cell Where are stem cells found? - correct answer In early human embryos or the bone marrow of adults What do embryonic stem cells do? - correct answer 1) Used to replace faulty cells in sick people - insulin-producing cells for diabetes and nerve cells for paralysed spinal injuries 2) Used to replace faulty blood cells What is diffusion? - correct answer Diffusion is the movement of particles from an area of high concentration to an area of low concentration Name the substances that can diffuse through cell membranes - correct answer Glucose, water, oxygen and amino acids Name two substances that can't diffuse through cell membranes - correct answer Protein and starch What is osmosis? - correct answer Osmosis is the passive movement of water molecules through a partially permeable cell membrane from an area of high water concentration to an area of low water concentration What are the two main differences between active transport and diffusion? - correct answer Active transport uses energy whereas diffusion doesn't. Active transport goes against the concentration gradient whereas diffusion goes along it Adaptations of Exchange Surfaces - correct answer 1) Large surface area - lots of substances can diffuse at once 2) Lots of blood vessels - to get stuff into and out of the blood quickly 3) Thin membrane - short distance for substances to diffuse 4) Often ventilated - air moves in & out Give two ways that the villi in the small intestine are adapted for absorbing digested food - correct answer 1) A single layer of surface cells 2) A very good blood supply to assist quick absorption Explain how the leaves are adapted to maximise the amount of carbon dioxide that gets into their cells - correct answer 1) The exchange surface in a leaf is covered in stomata which the carbon dioxide diffuses through 2) The leaf has a flattened shape which increases the area of its exchange surface, therefore it's more effective 3) The walls of the cells inside the leaf act as another exchange surface 4) The air spaces inside the leaf increase the area of the exchange surface which increases the chance for carbon dioxide to enter the cells What affects the rate of diffusion? - correct answer Concentration gradient - the steeper the gradient, the faster the rate Temperature - the higher the temperature, the faster the rate (the particles have more energy thus move around faster) Surface area - the larger it is, the faster the rate Diffusion distance - the shorter the distance, the faster the rate